Dl^M germline clones lead to the formation of compound egg chambers, in which multiple germline cysts are fused together and surrounded by a common set of epithelial follicle cells. In wild-type flies each egg chamber is unfused and is surrounded by its own follicle cells. A Dl^M cyst that is flanked by wild-type cysts can be produced by a mitotic recombination event that results in a single homozygous mutant cystoblast (and a wild-type daughter stem cell). These mutant cysts only ever fuse to the anterior adjacent wild-type cyst and never to the posterior adjacent wild-type cyst. The stalk is unable to form at the anterior of the Dl^M mutant cyst, where fusions occur, but the stalk does form at the posterior, where fusions never occur. The follicle cells migrate normally around the Dl^M mutant germline cyst but analysis of two adjacent mutant cysts shows that the double layer of follicle cells between the cysts begins to collapse at stage 7-8, with fusions between cysts mostly occurring at stage 8. Although mutant cysts cannot form polar cells at either the anterior or posterior, the oocyte is localized correctly. In contrast, the oocyte of the anterior wild-type cyst that becomes fused to the Dl^M cyst is mislocalized. Analysis of these wild-type anterior cysts at various stages of oogenesis reveals that the cysts flatten normally in region 2b of the germarium but fail to round up into a sphere, as normally occurs, which prevents the oocyte from protruding into the posterior follicle layer. Wild-type cysts with Dl^M mutant follicle cell clones do not form a stalk but are able to form polar cells at the anterior and posterior. These mutants can partially fuse to the anterior egg chamber and result in the mispositioning of the oocyte in this egg chamber.

Rank: RK2 Resembles Dl¹.