Santillo Alessandra, Falvo Sara, Di Fiore Maria Maddalena, Chieffi Baccari Gabriella
Dipartimento di Scienze e Tecnologie Ambientali, Biologiche e Farmaceutiche, Università degli Studi della Campania Luigi Vanvitelli, via Vivaldi, 43, 81100 Caserta, Italy.
Dipartimento di Scienze e Tecnologie Ambientali, Biologiche e Farmaceutiche, Università degli Studi della Campania Luigi Vanvitelli, via Vivaldi, 43, 81100 Caserta, Italy.
Gen Comp Endocrinol. 2017 May 15;246:226-232. doi: 10.1016/j.ygcen.2016.12.012. Epub 2016 Dec 24.
The brain of amphibians contains all the key enzymes of steroidogenesis and has a high steroidogenic activity. In seasonally-breeding amphibian species brain steroid levels fluctuate synchronously with the reproductive cycle. Here we report a study of gene expression of StAR protein, key steroidogenic enzymes and sex hormone receptors in the telencephalon (T) and diencephalon-mesencephalon (D-M) of male and female reproductive and post-reproductive Pelophylax esculentus, a seasonally breeding anuran amphibian. Significant differences in gene expression were observed between (a) the reproductive and post-reproductive phase, (b) the two brain regions and (c) male and female frogs. During the reproductive phase, star gene expression increased in the male (both T and D-M) but not in the female brain. Seasonal fluctuations in expression levels of hsd3b1, hsd17b1, srd5a1 and cyp19a1 genes for neurosteroidogenic enzymes occurred in D-M region of both sexes, with the higher levels in reproductive period. Moreover, the D-M region generally showed higher levels of gene expression than the T region in both sexes. Gene expression was higher in females than males for most genes, suggesting higher neurosteroid production in female brain. Seasonal and sex-linked changes were also observed in gene expression for androgen (ar) and estrogen (esr1, esr2) receptors, with the males showing the highest ar levels in reproductive phase and the highest esr1 and esr2 levels in post-reproductive phase; in contrast, females showed the maximum expression for all three genes in reproductive phase. The results are the first evidence for seasonal changes and sexual dimorphism of gene expression of the neurosteroidogenic pathway in amphibians.
两栖动物的大脑含有甾体生成的所有关键酶，且具有较高的甾体生成活性。在季节性繁殖的两栖动物物种中，大脑甾体水平随生殖周期同步波动。在此，我们报告了一项关于性成熟和繁殖后食用蛙（一种季节性繁殖的无尾两栖动物）的端脑（T）和间脑 - 中脑（D - M）中类固醇生成急性调节蛋白（StAR）、关键甾体生成酶和性激素受体基因表达的研究。在（a）生殖期和繁殖后期、（b）两个脑区以及（c）雄性和雌性青蛙之间观察到基因表达存在显著差异。在生殖期，雄性（T和D - M）的star基因表达增加，而雌性大脑中未增加。两性D - M区域中神经甾体生成酶hsd3b1、hsd17b1、srd5a1和cyp19a1基因的表达水平存在季节性波动，繁殖期水平较高。此外，两性的D - M区域基因表达水平通常高于T区域。大多数基因在雌性中的表达高于雄性，表明雌性大脑中神经甾体生成更高。雄激素（ar）和雌激素（esr1、esr2）受体的基因表达也观察到季节性和性别相关变化，雄性在生殖期ar水平最高，繁殖后期esr1和esr2水平最高；相比之下，雌性在生殖期这三个基因的表达均最高。这些结果首次证明了两栖动物神经甾体生成途径基因表达的季节性变化和性二态性。
