Intrinsic cell chirality of human embryonic stem cells and derived lineages

Abstract

Left-right (LR) asymmetry is an imperative part of embryonic development. The disruption of LR axis development can result in defects in organ morphology, positioning and physiological functions. The mechanisms behind LR symmetry breaking are under debate in the field with theories ranging from intracellular cytoskeletal chirality in the single cell embryo to morphogen gradients induced by cilial flow to unifying theories wherein LR asymmetry is established through an interplay of many different models. Recent studies have demonstrated that LR asymmetry at the cellular level, i.e., intrinsic cell chirality, plays an important role in embryonic development. The goal of this dissertation is to explore the possible role of intrinsic cellular chirality in the development of LR asymmetric organs and mechanisms behind its action. Current studies in embryonic development rely heavily on animal models, which do not always recapitulate human development. We propose to develop and utilize an in vitro model system consisting of human embryonic stem cells (hESCs) and a biomaterial-based chirality assay to assess intrinsic cell chirality and study embryonic LR asymmetry development. Evaluation of the differentiation of hESCs into heart, gut and brain tissues shows lineage-dependent chiral biases in 3D cell rotation at various stages of differentiation. The chiral biases correlate with the directionality of asymmetric looping during in vivo organ development. Pre-treatments of hESCs with activators and inhibitors of key LR asymmetry signaling pathways, Nodal and canonical Wnt, demonstrate that these pathways regulate inherent cellular chirality. Taken together, this research suggests that cell chirality regulated by developmental signaling pathways determines the LR asymmetry of organ development.