Identification and gene expression analysis of three GnRH genes in female Atlantic cod during puberty provides insight into GnRH variant gene loss in fish

► We have identified three pre-pro-gonadotropin releasing hormone (GnRH) genes in female Atlantic cod (Gadus morhua). ► One variant, gmGnRH1, appears to be a pseudogene based on sequence and phylogenetic analysis. ► The putative gmGnRH1 pseudogene is expressed in multiple tissues but at low levels in the brain. ► gmGnRH2 and gmGnRH3 are highly expressed in female brains and to a lesser extent in the pituitary and ovaries. ► gmGnRH3 is upregulated during spawning, suggesting that a functional shift has led to gmGnRH3 acting as the hypophysiotrophic form in Atlantic cod.