Identification and expression of lypc, a novel dark-inducible member of Ly6 superfamily in zebrafish Danio rerio

Snake venom neurotoxins and lymphocyte antigen-6 (Ly6) family members identified in many metazoans possess conserved LU domain containing eight or ten conserved cysteine residues which form 4 to 5 conserved disulfide bonds. They are found to execute a wide variety of biological effects, but information regarding Ly6 superfamily in zebrafish remains rather limited. Here we identified a novel Ly6 gene located on the chromosome 15 in zebrafish, and named it lypc highlighting its predominant expression in the pigment cells. Both homology modeling and sequence comparison revealed that lypc has features typical of Ly6 family members. Whole mount in situ hybridization showed that lypc was expressed in the trunk pigment cells and retinal pigment cells. Moreover, real-time quantitative PCR demonstrated that the expression of lypc was subjected to diurnal variation regulation, i.e. the expression of lypc displays a clear rhythmic pattern, and dark exposure apparently stimulated its expression. Collectively, these data indicate that lypc is a novel dark-inducible Ly6 member with a predominant expression in the pigment cells of zebrafish, laying a foundation for further elucidation of its functions.