Defining a “new normal” for campus research

Despite the trials and tribulations of the COVID-19 pandemic, Building 68 core facilities have remained open for business.

Raleigh McElvery
September 10, 2020

In mid-March, MIT closed its doors due to the COVID-19 pandemic, and Building 68 temporarily became a ghost town. Home to over 25 life science labs and three core facilities, the Department of Biology’s primary research hub usually teems with activity. But this spring, only a skeleton crew of essential workers came in and out, maintaining the equipment and running select experiments. Since then, the ghost town has gradually come back to life, as scientists are returning to their benches once again while taking safety precautions.

Three of the 24 core facilities affiliated with the life sciences are located in Building 68: the BioMicro Center, Structural Biology Core Facility, and Biophysical Instrumentation Facility. Known fondly as the “BIF,” the latter houses instruments that help researchers elucidate macromolecular structures. Select staff members remained available throughout the research shutdown to help biologists, biological engineers, and chemists run essential protocols.

One floor down, the BioMicro Center also continued to offer limited services — from maintaining multi-year cancer studies to running analyses probing SARS-CoV-2, the virus strain that causes COVID-19. The team there specializes in genomic and transcriptomic technologies, bioinformatics, and research computing.

Stuart Levine SB ’97,  who leads the BioMicro Center, says the facility handled anywhere from six to nine projects a day before the pandemic. But during the research shutdown, requests dwindled to a steady “trickle.”

“We did whatever we could to be helpful,” he adds. “I went to campus a few times early on, and it was eerie to be one of the only people in the building.”

Illustration of virus-like molecule
Illustration of the Bathe lab’s virus-like nanoparticle. Credit: Ella Maru Design Studio

Although the BioMicro Center is situated in Building 68, it serves a wide array of individuals and labs across campus. Chemical engineering graduate student, Grant Knappe, was also among the select few permitted to work in lab during the shutdown, and he relied heavily on the BioMicro Center for a key step in his experimental protocol. Knappe’s advisor, Professor of Biological Engineering Mark Bathe, began shifting his group’s focus to COVID-related projects almost immediately after campus emptied in mid-March.

The Bathe lab studies nanoparticles made from DNA “origami” that’s been folded into tiny geometric shapes. They’ve developed user-friendly algorithms to design these structures, and regularly employ the BioMicro’s oligonucleotide synthesizer to produce their DNA strands. With the help of the facility, Knappe and his colleagues recently created nanoparticles adorned with short DNA strands to mimic the SARS-CoV-2 spike protein — which induces the body’s immune response. They hope these geometric nanoparticles will eventually help develop COVID-19 vaccines.

“The scientific process is usually very collaborative,” Knappe says, “so at the beginning it was difficult to run experiments without other people nearby to bounce ideas back-and-forth.”

Focusing on just one project — rather than several simultaneously — was also a new experience. Knappe is excited to see where his COVID research will go, and what lab instruments will ultimately be key to the process. “You never know what equipment could end up fighting the virus,” he adds.

On June 1, Phase 1 of the research ramp-up began, and labs were permitted to begin operating at 25% capacity. Scientists started working in shifts with reduced hours, conducting their experiments many feet apart, and visiting MIT Medical for regular COVID-19 testing. Levine remembers that the number of requests for BioMicro services surged almost immediately as researchers returned.

At the same time, Robert Grant, the Research Scientist responsible for the Structural Biology Core Facility, started up the core’s state-of-the-art X-ray crystallography equipment. Leaving in March had been a “mad scramble,” and he remembers hastily terminating non-essential experiments and distributing extra resources (like liquid nitrogen tanks) to labs in-need. When he returned in June he already had project requests.

“A big part of my job is interacting with people, which I really enjoy,” he says. “But we’ve had to adapt, and and devise new ways to train people on equipment and data processing that don’t require close contact.”

Grant has recently started socially distant one-on-one trainings, where both parties remain as far apart as possible while wearing masks and gloves. In some cases, he’s processed samples and collected data for users, helping them perform analyses via Zoom. He’s also found ways to revive collaborations with other institutes. He recently sent crystals to Argonne National Laboratory in Chicago. The student who grew the crystals then remotely controlled an X-ray beamline at Argonne’s Advanced Photon Source synchrotron to collect diffraction data from home while Zooming with Grant.

“We’re definitely open for business, although things look a little different than before,” Grant says. “We’ve reached a new normal.”

Building 68's Structural Biology Core Facility
Building 68’s Structural Biology Core Facility
Posted: 9.10.20
School of Science grows by 10
School of Science
September 9, 2020

Despite the upheaval caused by the coronavirus pandemic, 10 new faculty members have joined MIT in the departments of Biology; Chemistry; Earth, Atmospheric and Planetary Sciences; Mathematics; and Physics. The School of Science welcomes these new faculty, most of whom began their appointment July 1, amidst efforts to update education and research plans for the fall semester. They bring exciting and valuable new areas of strength and expertise to the Institute.

Camilla Cattania is an earthquake scientist. She uses continuum mechanics, numerical simulations, and statistics to study fault mechanics and earthquake physics at different scales, from small repeating events to fault interaction on regional and global scales. The models she has developed can help forecast earthquake sequences caused by seismic or aseismic events, such as aftershocks and swarms induced by forcing mechanisms like magma moving under the Earth’s surface. She has also developed theoretical models to explain why certain faults rupture in predictable patterns while others do not. Cattania’s research plans include widening her focus to other tectonic settings and geometrically complex fault structures.

Cattania earned her bachelor’s and master’s degrees from Cambridge University in experimental and theoretical physics in 2011, after which she completed a PhD in Germany at the GFZ German Research Center for Geosciences and the University of Potsdam in 2015. Subsequently, she spent a few months as a researcher at Woods Hole Oceanographic Institution and as a postdoc at Stanford University and her doctoral institution. She joins the Department of Earth, Atmospheric and Planetary Sciences as an assistant professor.

Richard Fletcher researches quantum physics using atomic vapors one-millionth the density of air and one-millionth the temperature of deep space. By manipulating the gas with intricately sculpted laser beams and magnetic fields, he can engineer custom-made quantum worlds, which provide both a powerful test bed for theory and a wonderful playground for discovering new phenomena. The goal is to understand how interesting collective behaviors emerge from the underlying microscopic complexity of many interacting particles. Fletcher’s interests include superfluidity in two-dimensional gases, methods to probe the correlations between individual atoms, and how the interplay of interactions and magnetic fields leads to novel physics.

Fletcher is a graduate of Cambridge University, where he completed his bachelor’s in 2010. Before returning to Cambridge University to earn his PhD in 2015, he was a research fellow at Harvard University. He originally came to MIT as a postdoc in 2016 and now joins the Department of Physics as an assistant professor. Fletcher is a member of the MIT-Harvard Center for Ultracold Atoms.

William Frank investigates deformation of the Earth’s crust. He combines seismology and geodesy to explore the physical mechanisms that control the broad continuum of rupture modes and fault instabilities within the Earth. His research has illuminated the cascading rupture dynamics of slow fault slip and how the aftershocks that follow a large earthquake can reveal the underlying behavior of the host fault. Frank considers shallow shifts that cause earthquakes down to deep creep that is all-but-invisible at the surface. His insights work to improve estimates of seismic hazards induced by tectonic dynamics, volcanic processes, and human activity, which can then inform risk prediction and mitigation.

