title: Early vertebrate chromosome duplications and the evolution of the neuropeptide Y receptor gene regions.
abstract: BACKGROUND
  One of the many gene families that expanded in early vertebrate evolution is the neuropeptide (NPY) receptor family of G-protein coupled receptors. Earlier work by our lab suggested that several of the NPY receptor genes found in extant vertebrates resulted from two genome duplications before the origin of jawed vertebrates (gnathostomes) and one additional genome duplication in the actinopterygian lineage, based on their location on chromosomes sharing several gene families. In this study we have investigated, in five vertebrate genomes, 45 gene families with members close to the NPY receptor genes in the compact genomes of the teleost fishes Tetraodon nigroviridis and Takifugu rubripes. These correspond to Homo sapiens chromosomes 4, 5, 8 and 10.
  
  
  RESULTS
  Chromosome regions with conserved synteny were identified and confirmed by phylogenetic analyses in H. sapiens, M. musculus, D. rerio, T. rubripes and T. nigroviridis. 26 gene families, including the NPY receptor genes, (plus 3 described recently by other labs) showed a tree topology consistent with duplications in early vertebrate evolution and in the actinopterygian lineage, thereby supporting expansion through block duplications. Eight gene families had complications that precluded analysis (such as short sequence length or variable number of repeated domains) and another eight families did not support block duplications (because the paralogs in these families seem to have originated in another time window than the proposed genome duplication events). RT-PCR carried out with several tissues in T. rubripes revealed that all five NPY receptors were expressed in the brain and subtypes Y2, Y4 and Y8 were also expressed in peripheral organs.
  
  
  CONCLUSIONS
  We conclude that the phylogenetic analyses and chromosomal locations of these gene families support duplications of large blocks of genes or even entire chromosomes. Thus, these results are consistent with two early vertebrate tetraploidizations forming a paralogon comprising human chromosomes 4, 5, 8 and 10 and one teleost tetraploidization. The combination of positional and phylogenetic data further strengthens the identification of orthologs and paralogs in the NPY receptor family.
authors.affiliation: Department of Neuroscience, Uppsala University, Box 593, 75124 Uppsala, Sweden. Tomas.Larsson@neuro.uu.se
authors.forename: Tomas A
authors.initials: TA
authors.lastname: Larsson
authors.forename: Frida
authors.initials: F
authors.lastname: Olsson
authors.forename: Gorel
authors.initials: G
authors.lastname: Sundstrom
authors.forename: Lars-Gustav
authors.initials: LG
authors.lastname: Lundin
authors.forename: Sydney
authors.initials: S
authors.lastname: Brenner
authors.forename: Byrappa
authors.initials: B
authors.lastname: Venkatesh
authors.forename: Dan
authors.initials: D
authors.lastname: Larhammar
mesh_terms: D000818:Animals; D002875:Chromosomes / Q000235:genetics*; D019143:Evolution, Molecular; D020440:Gene Duplication; D006801:Humans; D051379:Mice; D005810:Multigene Family / Q000235:genetics; D010802:Phylogeny; D017476:Receptors, Neuropeptide Y / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D023741:Takifugu / Q000235:genetics; D023721:Tetraodontiformes / Q000235:genetics; D014714:Vertebrates / Q000235:genetics*
chemical_list: D017476:Receptors, