
Every person starts as one cell. That cell divides, and its descendants have to decide what to become: a neuron, a skin cell, part of a placenta. We study how those decisions get made, and what happens when they go wrong.
Getting it wrong early has consequences. If the tissue that forms the brain and spinal cord fails to close, a baby is born with a birth defect. If the placenta develops poorly, the pregnancy can turn dangerous for the mother. Cancer often works by switching these early programs back on in adult cells.
We work with mouse embryos, human stem cells, and tissue donated by patients. Following these questions has taken us into birth defects, pancreatic cancer, type 2 diabetes, and the complications of pregnancy.
We run the lab together. Ron is at Baylor College of Medicine. Jackie is at UTHealth Houston, where she also treats patients with high-risk pregnancies. Her patients are where a lot of our questions start.




Cranial neural crest cells pass through a transient window of open chromatin that permits both neuronal and ectomesenchymal fates. miR-302 holds that window open by targeting Sox9 to slow specification. Without it, cells commit early, accessibility narrows, and peripheral neurons are lost.
miR-302 directly represses three glycolytic enzymes in the closing neural tube. Loss upregulates glycolysis, shortens the cell cycle, and drives progenitor over-proliferation into cranial defects, confirmed by whole-embryo mass spectrometry. The first direct evidence linking a miRNA to metabolic control during neurulation.
Deletion of miR-302a-d causes a fully penetrant anterior neural tube defect, with thickened neuroepithelium, increased progenitor proliferation, decreased apoptosis, and precocious neuronal differentiation. Compound mutants with miR-290 die before neurulation, revealing redundancy between the two clusters.
Returning to the question a decade later with genetic loss-of-function, we showed the miR-290 and miR-302 clusters are not merely correlated with reprogramming but required for it.
Foxd3 simultaneously establishes and represses enhancers, using a single factor to hold a developmental program poised and then release it on schedule.
In human cells, the balance between miR-372 and let-7 decides whether a cell becomes germline or soma, placing an ancient heterochronic circuit at a fate boundary.
The miR-290 and miR-302 clusters mark two distinct paths through late-stage reprogramming. Cells arriving at pluripotency have not necessarily taken the same road, which reframed reprogramming as a landscape rather than a single trajectory.
A microRNA-based screen identified the roadblocks that keep a fibroblast from returning to pluripotency, mapping the cellular checkpoints reprogramming must clear.
miR-302 regulates the pancreatic progenitor pool and final organ size, extending its role in progenitor control well beyond the neural tube.
Reactivation of the G1 enhancer landscape underlies core regulatory circuitry addiction to SWI/SNF, linking a chromatin remodeler's essentiality to a developmental program the tumor has reawakened.
CHAF1A blocks neuronal differentiation and drives neuroblastoma through metabolic reprogramming, showing a tumor holding itself in an immature developmental state.
Hematologic DNMT3A reduction and high-fat diet synergize to promote weight gain and tissue inflammation, showing that a clonal hematopoiesis mutation and an environmental exposure are worse together than either alone.
hIAPP protofibrils are the toxic intermediate in type 2 diabetes, but they are transient and cannot be isolated, so they had never been drug targets. Working with collaborators at Rockefeller who locked hIAPP into the protofibril conformation, we showed these antibodies detect protofibrils in serum and islets without binding monomer, and that treating diabetic mice significantly extends survival. A species once considered undruggable is both a biomarker and a target.
Extracellular vesicles and cell-free RNA in amniotic fluid track how a fetus is adapting in twin-twin transfusion syndrome. The fluid around the fetus is not inert. It reports on the fetus inside it, which opens a route to monitoring a pregnancy without touching it.
Single-nucleus profiling of placentas from patients with COVID-19 revealed ER stress, unfolded protein response activation, and CEBPB phosphorylation in the syncytiotrophoblast. The signature overlaps preeclampsia, offering a mechanism for a clinical association obstetricians had long observed. The samples came from Jackie’s patients and the profiling was done on Ron’s side. Neither half of the lab could have done it alone.
In twin-twin transfusion syndrome, twins share a placenta but not blood flow equally. Profiling that natural experiment showed how a fetal heart under load shifts its metabolism to cope, in a setting where the affected and unaffected twin share a genome.
Loss of Stox1 in mice produces gestational hypertension driven by renin, alongside defects in the placenta itself. The result connects an inherited risk gene to a specific, and druggable, blood pressure pathway.
Placental growth factor falls in preeclampsia and is used clinically to predict it, which invited the assumption that losing it drives the disease. In mice, deleting it did the opposite and maternal hypertension improved. A marker of the disease is not the same as its mechanism.
A developmental biologist working on how cells decide what to become, and what happens when those decisions fail. His research spans birth defects, cancer, and metabolic disease, combining mouse genetics with single-cell genomics. B.S. and M.S. University of Illinois at Urbana-Champaign, Ph.D. UC Berkeley with Nipam Patel, postdoctoral fellowship UCSF with Robert Blelloch. Founded the lab at Baylor College of Medicine in 2015. His work is supported by the NIH, CPRIT, the V Foundation, the Lustgarten Foundation, and the Hydrocephalus Association.
A physician-scientist working on placental biology and the disorders of pregnancy, and what the maternal environment does to a developing embryo. Her research bridges the clinic and the bench, combining patient-derived tissue with cell culture and animal models. B.A. UC Berkeley, M.D. UCSF, OB/GYN residency UCSF, maternal-fetal medicine fellowship UCSF and Baylor College of Medicine, postdoctoral fellowship at MD Anderson with Raghu Kalluri. Co-director of the Mother Baby Biobank at UTHealth. She attends on labor and delivery at Memorial Hermann and Harris Health LBJ. Her work is supported by the NIH, the Doris Duke Foundation, the Burroughs Wellcome Fund, and the Preeclampsia Foundation.
Selected as Ph.D. Class Speaker for Baylor College of Medicine commencement.
Meg received an NIH Ruth L. Kirschstein Predoctoral Individual National Research Service Award (F31).
Department of Molecular and Cellular Biology Tsai Award.
Center for Cell and Gene Therapy Retreat.
International Conference on Neural Tube Defects. Rachel is the only trainee in the 25-year history of the conference to win this award at two consecutive meetings.
Impact score: 10. Percentile: 1%.
International Conference on Neural Tube Defects.
Center for Cell and Gene Therapy Retreat.
Society for Developmental Biology.
We are recruiting graduate students, postdocs, and technicians. These are the areas we are building in. If one of them is the question you want to spend years on, write to us.
Neural tube closure, hydrocephalus, and the progenitor populations that build the early brain.
Placental biology, preeclampsia, and how the maternal environment reaches the embryo.
How tumors reawaken the regulatory programs that built the embryo, in pancreatic cancer and neuroblastoma.
Protein misfolding in type 2 diabetes, and why it raises the risk of dementia.
The machinery that decides which genes are read, when, and in what order.
What commits a cell to a fate, and what allows it to go back.




During the pandemic, pregnant patients were asked to make decisions about a vaccine that had been tested on almost no one like them. Jackie spent that period explaining what was known and what was not, to reporters, to patients, and to Congress.
The lab is continuously funded by the NIH across both institutions, with additional support from foundations in cancer, birth defects, and maternal health.
Parchem Lab
Development & Disease
We're recruiting graduate students, postdocs, and technicians. Write to either of us.