Category: News Briefs

Cells use a little-known molecule to protect themselves from iron overload

Research from the Jain and Henry Labs in the Whitehead Institute and Koch Institute respectively have discovered that cells are protected from destructive levels of iron buildup by small molecules called polyamines, which act like storage lockers, safely holding the metal in a non-reactive state until cells need it.

Shafaq Zia | Whitehead Institute
August 14, 2026

Iron is essential. Our cells need it to produce energy, carry oxygen throughout the body, and power countless chemical reactions that sustain life. But this metal has a dark side. When too much of it is left free inside cells, it can trigger destructive reactions that break down DNA, proteins, and even cell membranes.

Now, Whitehead Institute Member Ankur Jain and Whitney Henry, an investigator in MIT’s Department of Biology and the Koch Institute for Integrative Cancer Research, together with graduate student Pushkal Sharma have discovered that cells rely on an unexpected protector against this threat: small molecules called polyamines.

The researchers’ detailed findings, published Aug. 14 in the journal Cell, reveal that polyamines act like storage lockers for iron, safely holding the metal in a non-reactive state until cells need it.

These findings solve a decades-old mystery about why cells maintain such extraordinarily high levels of polyamines and uncover a previously unknown defense mechanism that protects cells from toxic iron overload.

This work could also help scientists develop better cancer treatments, by allowing iron overload to trigger cancer cell death. It could also offer new clues about diseases like early-onset Parkinson’s disease, in which mutations affect polyamine levels within neurons.

The Jain Lab studies RNA, the intermediary between DNA and the tiny molecular machines called proteins that perform most of the essential tasks inside cells. The lab is particularly interested in how RNA folds, misfolds, and sometimes clumps inside cells.

Jain and Sharma first began studying polyamines because these molecules bind to RNA and help shape its structure. However, they suspected that polyamines must be playing other roles inside cells: they’re among the most abundant small molecules within cells, present at levels comparable to ATP, the molecule cells use as their energy currency.

“We’ve known that without polyamines, cells stop growing and dividing,” says Jain, who is also an associate professor of biology at the Massachusetts Institute of Technology (MIT). “But their best-known function only requires a small fraction of the polyamine levels cells actually have.”

To uncover polyamines’ hidden function inside cells, the researchers used a large-scale genetic approach that allows them to screen the entire genome at once, rather than testing genes one-by-one, in order to find out which cellular processes are impacted when polyamine levels are changed within cells.

The screen revealed that when cells have reduced levels of polyamines, a protein called GPX4 becomes essential for survival. GPX4 is known to prevent harmful chemical reactions that damage the fatty molecules that make up cell membranes.

The team also found that cells with lower polyamine levels have higher amounts of another protein that acts as an iron sponge and keeps the metal in a mineralized form. Together, these findings led the researchers to hypothesize that polyamines might be helping keep iron in a safe, non-reactive state within cells.

To test this idea, they developed a new fluorescent sensor that would allow them to measure chemically reactive iron inside living cells. The new sensor causes living cells to glow based on the amount of chemically reactive iron they contain, allowing researchers to track any changes under a microscope in real time.

The team paired the new iron sensor with another sensor they had previously developed that measures polyamine levels within cells. By employing them simultaneously, they observed a striking pattern: as polyamine levels dropped within cells, the amount of chemically reactive iron went up, offering new evidence that polyamines play a key role in preventing toxic iron build up inside cells.

Beyond answering a fundamental biological question, these findings could have implications for cancer treatment. Cancer cells often rely on high polyamine levels to support their rapid growth and division. However, cancer drugs designed to lower polyamine levels to stop cell division have had limited success.

“We saw that when polyamine levels fall, cells rely on GPX4 to protect themselves from iron toxicity,” says Sharma, who is also the first author of the study. “This could mean that combining drugs that lower polyamine levels with those that block GPX4 might be more effective for killing cancer cells than targeting either pathway alone.”

The discovery may also have implications beyond cancer. Mutations in genes that help move polyamines around cells are linked to a rare form of early-onset Parkinson’s disease, and scientists have long observed unusually high levels of iron in the brains of Parkinson’s patients.

While it is still unclear whether excess iron directly contributes to neuron death in Parkinson’s, the discovery that polyamines help buffer reactive iron inside cells offers a possible explanation for this link and opens new directions for future investigation.

In addition, the researchers expect the new iron sensor to be a valuable tool for other scientists. By allowing them to track chemically reactive iron inside living cells, it could power new discoveries in aging, cancer, and neurodegeneration.

“There are a lot of promising future directions for this work,” Jain says. “It’s exciting to think about how these tools and findings could help answer further questions about disease pathways and potentially help design better therapies.”

Sharma, P., Keys, H. R., Mansell, R. P., Stark, J., Girard, L., Ausler, C., Anderson, R., Müller, S., Imada, S., Pires, I. S., Kunchok, T., Waite, M., Yuan, B., Deik, A., Ferro, L., Hammond, P. T., Rodriguez, R., Pandelia, M., Henry, W. S., & Jain, A. (2026). Polyamines buffer labile iron to suppress ferroptosis. Cell. https://doi.org/10.1016/j.cell.2026.07.040

Research reported in this press release was supported by the National Institutes of Health under grant number R35GM151111 awarded to A.J., which funded 25% of the project’s costs. Additional support was provided by the Bumpus Foundation and the Pew Charitable Trusts. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.

How the Toxoplasma parasite adapts to crowded conditions in host cells

A new study by Whitehead Institute researchers identifies how the widespread parasite Toxoplasma gondii survives in crowded environments in infected cells, which helps it persist in long-lasting brain cysts.

Mackenzie White | Whitehead Institute
August 19, 2026

Toxoplasma gondii, or Toxoplasma, is a parasite that infects hundreds of millions of people around the world. Although cases are often mild, it can cause severe symptoms in in people with weakened immune systems, and in developing fetuses. It can also persist for years by forming long-lived cysts in tissues, allowing infection to become chronic.

