A Non–Cell Autonomous Role of E ( z ) to Prevent Germ Cells from Turning on a Somatic Cell Marker

Abstract

In many metazoans, germ cells are separated from somatic lineages early in development and maintain their identity throughout life. Here we show that a Polycomb group (PcG) component, Enhancer of Zeste [E(z)] H3K27me3-specific methyltransferase, maintains germline identity in Drosophila adult testes. We find excessive early-stage somatic gonadal cells in E(z) mutant testes, which originate from both overproliferative cyst stem cells and germ cells turning on an early-stage somatic cell marker. Using complementary lineage-tracing experiments in E(z) mutant testes, a portion of excessive early-stage somatic gonadal cells are found to originate from early-stage germ cells, including germline stem cells. Moreover, knocking down E(z) specifically in somatic cells caused this change, suggesting a non-cell autonomous role of E(z) to antagonize somatic identity in germ cells.

SUMO regulates somatic cyst stem cells maintenance and directly targets hedgehog pathway in adult Drosophila testis

“…1A). Several signaling pathways have been reported to regulate CySCs, including the JAK-STAT pathway (Issigonis et al, 2009;Kiger et al, 2001;Leatherman and DiNardo, 2010;Singh et al, 2010;Tulina and Matunis, 2001), the EGFR pathway (Eun et al, 2014;Kiger et al, 2000;Tran et al, 2000), the Hpo pathway (Amoyel et al, 2014) and the Hh pathway (Amoyel et al, 2013;Michel et al, 2012;Zhang et al, 2013b). Although these pathways govern stem cell behavior, the function of PTMs during this process is rarely reported.…”

Repression of somatic cell fate in the germline

“…In somatic gonadal cells, E(Z) might regulate signaling pathways involved in the proper communication between the germline and its cellular microenvironment. Supporting this hypothesis, ChIPseq experiments revealed that, in somatic gonadal cells, H3K27me3 is enriched at genes involved in Wnt and epidermal growth factor (EGF) signaling pathways [119].…”

“…By contrast, while Drosophila RBPs play a conserved role in translational control of germ stem cell differentiation (reviewed in [118]), experimental evidence supporting a function in repressing somatic genes expression in the germline and/or promoting maintenance of germ cell fate is lacking. Instead, repressive histone marks appear to be essential for the repression of somatic gene expression in the male germline [119]. Recent studies suggest that additional mechanisms, including chromatin regulation and P granules are also required for the repression of somatic fate in the adult germline of C. elegans [9].…”

“…The only study available so far points to a role of repressive chromatin in repressing expression of a somatic marker in Drosophila adult testes [119]. cyst stem cells (reviewed in [150,151]).…”

Regulation of Stem Cells in Their Niche

“…Interestingly, E(z) functions in CySCs in a non-cell autonomous manner to convert early stage-germ cells (GSCs, GBs, and/or 2-cell spermatogonia) to cyst cells. It has thus been hypothesized that lineage conversion occurs through E(z)-mediated changes to EGFR and Wg signaling between both germ-and cyst-cells, as H3K27me3 is enriched at the gene loci of components of both pathways, with removal of one copy of egfr (EGF receptor) sufficient to suppress E(z) null phenotypes [36].…”