Deciphering The Role Of Kisspeptin In The Mediation Of Photoperiod and Gonadal Steroid Signalling Throughout Reproduction

Kispeptin正在成为脊椎动物生殖的重要调节因子。在哺乳动物中，它被认为是通过感觉输入和传递到促性腺激素释放激素(GnRH)神经元的整合，将环境和内源性信息传递到下丘脑-垂体-性腺(HPG)轴的“缺失环节”。越来越多的证据表明，Kispeptin系统在硬骨鱼中的作用类似，硬骨鱼是脊椎动物中最大的一类。然而，对硬骨鱼Kispeptin的研究远远落后于哺乳动物。与只有单一形式的Kispeptin(Kiss1)及其受体(KiSS1R)的哺乳动物不同，在大多数硬骨鱼物种的大脑中表达两种Kispeptin亚型(Kiss1和Kiss2)和两种受体(Kiss1r和Kiss2r)。每种受体都被两种形式的kisspeptin激活，但表现出对一种形式的kisspeptin的偏好。斑点黑鱼的初步数据表明，这两种Kispeptin在控制生殖方面扮演着不同的角色。此外，Kiss1r和Kiss2r表达的神经元与下丘脑视前区的GnRH神经元以不同的方式相互作用。为了阐明每种形式的确切作用，我们将利用条纹鲈鱼的kisspeptins和同源受体来寻找硬骨鱼kisspeptin受体的特异性、选择性和高效的拮抗剂。作为第一步，我们将在体外筛选一套系统修饰的Kisspeptin多肽，通过两条信号转导途径PKC和PKA来阻断Kiss1r和Kiss2r在COS7细胞中稳定表达的能力。然后，将在体内评估选定的候选药物在短期和长期治疗中的生物学效力、有效性和特异性。在短期实验中，Kiss1或Kiss2将与被测试的拮抗剂共同注射到条纹鱼体内。控释植入物将用于长期实验。这些装置将在Kiss1或Kiss2注射前两周预先植入。阻断Kiss1和Kiss2的能力将通过比较已知的Kiss1/Kiss2对生殖系统内关键激素(GnRHs、Lh和FSH)的影响来确定。这项研究有望为每个Kispeptin受体产生至少一个有效的特异性拮抗剂，从而能够研究这两个Kispeptin系统在调节不同大脑通路中的不同信号方面的确切作用和意义，特别是那些影响生殖轴的通路。这一工具将为脊椎动物生殖内分泌学领域的更广泛研究铺平道路。潜在的影响包括改进对饲养和圈养动物的生殖控制。

Kisspeptin is emerging as an important regulator of reproduction in vertebrates. In mammals, it is considered to be the "missing link" that mediates environmental and endogenous information to the hypothalamic-pituitary-gonadal (HPG) axis via integration of sensory input and transmission to gonadotropin-releasing hormone (GnRH) neurons. Accumulating evidence suggests that the kisspeptin system acts similarly in teleosts, which comprise the largest class of vertebrates. However, the study of teleost kisspeptin lags significantly behind that of mammals. Unlike mammals that possess only single forms of kisspeptin (KiSS1) and its receptor (KiSS1R), two isoforms of kisspeptin (Kiss1 and Kiss2) and two receptors (Kiss1r and Kiss2r) are expressed in the brain of most teleost species. Each receptor is activated by the two kisspeptin forms but shows preference to one form of kisspeptin. Preliminary data in striped bass suggests that the two kisspeptins have differential roles in the control of reproduction. Moreover, kiss1r- and kiss2r-expressing neurons interact in different ways with GnRH neurons in the hypothalamic preoptic area. To elucidate the exact roles of each form, the kisspeptins and cognate receptors of the striped bass will be used to pursue specific, selective, and efficient antagonists for the teleost kisspeptin receptors. As a first step, a suite of systematically modified kisspeptin peptides will be screened in vitro for their ability to block kiss1r and kiss2r stably expressed in a COS7 cell line, via two signal transduction pathways, PKC and PKA. The selected candidates will then be evaluated in vivo for their biological potencies, efficiency and specificity in short term and long term treatments. In the short-term experiments, kiss1 or kiss2 will be co-injected with the tested antagonist into striped bass. Controlled release delivery implants will be utilized in the long term experiments. These devices will be pre-implanted two weeks prior to kiss1 or kiss2 injections. The ability to block kiss1 and kiss2 will be determined by comparison to known kiss1/kiss2 effects on key hormones within the reproductive system (GnRHs, LH and FSH). The study is expected to yield at least one potent specific antagonist for each kisspeptin receptor, thereby enabling studies on the exact roles and significance of each of the two kisspeptin systems in the mediation of different signals in various brain pathways, particularly those affecting the reproductive axis. This tool will pave the way for a wider range of studies in the field of reproductive endocrinology in vertebrates. The potential impacts include improvement of reproductive manipulations of farmed and captive animals.