During chronic infection, hundreds of Toxoplasma parasites can pack into a tissue cyst inside a brain or muscle cell. That crowded life carries a cost: Nutrients become harder to obtain, waste accumulates, and energy-producing reactions can become damaging.

How Toxoplasma reshapes its metabolism to keep growing under such strained conditions has been unclear. But a new study from the lab of MIT Associate Professor Sebastian Lourido, a member of the Whitehead Institute for Biomedical Research, identifies a parasite-specific protein that helps coordinate this response. The protein, named TgPRO, allows Toxoplasma to manage oxidative stress — the buildup of reactive oxygen molecules that can damage cells — by controlling genes involved in energy production and iron use.

The open-access findings, published on Aug. 11 in the journal Cell, reveal the first dedicated regulator of metabolic gene expression identified in apicomplexans, the group of parasites that includes Toxoplasma and the organisms that cause malaria. The study, led by co-first authors and Lourido lab affiliates Christopher Giuliano PhD ’26, a recent graduate student in biology, and Chinmay Kalluraya, a current graduate student in biology, reveals a previously unknown way that parasites regulate metabolism. The findings also point to a possible therapeutic strategy: Inhibiting pathways controlled by TgPRO could make Toxoplasma more vulnerable to antiparasitic drugs that induce oxidative stress, though this approach remains to be tested.

One gene at a time

To discover the genes that support Toxoplasma’s ability to live in crowded cells, the researchers used a genome-wide CRISPR screen to compare Toxoplasma growing at low and high densities. The screen tests the effects of turning off genes one by one at both population densities in order to determine which genes are essential specifically in crowded conditions. It highlighted pathways that make or recycle NAD and NADP, molecules important for energy production and defending against oxidative damage. It also pointed to TgPRO, a previously unstudied protein that was especially important when parasites became crowded.

“A genome-wide screen was a powerful way to ask how crowding affects parasite fitness,” Kalluraya says. “TgPRO emerged as very important at high density. Because almost nothing was known about it, we wanted to understand what it was doing.”

Parasites lacking functional TgPRO accumulated more reactive oxygen molecules and struggled to compete at high density. Experiments showed that the loss of TgPRO disrupted the mitochondrion — the structure that supplies much of a cell’s energy — and changed how parasites processed glucose and other nutrients. Providing additional iron or restoring an important chemical balance inside the mitochondrion improved parasite growth, connecting TgPRO’s effects to iron-dependent energy metabolism.

The team then traced the response to a molecular mechanism. TgPRO is an RNA-binding protein, meaning it attaches to the molecular messages (RNAs) that cells use to make proteins. The researchers found that it binds and stabilizes a select set of messages involved in nutrient use, mitochondrial activity, and the assembly of iron-sulfur clusters, small structures that many enzymes need to function. The experiments connected the original observation — that some parasites faltered only when crowded — to a precise interaction between a regulatory protein and its RNA targets.

“One of the really nice elements of the story is our ability to connect it all the way through — from the original observation and genome-wide screen to the metabolic consequences and the direct interaction between TgPRO and its target RNAs,” Lourido says.

The researchers found that lowering oxygen levels also reduced oxidative stress and partially restored the growth of parasites without TgPRO. Toxoplasma is commonly grown in laboratories at atmospheric oxygen levels, which are considerably higher than those found in most animal tissues. The result suggests that oxygen conditions can strongly shape parasite metabolism, and the researchers caution others studying Toxoplasma to take this into consideration.

Connecting TgPRO to chronic infection

After testing the role of TgPRO in artificially crowded settings, the team also tested whether TgPRO matters during chronic infection, when Toxoplasma forms cysts in the brain. Mice infected with parasites lacking functional TgPRO developed smaller brain cysts, suggesting TgPRO supports parasite growth in the naturally dense environment of a chronic-stage cyst.

“The chronic stage is still somewhat elusive,” Giuliano says. “Showing that TgPRO affects cyst growth suggests that these same metabolic changes are needed in the brain and gives us clues about how the parasites persist there for months or years.”

TgPRO bears little resemblance to the proteins that regulate similar metabolic programs in mammals, yeast, and bacteria, yet it controls many of the same kinds of genes that these organisms adjust when cells face oxidative stress or changing nutrient conditions. This is an example of convergent evolution: Distantly related organisms evolved different molecular machinery to solve a similar biological problem.

That convergence suggests that coordinating these metabolic pathways may be a fundamental requirement for cells adapting to stress.

Altogether, the study establishes a new paradigm for how apicomplexan parasites regulate their metabolism, and advances the foundation for investigating how Toxoplasma persists inside its hosts.

This work was supported by National Institutes of Health grants and by a Burroughs Wellcome Fund grant awarded to S.L. M.A.S is funded by an Early Career Award from the Wellcome Trust. C.R.H. is funded by a Sir Henry Dale Fellowship from the Wellcome Trust and the Royal Society. J.K. is supported through funding by a generous donor advised by CARIGEST SA and acquired by D.S.-F.

DNA shaper steers nervous system development

A team in the Horvitz Lab have discovered that cohesin, a protein complex that helps shape the structure of the genome, is also critical for establishing the identity of some neurons. This could help scientists find a way to treat rare developmental disorders caused by mutations to the cohesin complex.

Jennifer Michalowski | McGovern Institute
August 3, 2026

A functional nervous system depends on the cooperation of many kinds of cells. So as developing organisms build their nervous systems, their neurons must take on different forms and functions to fulfill their designated roles. That carefully orchestrated process gives rise to thousands of different cell types in the human brain.

In the tiny worm known as C. elegans, the nervous system is far simpler, comprising a mere 118 classes of neurons.

At MIT, scientists in H. Robert Horvitz’s lab are studying the worms to learn about how nervous systems develop. Horvitz is the David H. Koch Professor of Biology at MIT, an Investigator at the McGovern Institute for Brain Research at MIT, and an Investigator at the Howard Hughes Medical Institute. His team has just discovered that a protein complex called cohesin, which helps shape the three-dimensional structure of the genome in both worms and humans, is critical for establishing some neurons’ identities as development unfolds.

