title: The conserved kinase SRPK regulates karyosome formation and spindle microtubule assembly in Drosophila oocytes.
abstract: In Drosophila oocytes, after the completion of recombination, meiotic chromosomes form a compact cluster called the karyosome within the nucleus, and later assemble spindle microtubules without centrosomes. Although these oocyte-specific phenomena are also observed in humans, their molecular basis is not well understood. Here, we report essential roles for the conserved kinase SRPK in both karyosome formation and spindle microtubule assembly in oocytes. We have identified a female-sterile srpk mutant through a cytological screen for karyosome defects. Unlike most karyosome mutants, the karyosome defect is independent of the meiotic recombination checkpoint. Heterochromatin clustering found within the wild-type karyosome is disrupted in the mutant. Strikingly, a loss of SRPK severely prevents microtubule assembly for acentrosomal spindles in mature oocytes. Subsequently, bi-orientation and segregation of meiotic chromosomes are also defective. Therefore, this study demonstrates new roles of this conserved kinase in two independent meiotic steps specific to oocytes.
authors.affiliation: The Wellcome Trust Centre for Cell Biology, School of Biological Sciences, The University of Edinburgh, Edinburgh EH9 3JR,  UK.
authors.forename: Benjamin J
authors.initials: BJ
authors.lastname: Loh
authors.forename: C Fiona
authors.initials: CF
authors.lastname: Cullen
authors.forename: Nina
authors.initials: N
authors.lastname: Vogt
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Ohkura
mesh_terms: D000818:Animals; D059447:Cell Cycle Checkpoints; D002503:Centromere / Q000378:metabolism; D059006:Chromosomes, Insect / Q000378:metabolism*; D017124:Conserved Sequence; D029721:Drosophila Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000166:cytology* / Q000201:enzymology*; D005260:Female; D008540:Meiosis; D009154:Mutation / Q000235:genetics; D009865:Oocytes / Q000166:cytology / Q000201:enzymology*; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008941:Spindle Apparatus / Q000201:enzymology*
chemical_list: D029721:Drosophila Proteins; C580703:SRPK protein, Drosophila; D017346:Protein Serine-Threonine Kinases