Drosophila Polo Kinase Is Required for Cytokinesis

Abstract

A number of lines of evidence point to a predominance of cytokinesis defects in spermatogenesis in hypomorphic alleles of the Drosophila polo gene. In the pre-meiotic mitoses, cytokinesis defects result in cysts of primary spermatocytes with reduced numbers of cells that can contain multiple centrosomes. These are connected by a correspondingly reduced number of ring canals, structures formed by the stabilization of the cleavage furrow. The earliest defects during the meiotic divisions are a failure to form the correct mid-zone and mid-body structures at telophase. This is accompanied by a failure to correctly localize the Pavarotti kinesin- like protein that functions in cytokinesis, and of the septin Peanut and of actin to be incorporated into a contractile ring. In spite of these defects, cyclin B is degraded and the cells exit M phase. The resulting spermatids are frequently binuclear or tetranuclear, in which case they develop either two or four axonemes, respectively. A significant proportion of spermatids in which cytokinesis has failed may also show the segregation defects previously ascribed to polo1 mutants. We discuss these findings in respect to conserved functions for the Polo-like kinases in regulating progression through M phase, including the earliest events of cytokinesis.

SIAH-1 inhibits cell growth by altering the mitotic process

“…Monopolar spindles nucleated by centrosomes which appear duplicated but are not separated, can be observed. Drosophila polo mutants also show polyploid cells in larval brains along with multipolar spindles during male meiosis (Carmena et al, 1998). Citron kinase, a target of Rho protein, has been also implicated in cytokinesis.…”

Xenopus Polo-like kinase Plx1: a multifunctional mitotic kinase

“…Polo-like kinases have been shown to play a role in cytokinesis, and much of the evidence came from studies on Schizosacchanomyces pombe (Ohkura et al, 1995;Bahler et al, 1998), Drosophila (Carmena et al, 1998), and more recently, S. cerevisiae (Song and Lee, 2001). In the absence of Plo1 activity, formation of a division septum is impaired in fission yeast, whereas overexpression of Plo1 leads to formation of an ectopic septum.…”

“…In the absence of Plo1 activity, formation of a division septum is impaired in fission yeast, whereas overexpression of Plo1 leads to formation of an ectopic septum. In Drosophila, cytokinesis can fail at all stages of spermatogenesis in polo mutants (Carmena et al, 1998). In budding yeast, depletion of Cdc5 results in arrests at multiple points during mitosis, suggesting a failure of cytokinesis (Song and Lee, 2001).…”

Yeast polo-like kinases: functionally conserved multitask mitotic regulators

“…A growing body of evidence suggests that Plks play a role in cytokinesis of diverse organisms (Ohkura et al, 1995;Mundt et al, 1997;Bahler et al, 1998;Carmena et al, 1998;Lee et al, 1999;Song and Lee, 2001;Tanaka et al, 2001). In fission yeast, loss of Plo1 function leads to the generation of multinucleate cells with defects in actin ring and septum formation, suggesting that Plo1 activity may be required for at least two important cytokinetic events.…”