The findings, reported July 31, 2026, in the journal Science Advances, could help scientists find a way to treat a rare developmental disorder called Cornelia de Lange syndrome, which is caused by mutations that interrupt the cohesin complex.

Model organism

Postdoctoral researcher Dongyeop Lee explains that C. elegans is a powerful model for studying neurodevelopment not just because its nervous system has been comprehensively mapped, but also because of the ease and speed with which scientists can study the function of its genes.

Because many of the worm’s genes have been retained through evolution, findings from studies of C. elegans often reveal important aspects of human biology. The current study began with worms that, because of a genetic mutation, make too many neurons of a certain type.

Adrenergic neurons, named for the kind of neurotransmitter they use to communicate with other neurons, are vital for enabling worms to respond to both their environment and their own internal state. Normally, C. elegans has just two pairs of adrenergic neurons: two RIM neurons and two RIC neurons. But the worms Lee studied had extras of both.

Takashi Hirose, a former member of the Horvitz lab, first observed this change in 2007.

Lee later continued the study and discovered that worms carrying a mutation in a gene called coh-1 have extra adrenergic neurons. The coh-1 gene encodes one part of the cohesin complex.

When Lee tested other mutations that disrupt cohesin, he found the same effect: Worms without fully functional cohesin had too many RIM neurons and too many RIC neurons.

Molecular switch

With a series of experiments designed to tease apart how cohesin impacts neurons’ identities, Lee discovered that cohesin cooperates with a gene-regulating protein called EOR-1 (known in humans as PLZF) to direct some neurons to develop into neurons that communicate with the inhibitory neurotransmitter GABA.

By reorganizing the structure of the genome, cohesin can change the way gene regulators like EOR-1 interact with DNA. Lee’s experiments showed that when either cohesin or EOR-1 couldn’t do its job, cells that should have become GABA-producing neurons become adrenergic neurons instead.

“What we found is that there are two alternative possible fates of certain neurons, and cohesin acts as a molecular switch that decides one of the possible neuronal fates,” Lee explains. “This means the structure of genomic DNA in the nucleus is important for neuronal fate determination.”

Disease connection

Lee adds that extra adrenergic neurons were not the only abnormality he observed in worms with cohesin mutations. Cohesin is important for shaping cells and tissues throughout the body. “The mutants have severe developmental defects,” Lee says. “They grow slowly. They don’t move well, and they also have defects in reproduction.”

Notably, the problems Lee saw in the worms echo aspects of Cornelia de Lange syndrome, a rare genetic disorder that impacts physical, cognitive, and behavioral development. Cornelia de Lange syndrome can be caused by mutations in cohesin genes, and Lee says that the discovery of how cohesin mutations affect worm development and behavior opens new opportunities to study the disease and search for potential therapeutic targets in C. elegans.

The Horvitz lab already has some promising leads. Taking advantage of the quick genetic screens that are possible in worms, Lee has found additional mutations that can counteract impaired cohesin, improving the health of worms with cohesin mutations. The team is now working to identify the genes where these suppressor mutations occur, so they can investigate whether they might make good therapeutic targets in humans.

Meanwhile, the team is also exploring a potential role for cohesin in shaping the fates of other neuron types, as well as searching broadly for additional molecules that work with cohesin to guide development. “We expect we have opened up a new biology,” Lee says. “This paper is just the beginning.”

Paper.

Why are some bacterial genes high in purines?

In certain species of bacteria, the answer lies in shielding RNA transcripts from a quality-control factor called Rho. Understanding the requirements for expressible sequences is critical for expression engineering of therapeutic agents.

Lillian Eden | Department of Biology
July 2, 2026

In the study of bacteria, a longstanding dogma held that two molecular machines — RNA polymerase, which leads the way in transcribing DNA into RNA, and ribosomes, which bring up the rear translating RNA into proteins — worked so closely in tandem that they were effectively attached.

This close coupling of transcription and translation in bacteria was thought to be fundamental to gene expression in part because the trailing ribosome could shield nascent gene products from an effective and omnipresent quality-control protein called Rho.

In bacteria that exhibit something called runaway transcription, however, the polymerase instead speeds ahead, unhitched from its protective ribosome. Inexplicably, however, in bacteria that exhibit this runaway transcription, such as Bacillus subtilis, Rho targeted primarily noncoding, useless RNA products.

New research from the Department of Biology reveals that the secret to Rho’s quality-control specificity lies in the sequence composition of nucleotide bases that make up coding strands of DNA.

“We started with a hypothesis that Rho was regulated by sequence, but the fact that the sequence alone was enough to protect any gene in the entire B. subtilis genome from Rho was really surprising,” says Julia Dierksheide PhD ’26, a graduate student in the Li Lab and first author of a paper recently published in Nature Microbiology. “That’s a really diverse range of sequences — what sequence feature is shared by every single gene in the genome?”

Barricading with bias

Rho serves as a termination factor, meaning that it is a crucial mechanism for preventing bacteria from wasting precious resources by making RNA transcripts that serve no purpose.

All the information a bacterial cell needs is encoded in its DNA, which is made up of two strands of nucleic acids. These strands twist together to form a double helix, with genetic information codified in pairs of bases: purines guanine and adenine are matched with pyrimidines cytosine and thymine, respectively. Any sequence that gives rise to RNA transcripts is stored in complement to a parallel, noncoding strand, meaning that a large portion of genetic material is transcriptionally useless.

Coding DNA strands in certain bacteria were known to be significantly higher in purines guanine and adenine compared to the rest of the bacterial genome. The researchers found that this purine bias alone shields productive mRNA transcripts from Rho-mediated termination.

“I love having a big, complicated dataset and trying to reduce that to biological meaning,” Dierksheide says. “It seems like Rho itself has been broadly shaping the evolution of the B. subtilis genome to create these sequence composition biases.”

Bacterial species that, over generations, have lost Rho no longer exhibit this strong purine bias.

Rho also serves as a regulatory factor in bacteria becoming motile, forming biofilms, or sporulating, all of which are critical for biology and survival. The purine bias could also provide a layer of protection against the insertion of foreign DNA, for example, when a viral bacteriophage infects bacteria.

“Bacteria exist as single cells, so everything that they do, they have to do through gene expression,” Dierksheide says. “Understanding the fundamental details about how gene expression works, how a cell encodes all the information it needs to survive in the nucleotide sequence of the genome, is really exciting.”

Future directions

Although the exact mechanism underlying Rho’s specificity remains unclear, these results crack an underlying code in the composition of bacterial genomes.

Dierksheide said she hoped to perform a similar screen to characterize Rho’s specificity in Escherichia coli, which diverged from B. subtilis on the evolutionary tree an estimated 2 billion years ago and still exhibits coupled transcription-translation, where the transcribing RNA polymerase is closely followed by a translating ribosome.

The high sequence specificity of B. subtilis Rho is crucial for the protection of its runaway RNA polymerase, in which that molecular machine speeds ahead of the ribosome. A systematic comparison to E. coli Rho could help reveal how this heightened stringency arose.

This information will be critical for engineering diverse bacterial species for applications including the production of therapeutic agents. Other bacterial species, such as B. subtilis, may be better models for this process because they have abundant secretion pathways, according to Dierksheide, making it much easier to produce and isolate proteins in large quantities.

“Our findings reveal an important criterion for successful sequence design that must be considered in expression engineering,” says associate department head, associate professor of biology, and Howard Hughes Medical Institute investigator Gene-Wei Li, the lead author of the study. “There are so many cryptic messages in the genome, like the purine bias, and we are just beginning to be able to decipher what they mean.”

Two MIT faculty members named 2026 Pew Biomedical Scholars

Cell biologist Whitney Henry and immunologist Harikesh Wong will receive four years of flexible funding to advance early-career research on ferroptosis and immune decision-making.

Nina Tamburello | Nikolay Kolev | Koch Institute | Ragon Institute
June 29, 2026

Whitney Henry and Harikesh Wong have been named 2026 Pew Scholars in the Biomedical Sciences. The Pew Charitable Trusts announced the 21-member class of early-career researchers, which includes the two MIT scientists as well as two alumni, on June 16. Each scholar will receive four years of funding to pursue cutting-edge research into human health and disease. Xin Gu PhD ’22 of Dana-Farber Cancer Institute and Christina Tringides ’15 of Rice University were also selected as scholars.

Henry, the Robert A. Swanson (1969) Career Development Professor of Life Sciences and a faculty member at the Koch Institute for Integrative Cancer Research, will use the Pew scholarship to examine how a stress-induced cell death program called ferroptosis contributes to injury and regeneration in the liver. Wong, assistant professor of biology at MIT and core member at the Ragon Institute of Mass General Brigham, MIT, and Harvard, will use his award to investigate how groups of immune cells reach a “communal decision” about whether to tolerate or attack a particular target.

Whitney Henry

Henry’s research centers on ferroptosis — an iron-dependent form of regulated cell death — and its role in shaping cell fate and tissue remodeling. Her lab investigates why some cells can withstand stress while others cross the threshold for ferroptosis, focusing on the molecular, metabolic, and tissue-level cues that shape ferroptosis vulnerability. The work draws on chemical biology, metabolomics, functional genomics, and in vivo models. By defining the mechanisms that govern ferroptosis susceptibility, Henry’s group aims not only to identify novel therapies that target the most dangerous subpopulations of cancer cells, those that are highly metastatic and resistant to conventional treatment, but also to advance understanding of diseases in which ferroptosis drives tissue injury, fibrosis, or impaired repair.

Harikesh Wong

Wong investigates how groups of cells organize into networks that collectively process information and control immune responses within tissues. These networks must continually balance the body’s need to protect itself against pathogens and tumors with the need to preserve healthy tissue function. Combining the tools of immunology with high-resolution fluorescence microscopy, computational modeling, and gene manipulation, his lab seeks to map, model, and manipulate the cell-cell interactions that govern these decisions within intact tissues, revealing how subtle changes in multicellular organization and communication can shift immune responses toward pathogen clearance and tolerance, or toward autoimmunity, chronic inflammation, and cancer.

Pew scholars are chosen from applicants nominated by leading academic institutions across the United States. This year’s class of 21 was selected from 211 nominees. The incoming scholars join a legacy of more than 1,000 scientists supported by the program since 1985. During their time as scholars, they will meet annually with fellow Pew-funded scientists to build connections across a wide variety of disciplines.

“Scientific discovery is moving at a rapid pace, and now more than ever we need curious and creative researchers leading the charge,” says Lee Niswander, a 1995 Pew scholar and chair of the program’s national advisory committee. “These new biomedical scholars are prepared to meet that challenge, and I look forward to watching their research unfold.”

Raised in the “Kitchen”

Karen O’Leary, lab associate and acting supervisor in the Glassware Sterilization Facility, has become a cornerstone of the department’s operations.

Samantha Edelen | Department of Biology
June 25, 2026

Early mornings in the halls of Building 68 feature the sounds of rolling wheels on big metal carts, the rattling of glassware, the whooshing of faucets, and the clanking of autoclaves.

These aren’t the sounds of researchers at work, but rather those of keeping the labs sterilized and stocked with the sundries of research: pipette tips, test tubes, flasks, petri dishes, and more.

Orchestrating this sunrise cacophony and the staff that undertakes it is Karen O’Leary, lab associate and acting supervisor in the Glassware Sterilization Facility, also known as the “kitchen.”

Thanks, in part, to O’Leary’s proactivity and hard work, the kitchen staff were recently recognized with an MIT Excellence Award in 2025 for exceptional contributions in service of the community.

“My goal is to get the scientists everything they need to do their research,” O’Leary says. “I’m good at what I do.”

O’Leary admits she did not always possess such confidence. In almost 40 years at MIT, O’Leary has grown into this critical role for the department, and the department itself has evolved, moving into a brand-new building and away from previously standard practices like submerging equipment in acid for sterilization.

