Journal of Molecular Endocrinology

Phylogeny and synteny for the GCGR subfamily genes. (A) Maximum likelihood phylogenetic tree for the GCGR subfamily of human (hu), mouse (mo), chicken (ch), anole lizard (an), Xenopus (xe), zebrafish (zf), medaka (md), fugu (fu), stickleback (sb), tetraodon (to), and lamprey (lam) along with human SCTR, GHRHR, VIPRs, and ADCYAP1R1. The receptor sequences were aligned by using MUSCLE and a tree was constructed with MEGA 5.05. Bootstrap number indicates 100 replicates. (B) Synteny for human genome fragments having the GCGR subfamily genes. Chromosome numbers are indicated above the gene, and gene locations (megabase) are indicated below the gene. Paralogous genes are aligned on the same column with the same color. (C) Proposed evolutionary history of the GCGR subfamily genes in vertebrates. GLP2R, GLP1R, and GCGR have emerged by local duplication before 2R while GIPR and GCRPR arose by 2R in an osteichthyan ancestor. After divergence of teleosts and tetrapods, GLP1R disappeared and GCGR were doubled through teleost-specific 3R in teleosts. The absence of the gene in each species is indicated by white boxes with broken lines.