Deficiency of the membrane androgen receptor ZIP9 alters brain zinc distribution, reproductive endocrinology, and female fertility

Zinc is an essential trace element involved in numerous biological processes, including cellular signalling, development, and reproduction. Zinc homeostasis is regulated by zinc transporters, yet the physiological roles of many transporters remain poorly understood in vivo . Here, we investigated the function of the zinc transporter ZIP9 (SLC39A9) using a zebrafish ( Danio rerio ) knockout model. Elemental imaging using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) revealed altered zinc distribution in zip9 -deficient larvae. Synchrotron-based X-ray fluorescence (XRF) imaging further showed reduced zinc levels in the brain region of mutant zebrafish. Consistent with these observations, loss of zip9 was associated with altered expression of key neuroendocrine genes within the hypothalamic-pituitary-gonadal (HPG) axis. Zip9 mutant females exhibited disrupted ovarian follicle development, reduced spawning rates, and decreased egg production. In addition, embryos derived from zip9 mutant parents displayed reduced size, impaired early development, and decreased survival. Together, these findings identify ZIP9 as a regulator of zinc distribution in vivo and suggest that ZIP9-mediated zinc signalling contributes to reproductive regulation in zebrafish.