Gap junction gene innexin3 being highly expressed in the nervous system and embryonic stage of the mud crab Scylla paramamosain

Innexin proteins are a class of transmembrane proteins existing in invertebrates and they have diverse biological functions. The innexin protein Sp-inx2 has been demonstrated to play roles in immune response and promotion of cell apoptosis in the mud crab Scylla paramamosain. One novel innexin gene, named as Sp-inx3 was characterized from S. paramamosin in this study, with an open reading frame of 1 101 bp encoding 367 amino acid residues. Multiple sequence alignment revealed that the Sp-inx3 is highly homologous with innexin3 of Cancer boredis and Homorus americanus. Quantitative real-time PCR (qPCR) and the western blotting results revealed that Sp-inx3 gene was expressed predominantly in the eyestalk, brain, and thoracic ganglion mass in both female and male crabs. The immunohistochemistry assay (IHC) also showed the widespread and intense immunoreactivity of Sp-inx3 in the brain and thoracic ganglion mass. Sp-inx3 mRNA transcription profiles exhibited significantly higher expression from the embryo1 to embryo4 period and low level of expression at the prehatching period and zoea I larva period of S. paramamosain. These results indicate that the Sp-inx3 may play an important role in the nervous system and early embryonic development of S. paramamosain.