Comparative transcriptology reveals effects of circadian rhythm in the nervous system on precocious puberty of the female Chinese mitten crab.

In juvenile Chinese mitten crabs, ovarian maturation occurring in the first year is known as precocity, and can cause huge economic losses to crab breeding. To discover the molecular mechanisms underlying the regulation of the nervous system of female precocious crabs, eyestalk, brain, and thoracic ganglion transcriptome data were obtained in normal and precocious crabs via high-throughput sequencing technology. A total of 81, 4276, and 22,684 differentially-expressed genes were obtained from the eyestalk, brain, and thoracic ganglion groups, respectively. Functional analysis showed that these genes were significantly enriched in the categories of nutrition metabolism, immunity, endocrine regulation, and circadian rhythm. In precocious eyestalk, the expression of vrille was up-regulated significantly and the ribosome endocrine function decreased, which may result in the decline of gonad-inhibiting hormone secretion. In precocious brains, the expression of period2 with the function of delaying clock phase was down-regulated significantly. In precocious thoracic ganglion, expression changes in circadian rhythm-related genes were very complex, and the precocity of female crabs may be the concrete reflex of integrated actions of many endocrine hormones such as estradiol, ecdysteroid, and juvenile hormone, among others. In addition, we found that the mRNA of vitellogenin was highly expressed in the thoracic ganglion. This study discovered some clock genes and related molecular regulatory mechanisms by the RNA-sequence, which would provide foundational information to further study precocity in female Chinese mitten crabs.