Endocrine Abstracts

Introduction: Androgens mediate their physiological functions via the classical nuclear receptor, and androgen receptor. However, recent studies have identified a new plasma membrane (and non-genomic) androgen receptor- the Zn(II) channel, ZIP9. Indeed, ZIP9 has been reported to regulate oocyte growth and maturation in the teleost ovary. However, how ZIP9 impacts the reproductive hypothalamic-pituitary-gonadal (HPG) axis remains unknown.

Aim: To utilise CRISPR/Cas9 deletion of ZIP9 to determine how ZIP9 modulates HPG axis gene expression and reproductive function.

Methods: CRISPR/Cas9 was used to generate a global zebrafish zip9 knock-out line. Key reproductive gene expression in adult zip9^-/- zebrafish was determined via qPCR with a minimum n = 3 in triplicate.

Results & Conclusion: In wild-type (wt) adult male and female zebrafish, zip9 mRNA expression was detected in the brain (hypothalamus and pituitary), testis, ovary and liver. Interestingly, ZIP9 was highly expressed in the ovary and liver, suggesting potential sexual dimorphism in ZIP9 expression levels in these tissues. In the brain of male zip9^-/-zebrafish, gnrh3 expression was lower than wt while the expression of gnrh2 showed no change. In female zip9^-/-, gnrh3 expression was higher than wt while gnrh2 was unchanged. zip9 deletion resulted in lower expression of ar, esr, and lhr in both the ovary and the testis. Interestingly, fshr expression was significantly lower in the ovaries of zip9^-/-females compared to wt, this contrasted with zip9-/- testes where fshr expression was significantly increased in comparison to wt. Mating studies demonstrated zip9^-/- females were infertile while the males remained fertile, suggesting an essential role of Zip9 in female reproduction. Differences in key HPG axis gene expression provide a mechanism underpinning the sexual dimorphic roles of ZIP9 in zebrafish reproduction. This may suggest the role of Zip9 in influencing the physiological processes involved in follicle development and maturation in female zebrafish.