Aromatase expression in zebrafish and channel catfish brains: changes in transcript abundance associated with the reproductive cycle and exposure to endocrine disrupting chemicals

Cytochrome P450-aromatase (CYP19) is the critical steroidogenic enzyme controlling estrogen biosynthesis. In teleosts, two genes for CYP19 are found with CYP19A1 expressed mainly in the ovary and CYP19A2 expressed in both brain and pituitary. The promoters for these two homologous genes are considerably different. Exposure to estrogenic endocrine disrupting chemicals (EDC) such as ethinylestradiol and nonylphenol resulted in strong up-regulation of the CYP19A2 gene whereas the expression of CYP19A1 was largely unaffected. Moreover, CYP19A2 transcript abundance was shown to vary during the spawning cycle of both the catfish and the zebrafish which implies an association of the CYP19A2 gene in brain-pituitary endocrinology. Together these findings suggest that EDCs could affect the reproductive physiology of fish through disrupting the gene expression of CYP19A2 in the brain. Cytochrome P450-aromatase (CYP19) is the critical steroidogenic enzyme controlling estrogen biosynthesis. In teleosts, two genes for CYP19 are found with CYP19A1 expressed mainly in the ovary and CYP19A2 expressed in both brain and pituitary. The promoters for these two homologous genes are considerably different. Exposure to estrogenic endocrine disrupting chemicals (EDC) such as ethinylestradiol and nonylphenol resulted in strong up-regulation of the CYP19A2 gene whereas the expression of CYP19A1 was largely unaffected. Moreover, CYP19A2 transcript abundance was shown to vary during the spawning cycle of both the catfish and the zebrafish which implies an association of the CYP19A2 gene in brain-pituitary endocrinology. Together these findings suggest that EDCs could affect the reproductive physiology of fish through disrupting the gene expression of CYP19A2 in the brain.