Impaired chromosome segregation results in sperms with excess centrosomes inemb-27^APC6mutantC. elegans

Abstract

The anaphase-promoting complex (APC) is a major regulator of chromosome segregation and is implicated in centriole engagement, whose de-regulation causes abnormal number of centrosomes. The emb-27 gene in C. elegans encodes a subunit of APC. The paternal emb-27 mutant was reported to show cell division with multiple furrows, suggesting the presence of excess centrosomes. In this study, we examined the number of centrosomes and the mechanism underlying de-regulation of centrosome number in emb-27 mutants. Our observations indicated excess centrosomes in emb-27 sperms, which resulted in zygotes with excess centrosomes. Further, the secondary spermatocyte of emb-27 produced reduced number of spermatids, which is likely the direct cause of the excess number of centrosomes per sperm. We propose that a chromosome segregation defect in emb-27 induced centrosome separation defect, resulting in reduced number of buds. Additionally, treatment with cytoskeletal inhibiting drugs indicated presence of three kinds of forces working in combination to move the centrosomes into the spermatids. The present study suggested a novel role of microtubule in the budding cytokinesis of spermatocytes. Azimzadeh, J. and Bornens, M. (2007). Structure and duplication of the centrosome. J. Cell Sci. 120, 2139-2142. Bobinnec, Y., Fukuda, M. and Nishida, E. (2000). Identification and characterization of Caenorhabditis elegans gamma-tubulin in dividing cells and differentiated tissues.

Choice between 1- and 2-furrow cytokinesis inCaenorhabditis elegansembryos with tripolar spindles

“…In this manuscript, we call the cytokinesis that forms 2 cytokinetic furrows and divides the cell into 3 as "2-furrow cytokinesis", whereas "1-furrow cytokinesis" refers to a usual cytokinesis with 1 cytokinetic furrow that divides the cell into 2. We have recently shown that the paternal emb-27 mutant embryos possesses 3 or more centrosomes (Kondo and Kimura, 2018), as expected from the previous report . An unexpected result was the frequency of cells with 3 or more centrosomes in the mutant embryos was about 70% (Kondo and Kimura, 2018).…”

“…We have recently shown that the paternal emb-27 mutant embryos possesses 3 or more centrosomes (Kondo and Kimura, 2018), as expected from the previous report . An unexpected result was the frequency of cells with 3 or more centrosomes in the mutant embryos was about 70% (Kondo and Kimura, 2018). This high frequency is seemingly inconsistent with the defective mitosis observed only in one-third of the embryos .…”

“…We have previously quantified the number of the centrosomes in paternal emb-27 mutant embryos and found that ~70% of the mutant embryos possessed 3 or more centrosomes (Kondo and Kimura, 2018). This seemed inconsistent with the previous report that only one-third of the mutant embryos showed defective mitosis .…”

“…The strains used in this study are listed in Table S1, and made in our another study (Kondo and Kimura, 2018). Strains were maintained under standard conditions (Brenner, 1974).…”

“…Measurement of centrosome size using γ-tubulin::GFP fluorescence ( Fig. 5D) was conducted as described in our another study (Kondo and Kimura, 2018).…”