Role of sox30 in regulating testicular steroidogenesis of common carp.

Expression of transcription factors is crucial for the regulation of steroidogenesis and gonadal development in fish. SRY-related box (SOX) proteins regulate gene expression of various events related to vertebrate reproduction. This study reports the role of sox30 and its influence on sox9a/b in regulating testicular steroidogenesis of the common carp, Cyprinus carpio. Tissue distribution showed predominant expression of sox30 in gonads, while gonadal ontogeny indicated significant dimorphic expression of sox30 from 120 days post hatch. Higher sox30 transcripts during the spawning season, an elevation of sox30 after human chorionic gonadotropin induction, and 11-ketotestosterone (11-KT) treatment authenticate gonadotropin dependency. Treatment of 17α-methyl-di-hydroxy-testosterone to juvenile common carp for mono-sex induction, vis-à-vis elevated sox30 expression. Sox30 protein was detected abundantly in spermatocytes and spermatid/sperm of carp testis. Transient silencing of sox30 using small interfering RNAs decreased sox9a/b expression, lead to downregulation of certain molecule/factor, transcription factor, germ/stem cell marker, and steroidogenesis-related enzyme genes. Serum testosterone and 11-KT decreased significantly upon transient silencing of sox30, in vivo. Concomitantly, a reduction in testicular microsomal 11-β hydroxysteroid dehydrogenase activity was observed. These results demonstrate the influence of sox30 as well as sox9a/b in the regulation of testicular steroidogenesis in common carp.