Axin-1 Regulates Meiotic Spindle Organization in Mouse Oocytes.

Xiao-Qin He,Xiang-Jun Yang,Yue-Qiang Song,Bai-Hui Xu,Rui Liu,Hai-Long Wang,Fei Zhang,Ya-Long Wang,Ming-Huang Chen,Yu-Ting Shen,Yu Liu,Zhen Zhang,Lin Xu,Qing-Yuan Sun

doi:10.1371/journal.pone.0157197

Abstract

Axin-1, a negative regulator of Wnt signaling, is a versatile scaffold protein involved in centrosome separation and spindle assembly in mitosis, but its function in mammalian oogenesis remains unknown. Here we examined the localization and function of Axin-1 during meiotic maturation in mouse oocytes. Immunofluorescence analysis showed that Axin-1 was localized around the spindle. Knockdown of the Axin1 gene by microinjection of specific short interfering (si)RNA into the oocyte cytoplasm resulted in severely defective spindles, misaligned chromosomes, failure of first polar body (PB1) extrusion, and impaired pronuclear formation. However, supplementing the culture medium with the Wnt pathway activator LiCl improved spindle morphology and pronuclear formation. Downregulation of Axin1 gene expression also impaired the spindle pole localization of γ-tubulin/Nek9 and resulted in retention of the spindle assembly checkpoint protein BubR1 at kinetochores after 8.5 h of culture. Our results suggest that Axin-1 is critical for spindle organization and cell cycle progression during meiotic maturation in mouse oocytes.

Highlights

Mammalian oocyte maturation is a multi-stage, accurately orchestrated and orderly process [1, 2]
The spindle migrates to the cortex and the oocyte emits the first polar body (PB1), followed by the formation of the metaphase II (MII) spindle beneath the plasma membrane [3]
After Germinal vesicle breakdown (GVBD), an accumulation of dotted structures of Axin-1 appeared in the central part of the oocyte

Summary

Introduction

Mammalian oocyte maturation is a multi-stage, accurately orchestrated and orderly process [1, 2]. Chromosomes migrate to the spindle equator at metaphase I (MI). The spindle migrates to the cortex and the oocyte emits the first polar body (PB1), followed by the formation of the metaphase II (MII) spindle beneath the plasma membrane [3]. In this process, two critical events are Pro MI arrest and progression through the first meiotic division [4]. The correct formation and organization of the meiotic spindle is essential for PLOS ONE | DOI:10.1371/journal.pone.0157197. The correct formation and organization of the meiotic spindle is essential for PLOS ONE | DOI:10.1371/journal.pone.0157197 June 10, 2016

Methods

Results

Conclusion