SR Protein Kinase is expressed in Drosophila ovarian germline stem cells but is not essential for their self-renewal.

Germline stem cells (GSCs) are necessary for oocyte production in Drosophila . GSC maintenance is regulated by intrinsic factors that promote their self-renewal. One such factor, the beta-importin, Transportin-Serine/Arginine rich , mediates nuclear import of serine/arginine-rich (SR) proteins, which are phosphorylated by SR protein kinases. Here, we investigate whether the kinase encoded by SR protein kinase ( SRPK ) is essential for GSC self-renewal. We find that SRPK is expressed in GSCs and their mitotically-dividing daughters, but is not necessary for GSC establishment or maintenance. We conclude that SRPK is dispensable for GSC self-renewal, and postulate that other protein kinases can compensate for its absence.