Abstract

Naïve human pluripotent stem cells (hPSCs) resemble the pre-implantation epiblast and possess the ability to generate a broad range of embryonic and extraembryonic cell types. These properties make naïve hPSCs a powerful model for studying how signaling pathways and chromatin regulators influence lineage specification during early human development. However, naïve hPSCs alone cannot recapitulate tissue organization and the complex interactions among cell lineages during development. Furthermore, ethical and practical constraints on direct studies of human embryos remain. Consequently, alternative model systems are needed to examine these developmental processes. To investigate lineage specification during early human development, I utilized human blastocyst-like structures (blastoids) derived from naïve hPSCs as an experimental model. A major challenge in the field is that long-term naïve culture is frequently accompanied by genetic and epigenetic instability, limiting the utility of naïve hPSCs for developmental studies. To address this issue, I developed a rapid naïve induction strategy based on the 4iLAXGöF culture condition. This approach generates blastoid-competent naïve hPSCs within only a single passage of primed-to-naïve resetting and supports the formation of blastoids that can be maintained through post-implantation-like stages up to day 21. Compared with conventional 5i/L/A culture conditions, rapidly induced naïve hPSCs showed reduced genetic instability and improved preservation of parent-specific genomic imprints. Using this optimized blastoid platform, I investigated the developmental functions of BRG1, the ATP-dependent catalytic subunit of the BAF chromatin remodeling complex. By combining an inducible BRG1 degradation system with both two-dimensional lineage differentiation and three-dimensional blastoid models, I found that BRG1 plays cell-fate-specific roles across human developmental lineages. Loss of BRG1 impaired the specification of both embryonic and extraembryonic mesoderm lineages, whereas trophoblast development was less dependent on BRG1, likely due to functional compensation by BRM, a homologous ATPase of the BAF complex. Together, these findings demonstrate that chromatin remodeling requirements differ among developmental lineage specification and provide new insights into the functions of the BAF complex during early human development. Together, these studies demonstrate that rapid naïve induction with 4iLAXGöF can preserve developmentally competent blastoids while minimizing the genetic and epigenetic instability associated with long-term naïve culture. Using this system, I identified lineage-specific functions of the BAF chromatin remodeling complex during early human development. These findings provide both a practical strategy for improving the fidelity of stem-cell-based embryo models and new insight into the molecular mechanisms that regulate early lineage decisions.

Committee Chair

Thorold Theunissen

Committee Members

Andrew Yoo; Chun-Kan Chen; Kyunghee Choi; Michael Meers

Degree

Doctor of Philosophy (PhD)

Author's Department

Biology & Biomedical Sciences (Developmental, Regenerative, & Stem Cell Biology)

Author's School

Graduate School of Arts and Sciences

Document Type

Dissertation

Date of Award

7-23-2026

Language

English (en)

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Available for download on Saturday, July 22, 2028

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