Human embryonic stem cells maintain a state of self-renewal and pluripotency through a variety of genetic regulatory mechanisms. While we know a lot about how epigenetic and transcriptional control of gene expression affects cellular homeostasis, few studies have focused on the post-transcriptional control (PTC) of gene regulatory networks. In this proposal, we aim to identify which mRNAs are direct targets of microRNAs and the RNA binding protein LIN28. MicroRNAs and LIN28 are both important in stem cells and misregulation of either can cause cancer. We have adapted new advanced genome-wide approaches to analyze LIN28’s function in human stem cells and stable lines over-expressing LIN28 (to mimic cancer situations). The first and second year of funding has enabled us to identify more than 6000 genes that are direct targets of LIN28. A fraction of our results has been published, and the remainder is currently under review. We are currently comparing miRNA targets in
human pluripotent stem cells to LIN28 targets. In the next year of funding, we expect to accomplish our proposed aims to reveal the importance of PTC in controlling pluripotency and reprogramming of human stem cells.