dSTAM expression pattern during wild type and mutant egg chamber development in D. melanogaster

STAM (signal-transducing adaptor molecule) is a protein highly conserved from yeast to mammals. In Drosophila melanogaster the basic molecular architecture of the protein is comprised of a N-terminal VHS domain, an ubiquitin-interacting motif and a central Src homology-3 domain. In this paper we examine the expression pattern of the stam gene and the localisation of the STAM protein during D. melanogaster oogenesis. Its transcript is present throughout egg chamber development in all germ-line cells, including the oocyte. dSTAM is firstly detected in germarial region 2, where the protein is present in the newly formed germ-line cysts and is mainly accumulated into the oocyte. As oogenesis proceeds, dSTAM is enriched in the perinuclear region of the nurse cells and is also found in the somatic polar follicular cells. In the oocyte, the protein is more abundant posteriorly and becomes restricted to the posterior pole just before disappearing at stage 10b. We show that dSTAM localisation is unaffected in the oocyte of grk mutant egg chambers, indicating that it is not dependent on the polarity of the microtubule network. In contrast, dSTAM distribution is remarkably altered in cup mutant oocytes where the protein accumulates in a round central spot and never reaches the posterior pole.