Growth Differentiation Factor 9 (GDF-9)  (生长分化因子-9)

GDF-9 属于 TGFβ 家族。GDF-9 调节卵巢功能，对生育起着至关重要的作用。GDF-9主要表达于卵巢卵泡的卵母细胞，也在部分睾丸和垂体检测到。GDF-9 通常由卵母细胞分泌，促进人类卵泡的生长、发育和存活。GDF-9 与 TGF-β II 型受体 (ALK5 和 BMPRII) 结合并发挥其生物学作用sup>[1]^[2]。具体而言，激活的 II 型受体可磷酸化 Smad 2/3，pSmad 2/3 与 Smad4 相互作用，最终调控靶基因的表达。GDF-9 还刺激 FSHR 的表达，保护细胞免受闭锁，促进细胞增殖，降低 LHR 表达并影响颗粒细胞的类固醇生成^[3]。人类 GDF-9 与小鼠氨基酸序列同源性约为 74%。

GDF-9 belongs to TGFβ family. GDF-9 regulates ovarian function, and plays a vital role for fertility. GDF-9 is mainly expressed in the oocytes of ovarian follicles, and some testicular and hypophyseal expression has been detected. GDF-9 is normally secreted by oocytes, and promotes the growth, development, and survival of human ovarian follicles. GDF-9 binds to TGF-β type II receptors (ALK5 and to BMPRII) and exhibits its biological effect^[1][2]. Specifically, the activated type II receptor phosphorylates Smad 2/3 proteins. pSmad 2/3 interacts with Smad4, and finally regulates the expression of target genes. GDF-9 also stimulates the expression of the FSHR, protects cells against atresia, promotes cell proliferation, reduces LHR expression and affects the steroidogenesis of granulosa cells^[3]. Human GDF-9 shares about 74% aa sequence identity with mouse.

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