Frank holds a bachelor’s degree from the University of Michigan in earth systems science, which he received in 2009. The Institut de Physique du Globe de Paris awarded him a master’s degree in geophysics in 2011 and a PhD in 2014. He first joined MIT as a postdoc in 2015 before moving to the University of Southern California as an assistant professor in 2018. He now returns as an assistant professor in the Department of Earth, Atmospheric and Planetary Sciences.

Ronald Fernando Garcia Ruiz advances research on fundamental physics and nuclear structure largely through the development of novel laser spectroscopy techniques. He investigates the properties of subatomic particles using atoms and molecules made up of short-lived radioactive nuclei. Garcia Ruiz’s experimental work provides unique information about the fundamental forces of nature and offers new opportunities in the search beyond the Standard Model of particle physics. His previous research at CERN focused on the study of the emergence of nuclear phenomena and the properties of nuclear matter at the limits of existence.

Garcia Ruiz’s bachelor’s degree in physics was achieved in 2009 at Universidad Nacional de Colombia. After earning a master’s in physics in 2011 at Universidad Nacional Autónoma de México, he completed a doctoral degree in radiation and nuclear physics at KU Leuven in 2015. Prior to joining MIT, he was first a research associate at the University of Manchester from 2016-17 and then a research fellow at CERN. Garcia Ruiz has now joined the Department of Physics as an assistant professor. He began his appointment Jan. 1. He is also affiliated with the Laboratory for Nuclear Science.

Ruth Lehmann studies germ cells. The only cells in the body capable of producing an entire organism on their own, germ cells pass genomic information from one generation to the next via egg cells. By analyzing the organization of their informational material as well as the mechanics they regulate, such as the production of eggs and sperm, Lehmann hopes to expose germ cells’ unique ability to enable procreation. Her work in cellular and developmental biology is renowned for identifying how germ cells migrate and lead to the continuation of life. An advocate for fundamental research in science, Lehmann studies fruit flies as a model to unveil vital aspects of early embryonic development that have important implications for stem cell research, lipid biology, and DNA repair.

Lehmann earned her bachelor’s degree in biology from the University of Tubingen in Germany. She took an interlude from her education to carry out research at the University of Washington in the United States before returning to Germany. There, she earned a master’s equivalent from the University of Freiburg and a PhD from the University of Tubingen. Lehmann was subsequently a postdoc at the Medical Research Council Laboratory of Molecular Biology in the UK, after which she joined MIT. A faculty member and Whitehead Institute for Biomedical Research member from 1988 to 1996, she now returns after 23 years at New York University. Lehmann joins as a full professor in the Department of Biology and is the new director of the Whitehead Institute for Biomedical Research.

As an astrochemist, Brett McGuire is interested in the chemical origins of life and its evolution. He combines physical chemistry experiments and analyses with molecular spectroscopy in a lab, the results of which he then compares against astrophysics observation. His work ties together questions about the formation of planets and a planet’s ability to host and create life. McGuire does this by investigating the generation, presence, and fate of new molecules in space, which is vast and mostly empty, providing unique physical challenges on top of chemical specifications that can impact molecular formation. He has discovered several complex molecules already, including benzonitrile, a marker of carbon-based reactions occurring in an interstellar medium.

McGuire’s BS degree was awarded by the University of Illinois at Urbana-Champaign in 2009. He completed a master’s in physical chemistry in 2011 at Emory University and a PhD in 2015 at Caltech. He then pursued a postdoc at the National Radio Astronomy Observatory and the Harvard-Smithsonian Center for Astrophysics. He joins the Department of Chemistry as an assistant professor.

Dor Minzer works in the fields of mathematics and theoretical computer science. His interests revolve around computational complexity theory, or — more explicitly — probabilistically checkable proofs, Boolean function analysis, and combinatorics. With collaborators, he has proved the 2-to-2 Games Conjecture, a central problem in complexity theory closely related to the Unique-Games Conjecture. This work significantly advances our understanding of approximation problems and, in particular, our ability to draw the border between computationally feasible and infeasible approximation problems.

Minzer is not new to online education. After earning his bachelor’s degree in mathematics in 2014 and a PhD in 2018, both from Tel-Aviv University, he became a postdoc at the Institute for Advanced Study at Princeton University. He joins the Department of Mathematics as an assistant professor.

Lisa Piccirillo is a mathematician specializing in the study of three- and four-dimensional spaces. Her work in four-manifold topology has surprising applications to the study of mathematical knots. Perhaps most notably, Piccirillo proved that the Conway knot is not “slice.” For all other small knots, “sliceness” is readily determined, but this particular knot had remained a mystery since John Conway presented it in the mid-1900s. After hearing about the problem at a conference, Piccirillo took only a week to formulate a proof. She is broadly interested in low-dimensional topology and knot theory, and employs constructive techniques in four-manifolds.

Piccirillo earned her BS in mathematics in 2013 from Boston College. Her PhD in mathematics was earned from the University of Texas at Austin in 2019, and from 2019-20 she was a postdoc at Brandeis University. She joins the Department of Mathematics as an assistant professor.

Jonathan Weissman’s research interest is protein folding and structure, an integral function of life. His purview encompasses the expression of human genes and the lineage of cells, as well as protein misfolding, which can cause diseases and other physiological issues. He has made discoveries surrounding protein folding mechanisms, the development of CRISPR gene-editing tools, and other new therapeutics and drugs, and in the process generated innovative experimental and analytical methods and technologies. One of his novel methods is the ribosome profiling approach, which allows researchers to observe in vivo molecular translation, the process by which a protein is created according to code provided by RNA, a major advancement for health care.

Weissman earned a bachelor’s degree in physics from Harvard University in 1998 and a PhD from MIT in 1993. After completing his doctoral degree, he left MIT to become a postdoc at Yale University for three years, and then a faculty member at the University of California at San Francisco in 1996. He returns to MIT to join the Department of Biology as a full professor and a member of the Whitehead Institute for Biomedical Research. He is also a Howard Hughes Medical Institute investigator.

Yukiko Yamashita, a stem cell biologist, delves into the origins of multicellular organisms, asking questions about how genetic information is passed from one generation to the next, essentially in perpetuity, via germ cells (eggs and sperm), and how a single cell (fertilized egg) becomes an organism containing many different types of cells. The results of her work on stem cell division and gene transmission has implications for medicine and long-term human health. Using fruit flies as a model in the lab, she has revealed new areas of knowledge. For example, Yamashita has identified the mechanisms that enable a stem cell to produce two daughter cells with distinct fates, one a stem cell and one a differentiating cell, as well as the functions of satellite DNA, which she found to be crucial, unlike the “waste” they were previously thought to be.

Yamashita received her bachelor’s degree in biology in 1994 and her PhD in biophysics in 1999, both from Kyoto University. After being a postdoc at Stanford University for five years, she was appointed a faculty member at the University of Michigan in 2007. She joined the Department of Biology as a full professor with a July 1 start. She also became a member of the Whitehead Institute of Biomedical Research and is a standing investigator at the Howard Hughes Medical Institute.

Sebastian Lourido earns ASM Award for Early Career Basic Research
August 28, 2020

Washington, D.C. – August 27, 2020 – The 2021 American Society for Microbiology (ASM) awardees in research, education and leadership have now been announced. ASM congratulates all of the award recipients for their achievements. The ASM Awards program is managed by the American Academy of Microbiology, the honorific leadership group within ASM. The mission of the Academy is to recognize microbiologists for outstanding contributions to the microbial sciences and to provide microbiological expertise in the service of science and the public.

