Hypo-hydroxymethylation of rRNA genes in the precocious Eriocheir sinensis testes revealed using hMeDIP-seq.

Precocious puberty is a common phenomenon in crab breeding that seriously reduces the economic benefits for crab farmers. To address this problem, this study aimed to explore the potential functions of both methylation and hydroxymethylation of testis rRNA genes with respect to precocious puberty in Eriocheir sinensis. The results showed that the rRNA genes in normally developing testes of E. sinensis had low levels of methylation and high levels of hydroxymethylation; however, although methylation levels were similar, the level of hydroxymethylation in precocious testes was lower than normal. Highly significant differences (P < 0.01) in the hydroxymethylation of the 18S and 28S rRNA genes were found between precocious and normal testes. Our results suggested that both the 18S and 28S rRNA genes, which are normally downregulated by hypo-hydroxymethylation, might be involved in the process of precocious puberty. Our results also implied that hydroxymethylation of the 18S and 28S rRNA genes might be used as an important epigenetic molecular marker to evaluate economically significant potential for growth and breeding in this species.