From rookie to running the show

On Sept. 7, 1987, Karen O’Leary joined the MIT community as a staff member for the first time. The 18-year-old was fresh from vocational high school, where she studied cosmetology but felt too shy to pursue that as a career. She was also nervous about joining a research institution.

“When I started, I didn’t even know what a beaker was,” she recalls.

Too embarrassed to admit in her interview that she couldn’t remember her brand-new home phone number, “I just made one up.” Fortunately, this didn’t prevent her from getting the job, where she worked under the mentorship of Thelma Watkins, who would retire in 1996 after 21 years at MIT. Watkins was critical for instilling a good work ethic and boosting O’Leary’s confidence.

“She taught me to show up every day, and work hard, and laugh,” O’Leary says.

Even now, O’Leary continues to bring joy to that daily diligence, for herself and for her staff.

“Karen is always on top of things,” says longtime friend and fellow Lab Associate AnnMarie Budhai. “She doesn’t refuse work and always goes above and beyond.”

Facilities and Operations Manager Cesar Duarte says that O’Leary’s long tenure, support, and knowledge have been invaluable as he transitioned into his role in Building 68 starting in 2023.

“Karen is one of those people who makes everything around her run more smoothly and more pleasantly,” Duarte says.

Better, faster, safer

Although some might consider it drudgery, O’Leary says that washing glassware is her favorite task.

“I like that when I wash, I can see the job is complete at the end of the day,” she says.

Although washing glassware is a perennial task, safety and efficiency have come a long way in the past 38 years. More-effective autoclaves and dishwashers have eliminated steps like steaming to dissolve agar solvents before autoclaving, and scrubbing individual test tubes before washing.

O’Leary was working for the department in 2011 when Building 68 piloted a new approach to MIT’s management of regulated medical waste (RMW), such as petri dishes, blood, and needles — the new system, which is cheaper and produces less waste, is now used by all departments at MIT that produce RMW.

“EHS [the Environment, Health and Safety Office] has come really far — I’m glad we got away from acid,” O’Leary notes of the bygone era of submerging glass pipettes for sterilization. “Back then, no one knew of a better way.”

Other tasks include cleaning velvets, which are used for replicating bacterial colonies on petri dishes, and pouring agar plates.

“Everyone knows how to do almost every job, so we can take turns doing different tasks,” O’Leary says. “If you get sick, there’s always someone to cover.”

All in the family

For O’Leary, kinship with MIT has spanned generations. O’Leary was raised in Weymouth, Massachusetts, by a father who worked at MIT as a supervisor in the sheet metal shop. Having raised children of her own, now grown, O’Leary came to greatly appreciate the flexibility her job has granted her.

“I’ve had great work-family balance here,” she says. Even though she’s often at work more than an hour before the researchers that the kitchen serves, “The hours are great, and with MIT Health right across the street, it was easy to take everyone to doctors’ appointments.”

She’s also gained a chosen family at MIT, spending breaks at work taking long walks along the Charles River, “talking about anything and everything” with colleagues like Budhai and Lab Aide Janet Katin.

“We really grew up together,” she says.

Working at MIT has provided O’Leary with support and community, and she’d like to pay it forward. In addition to strolling with colleagues, she hits the gym to help maintain the energy required for her highly active work.

“I don’t like sitting around,” she says.

In addition to maintaining her stamina at work, she hopes that taking care of herself will keep her actively involved if she ever has grandchildren, and enable her to help neighborhood kids when she someday retires.

“I owe a lot to MIT,” she says. “I have been allowed to work hard and get satisfaction and have been appreciated and given space to care for my family.”

O’Leary returns this care to the Department of Biology in spades.

“It’s an understatement to say that Biology is lucky to have her,” says Duarte. “Karen’s overflowing energy, attention to detail, and care for the Biology research community are nothing short of amazing.”

Advancing stem cell research and building the next generation of biologists

Biology PhD student Giselle Valdes (Reddien Lab) studies stem cell regeneration while encouraging aspiring students and researchers.

Stefanie Koperniak | Division of Graduate and Undergraduate Education
June 11, 2026

As an undergraduate at Florida International University, Giselle Valdes tackled rigorous studies in the school’s Honors College while simultaneously caring for family members with medical needs.

“I think that the choice to pursue any field in the space of biology and medical research was entirely shaped by having to be there for my family,” says Valdes.

As a McNair Scholar and biomedical engineering major who also did extensive research in biochemistry, she leaned more toward undergraduate courses in mechanical and electrical engineering that were geared primarily toward equipping students to build medical devices. She began to shift her research interests more firmly into biology, however, the summer before her senior year in 2018. She spent 10 weeks on the MIT campus as a participant in the Bernard S. and Sophie G. Gould MIT Summer Research Program in Biology (BSG-MSRP-Bio), working in the lab of Associate Professor Eliezer Calo PhD ’11, also a former BSG-MSRP-Bio participant. The Calo Lab focuses on ribosomes, small cellular particles that translate RNA into proteins, and looks at how mutations in ribosome development can lead to disorders.

After working in Calo’s lab, she could see herself as a biology graduate student at MIT. In January 2019, she attended the MIT biology department’s Quantitative Methods Workshop, a weeklong, intensive workshop designed to introduce non-MIT undergraduates to tools and programming languages used to analyze experimental data in biology and neuroscience. While there, she was elated to receive an email from the department inviting her to interview for the PhD program. She was accepted and began her doctoral studies in the fall of that year.

“When I think about my experiences at MIT, both as an undergraduate in MIT programs and as a PhD candidate in biology, I think about all the great mentors who have helped me along the way,” says Valdes. “I’ve also really valued the richly collaborative community, and being able to take a lot of risks in how I address the questions I have the opportunity to pursue.”

Researching stem cell regeneration

Since she came from a biomedical engineering background, Valdes spent the first year of the biology doctoral program taking foundational biology courses and working in different labs to decide which type of research she wanted to do. She gravitated toward cell and developmental biology and joined the lab of Professor Peter Reddien, associate director of the Whitehead Institute for Biomedical Research. Valdes was awarded an MIT Fund for the Future of Science Fellowship to support her research.