The 2021 ASM Award Laureates:

ASM Alice C. Evans Award for Advancement of Women
Recognizes outstanding contributions toward the full participation and advancement of women in the microbial sciences. This award is given in memory of Alice C. Evans, the first woman to be elected ASM president (elected in 1928).
•    Jennifer Glass, Ph.D.

ASM Award for Applied and Biotechnological Research
Recognizes an outstanding scientist with distinguished research achievements in the development of products, processes and technologies that have advanced the microbial sciences.
•    Dennis Hruby, Ph.D.

ASM Award for Early Career Applied and Biotechnological Research
Recognizes an early career investigator with distinguished research achievements in the development of products, processes and technologies that have advanced the microbial sciences.
•    Kizzmekia Corbett, Ph.D.

ASM Award for Basic Research
Recognizes an outstanding scientist whose discoveries have been fundamental to advancing our understanding of the microbial world.
•    Sue Wickner, Ph.D.

ASM Award for Early Career Basic Research
Recognizes an early career investigator with distinguished basic research achievements in the microbial sciences.
•    Sebastian Lourido, Ph.D.

ASM Award for Environmental Research
Recognizes an outstanding scientist with distinguished research achievements that have improved our understanding of microbes in the environment, including aquatic, terrestrial and atmospheric settings.
•    Terry Hazen, Ph.D.

ASM Award for Early Career Environmental Research
Recognizes an early career investigator with distinguished research achievements that have improved our understanding of microbes in the environment, including aquatic, terrestrial and atmospheric settings.
•    A. Murat Eren, Ph.D.

ASM Award for Education
Recognizes general excellence in microbiology education. Education is broadly defined and meant to include any and all activities that inform and motivate students about the discipline of microbiology.
•    Nichole Broderick, Ph.D.

ASM Award for Research and Leadership in Clinical Microbiology
Recognizes an outstanding scientist/clinical microbiologist with distinguished research achievements, and a record of innovation and advancement of the clinical microbiology profession. This award represents the merging of the BD Research and Sonnenwirth Awards given annually since 1978 and 1986, respectively.
•    Melissa Miller, Ph.D.

ASM Award for Service
Recognizes outstanding contributions through service to the microbiological community.
•    Barbara Robinson-Dunn, Ph.D.

ASM Carski Award
Recognizes an educator for outstanding teaching of microbiology to undergraduate students and for encouraging them to subsequent achievement.
•    Jason Tor, Ph.D.

ASM D.C. White Award
Recognizes distinguished accomplishments in interdisciplinary research and mentoring in microbiology. This award honors D.C. White, who was known for his interdisciplinary scientific approach and for being a dedicated and inspiring mentor.
•    Ferran Garcia-Pichel, Ph.D.

ASM Lifetime Achievement Award
ASM’s premier award for sustained contributions to the microbiological sciences.
•    Bernard Moss, MD, Ph.D.

ASM Moselio Schaechter Award in Recognition of a Developing-Country Microbiologist
This award, named in honor of Professor Moselio Schaechter, former ASM president, recognizes a scientist who has shown exemplary leadership and commitment towards the substantial furthering of the profession of microbiology in research, education or technology in the developing world.
•    Gustavo Goldman, Ph.D.

ASM Scherago-Rubin Award for Clinical Microbiology
Recognizes an outstanding bench-level clinical microbiologist involved in routine diagnostic work that has distinguished her- or himself by excellent performance. The award was established by the late Sally Jo Rubin, an active member of ASM’s Clinical Microbiology Division, in honor of her grandfather, Professor Morris Scherago.
•    Brandon Ellis, B.S.

ASM William A. Hinton Award for Advancement of a Diverse Community of Microbiologists
Recognizes outstanding contributions toward fostering the research training of minorities and in increasing diversity in microbiology. It is given in memory of William A. Hinton, a physician-research scientist, and one of the first African-Americans to join ASM.
•    Eric Triplett, Ph.D.

###

The American Society for Microbiology is one of the largest professional societies dedicated to the life sciences and is composed of 30,000 scientists and health practitioners. ASM’s mission is to promote and advance the microbial sciences.

ASM advances the microbial sciences through conferences, publications, certifications and educational opportunities. It enhances laboratory capacity around the globe through training and resources. It provides a network for scientists in academia, industry and clinical settings. Additionally, ASM promotes a deeper understanding of the microbial sciences to diverse audiences.

“Runaway” Transcription

Researchers discover new rules governing bacterial gene expression that overturn fundamental assumptions about basic biological pathways.

Raleigh McElvery
August 26, 2020

On the evolutionary tree, humans diverged from yeast roughly one billion years ago. By comparison, two seemingly similar species of bacteria, Escherichia coli and Bacillus subtilis, have been evolving apart for roughly twice as long. In other words: walking, talking bipeds are closer on the tree of life to single-celled fungus than these two bacteria are to one another. In fact, it’s becoming increasingly clear that what is true of one bacterial type may not be true of another — even when it comes down to life’s most basic biological pathways.

E. coli has served as a model organism in scientific research for over a century, and helped researchers parse many fundamental processes, including gene expression. In these bacteria, as one molecular machine, the RNA polymerase, moves along the DNA transcribing it into RNA, it is followed in close pursuit by a second molecular machine, the ribosome, which translates the RNA into proteins. This “coupled” transcription-translation helps monitor and tune RNA output, and is considered a hallmark of bacteria.

However, an interdisciplinary team of biologists and physicists recently showed that the B. subtilis bacterium employs a different set of rules. Rather than working in tandem with the ribosome, the polymerase in B. subtilis speeds ahead. This system of “runaway” transcription creates alternative rules for RNA quality control, and provides insights into the sheer diversity of bacterial species.

“Generations of researchers, including myself, were taught that coupled transcription-translation is fundamental to bacterial gene expression,” says Gene-Wei Li, an associate professor of biology and senior author of the study. “But our very precise, quantitative measurements have overturned that long-held view, and this study could be just the tip of the iceberg.”

Grace Johnson, a graduate student in the Department of Biology, and Jean-Benoît Lalanne, a graduate student in the Department of Physics, are the lead authors on the paper, which appeared in Nature on Aug. 26.

A curious clue

In 2018, Lalanne developed an experimental technique to measure the boundaries of RNA transcripts. When DNA is transcribed into RNA, the resulting transcripts are generally longer than the DNA coding sequence because they also have to include an extra bit at the end to signal the polymerase to stop. In B. subtilis, Lalanne noticed there simply wasn’t enough space between the ends of the coding sequences and the ends of the RNA transcripts — the extra code was too short for both the polymerase and the ribosome to fit at the same time. In this bacterium, coupled transcription-translation didn’t seem possible.

“It was a pretty weird observation,” Lalanne recalls. “It just didn’t square up with the accepted dogma.”

To delve further into these puzzling observations, Johnson measured the speeds of the RNA polymerase and ribosome in B. subtilis. She was surprised to find that they were moving at very different rates: the polymerase was going roughly twice as fast as the ribosome.

During coupled transcription-translation in E. coli, the ribosome is so closely associated with the RNA polymerase that it can control when transcription terminates. If the RNA encodes a “premature” signal for the polymerase to stop transcribing, the nearby ribosome can mask it and spur the polymerase on. However, if something goes awry and the ribosome is halted too far behind the polymerase, a protein called Rho can intervene to terminate transcription at these premature sites, halting the production of these presumably non-functional transcripts.

