Immunological functional differentiation of two transmembrane variants of Dscam in Chinese mitten crab.

Down syndrome cell adhesion molecule (Dscam), also called hypervariable Dscam (Dscam-hv), is an important player in arthropod alternative splicing that connects neurons and immune regulation, acting as a pathogen-specific recognition molecule. Dscam-hv has two forms: transmembrane (TM) Dscam (mDscam) and soluble Dscam (sDscam). Herein, we investigated two transmembrane variants of mDscam resulting from alternative splicing of the transmembrane domain, focusing on differences in their immune regulation. We characterized the Dscam[TM1] and Dscam[TM2] genes of Chinese mitten crab (Eriocheir sinensis) through bioinformatics analysis. Both genes are expressed in the gill, intestine, and other immune tissues. Following gram-positive and gram-negative bacteria stimulation, EsDscam[TM1] and EsDscam[TM2] mRNA expression levels increased significantly in hemocytes. Sequencing showed that EsDscam[TM1] was more abundant in hemocytes than EsDscam[TM2]. Additionally, the two subtypes differ in their regulation of antimicrobial peptides, the proportion of exon 33 carried, and bacterial phagocytosis.