UCN3肽及其受体CRHR2对家鸡垂体卵泡刺激素(FSH)生成释放的调节机制解析

In vertebrates, anterior pituitary can produce two types of gonadotropins (GTH): follicle-simulating hormone (FSH) and luteinizing hormone (LH), which control the reproduction process of vertebrates. It is generally believed that hypothalamic gonadotropin-releasing hormone (GnRH) can stimulate the synthesis and secretion of FSH and LH in vertebrates including humans. However, in birds, GnRH cannot stimulate the synthesis and secretion of FSH, therefore, the identity of hypothalamic FSH-stimulating factor (FSH-RF) in birds remains an open question. Recently, we found that urocortin 3 (UCN3) and its specific receptor (CRHR2) are abundantly expressed in the hypothalamic-pituitary axis, and UCN3 can potently stimulate pituitary FSHβ expression in vitro. These findings lead us to hypothesize that UCN3 may be a potential novel factor to control FSH expression and secretion, and thus can regulate reproduction in birds. To test this hypothesis, using multiple experimental approaches, the present study aims to: 1) examine the spatio-temporal expression patterns of UCN3-CRHR2 in developing chicken hypothalamic-pituitary axis; 2) identify the hypothalamic factor (e.g. UCN3) and other neuroendocrine/endocrine/paracrine factors, which can control the FSH synthesis and secretion both positively and negatively; 3) investigate the potential roles of UCN3 peptide in ovarian follicle development and functions in birds. Our study will provide the direct evidence that UCN3 may be a novel potential FSH-releasing factor involved in controlling reproductions in chickens. Meanwhile, our study will also establish a basis to explain and improve the egg-laying performance in birds.

脊椎动物垂体分泌促性腺激素：卵泡刺激素(FSH)和黄体生成素(LH)，参与繁殖过程调节。一般认为，下丘脑产生的促性腺激素释放激素(GnRH)刺激两种垂体激素生成与释放。在家鸡中，GnRH不能有效刺激垂体FSH释放，由此，鉴定FSH释放的刺激因子成为领域内待解答的重要科学命题。近来，申请人开展转录组解析发现，尿皮质素3（UCN3）在下丘脑高表达，其特异性受体CRHR2在垂体中高表达，且UCN3可高效刺激垂体FSHβ基因表达，由此提示：UCN3或是下丘脑因子，参与垂体FSH生成释放的调节。为验证该假设，本项目拟系统探究：1）UCN3-CRHR2在发育家鸡下丘脑-垂体轴上的定位与表达规律；2）解析UCN3及相关因子对垂体FSH生成释放的正、负调节机制；3）在个体水平上，初步探究UCN3对家鸡卵巢发育与功能的调节。该项研究将有望首次证实UCN3是禽类FSH刺激因子，参与家禽繁殖过程调节。

脊椎动物垂体分泌促性腺激素：卵泡刺激素(FSH)和黄体生成素(LH)，参与繁殖过程调节。一般认为，下丘脑产生的促性腺激素释放激素(GnRH)刺激两种垂体激素生成与释放。在家鸡中，GnRH不能有效刺激垂体FSH释放，由此，在鸟类中鉴定FSH释放的刺激因子成为领域内待解答重要科学命题。项目主持人在开展下丘脑转录组解析发现，尿皮质素3（UCN3）及其特异性受体CRHR2在下丘脑-垂体轴高表达，且UCN3可高效刺激FSHβ基因表达，由此提示：UCN3或是下丘脑刺激因子，参与垂体FSH生成释放调节。本项目采用多种实验技术以验证该假设。我们的研究发现：1）下丘脑UCN3及垂体CRHR2 mRNA表达谱一致并在性成熟阶段最高；2）在培养家鸡垂体细胞中，UCN3肽可快速、高效刺激FSHβ mRNA的表达，但其对LHβ mRNA的表达无明显影响。相反，下丘脑GnRH1可刺激LHβ表达，而不能刺激FSHβ表达；3）UCN3肽通过激活CRHR2偶联的胞内AC/cAMP/PKA信号通路，刺激FSHβ表达。系列结果支持：在家鸡中，UCN3肽是一个潜在下丘脑“促FSH释放因子”，可通过其受体CRHR2，快速、高效、特异性刺激垂体FSH的生成。