However, in B. subtilis, the ribosome is always too far behind the polymerase to exert its masking effect. Instead, Johnson found that Rho recognizes signals encoded in the RNA itself. This allows Rho to prevent production of select RNAs while ensuring it doesn’t suppress all RNAs. However, these specific signals also mean Rho likely has a more limited role in B. subtilis than it does in E. coli.

A family trait

To gauge how common runaway transcription is, Lalanne created algorithms that sifted through genomes from over 1,000 bacterial species to identify the ends of transcripts. In many cases, there was not enough space at the end of the transcripts for both the RNA polymerase and the ribosome to fit, indicating that more than 200 additional bacteria also rely on runaway transcription.

“It was striking to see just how widespread this phenomenon is,” Li says. “It raises the question: How much do we really know about these model organisms we’ve been studying for so many years?”

Carol Gross, a professor in the Department of Microbiology and Immunology at University of California San Francisco who was not involved with the study, refers to the work as a “tour de force.”

“Gene-Wei Li and colleagues show transcription-translation coupling, thought to be a foundational feature of bacterial gene regulation, is not universal,” she says. “Instead, runaway transcription leads to a host of alternative regulatory strategies, thereby opening a new frontier in our study of bacterial strategies to thrive in varied environments.”

As researchers widen their experimental radius to include more types of bacteria, they are learning more about the basic biological processes underlying these microorganisms — with implications for those that take up residence in the human body, from helpful gut microbes to noxious pathogens.

“We’re beginning to realize that bacteria can have distinct ways of regulating gene expression and responding to environmental stress,” Johnson says. “It just shows how much interesting biology is left to uncover as we study increasingly diverse bacteria.”

Citation:
“Functionally uncoupled transcription–translation in Bacillus subtilis
Nature, online August 26, 2020, DOI: 10.1038/s41586-020-2638-5
Grace E. Johnson, Jean-Benoît Lalanne, Michelle L. Peters, and Gene-Wei Li

Top illustration: Researchers discovered a new system of transcription and translation in bacteria, where the polymerase (pink) in B. subtilis “runs away” from the ribosome (blue). Credit: Grace Johnson
Posted: 8.26.20
Antibiotic resistance: How to prevent the next public health emergency
Emma H. Yee, Steven S. Cheng, Grant A. Knappe, and Christine A. Moomau | MIT Science Policy Review
August 25, 2020

Article Summary

Antibiotics are a vital component of global health. By killing or inhibiting the growth of bacteria, antibiotics treat infections like pneumonia, staph, and tuberculosis.By preventing infections, they enable major medical procedures such as surgeries and chemotherapy. However,bacteria are becoming increasingly resistant to current antibiotics, causing an estimated 34,000 deaths annually in the US. Left unchecked, antibiotic resistance will have major public health consequences, causing over 5 million deaths each year by 2050. Major causes of this crisis are the misuse of existing antibiotics and the slow development of new antibiotics. To incentivize responsible use, governments and institutions are initiating education programs, mandating comprehensive hospital antibiotic stewardship programs, and funding the development of rapid diagnostics. To bring new antibiotic drugs to market, the US government and other non-governmental organizations are funding scientific research toward antibiotic development.Additional incentives are being pursued to improve the commercial viability of antibiotic development and protect drug developers from the unique challenges of the antibiotic market. With diligent efforts to improve responsible use and encourage novel antibiotic drug discovery, we can decrease the global disease burden, save money, and save lives.

Antibiotics are drugs that kill or inhibit the growth of bacteria, and we have them to thank for the 25-year increase in American life expectancy in the last century[1,2]. In 1900, the three leading causes of death were bacterial infections: pneumonia, tuberculosis, and diarrhea/enteritis[3]. Penicillin, the first antibiotic, was discovered in 1928. But it was not until World War II, when wounded soldiers were more likely to die from infections than the injuries themselves, that governments realized penicillin’s life-saving potential[4]. The US government began developing and mass-producing penicillin through unprecedented public, private, and international collaborations, prompting a new era of antibiotics. Antibiotics are now used to treat a myriad of common infections like strep throat, meningitis, tuberculosis, tetanus, urinary tract infections, and food poisoning. They also enable medical procedures that otherwise create a high risk of infection, such as invasive surgery, organ transplantation, and chemotherapy[5]. However, antibiotics are not “one size fits all”; certain types of antibiotics are only effective against certain kinds of bacteria, and all antibiotics are ineffective against viruses[6].

Antibiotics kill or inhibit bacterial growth via various mechanisms of action; they might attack the protective bacterial cell wall, interfere with bacterial reproduction, or interrupt production of molecules necessary for the bacteria’s survival[7]. However, bacteria reproduce and evolve rapidly, changing over time to resist an antibiotic’s destructive mechanism of action. In fact, the more we use antibiotics, the faster bacteria evolve to resist those antibiotics. As bacteria reproduce, random DNA mutations will occur. Most random mutations have no effect on the bacteria, but sometimes a mutation will give the bacteria a special ability to resist an antibiotic—for instance, the mutation may change the cellular target of the antibiotic, or allow the bacteria to pump the drug out of the cell. When an antibiotic is used on bacteria, most of the population will die, but if any of the bacteria have one of these resistance-conferring mutations, they will survive and continue to reproduce, until the entire population is resistant[5]. The use of antibiotics therefore creates environments where bacteria with antibiotic resistance mutations are more likely to survive and reproduce, while susceptible bacteria are gradually killed off.

Figure 1: Use of an antibiotic gradually increases the prevalence of resistant bacteria. If any cell has developed characteristics allowing it to resist attack by an antibiotic, it is more likely to survive and multiply.

This means that, over time, the bacteria that cause infections in humans are more and more likely to be resistant to common antibiotics. It is important to note that bacteria develop antibiotic resistance–not people. But when people use lots of antibiotics, they change bacterial populations such that more and more bacteria are resistant to those antibiotic drugs. This illustrates the double-edged sword nature of antibiotic use: antibiotics are immensely valuable for combating countless infections and enabling medical procedures, but the more we use them, the less valuable they become.

Today, antibiotic resistance is accelerating at alarming rates. The Centers for Disease Control and Prevention (CDC) estimates there are 3 million antibiotic resistant infections in the US every year, causing at least 34,000 deaths[5]. Globally, at least 700,000 deaths occur due to resistant infections, most of which are bacterial; the actual number is likely higher due to poor reporting and surveillance[8]. The prospect of widespread antibiotic resistance threatens to bring society into a post-antibiotic age where infections are more expensive and difficult to treat. This is a threat to not only public health but also the economic stability of the healthcare system[9] and national security[10].

Figure 2:Annual global deaths due to different factors. Antimicrobial resistance (AMR) accounts for resistance from bacteria, as well as fungi, viruses, parasites, and other microbes[15].
This review will focus on medical use of antibiotics in humans in the US, but antibiotic use in animals and agriculture are also major contributors to the current crisis[6]. It is also critical to understand that combating antibiotic resistance will require global cooperative action because infection-causing bacteria spread rapidly between cities, countries, and continents. A large part of addressing antibiotic resistance in the US is assisting and coordinating with other governments, especially those in low-income countries which have the highest instances of antibiotic resistance, but the fewest resources to deal with it[11]. It is also vital to understand the causes of antibiotic resistance in the US and effective actions US institutions can take.

Misuse and Overuse of Antibiotics

Overuse of antibiotics is a major contributor to the rapid proliferation of antibiotic resistant infections. It is estimated that US doctors’ offices and emergency departments prescribe about 47 million unnecessary antibiotic courses annually, amounting to 30% of all antibiotic prescriptions[12]. Many studies show that even when illnesses do require antibiotics, prescribed time courses are significantly longer than national guidelines[13, 14].

