P: Dopamine receptors for every species: Gene duplications and functional diversification in der Horst et al

The neuromodulatory effects of dopamine on the central nervous system of craniates are mediated by two classes of G protein-coupled receptors (D1 and D2), each comprising several subtypes. A systematic isolation and char-acterization of the D1 and D2-like receptors was carried out in most of the Craniate groups. It revealed that two events of gene duplications took place during vertebrate evolution, before or simultaneously to the emergence of Gnathostomes. It led to the conservation of two-to-four paralogous receptors (subtypes), depending on the spe-cies. Additional duplication of dopamine receptor gene occurred independently in the teleost fish lineage. Dupli-cated genes were maintained in most of the vertebrate groups, certainly by the acquisition of a few functional characters, specific of each subtypes, as well as by discrete changes in their expression territories in the brain. The evolutionary scenario elaborated from these data suggests that receptor gene duplications were the necessary conditions for the expansion of vertebrate forebrain to occur, allowing dopamine systems to exert their funda-mental role as modulator of the adaptive capabilities acquired by vertebrate species