Paranjpe, Monika; Yu, Hongshi; Pask, Andrew J.; Shaw, Geoff; Renfree, Marilyn B.
MAPKs affect gonadal differentiation in mice and humans, but whether this applies to all mammals is as yet unknown. We investigated MAPK expression during gonadal differentiation in a distantly related mammal, the marsupial tammar wallaby, using our model of oestrogen-induced gonadal sex reversal. MAPK pathway genes in the tammar were highly conserved at the sequence and amino acid level with those of mice and humans. Marsupial MAP3K1 and MAP3K4 clustered together in a separate branch from eutherian mammals. We characterised the transcriptome of the key sex differentiation genes and those of the MAPK pathway in developing testes and also after testis culture with exogenous oestrogen. There was a marked decrease in levels of mRNA of both male-determining genes SOX9 and AMH, while levels of the female marker FOXL2 increased in male tammar gonads exposed to exogenous oestrogen. Only MAP3K1 expression increased after male gonads were cultured in media to which oestrogen was added, but the other MAPK genes were not affected by oestrogen. This study suggests that MAP3K1 can be influenced by exogenous oestrogens during gonadal differentiation in this marsupial.