Embryonic expression and steroid regulation of brain aromatase cyp19a1b in zebrafish (Danio rerio)

Estradiol is produced from testosterone by the aromatase gene, cyp19. In the zebrafish Danio rerio, brain aromatase, cyp19a1b, is highly expressed during development. We report the developmental expression pattern of cyp19a1b using whole mount in situ hybridization and describe hormonal effects on the gene using RT-PCR. Expression is up-regulated between 24 and 48 hours postfertilization (hpf). Localized expression of cyp19a1b is first detected at 48 hpf in the preoptic area, hypothalamus, terminal nerve, and olfactory bulb. The gene is itself induced by estradiol in a positive feedback loop. Testosterone exposure also induces the cyp19a1b gene in zebrafish; however, a majority of this induction is blocked by an estrogen receptor antagonist. The expression pattern of aromatase in the brain and its control by steroid hormones is well conserved among the vertebrate lineage.