GENE NETWORKS IN HUMAN STEM CELLS

Abstract

The pluripotent state of embryonic stem cells (ESCs) is shaped by complex interactions between multiple genes, transcripts and proteins that form the ESC regulatory network. During differentiation, ESCs exit from pluripotency by shutting down this network. As the potential of human ESCs (hESCs) lies in their ability to differentiate into any specific somatic lineage, it is imperative to understand the genetic regulations governing the exit from pluripotency. In this thesis, we report the first high-throughput RNA interference screen for factors crucial for the exit from pluripotency of hESCs in a comprehensive set of differentiation conditions. This systematic study enabled the identification of both centrally important and context-dependent processes for the exit from pluripotency. Strikingly, we found that the cell cycle is a critical process deterministically regulating the exit from pluripotency. Cell cycle factors that primarily operate during the S and G2 phases, such as the ATM/ATR pathway and Cyclin B1, actively promote the pluripotent state and inhibit differentiation. Altogether, this study uncovers a multitude of novel regulators of the exit from pluripotency, and establishes a new paradigm where the pluripotency network is hardwired into the specific cell cycle pathways.