Principal Investigator • Senior Research Technician • Graduate Students • Postbaccalaureate • Postdoctoral Associates • Staff Scientist • Lab alumni
Principal Investigator
Thorold Theunissen, PhD
Thor grew up in the Netherlands and received his A.B. in Biology from Harvard in 2007. He became interested in stem cells and developmental biology during his undergraduate work in the laboratories of Christine Mummery (Hubrecht Institute) and Stuart Orkin (Harvard Medical School). He completed his graduate studies in Jose Silva’s laboratory at the University of Cambridge in 2011. His doctoral thesis focused on the role of the homeodomain transcription factor Nanog in epigenetic reprogramming. As a Sir Henry Wellcome Postdoctoral Fellow in Rudolf Jaenisch’s laboratory at the Whitehead Institute/MIT, Thor developed methods to isolate naive human pluripotent stem cells. He joined the Department of Developmental Biology at Washington University School of Medicine as Assistant Professor in 2017 and was promoted to Associate Professor in 2023. He is a recipient of the NIH Director’s New Innovator Award (DP2), the Edward Mallinckrodt Jr New Investigator Award, the Shipley Foundation’s Program for Innovation in Stem Cell Science Award, the NIH Outstanding Investigator Award (R35), and the Mallinckrodt Scholar Award. The Theunissen lab is affiliated with the Center of Regenerative Medicine and the Center for Women’s Health Engineering at WashU. Thor is a member of the Advisory Board of Cell Stem Cell and the Editorial Board of Stem Cell Reports.
Senior Research Technician
Brittany Meyer, MSc
Brittany received her Bachelor of Science in Biology from Eastern Illinois University. She also received her Master of Science in Biology from Eastern Illinois University in 2019. She joined the Theunissen lab in August 2022 as a Research Technician II and was promoted to Senior Research Technician in 2024. She previously worked as an Adjunct Biology instructor at Lake Land Community College in Mattoon, IL. Brittany is interested in researching stem cells and their applications in disease therapy and regenerative medicine. Brittany is an active member of the American Chemical Society and is a Women in STEM Mentor. Outside the lab, she spends time with her husband, daughter, and two huskies. In her free time, she loves to read!
Graduate Students
Peiheng Liu
Peiheng is a member of the Molecular Cell Biology (MCB) Program and joined the Theunissen lab in June 2024. She graduated from the University of Wisconsin Madison in 2023 with a degree in Animal Sciences and Genetics. While at UW Madison, she was an undergraduate researcher in Dr. Wei Guo’s lab, studying the function of the RBM20 RS domain in Dilated Cardiomyopathy. Additionally, she completed a summer internship in Dr. Songhai Shi’s lab at Tsinghua University, focusing on mitochondrial expression in radial glia progenitors during embryonic brain development. Intrigued by stem cell research during her first year at WashU, Peiheng decided to pursue her Ph.D. in the Theunissen lab. In her spare time, she cares for two schnauzers and three cats and enjoys playing guitar.
Serene Mattis
Serene is a Ph.D. student in Biomedical Engineering at the McKelvey School of Engineering. She graduated from the University of Miami in 2023 with a Bachelor of Science in Biomedical Engineering. During her undergraduate studies, she conducted research in the Neural Interfaces Laboratory under Dr. Abishek Prasad, focusing on optimizing and automating data analysis methods to enhance understanding of the foreign body response to microelectrode array implantation. This experience was pivotal in her decision to pursue a Ph.D. at WashU. Serene’s passion for women’s health engineering was sparked by a course titled “Engineering for Women’s Health.” She joined the Theunissen lab in August 2024, where she aims to bridge the gap between biology and engineering by developing new tools for studying placental development. Outside of the lab, Serene enjoys reading, watching anime, and baking.
