Abstract
RGS2 is a negative regulator of G protein signaling that contains a GTPase-activating domain and a β-tubulin binding region. This study aimed to determine the localization and function of RGS2 during mouse oocyte maturation in vitro. Immunofluorescent staining revealed that RGS2 was widely expressed in the cytoplasm with a greater abundance on both meiotic spindles and first/second polar bodies from the fully-grown germinal vesicle (GV) stage to the MII stages. Co-expression of RGS2 and β-tubulin could also be detected in the spindle and polar body of mouse oocytes at the MI, AI, and MII stages. Inhibition of the binding site between RGS2 and β-tubulin was accomplished by injecting anti-RGS2 antibody into GV-stage oocytes, which could result in oocytes arrest at the MI or AI stage during in vitro maturation, but it did not affect germinal vesicle breakdown. Moreover, injecting anti-RGS2 antibody into oocytes resulted in a significant reduction in the rate of first polar body extrusion and abnormal spindle formation. Additionally, levels of phosphorylated MEK1/2 were significantly reduced in anti-RGS2 antibody injected oocytes compared with control oocytes. These findings suggest that RGS2 might play a critical role in mouse oocyte meiotic maturation by affecting β-tubulin polymerization and chromosome segregation.
Highlights
In mammals, the ovarian follicle consists of an oocyte and one or more layers of granulosa cells, which represent the functional unit of the ovary[1]
We found that Rgs2 and β-tubulin were co-localized in the metaphase spindle (Fig 3A), anaphase spindle (Fig 3B), and polar body (Fig 3C), indicating the potential for an interaction between Rgs2 and βtubulin to occur during oocyte meiosis I stage
This present study establishes that Rgs2 can be spatio-temporally expressed in mouse oocytes during the process of in vitro maturation, and that anti-Rgs2 antibody could inhibit oocyte meiosis by inhibiting microtubule polymerization during spindle formation and migration
Summary
The ovarian follicle consists of an oocyte and one or more layers of granulosa cells, which represent the functional unit of the ovary[1]. An oocyte within the follicle is originally immature and arrested in the first meiotic prophase (prophase I); arrest is maintained by the somatic cell compartment of the follicles[2,3]. An oocyte arrested at prophase I has an intact nuclear envelope or germinal vesicle (GV), and germinal vesicle break down (GVBD) is the first visible event that indicates the resumption of meiosis. The PLOS ONE | DOI:10.1371/journal.pone.0159535 July 27, 2016
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