Deconstructing human body plan development with stem cells

在人体计划的发展过程中，精确的模式是如何实现的，由于

How the precise patterns are achieved during development of the human body plan remains obscure due to limited access to human embryos, while elucidating the mechanisms will advance knowledge of human development and contribute to regenerative medicine. The goal of my research is to reconstruct development of the human body axis and appendages using pluripotent stem cells (iPSC) and to illuminate general principles of pattern formation. I have used iPSC to successfully establish two 3D models recapitulating spatiotemporal features of human somite formation, which provide a valuable platform to decode mechanisms of body axis patterning with unprecedented resolution. Using these models, I found that active cell sorting underlies the antero-posterior (AP) polarity patterning of somites and put forward a novel framework explaining the formation of repeated structures along the body axis. In this proposal I will further utilize the in vitro models to expand and refine the cell sorting centered framework of somite AP patterning, as well as develop 3D models of human limb development to set up foundation for my future investigation of digit periodic patterning. In Aim1, I will investigate how cell sorting are coordinated with classical modules of somitogenesis. In the mentored phase, I will uncover roles of the segmentation clock in synchronizing the onset of cell sorting within a forming segment to ensure robust tissue-level patterning. In the independent phase, I will interrogate how somite size control is coordinated with AP pattern formation. Together these will bridge the novel finding of cell sorting with established concepts of somitogenesis. In Aim2, I will elucidate the molecular and cellular mechanisms of cell sorting and shine light on general cell biological principles of pattern formation. In parallel, I will set out to develop organoid models of human limb development using iPSCs. In Aim3, I will combine a preliminary 2D differentiation protocol of Limb bud cells in the Pourquie lab, the expertise in maintaining limb progenitors in vitro of the Tabin lab, and my specialty in 3D organoid culture to build 3D models recapitulating features of limb bud elongation and patterning. The proposed work will strengthen my knowledge of body axis development, equip me with expertise in limb development, and establish groundwork for my future career in elucidating periodic pattern formation during human development. Altogether, this proposal will provide valuable insights into the early development of human body plan and guide complex organ engineering to further dissect mechanisms and treat diseases.