Cloning and function analysis of novel LRRs receptor inCrassostrea hongkongensis

Leucine-rich repeats protein is a versatile ligand recognition domain present in receptors, which is involved in many important physiological processes such as development, immune responses and hormone regulation etc. A novel LRRs protein with significant high expression level during embryogenesis was identified in this study. Its function was investigated by various methods including cloning, sequences alignment, in situ hybridization and in vitro treatment with recombined proteins. SMART analysis indicated that an IG-like domain was located in the extracellular region besides the LRRs domain. Thus we designated it asCrassostrea hongkongensis LRRs and IG-like containing receptor (ChLIGR). Sequences alignment revealed that ChLIGR is a new member in the IG-like containing LRR proteins superfamily, and most of its homologous proteins belong to mollusk without any function related description. Consistent with its expression pattern during embryogenesis, the in situ hybridization results showed thatChLIGR was expressed most highly in blastula stage and was distributed to a distinct place in the embryo. Combining with the predicted ETS/AP-1 regulatory site upstream the promoter, we hypothesized thatChLIGR would be involved in gastrulation related epithelial-mesenchymal transition process. Notably, in vitro treatment with recombined extracellular domains of ChLIGR augments the expression of migration related genes, which partly supports our hypothesis. In conclusion, the function of this novel IG-like domain containing LRR receptor is preliminarily unveiled as an activator for gastrulation by promoting the cell migration.