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Evolution and divergence of sodium channel genes in vertebrates

2001; National Academy of Sciences; Volume: 98; Issue: 13 Linguagem: Inglês

10.1073/pnas.131171798

1091-6490

Gregory F. Lopreato, Ying Lü, Amber L. Southwell, Nigel S. Atkinson, David M. Hillis, Thomas P. Wilcox, Harold H. Zakon,

Developmental Biology and Gene Regulation

Invertebrate species possess one or two Na + channel genes, yet there are 10 in mammals. When did this explosive growth come about during vertebrate evolution? All mammalian Na + channel genes reside on four chromosomes. It has been suggested that this came about by multiple duplications of an ancestral chromosome with a single Na + channel gene followed by tandem duplications of Na + channel genes on some of these chromosomes. Because a large-scale expansion of the vertebrate genome likely occurred before the divergence of teleosts and tetrapods, we tested this hypothesis by cloning Na + channel genes in a teleost fish. Using an approach designed to clone all of the Na + channel genes in a genome, we found six Na + channel genes. Phylogenetic comparisons show that each teleost gene is orthologous to a Na + channel gene or gene cluster on a different mammalian chromosome, supporting the hypothesis that four Na + channel genes were present in the ancestors of teleosts and tetrapods. Further duplications occurred independently in the teleost and tetrapod lineages, with a greater number of duplications in tetrapods. This pattern has implications for the evolution of function and specialization of Na + channel genes in vertebrates. Sodium channel genes also are linked to homeobox (Hox) gene clusters in mammals. Using our phylogeny of Na + channel genes to independently test between two models of Hox gene evolution, we support the hypothesis that Hox gene clusters evolved as (AB) (CD) rather than {D[A(BC)]}.