Rapid Diagnostics and Antibiotic Prescriptions: A major cause of ubiquitous antibiotic overuse is a lack of rapid methods for diagnosing infections. Physicians rely on tests that usually take days to weeks to identify if an infection is bacterial and, if so, which antibiotics will be most effective. Waiting this long can be harmful or even fatal for patients[15]. Therefore, physicians usually prescribe broadly effective antibiotics while knowing little about the nature of the infection[15]. This can save lives, but if the infection is caused by a virus or resistant bacteria, the antibiotics will not treat the illness and will give resistant strains a chance to further multiply, leaving patients susceptible to additional infections.

With growing awareness in the last 5-10 years that appropriate antibiotic use is difficult with current diagnostics, the CDC, the National Institute of Allergy and Infectious Diseases (NIAID), and the Biomedical Advanced Research and Development Authority (BARDA) have collectively awarded hundreds of millions of dollars to state health departments, businesses, and universities to develop rapid diagnostics[16]. BARDA and NIAID also organized a $20 million prize, the Antimicrobial Resistance Diagnostic Challenge[17], and fund the global non-profit, CARB-X, which has invested $82.5 million in 55 projects worldwide for antibiotic resistance research, including diagnostics[18]. This surge in resources and funding has increased rapid diagnostic development. For example, the NIAID funded development of BioFire’s FilmArray[19], which is now an FDA-cleared diagnostic test available for purchase in the US[20]. In just an hour, it tests patient samples for several common types of bacteria, viruses, and yeast, including antibiotic resistant ones[21].

However, new diagnostic technologies have limited effectiveness when they fail to meet practical cost and resource requirements. Cepheid’s GeneXpert MTB/RIF test, for example, can diagnose tuberculosis infection and determine resistance to rifampicin, a common antibiotic for tuberculosis, in 2 hours[22]. Unfortunately, it has not been used as widely as initially expected[23], mainly because the equipment costs $17,000, not counting training and set-up costs[24]. This illustrates another major shortcoming of current diagnostic technologies: high healthcare infrastructure and cost requirements that render them inaccessible to many people.

Widespread access to rapid diagnostics is not just about fairness, it’s a necessity. Antibiotic resistance will remain a problem in the US as long as it is a problem anywhere in the country or the world due to inevitable intra- and international bacterial transmission. Many recently developed rapid diagnostics cost $100-$250 per test[25, 26]. These diagnostic innovations are promising and valuable in filling part of the gap in rapid diagnostics, but their benefits will not be felt by the majority of global hospitals and patients that cannot afford or support high cost, high tech diagnostic investments. Increasing institutional funding in the last 10 years has resulted in new rapid diagnostics for identifying and characterizing infections, a potential step towards reducing antibiotic misuse and subsequent development of antibiotic resistance. However, ensuring accessibility of technological improvements is essential in combating antibiotic resistance.

Prescribing Practices: Updating prescription standards and educating healthcare workers and patients on responsible antibiotic use is another key step in reducing antibiotic overuse. In the US, patients are often prescribed antibiotics for far longer than necessary. Two recent studies found that 70% of patients with sinus infections and 70% of adults hospitalized with pneumonia were given antibiotics for 3 or more days longer than recommended[13, 14]. Oftentimes, this stems from an out-of-date belief that longer is better in terms of preventing the development and spread of resistant bacteria. In fact, the opposite is true. Shorter courses of antibiotics lower the selective pressure for development of resistance. This was illustrated in a study of pediatric antibiotic use[27], where children prescribed 5 days of amoxicillin for the treatment of respiratory infections were less likely to carry antibiotic resistant Streptococcus pneumoniae in their nasal passage than their peers who were treated for 10 days. These children were also found to be less likely to transmit resistant bacteria to others.

In many cases, common antibiotic treatments can be shortened without affecting the outcome. A trial of pneumonia patients found that the standard 8-day course of amoxicillin can be shortened to just 3 days with equal symptom relief and fewer side effects[28]. Similarly, treatment of ventilator-associated pneumonia can be effectively shortened from 14 to 8 days[29]. In some cases, shortened antibiotic courses have actually improved patient outcomes. A reduced course for urinary tract infections from 14 days to 7 days is not only effective, it also prevents post-treatment yeast infections[30].

As scientists and clinicians become more aware of the dangers of resistance, more studies are being conducted to determine the minimum amount of antibiotic required to adequately treat infections. The Infectious Diseases Society of America has also updated their Clinical Practice Guidelines to reflect findings that shorter treatment schedules are often just as effective, are easier to comply with, and reduce development and spread of resistant bacteria[31]. Performing
minimum effective antibiotic treatment trials is costly in the short term, but necessary to safely revise guidelines and save on long-term healthcare costs.

Public misunderstanding and misinformation regarding antibiotics also contribute to their overprescription. In many clinical settings where antibiotics are not necessary, patients may believe antibiotics are the most effective treatment and push their doctors to inappropriately prescribe them. For example, patients often seek antibiotics for viral respiratory illnesses (i.e. cold and flu), despite antibiotics being ineffective against viral infections[5]. It has been demonstrated that patient expectation of antibiotics or physician perception of this desire have a significant influence on antibiotic prescription[32–34].

Table 1: Antibiotic overuse is caused largely by shortcomings in diagnostic technologies and prescribing practices, but there are many possible ways to address these challenges.

Efforts to address this issue include educational initiatives for the public and antibiotic stewardship programs for healthcare providers. One such initiative was France’s national campaign to reduce antibiotic use, launched in 2001[35]. France, Europe’s largest antibiotics consumer, sought to address the problem through physician training and a public health campaign called “Antibiotics are not automatic”. This campaign spread public awareness that overusing antibiotics leads to resistance, and, during the winter flu season, that antibiotics kill bacteria – not the viruses responsible for most respiratory infections. Concurrently with this initiative, antibiotic use in France dropped by over 25% from 2000 to 2007, highlighting the ability of public health education to change clinical outcomes. In recent years, steps have been taken both in the US and internationally to encourage responsible antibiotic use via education, updated prescribing standards, and other courses of action. In 2016, the Joint Commission on Hospital Accreditation, an organization that accredits US healthcare organizations, mandated antibiotic stewardship programs in US hospitals that participate in Medicare and Medicaid. The Joint Commission issued standards cited from the CDC’s Core Elements of Hospital Antibiotic Stewardship Programs[36], including educating staff, healthcare practitioners, patients, and their families on responsible antibiotic use and resistance, appointing a pharmacist leaders to improve hospitals’ antibiotic use, tracking and reporting antibiotic prescribing and resistance patterns, and developing protocols for specific antibiotic use cases, such as pneumonia. The number of hospitals reporting an antibiotic stewardship program that meets all the CDC’s Core Elements doubled between 2014 and 2017[37], and will likely increase further, with stewardship programs now tied to accreditation. On an international scale, the UN and CDC have pushed for global implementation of One Health responses by releasing recommendations for engaging all members of society—governments, businesses, healthcare workers, etc.—in coordinated and strategic efforts to address antibiotic resistance[8]. Comprehensive promotion of responsible antibiotic use is vital to maintaining their usefulness for as long as possible, especially given the difficulty of developing new antibiotics.

