PMID:27170181

Citation	Varadarajan, R, Ayeni, J, Jin, Z, Homola, E and Campbell, SD (2016) Myt1 inhibition of Cyclin A/Cdk1 is essential for fusome integrity and premeiotic centriole engagement in Drosophila spermatocytes. Mol. Biol. Cell 27:2051-63
Abstract	Regulation of cell cycle arrest in premeiotic G2 phase coordinates germ cell maturation and meiotic cell division with hormonal and developmental signals by mechanisms that control Cyclin B synthesis and inhibitory phosphorylation of the M-phase kinase, Cdk1. In this study, we investigated how inhibitory phosphorylation of Cdk1 by Myt1 kinase regulates premeiotic G2 phase of Drosophila male meiosis. Immature spermatocytes lacking Myt1 activity exhibit two distinct defects: disrupted intercellular bridges (fusomes) and premature centriole disengagement. As a result, the myt1 mutant spermatocytes enter meiosis with multipolar spindles. These myt1 defects can be suppressed by depletion of Cyclin A activity or ectopic expression of Wee1 (a partially redundant Cdk1 inhibitory kinase) and phenocopied by expression of a Cdk1F mutant defective for inhibitory phosphorylation. We therefore conclude that Myt1 inhibition of Cyclin A/Cdk1 is essential for normal fusome behavior and centriole engagement during premeiotic G2 arrest of Drosophila male meiosis. The novel meiotic functions we discovered for Myt1 kinase are spatially and temporally distinct from previously described functions of Myt1 as an inhibitor of Cyclin B/Cdk1 to regulate G2/MI timing.
Links	PubMed PMC4927279 Online version:10.1091/mbc.E16-02-0104
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
DROME:CCNA		GO:0045169: fusome	ECO:0000314:		C		Organism: Drosophila (fruit fly) Protein:G2/mitotic-specific cyclin-A Figure 1E: Arrows shown in myt1/+ mature spermatocytes indicate Cyclin A enrichment at fusomes	complete CACAO 12422
DROME:CCNA		GO:0005737: cytoplasm	ECO:0000314:		C		Organism: Drosphila (fruit fly) Protein: G2/mitotic-specific cyclin-A Figure 1E)Cyclin A is detected primarily in the cytoplasm in stage S6 myt1/+ and myt1 mutant spermatocytes	complete CACAO 12423
DROME:CCNA		GO:0001673: nucleus	ECO:0000314:		C		Organism: Drosophila (fruit fly) Protein: G2/mitotic-specific cyclin-A Figure 1E) Cyclin A is detected primarily in the cytoplasm in stage S6 myt1/+ and myt1 mutant spermatocytes, but by prometaphase I, it can also be seen in the nucleus.	complete CACAO 12424
DROME:CDK1		GO:0045169: fusome	ECO:0000314:		C		Drosophila melanogaster CDK1 Figure 2. Cdk1(WT)-GFP localizes to fusomes	complete CACAO 12339

References

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