Temporal expression and gonadotropic regulation of aromatase and estrogen receptors in the ovary of wall lizard,Hemidactylus flaviviridis: Correlation with plasma estradiol and ovarian follicular development
The current study in Indian wall lizard Hemidactylus flaviviridis for the first time demonstrates the reproductive phase-dependent expression pattern of aromatase (cyp19) and estrogen receptor subtypes (er-α and er-β) as well as their gonadotropic regulation in the ovary of a squamate. The expression of cyp19 remained low during regressed phase, increased markedly in recrudescent and declined sharply in breeding phase. Further, temporal profile of plasma estradiol 17-β (E2) was found to be relatively parallel to the expression pattern of ovarian cyp19. The expression pattern of estrogen receptors in the ovary showed subtype-specific variation along the reproductive cycle. Expression of ovarian er-α remained high from regressed to late recrudescence, while er-β expression that was low during regression dramatically increased with the initiation of follicular growth in early recrudescence and remained high until late recrudescence. Nonetheless, expression of both the receptors declined during breeding phase when ovary contained vitellogenic follicle. Regarding gonadotropic regulation, short-term treatment with Follicle stimulating hormone (3 injections of FSH) increased the ovarian expression of cyp19, er-α and er-β while prolongation of treatment (7 or 11 injections) resulted in a marked decrease in expression of these genes concomitant to formation of vitellogenic follicle. However, a marked increase in plasma E2 was recorded after 7 injections of FSH. The direct role of gonadotropin in regulation of cyp19 and estrogen receptors was established by an in vitro study where FSH upregulated the expression of these genes in all stages of ovarian follicles (early growing, previtellogenic and early vitellogenic) of wall lizards.