Author response: Neuronal octopamine signaling regulates mating-induced germline stem cell increase in female Drosophila melanogaster

Experiments in cultured cells with Ran-binding protein M (RanBPM) suggest that it links cell surface receptors and cell adhesion proteins. In this study, we undertake a genetic study of RanBPM function in the germline stem cell (GSC) niche of Drosophila melanogaster ovaries. We find that two RanBPM isoforms are produced from alternatively spliced transcripts, the longer of which is specifically enriched in the GSC niche, a cluster of somatic cells that physically anchors GSCs and expresses signals that maintain GSC fate. Loss of the long isoform from the niche causes defects in niche organization and cell size and increases the number of GSCs attached to the niche. In genetic mosaics for a null RanBPM allele, we find a strong bias for GSC attachment to mutant cap cells and observe abnormal accumulation of the adherens junction component Armadillo (β-catenin) and the membrane skeletal protein Hu-li tai shao in mutant terminal filament cells. These results implicate RanBPM in the regulation of niche capacity and adhesion.

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The Bric-à-Brac transcription factors are necessary for formation of functional germline stem cell niches through control of dpp expression in the Drosophila melanogaster ovary

10.1101/689323 ◽

2019 ◽

Author(s):

Laurine Miscopein Saler ◽

Mathieu Bartoletti ◽

Virginie Hauser ◽

Anne-Marie Pret ◽

Laurent Theodore ◽

...

Keyword(s):

Drosophila Melanogaster ◽

Stem Cell ◽

Transcription Factors ◽

Germ Cells ◽

Primordial Germ Cells ◽

Somatic Cells ◽

Bmp Signaling ◽

Germline Stem Cell ◽

Larval Stages ◽

Functional Germline

AbstractMany studies have focused on the mechanisms of stem cell maintenance via their interaction with a particular niche or microenvironment in adult tissues, but how formation of a functional niche is initiated, including how stem cells within a niche are established, is less well understood. Adult Drosophila melanogaster ovary Germline Stem Cell (GSC) niches are comprised of somatic cells forming a stack called a Terminal Filament (TF) and underlying Cap Cells (CCs) and Escort Cells (ECs), which are in direct contact with GSCs. In the adult, the Engrailed (En) transcription factor is specifically expressed in niche cells where it directly controls expression of the decapentaplegic gene (dpp) encoding a member of the Bone Morphogenetic Protein (BMP) family of secreted signaling molecules, which are key factors for GSC maintenance. In late third instar larval ovaries, in response to BMP signaling from newly-formed niches, adjacent primordial germ cells become GSCs. The bric-à-brac paralogs (bab1 and bab2) encode BTB/POZ-domain containing transcription factors, that are also expressed in developing GSCs niches where they are required for TF formation. Here, we demonstrate that Bab1 and Bab2 display redundant cell autonomous function for TF morphogenesis and we identify a new function for these genes in GSC establishment. Moreover, we show that Bab proteins control dpp expression in otherwise correctly specified CCs, independently of En and its paralog Invected (Inv). In fact, our results also indicate that en/inv function in larval stages are neither essential for TF formation, nor GSC establishment. Finally, when bab2 was overexpressed in ovarian somatic cells outside of the niche, where en/inv were not expressed, ectopic BMP signaling activation was induced in adjacent germ cells of adult ovaries, which formed GSC-like tumors. Together, these results indicate that Bab transcription factors are positive regulators of BMP signaling for acquisition of GSC status.

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Notch signaling is required for survival of the germline stem cell lineage in testes of Drosophila melanogaster

10.1101/682773 ◽

2019 ◽

Author(s):

Chun L. Ng ◽

Qian Yue ◽

Schulz Cordula

Keyword(s):

Drosophila Melanogaster ◽

Stem Cell ◽

Notch Signaling ◽

Transition Zone ◽

Cell Lineage ◽

Germline Stem Cell ◽

Germline Stem Cells ◽

Stem Cell Lineage ◽

Cyst Cells ◽

Germline Cells

AbstractIn all metazoan species, sperm is produced from germline stem cells. These self-renew and produce daughter cells that amplify and differentiate dependent on interactions with somatic support cells. In the male gonad of Drosophila melanogaster, the germline and somatic cyst cells co-differentiate as cysts, an arrangement in which the germline is completely enclosed by cytoplasmic extensions from the cyst cells. Notch is a developmentally relevant receptor in a pathway requiring immediate proximity with the signal sending cell. Here, we show that Notch is expressed in the cyst cells of wild-type testes. Notch becomes activated in the transition zone, an apical area of the testes in which the cyst cells express stage-specific transcription factors and the enclosed germline finalizes transit-amplifying divisions. Reducing the ligand Delta from the germline cells via RNA-Interference or reducing the receptor Notch from the cyst cells via CRISPR resulted in cell death concomitant with loss of germline cells from the transition zone. This shows that Notch signaling is essential for the survival of the germline stem cell lineage.

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