Department of Marine Biotechnology, Institute of Marine and Environmental Technology, University of Maryland Baltimore County, Baltimore, MD, USA.
Department of Marine Biotechnology, Institute of Marine and Environmental Technology, University of Maryland Baltimore County, Baltimore, MD, USA.
Gen Comp Endocrinol. 2019 Sep 1;280:15-23. doi: 10.1016/j.ygcen.2019.04.002. Epub 2019 Apr 2.
Many studies on Gnrh1, and the teleost Gnrh3, have elucidated the roles of these peptides in reproductive regulation. However, the role of the midbrain population of Gnrh, Gnrh2, has long been a mystery, despite its ubiquitous conservation in all jawed vertebrates except rodents. Previous behavioral studies in sparrows, musk shrews, mice, zebrafish, and goldfish show that Gnrh2 administrations both increase spawning behaviors and decrease feeding behaviors, suggesting a role of this peptide in metabolism regulation along with the canonical role in regulating reproduction. In order to more deeply explore the roles of Gnrh2, we used a cyprinid teleost, zebrafish, which has 2 forms of Gnrh, Gnrh2 and Gnrh3, to generate a knockout zebrafish line which contains a frameshift mutation and subsequent disruption of the coding for the functional Gnrh2 peptide. We examined differences in reproduction, feeding, growth, and mobility in this line, and discovered major differences in feeding and growth parameters, suggesting that Gnrh2 is a potent anorexigen in zebrafish. Additionally, there were no differences in mobility except for increased distances swam during feeding periods. There were no major differences in reproductive success, however, female gnrh2 zebrafish exhibited smaller oocytes and increased embryo mortality, indicating slightly decreased oocyte quality. Additionally, there were changes in the expression levels of many feeding, growth, and reproductive neuropeptides in gnrh2 zebrafish. Taken together, these findings suggest a role for Gnrh2 in controlling satiation in zebrafish along with a minor role in maintaining optimal oocyte quality in females.
许多关于 Gnrh1 和硬骨鱼 Gnrh3 的研究已经阐明了这些肽在生殖调控中的作用。然而，中脑群体 Gnrh2 的作用长期以来一直是个谜，尽管它在除啮齿动物以外的所有有颌脊椎动物中普遍存在。麻雀、麝鼩、小鼠、斑马鱼和金鱼的先前行为研究表明，Gnrh2 的给药既增加了产卵行为，又减少了摄食行为，这表明这种肽在代谢调节中具有作用，同时在调节生殖方面也具有经典作用。为了更深入地探讨 Gnrh2 的作用，我们使用了一种鲤科硬骨鱼，斑马鱼，它有 2 种形式的 Gnrh，Gnrh2 和 Gnrh3，来产生一种包含移码突变和随后破坏功能性 Gnrh2 肽编码的斑马鱼敲除系。我们检查了这条系在繁殖、摄食、生长和运动方面的差异，并发现了摄食和生长参数的主要差异，这表明 Gnrh2 是斑马鱼的一种有效的厌食肽。此外，除了摄食期间游泳距离增加外，运动能力没有差异。繁殖成功率没有差异，但 gnrh2 雌鱼的卵母细胞较小，胚胎死亡率增加，表明卵母细胞质量略有下降。此外，gnrh2 斑马鱼的许多摄食、生长和生殖神经肽的表达水平也发生了变化。总之，这些发现表明 Gnrh2 在控制斑马鱼的饱腹感方面具有作用，同时在维持雌性卵母细胞的最佳质量方面也具有次要作用。
