| SOX2 is a transcription factor critical for maintenance of the stem cell state. It plays a major role in the development of the central nervous system (CNS), as it is required for the proliferation and maintenance of neural stem cells as well as neurogenesis. In this work, I show that SOX2 is a crucial factor for the maintenance of pluripotency and self-renewal in hES cells and further elucidate its role in the regulation of the survival gene, TRKC. I also present evidence that SOX2 can interact with the POU transcription factor OCT1 in the regulation of TRKC, demonstrating a novel SOX2 protein-protein interaction in human embryonic stem (hES) cells.;By using siRNA to reduce levels of SOX2 expression, I find that loss of SOX2 significantly affects the morphology of hES cells as well as downregulates markers of pluripotent hES cells, OCT4, TRA-1-81, SSEA-3, and SSEA-4. In addition to reducing SOX2 levels, I knocked down expression of OCT4 and NANOG and find that the expression of the three factors depends on each other to maintain the stem cell state. Loss of SOX2 also causes hES cells to differentiate into trophectoderm, as well as affect a number of downstream target genes, which may be important for the stem cell state. I also demonstrate that SOX2 can regulate the TRKC gene, a gene important for the survival of single hES cells. Through RNAi of SOX2, I found the expression of TRKC to be significantly downregulated indicating that SOX2 has a regulatory effect on TRKC gene expression. SOX2 is able to physically bind to a particular SOX2 binding motif on the regulatory region of the gene and efficiently drive expression. I also present data that suggests SOX2 can interact with the OCT1 transcription factor to possibly regulate TRKC. This data is novel in hES cells, indicating that there may be many undiscovered interactions between SOX2 and other transcription factors. |
