Centre of Reproduction, Development and Aging, Faculty of Health Sciences, University of Macau, Macau, China.
Endocrinology. 2019 Mar 1;160(3):568-586. doi: 10.1210/en.2018-00878.
As a master hormone controlling growth and metabolism, GH is also known to regulate reproduction. Studies in mammals have shown that mutations in GH or its receptor (GHR) not only result in retardation in body growth but also reproductive dysfunctions in both sexes. However, the roles of GH in reproduction of other vertebrates are poorly defined. In this study, we created two zebrafish GH (gh1) mutant lines using CRISPR/Cas9. The mutant developed normally up to 14 days postfertilization (dpf); however, a high rate of mortality was observed afterward in both lines, and only a small number of mutant fish could survive to adult stage. The body growth of the mutants was significantly retarded in both sexes in a gene dose-dependent manner compared with their wild-type siblings. A severe dysfunction of gonadal development was observed in survived mutant females, with ovarian folliculogenesis being arrested completely at primary growth stage until 100 dpf. Interestingly, the folliculogenesis in the mutant resumed after months of delay with a certain number of follicles entering vitellogenic growth. As for male reproduction, although the spermatogenesis in mutant males seemed normal in adults, the GH-insufficient heterozygote showed an obvious delay of spermatogenesis (puberty onset) at early developmental stages. The adult mutant males could not breed with wild-type females through natural spawning; however, the sperm isolated from the mutant testes could fertilize eggs through artificial fertilization. This study provides further genetic evidence for the dependence of puberty onset on somatic growth, but not age, in fish.
作为一种控制生长和代谢的主激素，GH 也被认为可以调节生殖。哺乳动物的研究表明，GH 或其受体（GHR）的突变不仅导致身体生长迟缓，而且还会导致两性生殖功能障碍。然而，GH 在其他脊椎动物生殖中的作用尚未得到明确界定。在这项研究中，我们使用 CRISPR/Cas9 技术创建了两种斑马鱼 GH（gh1）突变系。突变体在受精后 14 天（dpf）之前正常发育；然而，此后两条系的死亡率都很高，只有少数突变鱼能够存活到成年阶段。与野生型兄弟姐妹相比，突变体在两性中的生长均明显迟缓，且呈基因剂量依赖性。存活的突变雌性的性腺发育严重功能障碍，卵巢卵泡发生完全停滞在初级生长阶段，直到 100 dpf。有趣的是，经过数月的延迟，突变体中的卵泡发生恢复，一定数量的卵泡进入卵黄生成生长。对于雄性生殖，尽管突变雄性的精子发生在成年时似乎正常，但 GH 不足的杂合子在早期发育阶段表现出明显的精子发生（青春期开始）延迟。成年突变雄性不能通过自然交配与野生型雌性繁殖；然而，从突变睾丸中分离出的精子可以通过人工受精使卵子受精。这项研究为青春期开始依赖于身体生长而不是年龄提供了进一步的遗传证据。
