Gonadal transcriptome of sex change in fishes: quest for causal factors common to phylogenetically distributed protogynous species

Protogyny, capable of changing from female to male during their lifetime, is prevalent in 20 families of teleosts but believed to have evolved within specific evolutionary lineages. Therefore, shared regulatory factors governing this process are expected to be conserved across protogynous fish. However, a comprehensive understanding of this mechanism remains elusive. To identify these factors, we conducted a meta-analysis using gonadal transcriptome data from seven species. We curated data pairs of ovarian tissue and transitional gonad, and employed ratios of expression level as a unified criterion for differential expression, enabling a meta-analysis across species. Our approach revealed that classical sex change-related genes exhibited differential expression levels between the ovary and transitional gonads, consistent with previous reports on protogynous fishes. These results validate our methodology’s robustness. Additionally, we identified novel factors not previously linked to gonadal sex change in fish. Notably, changes in the expression levels of acetoacetyl-CoA synthetase ( aacs ) and apolipoprotein Eb ( apoeb ), which are involved in cholesterol synthesis and transport, respectively, suggest that the levels of cholesterol, a precursor of steroid hormones crucial for sex change, are decreased upon sex change onset in the gonads. This implies a potential universal influence of cholesterol dynamics on gonadal transformation in protogyny. ### Competing Interest Statement The authors have declared no competing interest.