Search

Testicular receptor 2 (TR2; also known as Nr2c1) is one of the first orphan nuclear receptors identified and known to regulate various physiological process with or without any ligand. In this study, we report the cloning of full length nr2c1 and its expression analysis during gonadal development, seasonal testicular cycle and after human chorionic gonadotropin (hCG) induction. In addition, in situ hybridization (ISH) was performed to localize nr2c1 transcripts in adult testis and whole catfish (1 day post hatch). Tissue distribution and gonadal ontogeny studies revealed high expression of nr2c1 in developing and adult testis. Early embryonic stage-wise expression of nr2c1 seems to emphasize its importance in cellular differentiation and development. Substantial expression of nr2c1 during pre-spawning phase and localization of nr2c1 transcripts in sperm/spermatids were observed. Significant upregulation after hCG induction indicate that nr2c1 is under the regulation of gonadotropins. Whole mount ISH analysis displayed nr2c1 expression in notochord indicating its role in normal vertebrate development. Taken together, our findings suggest that nr2c1 may have a plausible role in the testicular and embryonic development of catfish. [ABSTRACT FROM AUTHOR]

Abstract: The maturation inducing hormone, 17α,20β-dihydroxy-4-pregnen-3-one (17α,20β-DP) is required for the meiotic maturation and is produced from the precursor 17α-hydroxyprogesterone by the enzyme 20β-hydroxysteroid dehydrogenase (20β-HSD) in several teleosts. Central role of 20β-HSD in ovarian cycle and final oocyte maturation is well studied when compared to spermatogenesis. In the present study, we investigated the localization and expression of 20β-HSD in testicular cycle and gonadotropin induced sperm maturation. During testicular ontogeny, 20β-HSD expression was detectable at 50 and 100days post-hatch (dph), while the expression was high at 150dph. In testicular cycle, highest levels of mRNA and protein of 20β-HSD were observed during spawning phase. Intraperitoneal injection of human chorionic gonadotropin (hCG) to prespawning catfish elevated both 20β-HSD transcripts and protein levels when compared to saline treated controls in a time-dependent manner. Serum 17α,20β-DP levels, measured during different phases of testicular cycle as well as following the treatment of hCG, showed a positive correlation with the expression of 20β-HSD. Immunolocalization revealed the presence of 20β-HSD protein predominantly in interstitial cells and spermatogonia/spermatocytes while 20β-HSD was undetectable in haploid cells (spermatids/sperm). These results together with high expression during spawning phase of testicular cycle and after hCG treatment in the prespawning catfish suggests a pivotal role for 20β-HSD during testicular recrudescence leading to sperm maturation. Further studies using various fish models on testicular 20β-HSD may provide interesting details to understand its importance in teleostean spermatogenesis. [Copyright &y& Elsevier]