Augmin promotes meiotic spindle formation and bipolarity in Xenopus egg extracts.

TitleAugmin promotes meiotic spindle formation and bipolarity in Xenopus egg extracts.
Publication TypeJournal Article
Year of Publication2011
AuthorsPetry, S, Pugieux, C, Nédélec, FJ, Vale, RD
JournalProc Natl Acad Sci U S A
Volume108
Issue35
Pagination14473-8
Date Published2011 Aug 30
ISSN1091-6490
KeywordsAnimals, Centrosome, Female, Meiosis, Microtubule-Associated Proteins, Microtubules, Multiprotein Complexes, Ovum, Protein Subunits, Spindle Apparatus, Xenopus laevis, Xenopus Proteins
Abstract

<p>Female meiotic spindles in many organisms form in the absence of centrosomes, the organelle typically associated with microtubule (MT) nucleation. Previous studies have proposed that these meiotic spindles arise from RanGTP-mediated MT nucleation in the vicinity of chromatin; however, whether this process is sufficient for spindle formation is unknown. Here, we investigated whether a recently proposed spindle-based MT nucleation pathway that involves augmin, an 8-subunit protein complex, also contributes to spindle morphogenesis. We used an assay system in which hundreds of meiotic spindles can be observed forming around chromatin-coated beads after introduction of Xenopus egg extracts. Spindles forming in augmin-depleted extracts showed reduced rates of MT formation and were predominantly multipolar, revealing a function of augmin in stabilizing the bipolar shape of the acentrosomal meiotic spindle. Our studies also have uncovered an apparent augmin-independent MT nucleation process from acentrosomal poles, which becomes increasingly active over time and appears to partially rescue the spindle defects that arise from augmin depletion. Our studies reveal that spatially and temporally distinct MT generation pathways from chromatin, spindle MTs, and acentrosomal poles all contribute to robust bipolar spindle formation in meiotic extracts.</p>

DOI10.1073/pnas.1110412108
Alternate JournalProc. Natl. Acad. Sci. U.S.A.
PubMed ID21844347
PubMed Central IDPMC3167534
Grant List38499 / / PHS HHS / United States
K99 GM100013 / GM / NIGMS NIH HHS / United States
/ / Howard Hughes Medical Institute / United States