Androgen receptor alpha deficiency impacts aromatase expression in the female cichlid brain.

Steroid hormones bind to specific receptors that act as transcription factors to modify gene expression in the brain to regulate physiological and behavioural processes. The specific genes controlled by steroid hormones in the brain are not fully known. Identifying these genes is integral to establishing a comprehensive understanding of how hormones impact physiology and behaviour. A popular organism for answering this question is the cichlid fish . Recently, CRISPR/Cas9 was used to engineer that lack functional androgen receptor (AR) genes encoding ARα. ARα mutant male produced fewer aggressive displays and possessed reduced expression of the gene encoding brain-specific aromatase, , in the ventromedial hypothalamus (VMH), an aggression locus. As a follow-up, we investigated whether ARα deficiency affected expression in female using the same genetic line. We find that female possessing one or two non-functional ARα alleles had much higher expression of in the preoptic area (POA), while females with one non-functional ARα allele possessed lower expression of in the putative fish homologue of the bed nucleus of the stria terminalis (BNST). Thus, ARα may have a sex-specific role in modifying expression in the teleost POA and BNST, regions that underlie sex differences across vertebrates.