title: Katanin maintains meiotic metaphase chromosome alignment and spindle structure in vivo and has multiple effects on microtubules in vitro.
abstract: Assembly of Caenorhabditis elegans female meiotic spindles requires both MEI-1 and MEI-2 subunits of the microtubule-severing ATPase katanin. Strong loss-of-function mutants assemble apolar intersecting microtubule arrays, whereas weaker mutants assemble bipolar meiotic spindles that are longer than wild type. To determine whether katanin is also required for spindle maintenance, we monitored metaphase I spindles after a fast-acting mei-1(ts) mutant was shifted to a nonpermissive temperature. Within 4 min of temperature shift, bivalents moved off the metaphase plate, and microtubule bundles within the spindle lengthened and developed a high degree of curvature. Spindles eventually lost bipolar structure. Immunofluorescence of embryos fixed at increasing temperature indicated that MEI-1 was lost from spindle microtubules before loss of ASPM-1, indicating that MEI-1 and ASPM-1 act independently at spindle poles. We quantified the microtubule-severing activity of purified MEI-1/MEI-2 complexes corresponding to six different point mutations and found a linear relationship between microtubule disassembly rate and meiotic spindle length. Previous work showed that katanin is required for severing at points where two microtubules intersect in vivo. We show that purified MEI-1/MEI-2 complexes preferentially sever at intersections between two microtubules and directly bundle microtubules in vitro. These activities could promote parallel/antiparallel microtubule organization in meiotic spindles.
authors: Department of Molecular and Cellular Biology, University of California, Davis, Davis, CA 95616 Genes and Development Research Group, Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, AB T2N 4N1, Canada.
authors: Karen
authors: K
authors: McNally
authors: Evan
authors: E
authors: Berg
authors: Daniel B
authors: DB
authors: Cortes
authors: Veronica
authors: V
authors: Hernandez
authors: Paul E
authors: PE
authors: Mains
authors: Francis J
authors: FJ
authors: McNally
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000483:Alleles; D000818:Animals; D017173:Caenorhabditis elegans / Q000166:cytology* / Q000378:metabolism; D029742:Caenorhabditis elegans Proteins / Q000378:metabolism*; D002875:Chromosomes / Q000378:metabolism*; D005260:Female; D000074201:Katanin; D008540:Meiosis; D008677:Metaphase; D008870:Microtubules / Q000378:metabolism*; D008954:Models, Biological; D017354:Point Mutation; D011485:Protein Binding; D021381:Protein Transport; D008941:Spindle Apparatus / Q000378:metabolism*; D013696:Temperature
chemical_list: D029742:Caenorhabditis elegans Proteins; D000251:Adenosine Triphosphatases; C086678:MEI-1 protein, C elegans; C409220:MEI-2 protein, C elegans; D000074201:Katanin