Kyoung Park
Kyoung earned a Master of Science in Biology from Yonsei University, South Korea, and previously served as a Research Technician in our lab from 2018 to 2022. She played a key role in starting the lab and collaborated closely with Dr. Jianlong Wang’s lab at Columbia University on the OCT4 protein interaction network in naive and primed hPSCs, identifying pluripotent-state-specific interactions with distinct subunits of the BAF chromatin remodeling complex. She enrolled in the Developmental, Regenerative, and Stem Cell Biology Program in 2022 and re-joined our lab as a graduate student in March 2023.
Richard Yin
Richard is a member of the Developmental, Regenerative, and Stem Cell Biology Program and joined the Theunissen lab in August 2023. He earned his B.S. from the University of Toronto in 2022. He started his research journey as a volunteer in Dr. Phedias Diamandis’ lab, studying potential therapeutic targets in glioblastoma tumour microenvironments. As an undergraduate researcher under Dr. Jennifer A. Mitchell, he investigated the evolutionary role of human-specific KLF4 enhancer candidates in pluripotent stem cells. His passion for stem cell research led him to pursue a Ph.D. at WashU. Outside the lab, he enjoys cooking, rock-climbing, gaming, and movies.
Postbaccalaureate
Rosa Loewenstein
Rosa is a postbaccalaureate researcher in the Developmental Biology, Cell Biology, and Regenerative Medicine research program and joined the Theunissen lab in August 2024. She graduated from Carnegie Mellon University in 2021 with a degree in Biological Sciences and a minor in Biomedical Engineering. She worked as a Research Technician in Dr. Andrew Duncan’s lab at the University of Pittsburgh, focusing on characterizing cellular regeneration and gene expression in chronic liver disease development. In her free time, she enjoys baking, playing tennis, and bullet journaling.
Postdoctoral Associates
Xiangyu Kong, PhD
Kong comes from the ancient bloodline of Confucius in China and earned his Bachelor of Agriculture at Kyoto University in Japan. He moved to the US in 2017 to pursue his PhD at Rice University in Houston. This is where he officially became “Kong” as his first name is impossible to pronounce. This is also where he became fascinated by developmental biology and particularly in vitro structures generated from human embryonic stem cells. He joined the lab of Dr. Aryeh Warmflash to study human gastrulation and developed a 2D model to recapitulate amnion-epiblast interaction. This experience made him wonder how this and other embryonic-extraembryonic interactions would work in a developmental context that bears more resemblance to in vivo development, and this is why he decided to join the Theunissen lab in October 2024 to study embryonic-extraembryonic interactions in the stem-cell-based embryo models previously constructed here. Despite the common portrayal of Confucius himself being a very serious man, Kong does not appear to inherit the sternness and can be a goofball from time to time. He enjoys traveling and having random conversations with strangers about random topics.
Regan Scott, PhD
Regan joined the Theunissen Lab in January 2026 as a Postdoctoral Associate. She received her B.S. from Kansas State University and M.S. in Biomedical Sciences from Kansas City University. She completed her graduate work in the laboratory of Michael J. Soares at the University of Kansas Medical Center studying placental development with a focus on trophoblast stem cell differentiation to the invasive lineage. After receiving her Ph.D. in 2025, she joined the Theunissen lab to continue advancing the field of stem cell and developmental biology. Regan is a strong advocate for scientific research and reproductive health, and in her spare time she enjoys baking, doing puzzles, being outdoors, and spending time with family, friends, and her pets.
Staff Scientist
Shafqat Ali Khan, PhD
Shafqat joined the Theunissen lab in January 2019 as a Postdoctoral Associate and was promoted to Staff Scientist in 2023. He is interested in the mechanisms involved in the maintenance, resetting and differentiation of primed and naive human pluripotent stem cells. Previously, as a CRG/Marie Curie Postdoctoral Fellow, he worked on human germ cell differentiation and X chromosome reactivation using pluripotent stem cells with Dr. Bernhard Payer at the Centre for Genomic Regulation in Barcelona, Spain. For his doctoral thesis, Shafqat investigated the role of histone modifications and other chromatin modifiers in human gastric cancer in the laboratory of Dr. Sanjay Gupta at Tata Memorial Centre-ACTREC, India.
