The functional diversity of GPCR genes observed from comparative genome analysis

G protein-coupled receptor (GPCR) is a huge family of about 1000~2000 members in the mammal, and it has indeed various functions. The gene numbers in families are not equally distributed but show significant bias, in which species specific family are dominant. For instance, odorant receptors occupy more than 50% of GPCRs in mammals. Many previous works suggested that the species specific families are forming gene clusters on the genome sequences (1~4). It may be that such GPCR clusters are constructed not by the simple gene duplication alone, but by more positive mechanism to show explosive amplification. Since the GPCR gene cluster dispersion on genome is a snapshot at the middle stage of repeating of gene birth, growth and death dynamically by a process of the gene evolution, we aim to understand the diversification mechanism by overlooking them on the genome.