The role of anillin in meiotic cytokinesis of Drosophila males

Anillin is a 190 kDa actin-binding protein that concentrates in the leading edges of furrow canals during Drosophila cellularization and in the cleava ge furrow of both somatic and meiotic cells. We analyzed anillin behavior d uring D, melanogaster spermatogenesis, and focused on the relationships bet ween this protein and the F-actin enriched structures. In meiotic anaphases anillin concentrates in a narrow band around the cell equator. Cytological analysis of wild-type meiosis and examination of mutants defective in cont ractile ring assembly (chickadee and KLP3A), re revealed that the formation of the anillin cortical band occurs before, and does not require the assem bly of the F-actin based contractile ring. However, once the acto-myosin ri ng is assembled, the anillin band precisely colocalizes with this cytokinet ic structure, accompanying its contraction throughout anaphase and telophas e. In chickadee and KLP3A mutant ana-telophases the cortical anillin band f ails to constrict, indicating that its contraction is normally driven by th e cytokinetic ring. These findings, coupled with the analysis of anillin be havior in twinstar mutants, suggested a model on the role of anillin during cytokinesis, During anaphase anillin would concentrate in the cleavage fur row before the assembly of the contractile ring, binding the equatorial cor tex, perhaps through its carboxy-terminal pleckstrin homology (PH) domain. Anillin would then interact with the actin filaments of the acto-myosin rin g through its actin-binding domain, anchoring the contractile ring to the p lasma membrane throughout cytokinesis.