Lab alumni
Georgia Bland – High School Student from 2023 to 2024
Georgia was a high school student from Ladue Horton Watkins High School, who worked in the Theunissen lab from January 2024 until August 2025. While in our lab, Georgia assisted Brittany with the generation of stem-cell-based models of human trophoblast development. In August 2025, she began her undergraduate studies at The University of Texas at Austin.
Chaoyi Cheng – Summer Intern in 2025
Chaoyi was a summer intern in the Theunissen lab in 2025. He worked closely alongside Kong on the generation of advanced stem-cell-based embryo models. He returned to Peking University in September 2025, where he is completing his senior year and conducting research on the molecular mechanisms underlying autism-related neurodevelopmental disorders using mouse and Drosophila models.
Brian Chew – Research Technician from 2020 to 2022
Brian was a Research Technician in the Theunissen lab from 2020 to 2022. He contributed to our studies on naive pluripotency, working closely with Shafqat Khan, and 2D and 3D models of trophoblast development, working under supervision of Chen Dong and Rowan Karvas. In 2022 Brian joined the Interdisciplinary Biomedical Graduate Program at the University of Pittsburgh.
Chen Dong – Graduate Student from 2018 to 2022
Chen was a graduate student in the Developmental, Regenerative, and Stem Cell Biology (DRSCB) Program from 2018 to 2022. His PhD thesis was focused on methods for deriving human trophoblast stem cells (hTSCs) and specialized trophoblast cell types from naive hPSCs. He also performed a genome-wide CRISPR screen in collaboration with Bo Zhang’s lab at WashU, identifying essential and growth-restricting genes in hTSCs. Chen holds the distinction of being the first student to graduate from our lab. In 2022 he joined the Boston Consulting Group as a Consultant.
Laura Fischer – Graduate Student from 2018 to 2024
Laura was a graduate student in the Developmental, Regenerative, and Stem Cell Biology (DRSCB) Program from 2018 to 2024. During her PhD project, she developed methods to track and mitigate imprint erasure during induction of naive pluripotency. She also contributed to our studies on the derivation of trophoblast stem cells, organoids, and blastoids. After a brief stint as a postdoc in our lab, she took over as Director of the Human Cells, Tissues, and Organoids Core at WashU.
Rowan Karvas – Postdoctoral Associate from 2020 to 2024
Rowan was a postdoctoral associate in our lab from 2020 to 2024. She derived 3D trophoblast organoids from naive hPSCs and demonstrated their utility in modeling placental development and susceptibility to emerging viral pathogens. She also pioneered the derivation of blastocyst-like structures (“blastoids”) from naive hPSCs and showed that this integrated embryo model could recapitulate hallmarks of early human post-implantation development during extended culture on appropriate extracellular matrices. In 2024 she launched her independent research group at the University of Colorado Anschutz Medical Campus.
Jinyu “Jane” Liu – Summer Intern in 2025
Jinyu (or Jane) Liu was a summer intern in the Theunissen lab in 2025, working closely alongside Peiheng on modeling the human maternal-fetal interface using stem cells. She returned to the University of Oxford in October 2025 to complete her undergraduate degree in biology. For her master’s research project, she has joined Dr. Berta Verd’s lab, studying the role of maternal factors in somitogenesis in cichlids.
Eshan Sane – Undergraduate from 2020 to 2023
Eshan was an undergraduate in our lab from 2020 to 2023. He contributed to our studies on trophoblast organoids and human embryo models, working closely alongside Rowan Karvas. After graduating with a BS in Biomedical Engineering and Psychology, Eshan enrolled in the MD program at Washington University School of Medicine.
Joey Zemke – Graduate Student from 2022 to 2024
Joey was a Developmental, Regenerative, and Stem Cell Biology (DRSCB) graduate student in our lab from 2022 to 2024. They contributed to the generation of our stem-cell-derived blastoid model and investigated the signaling pathways driving human trophoblast specification and differentiation using naive hPSCs.
Theunissen Lab 