Divergent Expression Patterns and Function of Two cxcr4 Paralogs in Hermaphroditic Epinephelus coioides.

Chemokine receptor Cxcr4 evolved two paralogs in the teleost lineage. However, and have been characterized only in a few species. In this study, we identified two paralogs from the orange-spotted grouper, . The phylogenetic relationship and gene structure and synteny suggest that the duplicated should result from the teleost-specific genome duplication (Ts3R). The teleost gene clusters in two paralogous chromosomes exhibit a complementary gene loss/retention pattern. and show differential and biased expression patterns in grouper adult tissue, gonads, and embryos at different stages. During embryogenesis, are abundantly transcribed from the neurula stage and mainly expressed in the neural plate and sensory organs, indicating their roles in neurogenesis. Cxcr4a and Cxcr4b possess different chemotactic migratory abilities from the human SDF-1α, Cxcl12a, and Cxcl12b. Moreover, we uncovered the N-terminus and TM5 domain as the key elements for specific ligand⁻receptor recognition of Cxcr4a-Cxcl12b and Cxcr4b-Cxcl12a. Based on the biased and divergent expression patterns of /, and specific ligand⁻receptor recognition of Cxcl12a/b⁻Cxcr4b/a, the current study provides a paradigm of sub-functionalization of two teleost paralogs after Ts3R.