title: Lateral and End-On Kinetochore Attachments Are Coordinated to Achieve Bi-orientation in Drosophila Oocytes.
abstract: In oocytes, where centrosomes are absent, the chromosomes direct the assembly of a bipolar spindle. Interactions between chromosomes and microtubules are essential for both spindle formation and chromosome segregation, but the nature and function of these interactions is not clear. We have examined oocytes lacking two kinetochore proteins, NDC80 and SPC105R, and a centromere-associated motor protein, CENP-E, to characterize the impact of kinetochore-microtubule attachments on spindle assembly and chromosome segregation in Drosophila oocytes. We found that the initiation of spindle assembly results from chromosome-microtubule interactions that are kinetochore-independent. Stabilization of the spindle, however, depends on both central spindle and kinetochore components. This stabilization coincides with changes in kinetochore-microtubule attachments and bi-orientation of homologs. We propose that the bi-orientation process begins with the kinetochores moving laterally along central spindle microtubules towards their minus ends. This movement depends on SPC105R, can occur in the absence of NDC80, and is antagonized by plus-end directed forces from the CENP-E motor. End-on kinetochore-microtubule attachments that depend on NDC80 are required to stabilize bi-orientation of homologs. A surprising finding was that SPC105R but not NDC80 is required for co-orientation of sister centromeres at meiosis I. Together, these results demonstrate that, in oocytes, kinetochore-dependent and -independent chromosome-microtubule attachments work together to promote the accurate segregation of chromosomes.
authors.affiliation: Waksman Institute of Microbiology, Rutgers, The State University of New Jersey, Piscataway, New Jersey, United States of America.
authors.forename: Sarah J
authors.initials: SJ
authors.lastname: Radford
authors.affiliation: Waksman Institute of Microbiology, Rutgers, The State University of New Jersey, Piscataway, New Jersey, United States of America; Department of Genetics, Rutgers, The State University of New Jersey, Piscataway, New Jersey, United States of America.
authors.forename: Tranchau L
authors.initials: TL
authors.lastname: Hoang
authors.affiliation: The Wellcome Trust Centre for Cell Biology, School of Biological Sciences, The University of Edinburgh, Edinburgh, United Kingdom.
authors.forename: A Agata
authors.initials: AA
authors.lastname: Głuszek
authors.affiliation: The Wellcome Trust Centre for Cell Biology, School of Biological Sciences, The University of Edinburgh, Edinburgh, United Kingdom.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Ohkura
authors.affiliation: Waksman Institute of Microbiology, Rutgers, The State University of New Jersey, Piscataway, New Jersey, United States of America; Department of Genetics, Rutgers, The State University of New Jersey, Piscataway, New Jersey, United States of America.
authors.forename: Kim S
authors.initials: KS
authors.lastname: McKim
mesh_terms: D000818:Animals; D018385:Centrosome / Q000378:metabolism; D002868:Chromosomal Proteins, Non-Histone / Q000235:genetics*; D020090:Chromosome Segregation / Q000235:genetics; D002875:Chromosomes / Q000235:genetics; D029721:Drosophila Proteins / Q000235:genetics*; D004331:Drosophila melanogaster / Q000235:genetics; D018386:Kinetochores; D008540:Meiosis / Q000235:genetics; D008869:Microtubule-Associated Proteins / Q000235:genetics*; D008870:Microtubules / Q000235:genetics; D009865:Oocytes / Q000254:growth & development; D008941:Spindle Apparatus / Q000235:genetics
chemical_list: D002868:Chromosomal Proteins, Non-Histone; D029721:Drosophila Proteins; D008869:Microtubule-Associated Proteins; C547532:Ndc80 protein, Drosophila; C541602:Spc105R protein, Drosophila; C068688:centromere protein E