Identifying target genes for the stem cell transcription factor Zfh1 in the Drosophila testis. Qi Zheng^1,3, Stephen DiNardo^2,3. 1) Department of Biology, School of Arts and Sciences, Univ Pennsylvania, Philadelphia, PA; 2) Dept Cell & Developmental Biol, Perelman Sch Med, Univ Pennsylvania, Philadelphia, PA; 3) Penn Institute for Regenerative Medicine, Philadelphia, PA.

   Understanding how stem cells are maintained in their microenvironment (the niche) is vital for their application in regenerative medicine. Studies of Drosophila male germline stem cells (GSCs) have served as a paradigm in niche-stem cell biology. Recent work from our lab identified the transcription factor Zfh1, which is necessary and sufficient for cyst stem cell (CySC) self-renewal (Leatherman and DiNardo, 2008). Interestingly, sustained zfh1 expression in the cyst lineage can also nonautonomously cause neighboring germ cells to become GSCs (Leatherman and DiNardo, 2008). Therefore CySCs function as part of the niche, in a role governed by Zfh1. Since we find that neither STAT nor BMP pathway activation intrinsically in germline cells, nor both STAT and BMP together, is sufficient to generate GSCs, there must exist an unidentified GSC renewal signal(s) from CySCs that is controlled by Zfh1. Here we report our progress in attempting to identify Zfh1 target genes in CySCs using a ChIP-Seq approach.