“Giselle is doing terrific work on a fundamental problem related to adult stem cells and regeneration — how do progenitor cells choose what cell types to make? Fate choice in progenitors is typically studied in embryogenesis, and how it occurs in the context of adult regeneration is poorly understood and very important to address,” says Reddien.

Valdes has worked extensively with stem cells in highly regenerative flatworms, called planaria. analyzing the process of “cell fate choice,” or how cells determine which specific cell types and functions to develop. To date, Valdes, Reddien, and other researchers have studied “neighborhoods” of neoblasts (adult stem cells) and their fate choices, finding that different neighboring stem cells often chose different fate options — suggesting that cell fate choices are largely made by processes autonomous to individual cells.

Her current research aims to better understand the driving mechanism for cell fate choice, both within planaria and an additional model system: the evolutionarily distant acoel Hofstenia miamia.

“A lot of the things I’m doing in my current project have involved developing techniques that didn’t previously exist in our model organism,” says Valdes.

Working on model systems with limitations in the toolkit traditionally available to more well-established systems, such as transgenics, has allowed her to be creative in the techniques she applies to determine how stem cells choose what to become. It has also opened doors to collaborations, such as one with Ye Zhang of the Manalis Lab in the biological engineering department (now an assistant professor of biomedical engineering at Virginia Tech), that have allowed Valdes and team to sort neoblasts in novel ways based on their morphology, and better relate that to their dynamic state.

In summer 2024, Valdes mentored a BSG-MSRP-Bio student who now works with her on a current research project.

“She’s been with me as a technical assistant in the lab now for over a year, and we’ve been able to work on one of my projects together,” says Valdes. “It’s been exciting to come full circle in this way.”

Teaching and mentoring, near and far

In addition to her research, Valdes devotes a lot of her time to teaching and mentoring, both for MIT biology students and younger students discovering an interest in STEM.

“It’s been so rewarding to have a lot of opportunities to do for others what has been done for me,” she says.

Valdes has worked with secondary students both locally and abroad. She participates in the biology department’s developmental biology lab for high-school students and teaches in an annual biology lecture series for high schoolers. She has worked with the Enroot program from Cambridge Community Services, acting as a direct mentor to local high-school and community college students. At the Whitehead Institute’s Expedition: Bio program, for middle- and high-school students, she runs a planarian workshop. And she gives lab tours through the Whitehead Discovery Lab initiative, engaging in discussion with local high-school students.

Valdes has also assisted with a hackathon for Sprouting, a social impact venture providing STEM education opportunities to under-resourced communities in Puerto Rico. Sprouting was launched by Taylor Baum, a doctoral student in MIT’s Department of Electrical Engineering and Computer Science. Valdes taught coding essentials to Spanish-speaking middle- and high-school students in Puerto Rico.

“That was really emotional,” says Valdes. “The parents were so grateful, and there were kids who were clearly brilliant and gifted. They were able to really take off with the tools that we gave them.”

In her department, Valdes has been a teaching assistant for classes 7.003 (Applied Molecular Biology Laboratory) and 7.03 (Genetics). She is also a teaching assistant for the Quantitative Methods Workshop and teaches a Python module to students in the program.

“Giselle may be quite small in physical stature, yet she dominates the room when she speaks, and commands the full attention of an audience of 80 students when giving a lecture,” says Mandana Sassanfar, a biology senior lecturer and director of outreach who runs the Quantitative Methods Workshop. “She is highly respected both for her knowledge and the way she interacts with people. She is extremely approachable, very generous with her time, and always very supportive and encouraging. She is a wonderful mentor, teacher, and scientist.”

Valdes says she is always happy to help mentor undergrads and graduate students. She is co-founder and coordinator of the MIT Biology Application Assistance Program (BAAP), which aims to demystify the graduate school application process and offer interested applicants the tools and direct mentorship necessary for putting together a successful application. She also helped to coordinate, and has been an active participant in, the MIT BioPals Program, a student-organized peer mentorship initiative within the department that connects incoming first-year graduate students with senior graduate students. During the Covid-19 pandemic, this program provided critical support and social connection for new students navigating remote learning and social distancing.

After she completes her doctoral program, she envisions pursuing a postdoc and, ultimately, a faculty role, citing her passion for both academic research and teaching.

“My goal is to stay in academia in some way,” says Valdes. “I love mentorship and curiosity-driven science.”

Enzymes that assemble into droplets can speed up cellular reactions

MIT biologists find highly concentrated droplets can help cells keep enzymes organized and control growth signals.

Anne Trafton | MIT News
June 1, 2026

Within the past decade, biologists have discovered that one strategy cells use to keep their contents organized is a phenomenon known as phase separation.

Similar to the way oil forms droplets that float in a vinegar solution, proteins inside cells can phase separate to form highly concentrated droplets that keep them organized within the cell. In a new study, MIT researchers have now shown that this droplet formation is critical for controlling the function of a class of enzymes called kinases.

The researchers found that condensing into droplets optimizes the biochemical conditions needed for kinases to catalyze reactions, allowing them to more rapidly activate cell signaling pathways. In some cases, droplet formation can even change which reactions the kinases perform.

“Many biological molecules have this propensity to spontaneously separate. We were really interested in asking, if we have these kinases forming droplets, what is the consequence of that in the context of signaling?” says Lindsay Case, an assistant professor of biology at MIT and the senior author of the study.

Learning more about how these droplets form could help researchers design drugs that target kinases, some of which can be overactive in cancer cells.

“Understanding the chemistry of these compartments, and what molecules go into them and what molecules don’t go into them, could help us design drugs that better localize to their target of interest,” Case says.

Nicholas Lea, an MIT graduate student, is the lead author of the paper, which appears today in Cell Reports.

Forming droplets

Since her days as a graduate student, Case has been studying how the physical organization of molecules inside cells affects their function. As a postdoc, she began studying how phase separation might affect a signaling pathway that allows cells to sense when they’re attached to their environment, so they can respond appropriately.

