Augmin promotes meiotic spindle formation and bipolarity in Xenopus egg extracts

Sabine Petry, Ceĺine Pugieux, Franco̧is J. Ned́eĺec, Ronald D. Vale

Research output: Contribution to journalArticle

55 Scopus citations

Abstract

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.

Original languageEnglish (US)
Pages (from-to)14473-14478
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume108
Issue number35
DOIs
StatePublished - Aug 30 2011
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • General

Keywords

  • Microtubule nucleation
  • γ-tubulin
  • γ-tubulin ring complex

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