linesandbowlaffect the specification of cyst stem cells and niche cells in theDrosophilatestis

Abstract

To function properly, tissue-specific stem cells must reside in a niche. The Drosophila testis niche is one of few niches studied in vivo. Here, a single niche, comprising ten hub cells, maintains both germline stem cells (GSC) and somatic stem cells (CySC). Here, we show that lines is an essential CySC factor. Surprisingly, lines-depleted CySCs adopted several characteristics of hub cells, including the recruitment of new CySCs. This led us to examine the developmental relationship between CySCs and hub cells. In contrast to a previous report, we did not observe significant conversion of steady-state CySC progeny to hub fate. However, we found that these two cell types derive from a common precursor pool during gonadogenesis. Furthermore, lines mutant embryos exhibited gonads containing excess hub cells, indicating that lines represses hub cell fate during gonadogenesis. In many tissues, lines acts antagonistically to bowl, and we found that this is true for hub specification, establishing bowl as a positively acting factor in the development of the testis niche.

The stem cell niche: lessons from theDrosophilatestis

“…Hub cell specification also requires the gene bowl, which encodes a transcription factor . CySCs are also formed from SGPs, and the lines gene, which encodes an antagonist of Bowl, is required to prevent CySCs from expressing markers of hub cell fate (Hatini et al, 2005;DiNardo et al, 2011). Taken together, these studies suggest that CySCs and hub cells are derived from a common pool of precursor cells in the embryo, and that signaling through multiple pathways is required to specify the appropriate number of each cell type.…”

“…In wild-type testes, similar experiments suggest that hub cells might turn over and be replaced by neighboring somatic cells, but these results are controversial. Marked cells can be incorporated into the hub as flies age, but the number of hubs that incorporate marked cells differs significantly between experiments (Voog et al, 2008;DiNardo et al, 2011). Therefore, although it is possible that CySCs can give rise to hub cells in wild-type testes, more experiments are needed to test this model.…”

The miR-310/13 cluster antagonizes β-catenin function in the regulation of germ and somatic cell differentiation in theDrosophilatestis

“…Dividing germ cells do not undergo complete cytokinesis, but are linked by actin-rich cytoskeletal structures called fusomes (Lin et al, 1994). It has been shown that the interactions between somatic cyst cells and germ cells are crucial for a proper differentiation program (DiNardo et al, 2011;Flaherty et al, 2010;Issigonis and Matunis, 2012;Leatherman and DiNardo, 2008;Lim and Fuller, 2012). Understanding the exact mechanisms of this signaling crosstalk remains an area of active study.…”

“…Previous reports have indicated that BMP ligands, such as Dpp and Gbb, secreted from the hub and CySCs are required to inhibit differentiation of GSCs by inhibiting Bam expression (DiNardo et al, 2011;Flaherty et al, 2010;Li et al, 2007). Moreover, once Bam expression is turned off, TGFβ signaling is no longer required for the continued proliferation of the germ cells (DiNardo et al, 2011). We evaluated the levels of phosphorylated Mad (p-Mad) as a readout for TGFβ signaling in the d59 mutant testes.…”

Simultaneous control of stemness and differentiation by the transcription factor Escargot in adult stem cells: How can we tease them apart?

“…Hub cells are specified during development. [29][30][31] However, using several lineage-tracing strategies, our data suggest that under circumstances that remain to be better understood CySCs can either become and/or generate new hub cells in adult males. 1 …”