Identification, expression and functional analysis of activin type I receptor in common Chinese Cuttlefish, Sepiella japonica.

Activin, a member of the transforming growth factor-β(TGF-β) superfamily, exerts its actions by binding to specific transmembrane serine/threonine kinase receptors, known as types II and I receptors. In this study, a full-length cDNA encoding for activin type Ⅰ receptor (SjActRⅠ) was cloned, characterized, and functionally studied in S.japonica. The full-length cDNA of SjActRⅠwas 2264 bp and encoded 505 amino acids. Subcellular localization analysis showed that SjActRⅠwas distributed in the plasma membrane in HEK293T cells. qRT-PCR showed that expressions of SjActRⅠ were ubiquitously expressed in all examined tissues, with the highest expression in the ovary. During the different ovarian development, the expression levels of SjActRⅠ in these three tissues (ovary, brain, and liver) increased from stage I to stage Ⅲ and then decreased from stage III to stage IV. Injection of exogenous GnRH significantly increased the mRNA levels of SjActRⅠ in the ovary and liver, while the expression level of sjActRI in the brain showed no significant difference. Knock-down of SjActRⅠ, by injection of double-strand RNA (dsRNA) significantly reduced the expression levels of SjActRⅠ. Furthermore, silencing SjActRⅠsignificantly reduced the expression of Vitellogenin in the ovary, suggesting that SjActRⅠ might promote ovarian development by stimulating the expression of Vitellogenin. These findings implied that SjActRⅠ might play a crucial role in ovarian development in S.japonica. In conclusion, our results provide novel insights into the evolution and roles of the ActRⅠgene in cuttlefish.