Revitalizing the Antibiotic Pipeline

While it is important that existing antibiotics are prescribed cautiously and used responsibly, all antibiotics inevitably encounter resistance[38]. Consequently, continuously developing antibiotics with novel mechanisms of action—the method that an antibiotic uses to kill bacteria—that circumvent existing resistances will remain essential. However, developing these new drugs is costly; it can take well over a decade and cost more than $2 billion, with a 90% failure rate looming over the project[38]. Clinical trials, which require large, diverse populations to demonstrate evidence of drug superiority, account for 65% of the risk-adjusted cost for developing antibiotics[15]. The difficulty of antibiotic drug development is illustrated by the 2019 FDA approval of lefamulin, which marked the first approval of an IV/orally-administered antibiotic with a novel mechanism of action in two decades[39]. Scientific challenges inhibit discovery significantly. The immediately apparent antibiotic candidates have been developed, and discovering antibiotics with new mechanisms of action is challenging. It is now thought that any new, effective antibiotics will need multiple capabilities for killing bacteria, making their discovery more complex[3]. Emerging approaches in antibiotic discovery such as deep learning algorithms are promising technologies to solve these scientific challenges, but are far from bringing new antibiotics to patients[40].

In addition to scientific obstacles, the economics of antibiotic development have reduced innovation and output. The free market is failing to meet society’s antibiotic needs via multiple pathways[41]. Traditional sales-based models, in which revenue is directly proportional to the volume of sales, are antagonistic towards society’s goal of sustainable antibiotic use[2]. Evidence of the current system’s failure is the drastic decrease in antibiotic research programs[3] and the sparse output of new [2]. To address these challenges, policymakers are crucial actors; they can facilitate fertile economic conditions using a combination of 1) “push” policies to galvanize antibiotic discovery and development efforts and 2) “pull” policies to create profitable
economic conditions, incentivizing industry to work in this area. Simultaneously, these policies must be supplemented by sufficient regulations to ensure sustainable and equitable usage, broadly maximizing overall societal benefits.

Push Policies: Push policies drive companies to conduct antibiotic research and clinical trials[42] by providing monetary resources to antibiotic developers. Push policies are realized via grants and pipeline coordinators. Government grants allow both academia and industry to investigate antibiotic candidates and conduct clinical trials. Pipeline coordinators are agencies that ensure governmental funding is distributed efficiently across development stages. Coordinators are essential to ensuring equitable funding distribution across antibiotic candidates and identifying gaps and needs in the antibiotic pipeline from basic research through production. These vehicles have broad precedents and have demonstrated effectiveness at stimulating early stage scientific research. Current estimates show $550 million is spent annually on push spending, though some recommendations show that this number should be $800 million to fully meet the demand for antibiotic research[42]. However, push policies and spending do not completely address the major economic issues.

Figure 3:A combination of push and pull policies are necessary to generate conditions to revitalize the antibiotic pipeline. Currently, only push policies are implemented. Pull policies can de-link an antibiotic’s development from its economic success, which is projected to increase the development rate of antibiotics that society needs.

Pull Policies: The primary goal of push policies is to jump start research and development in antibiotic discovery, but issues remain with the current market structure for antibiotics. This is illustrated by the fact that companies are failing after bringing important antibiotics to market. For instance, the biopharmaceutical company Achaogen successfully developed the antibiotic plazomicin in 2018, but filed for bankruptcy the following year due to insufficient profits from plazomicin[43]. Why would a company that successfully brings a new antibiotic to market fail? Antibiotics are generally prescribed for short periods of time (usually under two weeks), modern health policies support reducing or delaying the use of new antibiotics, and the market lifetime of antibiotics is reduced due to the inevitable development of resistance[44].Overall, these realities minimize sales of the new antibiotic and thus the profits of the developing company. In response, policymakers have proposed pull policies to de-link the sales of the new antibiotic to the economic reward given to the developers, improving the economic viability of developing new antibiotics. These pull policies are supported by the Infectious Diseases Society of America[45]. By de-linking sales from economic reward, the revenue from a new antibiotic is not purely based on the sales volume of that antibiotic. For example, a market entry reward (MER) — a large monetary sum given to developers of novel antibiotics upon successful drug approval — can be used to partially or fully de-link the number of sales from the economic reward. Multiple groups, such as the Boston Consulting Group, have estimated that a $1 billion MER per antibiotic is sufficient, suggesting that this award amount would lead to twenty novel antibiotics for society over the next three decades[42, 46].

An important supplement to any MER policy is the antibiotic susceptibility bonus (ASB)[47]. The ASB rewards companies that develop antibiotics that are effective over long periods of time. As an antibiotic remains effective against target bacteria, companies receive monetary awards. This policy helps better align all stakeholders’ (companies, patients, hospitals, insurance networks) interests towards generating and maintaining effective antibiotics. Companies will no longer have an incentive to oversell antibiotics, as they will receive more money the longer their drug is effective. This supplemental policy could safeguard MERs against abuse, and incentivize the development of antibiotics that act in society’s best interest: to develop effective treatments for long periods of time.

Another potential pull policy is the long-term supply continuity model (LSCM)[42], which addresses how companies respond once market exclusivity for a drug ends due to patent expiration. Suppliers may respond to loss of market exclusivity by either manufacturing fewer units in the case of a modest market or by increasing sales through marketing and promotion. Both actions are detrimental to public health in the case of an antibiotic, either promoting antibiotic overuse or making it harder for people who need the antibiotic to get it. The LSCM addresses this by having a country or group of countries make an agreement with manufacturers to produce a predetermined amount of the respective antibiotic for a specified price. This model to generate a predictable supply of an antibiotic acts as a pull mechanism by making the market for novel, essential antibiotics more sustainable for manufacturers.

Pull policies also have some downsides. For one, pull policies only reward successful antibiotic discovery campaigns; the inherent risk in developing these drugs may still dissuade companies. Also, while push policies have been validated with real world results, pull policies have not been evaluated as extensively. To encourage companies to work in this area, push policies, as well as pull policies, are needed to lower the risk of failed discovery programs. To develop the new drugs that society needs, companies need funding to start research and development and economic incentives to take the drugs to market.

Conclusion Proliferation of antibiotic resistance in bacteria is a major public health problem that is only accelerating. This crisis is caused by overuse of existing antibiotic drugs and lagging development of new ones. To address the former, many US and international institutions are working to improve current diagnostic practices and adopt standards for responsible antibiotic use. Increasing funding for rapid diagnostics R&D, initiating educational programs, and mandating the adoption of comprehensive hospital antibiotic stewardship programs are possible ways to reduce antibiotic overuse. To encourage the development of novel antibiotic drugs, many organizations have also subsidized research and development in this area. Additional incentives are being pursued to improve the commercial viability of antibiotic development and protect drug developers from the risks of the antibiotic market. Antibiotic resistance is a major global health crisis, but with efforts to improve responsible use and end the almost 40-year drought of novel antibiotic drug discovery[48], we can take steps to prevent the next public health emergency. 4“The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no warrants shall issue, but upon probable cause supported by oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized.”

Acknowledgements

We thank Erika Madrian for her input in shaping the manuscript.

Citation

Yee, E. H., Cheng, S. S., Knappe, G. A. & Moomau, C. A. Antibiotic resistance: How to prevent the next public health emergency. MIT Science Policy Review 1, 10-17 (2020).

A computational approach to cancer

Toni-Ann Nelson transformed remote summer research into an opportunity to learn a new set of tools for analyzing tumors.