Some of the proteins in this pathway are kinases, which activate other proteins by adding phosphate groups to them. Kinases can also activate themselves through a process called autophosphorylation.

“Inside of the cell, you have these kinase molecules that are responsible for carrying a signal through the cell, and we know that the organization of these molecules changes. When the information is present, they’re organized in a different way than when the information is not present,” Case says. “We think that having the right molecules in the right place is incredibly important for the right biochemistry to occur.”

Phase separation is one of the methods that cells appear to use for this organization. The most familiar example of phase separation can be seen in a salad dressing, where oil forms droplets to minimize contact with water-based vinegar. Proteins can phase separate when they are highly concentrated, leading them to self-assemble into dense droplets floating in the cell’s cytoplasm.

Case hypothesized that this phase separation, which brings kinases together at a high density, might help cells to boost the enzymes’ activity because they are more likely to bump into and phosphorylate each other.

In this study, Case and Lea set out to test that hypothesis, focusing on an enzyme called focal adhesion kinase (FAK). This kinase, which becomes activated when cells attach to their surrounding environment, activates pro-growth and pro-survival signals. In cancer cells, this signaling pathway can go awry, allowing cells to proliferate even when they detach from their original locations.

Scientists already knew that when cells are properly attached to their environment, that adhesion signal causes FAK to accumulate at the cell membrane. In the new study, the MIT team mimicked that effect by overexpressing FAK in cells. These cells were floating freely in a solution, not attached to any surface. Even so, the high concentration of FAK caused the kinase to phase separate into droplets, which turned on the pro-growth signal.

“It was surprising that just by condensing this protein into a droplet, you can actually turn on a signaling pathway that should be turned off,” Case says. “If FAK concentration is too high, you’re always getting these droplets and you’re always signaling, regardless of what the receptors that are supposed to be controlling this are doing.”

The findings suggest that in cancer cells, overexpression of FAK may lead to phase separation, which then helps to drive cancer progression and metastasis.

“It may be that for some kinases, you’re not supposed to form these droplets in the cytoplasm because it leads to this always-on signal, and then the cells no longer listen to the information coming from the environment,” Case says.

Interfering with FAK’s ability to form droplets could offer a new strategy for cancer drug development, she says.

Controlling reactions

The researchers also studied two other kinases, Mst2 and Abl. They found that these enzymes could also phase separate at high concentrations, and that this increased their activity. While phase separation of FAK in the cytoplasm may occur only in cancerous cells, for Mst2, it appears to be a strategy that healthy cells use to control a signaling pathway called Hippo, which promotes cell growth and survival.

Additionally, for both Mst2 and Abl, the researchers discovered that phase separation can lead the enzymes to phosphorylate additional targets, which may lead them to activate different signaling pathways.

“It’s not just that you’re getting faster phosphorylation, but in those cases, the patterns of what is actually getting phosphorylated were very different inside of the droplet compared to what might be happening in a non-droplet context,” Case says. “The kinase is able to phosphorylate amino acid residues beyond the set of canonical sites that have been described before.”

The researchers also found that when these droplets form, they attract high concentrations of ATP, the molecule that kinases use as a source of phosphate. This occurs because kinases tend to contain floppy sections containing many positively charged amino acids, which attract negatively charged ATP.

Using a machine-learning model, the researchers predicted that about 45 percent of the 500 kinases found in human cells would have the ability to form droplets like those seen in this study. Those kinases were also more likely to be highly positively charged, which could help them to recruit ATP into the droplets.

In future work, Case hopes to explore the possibility of designing drugs that could mimic ATP’s ability to be attracted into droplets within a cell, which could help reduce negative side effects of the drugs.

“By localizing drugs to the compartment where your target localizes, that could reduce off-target effects by concentrating the drug with the target of interest and reducing interactions with other molecules,” Case says.

The research was funded by a Searle Scholars Program Award, the U.S. Air Force Office of Scientific Research, the National Institutes of Health, the Royal G. and Mae H. Westaway Family Memorial Fund, and a David H. Koch Graduate Fellowship.

Scientists map which genes are active in a developing seed to build hardier crops

Many of the basic biological processes that allow seeds of global food staples like wheat, rice, and corn, to grow, transport nutrients, and develop useful traits like withstanding heat and drought are not yet fully understood. A new gene expression map of seed development offers a framework to better understand, and even guide, seed development to improve crop productivity.

Shafaq Zia | Whitehead Institute
May 19, 2026

Seeds like wheat, rice, and corn are at the center of the global food supply and provide most of the daily calories consumed worldwide. But despite their importance, scientists still do not fully understand many of the basic biological processes that allow these seeds to grow, transport nutrients, and develop traits that determine crop resiliency.

With fluctuating environmental conditions and other stressors threatening agriculture, there is a need to develop hardier crops better able to withstand heat, drought, and changing soil conditions. Scientists are increasingly looking to understand the hidden biology of seed development that could one day help them achieve this.

Now, researchers in the lab of Mary Gehring have created a detailed gene expression “map” of seed development in Arabidopsis thaliana, a small flowering plant in the mustard family that is widely used to study plant biology and is closely related to major crops like canola.

This map, also known as a transcriptional atlas, shows which genes are turned on or off in different cell types as the seed develops. Active genes make messenger RNA (mRNA) that guides the production of proteins necessary for cellular processes. By tracking which genes are active where, researchers can better understand the role each cell type plays across different stages of seed development.

The work, published May 21 in Nature Plants, offers scientists new clues about how plants coordinate key biological processes tied to agriculturally significant traits, including seed size and nutrient storage.

“Seeds are fundamental to sustaining human life,” says Caroline (Carly) Martin, lead author of the paper and a graduate student in the Gehring Lab. “By building this atlas, we now have a framework researchers can use to start asking much more precise questions about how seeds develop and if those processes might eventually be improved in different crops.”

