This research proposal integrates into our long-term goal to identify and characterize the specific molecular determinants (both genetic and epigenetic) that define the identity of human embryonic stem cells (hESCs). Recent discoveries in mouse embryonic stem cells (mESCs) have identified the protein MYC as a "master" regulatory molecule that maintains the ability of embryonic stem cells to divide indefinitely and to give rise to all tissues of the human body. The MYC protein (in conjunction with 3 other factors) when introduced into an adult tissue cell (for instance a skin cell that has limited life span) can "rejuvenate" the adult cell into a pluripotent stem cell that can divide indefinitely and give rise to all types of tissues in vitro. This is a major step toward being able to generate an unlimited supply of hESCs for regenerative medicine. Howeve MYC also has a "dark side". In our lab we have been working for several years at understanding how MYC immortalizes cells in the context of cancer. Indeed most human tumors contain large amounts of MYC and MYC stimulates tumor formation when aberrantly overexpressed. So MYC can have both beneficial (rejuvenation/immortalization) and detrimental (tumor formation) effects on cells. We do not understand yet how this balance is regulated. The current project aims at understanding (i) how MYC and one important cooperating partner of MYC called GCN5 regulate genes in hESCs, (ii) which genes are directly regulated, and (iii) how MYC functions might be modified in hESCs as compared to cancer cells and other adult body cells. This understanding will be critical to eventually develop safe methods to generate large amounts of hESCs for regenerative therapy from adult body cells by exploiting selectively the beneficial functions of MYC (or its partners such as GCN5) while avoiding its oncogenic activities (i.e., its "dark side").
The proposed research project will investigate at the molecular level the role of emerging"key" regulators of human embryonic stem cell identity and self-renewal. It is speculated that these factors control the self-renewal and pluripotency of human embryonic stem cells by modifying the structure of chromatin and the expression of specific genes in the nucleus of these cells. The network of genes regulated by these key factors in human embryonic stem cells will be identified by the proposed analyses.
These studies will contribute to a better understanding of the molecular genetic mechanisms and gene regulatory networks that identify specifically human embryonic stem cells and differentiate them from all other human cells. This fundamental undertanding of the molecular biology of human stem cells will be essential for the eventual rational design of methods to control the self-renewal and differentiation of these cells and, in the longer term, to exploit their therapeutic potential. As such the proposed research will contribute to the effort of the State of California and its many research institutions and dedicated individuals to accelerate discovery in the stem cell field in order to advance at a faster pace towards the goal of curing many degenerative diseases and tissue injuries that affect many, if not most, people at some point in life.