Raleigh McElvery
August 20, 2020

Toni-Ann Nelson has wanted to find a cure for cancer ever since she was nine years old and lost her grandfather to the disease. “I remember thinking there must be something that the doctors and scientists were missing,” she recalls. “It just couldn’t be that complicated.” Now one semester away from earning her degree in molecular biology, Nelson is realizing cancer is just that — complicated. After conducting cancer research during MIT’s Summer Research Program in Biology (MSRP-Bio), she understands much more about the intricacies of tumors and metastasis. But she’s also glimpsed just how many cellular puzzles remain to be solved.

Growing up in Jamaica, Nelson enjoyed all her science classes, but preferred biology because she knew it would provide the foundation to probe cancer. She graduated as the valedictorian of her high school class, and earned a scholarship to Alcorn State University in Mississippi, where she began in the spring of 2017.

Alcorn doesn’t have any cancer research facilities, so Nelson secured a position as an undergraduate researcher in Yan Meng’s plant tissue culture lab. For three years, Nelson aimed to improve viral disease resistance in sweet potatoes. Even though she wasn’t conducting clinical research, she mastered key molecular biology techniques like PCR, gel electrophoresis, and tissue culture.

“Fundamental research is important because many times finding a cure requires starting with the basics, and understanding what’s going on inside the cell,” she says.

When Nelson was accepted into MSRP-Bio as a Gould Fellow and assigned to work in Tyler Jacks’ lab, she was elated to get her first hands-on cancer research experience. But in April 2020 — two months before the program was slated to begin — MIT’s campus temporarily shut down due to the COVID-19 pandemic, and MSRP-Bio 2020 became a remote learning experience.

As a result, Nelson and her MSRP-Bio cohort conducted their research from home. She took on a computationally-intensive project that was conducive to remote work and required taking an online quantitative methods class. In a manner of weeks, she learned an entirely new set of skills, including programming languages like Python.

“I always thought that I wouldn’t need those types of computational tools as part of my cancer research,” she explains. “But working at MIT was enlightening, because it showed me that they are key to understanding disease. I can definitely see myself using them on my own projects in the future.”

Pink and purple histology image
Light micrograph of a lung adenocarcinoma. Credit: Vasilena Gocheva/Jacks Lab, Koch Institute

The Jacks lab studies the genetic events that contribute to cancer, and Nelson’s project centered on lung adenocarcinoma. The predominant form of non-small cell lung cancer, it begins in alveolar type II (AT2) cells. Past studies showed that, as the tumor progresses, AT2 cells change state and lose their original identity. Nelson wanted to determine which genes and proteins underlie this evolution. Her analyses showed that genetic markers characteristic of AT2 cells tend to decrease over time, while markers denoting faster-growing “high grade” tumors become more prevalent.

“The kinetics of these gene expression changes that are happening early on are still poorly understood,” she explains. “It just goes to show how complicated this pathology is, which I find even more fascinating.”

Once researchers can pinpoint the genes and proteins that drive changes in cancer cell state, they’ll be better equipped to design drugs that target and prevent metastatic processes.

Although Nelson couldn’t visit the lab in person, as on-campus research slowly began ramping up again, her graduate student mentor Amanda Cruz would show her around during their video conference calls. Cruz also helped Nelson explore the scientific literature, choose studies for the lab’s journal club, and perform computational analyses.

Given the unprecedented circumstances, Nelson says having a solid support system was key to her success. Nelson and her MSRP cohort also relied on one another for encouragement, and were each assigned a graduate student “pal” for guidance outside of lab.

“The program catered to our every need, and it’s structured to ensure that someone will always check up on you if you’re feeling alone,” Nelson says. “I never expected to get so much from this experience, especially because I’m not physically on campus. But what I learned this summer was so much more than I could ever have anticipated.”

Her time in the Jacks lab has solidified her fervor for cancer research, and she intends to apply to cancer biology PhD programs in order to continue this line of inquiry. “I’ve realized there’s still so much more to learn,” she says, “but we’re getting there.”

Top image courtesy of Toni-Ann Nelson
Posted: 8.19.20
Solving molecular mysteries

Diego Detrés spent the summer probing protein function and collaborating with MIT researchers remotely from his home in Puerto Rico.

Raleigh McElvery
August 17, 2020

When he was young, Diego Detrés wanted to become a magician in order to learn the tricks of the trade and transform enigma into fact. Now a fourth-year industrial microbiology major at University of Puerto Rico at Mayagüez, he’s on track to become a researcher while chasing a similar aim. To Detrés, the complex biological processes that continue to stump researchers are akin to acts of magic — although deciphering them is much more complicated than pulling a rabbit out of a hat. As a participant in MIT’s Summer Research Program in Biology (MSRP-Bio), he’s getting closer to parsing the mechanisms behind molecular mysteries.

After his magician phase but before developing an affinity for biology, Detrés was on track to become a professional boxer in Puerto Rico. In high school, he spent hours each night reading about nutrition to supplement his training. Before long, he found himself entranced by the intricacies of the metabolic processes that allow cells to convert food into energy.

At the University of Puerto Rico at Mayagüez, he wanted to continue exploring biology and focus on medicine. “My plan was to become a doctor, because I thought that’s what you do with a biology degree,” he says. “It also seemed like the best way to make an impact on people’s lives.”

But Detrés’ first semester was cut short when hurricane Maria tore through Puerto Rico in September 2017. His spring classes were canceled as the island reeled in the aftermath, so he joined a relief project headed by his university to bring help and legal aid to local communities. “It wasn’t scientific research, but it did show me that understanding a problem is critical to finding an effective solution,” he recalls. “It also allowed me to explore other ways in which I could impact other people.”

Group photo
Detrés (third from left) and his undergraduate research mentor, Carlos Ríos Velázquez (fourth from left)

Detrés’ first lab experience came the next summer at the University of Minnesota, where he studied the genetics of maize. That internship affirmed his interest in biology but shifted his gaze away from medicine and towards fundamental research.

“I really liked being at the bench,” he says. “I fell in love with working in lab and basic science. It’s fundamental knowledge that’s important for the building blocks of science; you might discover something today that will help a lot of people later on.”

When he returned home to the University of Puerto Rico at Mayagüez that August, Detrés was accepted into the Maximizing Access to Research Careers (MARC) Program, which is sponsored by the National Institute of General Medical Sciences and provides research-related opportunities and a special science curriculum. He joined the lab of Carlos Ríos Velázquez, investigating novel antibiotic resistance genes within the gut microbiome of the Caracolus marginella snail, and helping Ríos Velázquez teach biology workshops to high school students.

“He gave me a background in science when I didn’t have one, and I want to do the same for other people,” Detrés says. “I hope to teach eventually.”

In January 2020, Detrés was invited to come to MIT for the annual Quantitative Methods Workshop, a seven-day boot camp that introduces students to tools for analyzing experimental data. He enjoyed the “feel” of campus, and decided to apply to MSRP-Bio in hopes of returning in June.

Although the Covid-19 pandemic prevented the Institute from hosting in-person summer programs, Detrés has been gleaning the MIT experience from his apartment in Puerto Rico. His days are filled with Zoom meetings featuring faculty and graduate student talks, group hangouts, informal exercise sessions, musical jams, and cooking classes. He was also named a 2020 MSRP-Bio Gould Fellow. “Even remotely, I’ve gotten to know the MSRP cohort really well, and the faculty have been very interactive,” he says.

He’s been conducting research in Eliezer Calo’s lab for the past two months, running literature searches and bioinformatic analyses. Like Detrés, Calo grew up in Puerto Rico and attended MSRP-Bio. Now, Calo is a professor in MIT’s Department of Biology. His lab investigates RNA metabolism to inform developmental disorders and cancer research.

