Estrogen-regulated expression of P450arom genes in the brain and ovaries of adult female Indian climbing perch, Anabas testudineus.

Abstract

Cytochrome P450arom (CYP19), a product of cyp19a1 gene, catalyzes the conversion of androgens to estrogens and is essential for regulation of reproductive function in vertebrates. In the present study, we isolated partial cDNA encoding the ovarian (cyp19a1a) and brain (cyp19a1b) P450arom genes from adult female perch, Anabas testudineus and investigated their regulation by estrogen in vivo. Results demonstrated that cyp19a1a and cyp19a1b predominate in ovary and brain respectively, with quantity of both attuned to reproductive cycle. To elucidate estrogen-regulated expression of cyp19a1b in brain and cyp19a1a in ovary, dose- and time-dependent studies were conducted with estrogen in vitellogenic-stage fish in the presence or absence of specific aromatase inhibitor fadrozole. Results demonstrated that treatment of fish with 17β-estradiol (E2; 1.0 μM)) for 6 days caused significant upregulation of cyp19a1b transcripts, aromatase B protein, and aromatase activity in brain in a dose- and time-dependent manner. Ovarian cyp19a1a mRNA, aromatase protein, and aromatase activity, however, was less responsive to E2 than brain. Treatment of fish with an aromatase inhibitor fadrozole for 6 days attenuated both brain and ovarian cyp19a1 mRNAs expression and stimulatory effects of E2 was also significantly reduced. These results indicate that expression of cyp19a1b in brain and cyp19a1a in ovary of adult female A. testudineus was closely associated to plasma E2 levels and seasonal reproductive cycle. Results further show apparent differential regulation of cyp19a1a and cyp19a1b expression by E2/fadrozole manipulation.