Wawersik, M. | bioRxiv Science

bioRxiv2022

Bone Morphogenetic Protein (BMP) signaling regulates germline stem cell self-renewal in the newly formed Drosophila testis stem cell niche

Bone morphogenetic proteins (BMPs) are a group of multifunctional cytokines and metabologens highly conserved in the transforming growth factor-{beta} (TGF-{beta}) superfamily. BMPs have an established role in controlling cell fate and tissue morphogenesis in a diverse range of organisms and are known to maintain stem cells in adult Drosophila testes. Additional studies in embryonic and larval testes suggest BMP regulates germ cell behavior. However, the roles of BMP signaling in controlling testis stem cell formation have yet to be directly examined. Here, we explore the pattern of BMP activation during embryonic testis niche morphogenesis as well as niche maturation in larval testes. We also assess the impact of altered BMP signaling on these stages of development. Our data suggest that BMP signaling is critical for promoting germ cell identity in primordial germ cells during embryonic niche formation. During niche maturation, we also find that that BMP signaling is both necessary and sufficient for maintenance of a self- renewing germline stem cell (GSC) population, and that newly formed cyst stem cells (CySCs) are a source of BMP activating ligand. As development progresses, however, BMP activation is no longer sufficient to alter GSC self-renewal. Collectively, our work promotes a more thorough understanding of BMP as a key mechanism controlling stem cell development in Drosophila testes that has implications for the development of other organ systems.

developmental biology↗

bioRxiv2021

Chigno/CG11180 and SUMO are Chinmo-Interacting Proteins with a Role in Drosophila Testes Stem Cells

Maintenance of sexual identity on the cellular level ensures the proper function of sexually dimorphic genes expressed in the brain and gonads. Disruption of genes that regulate sex maintenance alters the cellular structure of these tissues and leads to infertility and diseases, such as diabetes, obesity, and gonadal cancers. Sex maintenance in the testis of Drosophila melanogaster depends on the previously identified gene chinmo (Chronologically inappropriate morphogenesis). Chinmos effect on testis differentiation has been investigated in detail, but there is still much to be elucidated about its structure, function, and interactions with other proteins. Using a two-hybrid screen, we find that Chinmo interacts with itself, the small ubiquitin-like modifier SUMO, the novel protein CG11180, and four other proteins (CG4318, Ova (Ovaries absent), Taf3 (TBP-associated factor 3), and CG18269). Since both Chinmo and CG11180 contain sumoylation sites and SUMO-interacting motifs (SIMs), we analyzed their interaction in more detail. Using site-directed mutagenesis of a unique SIM in CG11180, we demonstrate that Chinmos interaction with CG11180 is SUMOdependent. Furthermore, to assess the functional relevance of both SUMO and CG11180, we performed RNAi-mediated knockdown of both proteins in somatic cells of the Drosophila testis. Using this approach, we find that CG11180 and SUMO are required in somatic cells of adult testes, and that reduction of either protein causes formation of germ cell tumors. Overall, our work indicates that SUMO functionally links Chinmo and CG11180 in somatic cells of the adult Drosophila testis. Consistent with the CG11180 knockdown phenotype in male testes, and to underscore its connection to Chinmo, we propose the name Childless Gambino (Chigno) for CG11180.

developmental biology↗