PgmNr D1227: The Role of PVR in Drosophila Testis Stem Cells.

Authors:
Nastaran SoleimaniBarzi; Jade Koretko; Kenneth Hammer; Judith Leatherman


Institutes
University of Northern Colorado, Greeley, CO.


Keyword: niche and other local signaling

Abstract:

Adult stem cells live in different tissues and they support the tissue they reside in. The stemness behavior is regulated by the environment they reside in, called the stem cell niche. The niche environment in mammals is complex, which makes it hard to study, therefore we use the Drosophila testis as a simple model to study adult stem cells in their niche. In the Drosophila testis niche there are two populations of stem cells: germline stem cells (GSCs), which will differentiate into sperm, and cyst stem cells (CySCs) that will differentiate into cyst cells. These stem cells are physically in contact with a group of somatic cells known as the hub. As long as they stay in contact to the hub, they will remain stem cells. CySCs and their lineage play a crucial role in self-renewal and differentiation of GSCs. EGFR, a member of Receptor Tyrosine Kinase (RTK) family, is known to promote differentiation in cyst lineage. PVR (PGFG-VEGF-related receptor) is another member of RTK family that is expressed in the cyst lineage. This led us to ask the question whether PVR functions similarly to EGFR, or whether it has a distinct function. Pvf1, the ligand for PVR, is restricted to the hub, suggesting that PVR signaling is only activated in CySCs, not cyst cells. We hypothesize that PVR is one required factor in CySC self-renewal. In order to test our hypothesis we used two strategies, PVR gain of function and PVR loss of function. For gain of function we expressed a constitutive PVR transgene, which caused cyst-lineage cells to divide away from the hub, where they would normally differentiate. For loss of function we expressed PVR RNAi transgenes, a dominant negative PVR transgene, and performed mosaic analysis.   Our results show a reduction in CySC number when PVR is ablated in the cyst lineage.  In conclusion, PVR is required to maintain the normal cyst stem cell population in Drosophila testes. Future work will examine whether PVR is required to maintain normal cell division rates in these stem cells.



Flybase Genetic Index:
1. FlyBase gene symbol: Pvr; FBgn: FBgn0032006