Cloning, partial sequencing and expression analysis of the neural form of P450 aromatase (cyp19a1b) in the South America catfish Rhamdia quelen

Brain aromatase is a key enzyme exclusively expressed in fish radial glial cells that convert androgens into estrogens, thus controlling neuroendocrine functions and neurogenesis. As an important step in characterizing the neuroendocrine systems of Rhamdia quelen (jundiá), a partial cDNA sequence (1045 bp) of brain aromatase (cyp19a1b) was cloned and sequenced. At the nucleotide level the cDNA sequence was found to be 88% identical to cyp19a1b of two species of catfish, Ictalurus punctatus and Silurus meridionalis. The predicted amino acid sequence was between 80 and 91% similar to other teleosts. Real-time RT-qPCR analysis revealed that cyp19a1b was detected in pituitary, hypothalamus, telencephalon, head and posterior kidneys, liver and gonads (testis and ovary) of both males and females. The effects of E2 on cyp19a1b expression are sexually dimorphic in R. quelen. The injection of 17β-estradiol (E2) decreased head kidney mRNA levels of cyp19a1b in males and increased cyp19a1b mRNA levels in the pituitary and head kidney of females. This study demonstrated that the R. quelen cyp19a1b gene is expressed in brain, pituitary and peripheral tissues in both males and females.