Anhui Province Key Laboratory of Local Livestock and Poultry, Genetical Resource Conservation and Breeding, College of Animal Science and Technology, Anhui Agricultural University, Hefei, 230036, China.
Anhui Province Key Laboratory of Local Livestock and Poultry, Genetical Resource Conservation and Breeding, College of Animal Science and Technology, Anhui Agricultural University, Hefei, 230036, China.
Theriogenology. 2020 Jan 15;142:158-168. doi: 10.1016/j.theriogenology.2019.09.048. Epub 2019 Sep 28.
SIRT6, a member of the sirtuin family, is a NAD + dependent protein deacetylase and has been implicated in transcriptional regulation of somatic cells and post-transcriptional regulation of oocyte meiosis. However, the function of cumulus cell-derived and maternal SIRT6 in meiotic maturation of porcine oocytes is not yet known. Here, we report that SIRT6 mRNA and protein exists in the oocyte and its surrounding cumulus cells during meiotic maturation. Functional studies using a specific inhibitor in cumulus-enclosed oocytes revealed important roles for SIRT6 in germinal vesicle breakdown (GVBD) and cumulus expansion. Moreover, inhibitor treatment led to a significant reduction in the rate of first polar body (PB1) extrusion and early development of parthenogenetically activated embryos. In contrast, SIRT6 inhibition in cumulus-free oocytes only resulted in a significant reduction in the rate of PB1 extrusion. Furthermore, SIRT6 dysfunction regardless of the origin in both cumulus cells and oocytes severely impaired spindle organization and chromosome alignment at the metaphase stage. Molecularly, SIRT6 inhibition in cumulus cells significantly reduced expression of genes associated with cumulus expansion and gap junctional communication and even expression levels of active phosphorylated CDK1 in oocytes. Importantly, adenylate cyclase inhibition could partially rescue GVBD and PB1 extrusion in SIRT6-inhibited cumulus-enclosed oocytes. Taken together, these results demonstrate that cumulus cell-expressed and maternal SIRT6 differentially regulates porcine oocyte meiotic maturation.
SIRT6 是 sirtuin 家族的一员，是一种 NAD+依赖的蛋白去乙酰化酶，参与体细胞的转录调控和卵母细胞减数分裂的转录后调控。然而，卵丘细胞来源的和母体 SIRT6 在猪卵母细胞减数成熟中的功能尚不清楚。在这里，我们报告 SIRT6mRNA 和蛋白在减数成熟过程中存在于卵母细胞及其周围的卵丘细胞中。使用特异性抑制剂在卵丘包被的卵母细胞中的功能研究表明 SIRT6 在生发泡破裂（GVBD）和卵丘扩展中起重要作用。此外，抑制剂处理导致第一次极体（PB1）挤出率和部分激活胚胎早期发育的显著降低。相比之下，在无卵丘的卵母细胞中抑制 SIRT6 仅导致 PB1 挤出率的显著降低。此外，无论卵丘细胞还是卵母细胞中的 SIRT6 功能障碍都会严重损害纺锤体的组织和中期染色体的排列。从分子水平上看，抑制卵丘细胞中的 SIRT6 显著降低了与卵丘扩展和缝隙连接通讯相关的基因的表达，甚至降低了卵母细胞中活性磷酸化 CDK1 的表达水平。重要的是，腺苷酸环化酶抑制可以部分挽救 SIRT6 抑制的卵丘包被卵母细胞中的 GVBD 和 PB1 挤出。综上所述，这些结果表明，卵丘细胞表达的和母体 SIRT6 对猪卵母细胞减数成熟有不同的调节作用。
