361C Poster - 04. Stem cells, regeneration and tissue injury
Saturday April 09, 1:30 PM - 3:30 PM

Authors:
Anna Williams; Elizabeth Ables

Affiliation: East Carolina University

Keywords:
b. germline stem cell; b. oogenesis

The maintenance of species is dependent on parental genetic information being passed onto the next generation. Germ cells are crucial for this transfer and therefore drive evolution. Evolutionarily conserved across phyla, germ cells in many systems are supported by a stem cell population (GSCs). In Drosophila, these stem cells divide via incomplete cytokinesis to form interconnected daughter cells that will mitotically divide and differentiate to form oocytes and nurse cells, which supply the oocyte with maternal factors necessary for embryogenesis. Connection of daughter cells is facilitated by the fusome, an endoplasmic reticulum-like structure with cytoskeletal and membranous components. The fusome is remodeled after every division and becomes increasingly branched as the cysts continue to divide. Tnpo-SR, an ecdysone-responsive gene, was identified in a genetic screen for its putative role in stem cell self-renewal. Tnpo-SR shares amino acid similarity to mammalian β-importin proteins; however, its specific roles in gamete production has not been characterized. Using genetic mosaic mutants alongside germline-specific RNAi, we found that Tnpo-SR is necessary in GSCs for their self-renewal. Depletion of Tnpo-SR in dividing germ cells generates egg chambers with cells varying from the typical 16 suggesting abnormal cyst development and cyst fragmentation. Here, we investigated the cytoskeletal dynamics of Tnpo-SR mutant GSCs and cystoblasts in order to further characterize the role of Tnpo-SR in GSC self-renewal. We find that GSC fusome density is decreased when Tnpo-SR is depleted, suggesting its role in GSC fusome morphogenesis. The alteration of cyst formation also impacts oocyte selection. This research identifies a novel role of the karyopherin Tnpo-SR on not only GSC formation and maintenance but also the formation of a healthy egg needed to drive the maintenance of species.