Stella Regulates the Development of Female Germline Stem Cells by Modulating Chromatin Structure and DNA Methylation.

Female germline stem cells (FGSCs) have the ability to self-renew and differentiate into oocytes. Stella, encoded by a maternal effect gene, plays an important role in oogenesis and early embryonic development. However, its function in FGSCs remains unclear. In this study, we showed that CRISPR/Cas9-mediated knockout of Stella promoted FGSC proliferation and reduced the level of genome-wide DNA methylation of FGSCs. Conversely, Stella overexpression led to the opposite results, and enhanced FGSC differentiation. We also performed an integrative analysis of chromatin immunoprecipitation followed by high-throughput sequencing (ChIP-seq), high-throughput genome-wide chromosome conformation capture (Hi-C), and use of our published epigenetic data. Results indicated that the binding sites of STELLA and active histones H3K4me3 and H3K27ac were enriched near the TAD boundaries. Hi-C analysis showed that Stella overexpression attenuated the interaction within TADs, and interestingly enhanced the TAD boundary strength in STELLA-associated regions. Taking these findings together, our study not only reveals the role of Stella in regulating DNA methylation and chromatin structure, but also provides a better understanding of FGSC development.