Expression analysis of cyp11a1 during gonadal development, recrudescence and after hCG induction and sex steroid analog treatment in the catfish, Clarias batrachus.

In teleosts, the levels of steroids are critical for sexual development and hence, expression of steroidogenic enzyme genes and specific substrate availability are indispensable for gonadal steroidogenesis. Early stages of steroidogenesis specifically cholesterol to pregnenolone conversion by Cyp11a1 is crucial for estradiol and testosterone biosynthesis. Based on this, in this study, full length cDNA of cyp11a1 (2581bp) was cloned from catfish testis to investigate the importance of Cyp11a1 by analyzing the expression of cyp11a1 during gonadal development, seasonal reproductive cycle, after human chorionic gonadotropin (hCG) induction and sex steroid analog treatment. Phylogenetic analysis revealed that the Cyp11a1 is more conserved across teleosts. Tissue distribution analysis showed that the cyp11a1 expression was higher in the testis followed by the brain, head kidney, muscle and ovary compared to other tissues analyzed. High expression of cyp11a1 in the head kidney and muscle revealed that Cyp11a1 could potentially regulate the extra-gonadal and/or circulating steroid levels in teleosts. Developing and mature testes showed higher expression of cyp11a1 than the ovary of corresponding age group. Further, cyp11a1 expression was found to be higher during pre-spawning and spawning phases of testicular cycle and was upregulated by hCG, in vivo and in vitro, which indicates the possible regulation by gonadotropin. Exposure of methyltestosterone (1μg/L) and ethinylestradiol (1μg/L) for 21days during catfish testicular development showed lower cyp11a1 expression levels in the testis and brain indicating a certain feedback intervention. These results suggest possible role for Cyp11a1 in the testis development and recrudescence.