Hu Shenqiang, Liu Hehe, Pan Zhixiong, Xia Lu, Dong Xia, Li Liang, Xu Feng, He Hua, Wang Jiwen
Institute of Animal Genetics and Breeding, College of Animal Science and Technology, Sichuan Agricultural University, Ya'an, Sichuan 625014, PR China.
Institute of Animal Genetics and Breeding, College of Animal Science and Technology, Sichuan Agricultural University, Ya'an, Sichuan 625014, PR China.
Anim Reprod Sci. 2014 Oct;149(3-4):281-96. doi: 10.1016/j.anireprosci.2014.06.024. Epub 2014 Jun 28.
Very low density lipoprotein receptor (VLDLR)-mediated endocytosis of plasma lipoproteins into the ovary is essential for ovarian follicle development. Two splice variants of VLDLR have been identified in several species, yet little is known about their distinctive roles in ovarian developing follicles. In the present study, the full-length cDNAs of two splice isoforms of VLDLR were obtained from geese (Anser cygnoide) ovaries using the RACE method. The longer isoform (TypeI VLDLR) is 3141bp and contains five conserved structural domains, while the other (TypeII VLDLR) lacks 90bp encoding for the O-linked sugar domain. TypeII VLDLR was predominantly expressed in the ovary, with greater amounts of mRNA in theca and granulosa cells from early stages of follicle development but decreased during vitellogenesis. However, there was minimal expression of the TypeI VLDLR gene in theca cells and expression was almost undetectable in granulosa cells throughout follicle development. Yolk VLDL concentrations decreased as stage of development advanced while yolk triglyceride and cholesterol concentrations increased in a follicular size-dependent manner. The significant correlations between transcripts of TypeII VLDLR and yolk lipids supported its important role on yolk lipid deposition. In addition, in vitro experiments suggested that exogenous cholesterol, 25-hydroxycholesterol and mevinolin (a highly potent competitive inhibitor of HMG-CoA) treatment could significantly alter TypeII VLDLR gene expression in granulosa cells from both pre-hierarchical and pre-ovulatory follicles. Collectively, data from the present study indicate that TypeII VLDLR is more important for the transport of plasma lipoproteins into developing follicles than TypeI VLDLR, and provide new evidence about the influence of steroids in modulating VLDLR gene expression in ovarian cells.
极低密度脂蛋白受体（VLDLR）介导的血浆脂蛋白内吞进入卵巢对于卵泡发育至关重要。在多个物种中已鉴定出VLDLR的两种剪接变体，但对它们在卵巢发育卵泡中的独特作用知之甚少。在本研究中，使用RACE方法从鹅（Anser cygnoide）卵巢中获得了VLDLR两种剪接异构体的全长cDNA。较长的异构体（I型VLDLR）为3141bp，包含五个保守结构域，而另一种（II型VLDLR）缺少编码O-连接糖结构域的90bp。II型VLDLR主要在卵巢中表达，在卵泡发育早期的卵泡膜细胞和颗粒细胞中有较多的mRNA，但在卵黄生成过程中减少。然而，I型VLDLR基因在卵泡膜细胞中的表达极少，并且在整个卵泡发育过程中颗粒细胞中的表达几乎检测不到。随着发育阶段的推进，卵黄VLDL浓度降低，而卵黄甘油三酯和胆固醇浓度以卵泡大小依赖的方式增加。II型VLDLR转录本与卵黄脂质之间的显著相关性支持了其在卵黄脂质沉积中的重要作用。此外，体外实验表明，外源性胆固醇、25-羟基胆固醇和洛伐他汀（一种高效的HMG-CoA竞争性抑制剂）处理可显著改变来自分级前和排卵前卵泡的颗粒细胞中II型VLDLR基因的表达。总的来说，本研究的数据表明，II型VLDLR在将血浆脂蛋白转运到发育中的卵泡中比I型VLDLR更重要，并为类固醇调节卵巢细胞中VLDLR基因表达的影响提供了新证据。
