Spermatocyte cytokinesis requires rapid membrane addition mediated by ARF6 on central spindle recycling endosomes

Abstract

The dramatic cell shape changes during cytokinesis require the interplay between microtubules and the actomyosin contractile ring, and addition of membrane to the plasma membrane. Numerous membrane-trafficking components localize to the central spindle during cytokinesis, but it is still unclear how this machinery is targeted there and how membrane trafficking is coordinated with cleavage furrow ingression. Here we use an arf6 null mutant to show that the endosomal GTPase ARF6 is required for cytokinesis in Drosophila spermatocytes. ARF6 is enriched on recycling endosomes at the central spindle, but it is required neither for central spindle nor actomyosin contractile ring assembly, nor for targeting of recycling endosomes to the central spindle. However, in arf6 mutants the cleavage furrow regresses because of a failure in rapid membrane addition to the plasma membrane. We propose that ARF6 promotes rapid recycling of endosomal membrane stores during cytokinesis, which is critical for rapid cleavage furrow ingression.

Mutations inCog7affect Golgi structure, meiotic cytokinesis and sperm development duringDrosophilaspermatogenesis

“…However, loss of Cog7 and the consequent Golgi defects did not substantially affect cytokinesis of neuroblasts. Other mutations in membrane traffic components such as fwd, fws, bru, gio and Arf6 disrupt spermatocyte cytokinesis causing little or no effects on cytokinesis of larval neuroblasts or S2 cells (Brill et al, 2000;Eggert et al, 2004;Farkas et al, 2003;Giansanti et al, 2004;Giansanti et al, 2006;Dyer et al, 2007;Robinett et al, 2009). The large size of spermatocytes and the rapid succession of two meiotic divisions might explain the particular requirement of male meiotic cytokinesis for vesicle trafficking pathways.…”

“…For example, Drosophila spermatocytes are quite large cells (more than 20 mm in diameter), that complete two meiotic divisions in less than two hours (Fuller, 1993;Giansanti et al, 2012). Spermatocyte cytokinesis proved to be sensitive to mutations affecting vesicle traffic components (Brill et al, 2000;Farkas et al, 2003;Dyer et al, 2007;Gatt and Glover, 2006;Giansanti et al, 2006;Giansanti et al, 2007;Polevoy et al, 2009;Robinett et al, 2009;Xu et al, 2002a;Zhou et al, 2011). During Drosophila spermiogenesis, round spermatids, ,12 mm in diameter, undergo drastic morphological changes in cell surface before reaching the impressive 1.8 mm in length of sperm tails (Fuller, 1993;Tates, 1971;Zhou et al, 2011).…”

Cytokinesis in Animal Cells

“…Nuf fails to bind to Arf6 and depends on Rab11 for its recruitment to the cell midzone Riggs et al 2003;Giansanti et al 2007). However, Arf6 is still required for furrow ingression in Drosophila spermatocytes, in which it acts downstream of Rab4/Rab11 endosomes (Dyer et al 2007). Interestingly, Drosophila ARF6 binds to the centralspindlin component Pav ( Table 1), suggesting that this association might contribute to Arf6 recruitment to central spindle endosomes (Dyer et al 2007).…”

The BRAG/IQSec family of Arf GEFs

“…10 In this regard, BRAG2 has been reported to drive endocytosis of another cadherin, E-cadherin, in vertebrate cells in response to both EGF 7 and HGF. 11 It should be noted that while loner was originally characterized as an Arf6 GEF, complete loss of Arf6 in flies does not inhibit myoblast fusion; 12 it is therefore possible that one or more other Arfs fulfill that role. However, vertebrate myoblasts (C2C12 cells) do appear to require Arf6 for fusion, at least in part through its downstream activation of the lipid modifying enzymes phospholipase D and the PI4P5 kinase PIP5Kg.…”