Abstract
Src-homology-2-containing phosphotyrosine phosphatase (SHP2), a classic cytoplasmic protein and a major regulator of receptor tyrosine kinases and G protein-coupled receptors, plays a significant role in preimplantation embryo development. In this study, we deciphered the role of SHP2 in the somatic compartment of oocytes during meiotic maturation. SHP2 showed nuclear/cytoplasmic localization in bovine cumulus and human granulosa (COV434) cells. Follicle-stimulating hormone (FSH) treatment significantly enhanced cytoplasmic SHP2 localization, in contrast to the E2 treatment, which augmented nuclear localization. Enhanced cytoplasmic SHP2 was found to negatively regulate the expression of the ERα-transcribed NPPC and NPR2 mRNAs, which are vital for oocyte meiotic arrest. The co-immunoprecipitation results revealed the presence of the SHP2/ERα complex in the germinal vesicle-stage cumulus–oocyte complexes, and this complex significantly decreased with the progression of meiotic maturation. The complex formation between ERα and SHP2 was also confirmed by using a series of computational modeling methods. To verify the correlation between SHP2 and NPPC/NPR2, SHP2 was knocked down via RNA interference, and NPPC and NPR2 mRNAs were analyzed in the control, E2, and FSH-stimulated COV434 cells. Furthermore, phenyl hydrazonopyrazolone sulfonate 1, a site-directed inhibitor of active SHP2, showed no significant effect on the ERα-transcribed NPPC and NPR2 mRNAs. Taken together, these findings support a novel nuclear/cytoplasmic role of SHP2 in oocyte meiotic resumption and maturation.
Highlights
In mammals, dormant oocytes surrounded by somatic cells enter meiotic cell division during embryonic development and meiotic arrest during the first meiotic prophase (MI) stage for a prolonged period (Guo et al, 2018)
The results showed that SHP2 had a localization pattern similar to that identified in granulosa cells
To examine the function of SHP2, cultured cumulus cells were treated with EGF and Follicle-stimulating hormone (FSH), and samples were prepared for RT-qPCR (Figure 1E)
Summary
Dormant oocytes surrounded by somatic cells enter meiotic cell division during embryonic development and meiotic arrest during the first meiotic prophase (MI) stage for a prolonged period (Guo et al, 2018). Several molecular mechanisms in somatic cells work together to preclude the activation of meiotic-progression-related machinery in oocytes (Zhang et al, 2010). The estradiol (E2)–estrogen receptor (ER) system is one of the mechanisms of oocyte meiotic arrest maintained by granulosa cells (Liu et al, 2017). Ligand-activated ERα regulates the transcription of natriuretic peptide type C (NPPC) and natriuretic peptide receptor 2 (NPR2) by directly binding to their promoter regions and enhancing their expression in granulosa cells (Liu et al, 2017). The NPPC and NPR2 genes further regulate the production of cyclic guanosine monophosphate in granulosa cells, which enters the oocyte via gap junctions, inhibit phosphodiesterase 3A-induced cyclic adenosine monophosphate degradation, and maintain oocyte meiotic arrest (Zhang et al, 2010; Kiyosu et al, 2012; Wigglesworth et al, 2013)
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