Detrés is focusing on a family of RNA helicases called DEAD-box ATPases, or “DDXs,” which are involved in every step of RNA metabolism. These proteins are conserved across many species, and contain a core amino acid sequence that helps catalyze reactions with other molecules in the cell.

However, the Calo lab suspects that the less-conserved sequences near the ends of the proteins may be more critical for specialized function. Detrés is investigating what it is about these terminal sequences that determines DDXs’ specific roles in RNA metabolism.

Student with Bunsen burner
Detrés in the Ríos Velázquez lab at the University of Puerto Rico at Mayagüez

This summer, he showed that DDX proteins are more likely to lack a stable structure near one end, known as the C-terminus, compared to other closely-related helicases. These findings will help the Calo lab better understand the relationship between DDX’s functional specificity and its intrinsically disordered regions like the C-terminus.

“Most of these proteins are essential for life, and yet we don’t really know how they’re involved in so many dynamic processes,” Detrés says. “It’s been interesting to analyze already-existing data in ways that allow us to investigate novel possibilities.”

Working from home has been challenging to say the least. Not having the in-person support from his labmates has been difficult. On the other hand, spending so much time with his family has been enjoyable.

“I had to make a routine for myself that allowed me to work effectively from home, as well as maintain my physical and mental well-being,” he says. “Program activities also gave us the chance to be physically active and to interact with other students”.

Detrés aims to return for a second summer of MSRP next year, hopefully in person.

“Since starting MSRP, I’ve noticed a lot of changes in myself,” he says. “The more I get into research, even remote research, the more I realize it’s what I want to do. Science is not about being really smart; it’s about being really curious.”

As Detrés continues to follow his curiosity, the inner workings of the cell are becoming more comprehensible — but no less mesmerizing.

Photos courtesy of Diego Detrés
Posted: 8.18.20
New gene regulation model provides insight into brain development

A well-known protein family binds to many more RNA sequences than previously thought to help neurons grow.

Raleigh McElvery
August 17, 2020

In every cell, RNA-binding proteins (RBPs) help tune gene expression and control biological processes by binding to RNA sequences. Researchers often assume that individual RBPs latch tightly to just one RNA sequence. For instance, an essential family of RBPs, the Rbfox family, was thought to bind one particular RNA sequence alone. However, it’s becoming increasingly clear that this idea greatly oversimplifies Rbfox’s vital role in development.

Members of the Rbfox family are among the best-studied RBPs and have been implicated in mammalian brain, heart, and muscle development since their discovery 25 years ago. They influence how RNA transcripts are “spliced” together to form a final RNA product, and have been associated with disorders like autism and epilepsy. But this family of RBPs is compelling for another reason as well: until recently, it was considered a classic example of predictable binding.

More often than not, it seemed, Rbfox proteins bound to a very specific sequence, or motif, of nucleotide bases, “GCAUG.” Occasionally, binding analyses hinted that Rbfox proteins might attach to other RNA sequences as well, but these findings were usually discarded. Now, a team of biologists from MIT has found that Rbfox proteins actually bind less tightly — but no less frequently — to a handful of other RNA nucleotide sequences besides GCAUG. These so-called “secondary motifs” could be key to normal brain development, and help neurons grow and assume specific roles.

“Previously, possible binding of Rbfox proteins to atypical sites had been largely ignored,” says Christopher Burge, professor of biology and the study’s senior author. “But we’ve helped demonstrate that these secondary motifs form their own separate class of binding sites with important physiological functions.”

Graduate student Bridget Begg is the first author of the study, published on August 17 in Nature Structural & Molecular Biology.

“Two-wave” regulation

After the discovery that GCAUG was the primary RNA binding site for mammalian Rbfox proteins, researchers characterized its binding in living cells using a technique called CLIP (crosslinking-immunoprecipitation). However, CLIP has several limitations. For example, it can indicate where a protein is bound, but not how much protein is bound there. It’s also hampered by some technical biases, including substantial false-negative and false-positive results.

To address these shortcomings, the Burge lab developed two complementary techniques to better quantify protein binding, this time in a test tube: RBNS (RNA Bind-n-Seq), and later, nsRBNS (RNA Bind-n-Seq with natural sequences), both of which incubate an RBP of interest with a synthetic RNA library. First author Begg performed nsRBNS with naturally-occurring mammalian RNA sequences, and identified a variety of intermediate-affinity secondary motifs that were bound in the absence of GCAUG. She then compared her own data with publicly-available CLIP results to examine the “aberrant” binding that had often been discarded, demonstrating that signals for these motifs existed across many CLIP datasets.

To probe the biological role of these motifs, Begg performed reporter assays to show that the motifs could regulate Rbfox’s RNA splicing behavior. Subsequently, computational analyses by Begg and co-author Marvin Jens using mouse neuronal data established a handful of secondary motifs that appeared to be involved in neuronal differentiation and cellular diversification.

Based on analyses of these key secondary motifs, Begg and colleagues devised a “two-wave” model. Early in development, they believe, Rbfox proteins bind predominantly to high-affinity RNA sequences like GCAUG, in order to tune gene expression. Later on, as the Rbfox concentration increases, those primary motifs become fully occupied and Rbfox additionally binds to the secondary motifs. This results in a second wave of Rbfox-regulated RNA splicing with a different set of genes.

Begg theorizes that the first wave of Rbfox proteins binds GCAUG sequences early in development, and she showed that they regulate genes involved in nerve growth, like cytoskeleton and membrane organization. The second wave appears to help neurons establish electrical and chemical signaling. In other cases, secondary motifs might help neurons specialize into different subtypes with different jobs.

John Conboy, a molecular biologist at Lawrence Berkeley National Lab and an expert in Rbfox binding, says the Burge lab’s two-wave model clearly shows how a single RBP can bind different RNA sequences — regulating splicing of distinct gene sets and influencing key processes during brain development. “This quantitative analysis of RNA-protein interactions, in a field that is often semi-quantitative at best, contributes fascinating new insights into the role of RNA splicing in cell type specification,” he says.

A binding spectrum

The researchers suspect that this two-wave model is not unique to Rbfox. “This is probably happening with many different RBPs that regulate development and other dynamic processes,” Burge says. “In the future, considering secondary motifs will help us to better understand developmental disorders and diseases, which can occur when RBPs are over- or under-expressed.”

Begg adds that secondary motifs should be incorporated into computer models that predict gene expression, in order to probe cellular behavior. “I think it’s very exciting that these more finely-tuned developmental processes, like neuronal differentiation, could be regulated by secondary motifs,” she says.

Both Begg and Burge agree it’s time to consider the entire spectrum of Rbfox binding, which are highly influenced by factors like protein concentration, binding strength, and timing. According to Begg, “Rbfox regulation is actually more complex than we sometimes give it credit for.”

Citation:
“Concentration-dependent splicing is enabled by Rbfox motifs of intermediate affinity”
Nature Structural & Molecular Biology, online August 17, 2020, DOI: 10.1038/s41594-020-0475-8
Bridget E. Begg, Marvin Jens, Peter Y. Wang, Christine M. Minor, and Christopher B. Burge

Top illustration: Some RNA-binding proteins like Rbfox (gold ellipses) help tune gene expression and control biological processes by latching onto more RNA sequences (black and gold lines) as their concentration increases (teal shading). Credit: Bridget Begg
Posted: 8.17.20