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The study of adult stem cells in modern day research provides pertinent information about the development of organisms, how they grow, and how tissue is maintained. Drosophila melanogaster provide an ideal model for in vivo stem cell research, with one of the best-characterized niches in the testis. The testis stem cell niche consists of a hub that provides signals to the local stem cells, germline stem cells (GSCs), and cyst stem cells (CySCs). The CySCs produce cyst cell lineage that will provide support for the GSC daughter cells, which differentiate into sperm. Previously, Matunis, et al. determined the function of shn, a cofactor in the BMP signaling pathway, within the cyst cell lineage. Shn was found to non-autonomously control the ability of the cyst cell lineage to regulate the transit amplification of encysted germline cells. Without shn in cyst lineage cells, germline cells overproliferated and failed to undergo spermatid differentiation (Matunis et al., 1997). We hypothesize that Schnurri (Shn) promotes the differentiation of cyst cells and is sufficient to induce differentiation of CySCs within the stem cell niche. We found that schnurri expression is specifically repressed in the CySCs. When we inhibited shn within the cyst lineage cells by RNAi, we found a significant increase in the number of CySCs and early cyst lineage cells, supporting the hypothesis that Shn is necessary for differentiation. Furthermore, the UAS/Gal4 system was utilized to misexpress shn within the CySCs. We observed a significant decrease in the number of CySCs, which we hypothesize is due to the increased differentiation of CySCs. However, there was only a reduction, suggesting shn is not a master regulator, but rather a part of the process. Interestingly, we also saw an increase in the number of early cyst lineage cells suggesting a misregulation in the cyst lineage differentiation process. In the future, the understanding of the misregulation occurring in the cyst lineage and germline cell during their differentiation processes should be explored to further understand the role of shn in the testis niche.

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Available for download on Wednesday, December 01, 2021