Rajagopal, JayarajRosado-Olivieri, Edwin2019-12-112019-112019-09-102019Rosado-Olivieri, Edwin. 2019. In Vitro Modeling of Human β Cell Differentiation, Regeneration and Function. Doctoral dissertation, Harvard University, Graduate School of Arts & Sciences.http://nrs.harvard.edu/urn-3:HUL.InstRepos:42013108Stem cell-derived β cells offer an inexhaustible source of functional β cells for cell therapy and disease modeling for diabetes. We capitalize on the in vitro differentiation of β cells as a model of human development to identify regulators of cell fate. Our analysis identified YAP, an effector of the Hippo pathway, as a factor critical for the differentiation of multipotent pancreatic progenitors. Its downregulation in progenitors promotes cell cycle exit and endocrine differentiation in vitro. We further show evidence for the utility of a YAP inhibitor to enhance the differentiation of glucose-responsive β cells. Our analysis also indicated that YAP re-activation in β cells promotes cell cycle re-entry, a process essential for the control of β cell mass. To identify novel regulators of β cell proliferation, we performed single cell RNA-sequencing of YAP-overexpressing β cells. This led to the identification of a LIF-responsive subpopulation of β cells that can be expanded in vitro and in vivo. Our work also delineated downstream gene regulatory networks that control β cell replication. Finally, we developed a technology to discover novel hormones expressed in β cells. We identified an uncharacterized gene, ER-seq08, that reduces blood glucose levels in vivo in an insulin-independent manner. Our work suggests that this axis may represent a second system by which β cells regulate glucose metabolism. In all, our work highlights the potential of using in vitro-derived β cells for the study of human development, regeneration and function.application/pdfenstem cellsbeta cellsdiabetesdevelopmental biologyorgan regenerationThesis or Dissertation2019-12-110000-0003-4756-0956