Jumonji family histone demethylases in Epinephelus coioides gonad

The Jumonji family (Jmj family) is a large family of proteins that contain the JmjC domain. Various members of this family are lysine (K)-specific demethylases, which remove methylation from the lysines of histones, and thus, are known as Jmj-KDMs. In this study, all Jmj-KDMs were identified in the orange-spotted grouper Epinephelus coioides and compared with those from Homo sapiens, Danio rerio, Takifugu rubripes, Oreochromis niloticus, and Xenopus tropicalis. The comparison revealed the teleost-specific loss of jmjd1a and the teleost-specific expansion of kdm5b, jmjd3, jmjd2a, and kdm6a in E. coioides. Analysis of the temporal expression pattern of Jmj-KDM genes in E. coioides enabled their division into different types according to their sex-related expression patterns. The kdm6 subfamily genes kdm6aa and jmjd3 (kdm6bb), which are also teleost specific, were selected for further analysis. Quantitative PCR analysis revealed the significantly higher expression of kdm6bb in bisexual-phase gonads and testes compared with ovary. Histological expression pattern analysis based on in situ hybridization (ISH) showed the high expression of kdm6aa in primary-growth stage oocytes, cortical-alveolus stage oocytes and granulosa cells, whereas kdm6aa and jmjd3 were highly expressed in Sertoli cells and spermatogonium. These results suggest that Jmj-KDMs, especially the kdm6 subfamily genes kdm6aa and jmjd3, are involved in sex-related processes in E. coioides.