GENE REGULATION IN PLURIPOTENT STEM CELLS

Abstract

Murine endogenous retrovirus with leucine tRNA primer (MERVL) repeats belong to type III endogenous retroviruses and are specifically expressed at the 2C stage. Use of 5’ long terminal repeat (LTR) of MERVL as a functional promoter in reporter line enabled identification of 2C-like cells, which are totipotent-like cells that have been reported to arise spontaneously in normal mouse embryonic stem cell (mESCs) cultures, and able to reactivate MERVL transcripts. In this study, I performed gain-of-function screening and identified ZFP352 that can increase percentage of 2C-like cells. Further characterization shows that overexpression of ZFP352 in mESCs can increase the expression level of several 2C-enriched markers, including MERVL transcripts, albeit no significant changes in pluripotency markers. I generated Zfp352-knockout clonal lines and found that there is a reduction of MERVL-transcripts and those 2C-enriched markers as compared to wild type. ZFP352-Chromatin immunoprecipitation followed by sequencing (ChIP-Seq) revealed evidence of strong enrichment of ZFP352 peaks at MT2 repeat element, as well as discovered that the de novo motif is octamer ATTAAAGG, which is also enriched in MT2 class.