Unlike previous atlases of Arabidopsis, which do not distinguish many cell types due to technological limitations, the new atlas provides a more complete and higher resolution view of the developing seed. The researchers have captured seed development at three precisely timed stages after pollination when the plant embryo, the nutrient-rich tissue that feeds it (called the endosperm), and the surrounding tissues from the mother plant rapidly grow and reorganize. Using this dataset, they have identified where genes that regulate how seeds grow and store nutrients are active.

The researchers have found a small group of cells near the plant embryo that activate genes involved in producing brassinosteroids, plant hormones that regulate growth. Previous studies had shown that disrupting the production of this hormone can reduce seed size, but it was not known where within the developing seed the hormone is made.

The new data shows that these hormone-producing cells sit directly next to cells in the endosperm that might respond to the hormone. This close arrangement suggests the two cell types may work together to help fine-tune seed size.

The atlas has also revealed that the endosperm, which nourishes the embryo during development and later becomes the edible portion of many staple crops, contains far more specialized cell types than previously understood by researchers.

The team has identified a small “founder” population of cells that may help establish a key region of the endosperm located at the boundary where nutrients enter the seed from the mother plant.

Because the amount and timing of resources supplied by the mother plant determine how much energy the seed can store, this region of the endosperm helps shape the seed’s nutritional profile. These reserves — oils, starches, and proteins — are essential for both seed development and human nutrition.

These findings, taken together, could allow researchers to better understand — and even guide — seed development to improve crop productivity.

“We’re already seeing that seed filling in many crops is vulnerable to heat stress,” says Gehring, who is also a professor of biology at MIT and an investigator at the Howard Hughes Medical Institute (HHMI). “If we are to solve the humanitarian crises of food insecurity and malnutrition, we need to understand, at a fundamental level, how seeds of different crops form, store nutrients, and survive environmental stress.”

Caroline A. Martin, Kylee R. Cogdill, Alesandra L. Pusey, and Mary Gehring. “A transcriptional atlas of early Arabidopsis seed development suggests mechanisms for inter-tissue coordination.” Nature Plants, May 21, 2026. https://doi.org/10.1038/s41477-026-02295-8

How tissues tune immune responses to match the threat

Organs which interface with the outside world, like the lungs, skin, and intestines, must balance responding quickly to threats while also avoiding triggering unnecessary inflammation. A new study has found that immune sensitivity in the communities of epithelial cells that line the lungs is not evenly distributed, with cells deeper in the tissue more likely to sound the alarm in response to a threat such as viruses, microbes, allergens, and other particles.

Mackenzie White | Whitehead Institute
May 14, 2026

Barrier organs that form boundaries between the body and the outside environment, such as the lungs, skin, and intestines, face a difficult balancing act. They must respond quickly to threats such as infection, but they also need to avoid triggering unnecessary inflammation that can damage the tissue. A new study led by Whitehead Institute member Pulin Li and graduate student in her lab Diep Nguyen reveals one way the lung manages that tradeoff.

Published on May 15 in Cell Systems, the research found that immune sensitivity is not evenly distributed across the lung. Instead, it arranges in tiers: cells at the outer surface respond cautiously, while cells deeper in the tissue are more likely to sound the alarm when a threat breaks through.

“The central question was how tissues balance the benefits and harmful effects of immune activation when they face different degrees of danger or stress,” says Li, who is also a professor of biology at MIT. “Too little immune activation leaves the tissue unprotected, but too much can create inflammation and damage.”

The team focused on the lung, where epithelial cells line the airways and air sacs and form a physical barrier between the body and the outside world. These cells sit at the point of first contact with inhaled viruses, microbes, allergens, and other particles. For that reason, they are often thought of as front-line defenders.

But the new study suggests that the lung’s outermost defenders are deliberately cautious.

Using mouse models of influenza infection and imaging methods that allowed them to measure infection and immune responses in individual cells, the researchers found that epithelial cells were the least likely to respond to infection by producing interferons, signaling proteins that help alert the immune system. Cells deeper in the tissue, especially endothelial cells that line blood vessels, were much more likely to respond.

This arrangement suggests that the lung uses location as a clue to the seriousness of a threat. A stimulus that remains at the surface may not require a large immune response. But when infection breaches the epithelial barrier and reaches deeper tissue, the lung treats that as a more dangerous threat and activates a stronger defense.

“A less severe threat only requires a lower level of immune response,” says Nguyen. “As a threat goes deeper into the tissue, the inner cell types can encode that information and indicate that the threat has invaded further.”

The researchers traced these differences in sensitivity, in part, to immune-sensing proteins called pattern recognition receptors. These receptors detect molecular signs of infection or damage. One receptor, RIG-I, helps cells recognize viral RNA. Epithelial cells had relatively low levels of RIG-I and related sensors, while deeper stromal cells had higher levels.

That lower sensitivity appears to protect the lung from unnecessary damage. When the researchers increased RIG-I levels in lung epithelial cells in mice, the animals mounted a stronger immune response to a non-infectious inflammatory trigger. But the heightened response caused more tissue damage and interfered with repair.

The finding helps explain why the lung’s surface cells may be tuned not to overreact. The lung constantly encounters harmless or low-level irritants. If epithelial cells responded too readily, they could turn minor disturbances into damaging false alarms.

The researchers also found evidence that similar patterns may exist in other barrier organs, including the intestine and trachea. That raises the possibility that spatially tiered immune sensing is a broader strategy for protecting organs that face the outside world.

“One impact of this work is that it helps us look at an old question in a new way: how do tissues balance protection with tissue damage?” says Nguyen. “We can start to understand that when we look at the building blocks of the tissue and how they work together.”

Li says the work also reflects the value of studying tissues as communities of cells rather than collections of identical responders.

“To understand physiology, you have to take a multicellular approach,” she says. “Thinking about tissues as communities of cells can reveal new insights into how they function.”

Diep H. Nguyen, Jiakun Tian, Sean-Luc Shanahan, Connie Kangni Wang, Tyler Jacks, Xiao Wang, and Pulin Li. “A tissue-scale strategy for sensing threats in barrier organs.” Cell Systems, May 14, 2026. https://doi.org/10.1016/j.cels.2026.101611