We are in the process of characterizing the microRNA expression profiles and testing the function of the key miRNAs in Human Embryonic Stem Cells (HESCs). 

microRNAs are small (20-23nt) RNA molecules that can regulate gene expression.  Previous work has demonstrated that miRNAs are required for normal stem cell function in mouse, Drosophila and plants.  In addition, miRNA function is implicated in cancers.  These two themes might connect as cancer is thought to derive from cancer stem cells.  We now proceed toward understanding the function of microRNAs in HESCs in hopes of better controlling HESCs in future applications, including regenerative medicine

miRNAs, small non-coding RNA molecules are transcribed by Pol II from endogenous genes as pri-miRNAs that contain 5’ 7-methylguanosine cap and 3’ polyA-tail.  These pri-miRNAs are processed by Drosha in the nucleus to produce a stem-loop-containing pre-miRNA.  The pre-miRNA is then transported out of the nucleus, further processed by Dicer to mature 223nt long miRNAs, and incorporated into the RNA induced silencing complex (RISC).  The mature miRNA in RISC then provides the information that results in silencing of target mRNAs. To date, 462 human miRNAs have been isolated (http://microrna.sanger.ac.uk/sequences/index.shtml ), however, the cellular processes in which each of these miRNAs participate are poorly understood.  We have shown that miRNAs are essential for stem cell self-renewal in Drosophila (Hatfield et al., 2005).  Our goal is now to identity of the critical miRNAs for stem cell function in HESCs.

The goal of the project is to generate a miRNA fingerprint for different HESC lines and to identify candidate miRNAs for further functional analysis in HESCs.