The Hippo/MST Pathway Member SAV1 Plays a Suppressive Role in Development of the Prehierarchical Follicles in Hen Ovary.
The Hippo/MST Pathway Member SAV1 Plays a Suppressive Role in Development of the Prehierarchical Follicles in Hen Ovary.
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Hippo/MST 通路成员 SAV1 在母鸡卵巢分级前卵泡的发育中发挥抑制作用
DOI：
10.1371/journal.pone.0160896
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发表时间：
2016
期刊：
影响因子：
3.7
通讯作者：
Xu R
中科院分区：
文献类型：
--
作者：
Lyu Z;Qin N;Tyasi TL;Zhu H;Liu D;Yuan S;Xu R
Hippo/MST信号通路在控制不同物种的大多数组织和器官的细胞增殖、自我更新、分化和凋亡中起关键作用。萨尔瓦多同源物1（SAV 1）是一种在信号转导系统中起作用的支架蛋白，在哺乳动物卵巢中表达，在调控卵泡发育中起重要作用。但是鸡SAV 1在前等级卵泡发育中的确切生物学作用仍然知之甚少。在本研究中，我们证明SAV 1蛋白主要表达在卵母细胞和未分化的颗粒细胞在不同大小的前分级卵泡的母鸡卵巢，SAV 1的mRNA的内源性表达水平出现下调，从原始卵泡到最大的排卵前卵泡（F2-F1），分别通过免疫组织化学和实时RT-PCR。此外，我们发现细胞内SAV 1与每个途径成员，包括STK 4/MST 1，STK 3/MST 2，LATS 1和MOB 2，使用蛋白质印迹进行物理相互作用。SAV 1在体外能显著促进STK 4或STK 3激酶诱导的LATS 1磷酸化。BrdU掺入法显示，SAV 1基因的siRNA敲除可显著促进卵泡颗粒细胞的增殖，其中GDF 9、星星和FSHR mRNA的表达水平显著提高。同时，SAV 1过表达的数据巩固了这些发现。综上所述，本研究结果表明，SAV 1可以抑制颗粒细胞的增殖，从而负调节GDF 9，星星和FSHR mRNA的表达水平。因此，SAV 1作为hippo/MST信号通路的成员，通过促进下游LATS 1的磷酸化和活性而在卵泡发育中起抑制作用，从而可能导致阻止卵巢发育期间的卵泡选择。
The Hippo/MST signaling pathway is a critical player in controlling cell proliferation, self-renewal, differentiation, and apoptosis of most tissues and organs in diverse species. Previous studies have shown that Salvador homolog 1 (SAV1), a scaffolding protein which functions in the signaling system is expressed in mammalian ovaries and play a vital role in governing the follicle development. But the exact biological effects of chicken SAV1 in prehierarchical follicle development remain poorly understood. In the present study, we demonstrated that the SAV1 protein is predominantly expressed in the oocytes and undifferentiated granulosa cells in the various sized prehierarchical follicles of hen ovary, and the endogenous expression level of SAV1 mRNA appears down-regulated from the primordial follicles to the largest preovulatory follicles (F2-F1) by immunohistochemistry and real-time RT-PCR, respectively. Moreover, we found the intracellular SAV1 physically interacts with each of the pathway members, including STK4/MST1, STK3/MST2, LATS1 and MOB2 using western blotting. And SAV1 significantly promotes the phosphorylation of LATS1 induced by the kinase of STK4 or STK3 in vitro. Furthermore, SAV1 knockdown by small interfering RNA (siRNA) significantly increased proliferation of granulosa cells from the prehierarchical follicles (6–8 mm in diameter) by BrdU-incorporation assay, in which the expression levels of GDF9, StAR and FSHR mRNA was notably enhanced. Meanwhile, these findings were consolidated by the data of SAV1 overexpression. Taken together, the present results revealed that SAV1 can inhibit proliferation of the granulosa cells whereby the expression levels of GDF9, StAR and FSHR mRNA were negatively regulated. Accordingly, SAV1, as a member of the hippo/MST signaling pathway plays a suppressive role in ovarian follicle development by promoting phosphorylation and activity of the downstream LATS1, may consequently lead to prevention of the follicle selection during ovary development.