A Balancing Act: Decoupling the Coordinators of Early Human Development Using a Stem Cell-Based Platform

Date of Award

Spring 1-1-2025

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Genetics

First Advisor

Sozen, Berna

Abstract

Investigating the origins and early differentiation events of our species’ development has perplexed and fascinated thinkers for centuries. Yet, understanding and accessing the human embryo after it implants in the uterus remains one of the most challenging and obscure topics, as the embryo is protected not only by the surrounding endometrium but also by ethical and legal considerations. A solution that carries significantly less technical and ethical weight is leveraging the differentiation potential and self-organizing capabilities of human pluripotent stem cells to reconstruct aspects of the human embryo during post-implantation stages. Using a multi-lineage, self-organization strategy in 3D, we analyzed coordinated development of embryonic and extra-embryonic lineages. This strategy demonstrated distinct spatiotemporal differentiation events, including the spatially confined expression of post-implantation-specific cell types, such as amnion-like and mesoderm-like populations, as well as the emergence of an antagonizing cellular population, validated by single-cell RNA sequencing and immunofluorescence. The dynamic crosstalk between these cellular populations enabled us to examine a temporary emergence of enriched signals for BMP, WNT, and NODAL, which influence the spatial localization and specification of developing lineages, akin to the post-implantation mammalian embryo. Besides signaling factors, we explored mechanical cues that shift the balance from a pluripotent state to a differentiated amnion-like fate. Since our stem cell-based system exhibits distinct morphological signatures of pluripotent, epiblast, and differentiated amnion-like configurations, we conducted a morphological quantitative analysis and utilized a 3D embryo model along with 2D directed differentiation stem cell-based systems to investigate amnion as a mechanosensitive tissue. Collectively, this multi-lineage system captures the simultaneous differentiation and morphogenesis of embryonic and extra-embryonic progeny in a spatiotemporally resolved manner. It provides an unprecedented opportunity to dissect the molecular, cellular, and mechanical mechanisms underlying early fate decisions, thus offering a gateway to understanding the origins of developmental disorders.

This document is currently not available here.

Share

COinS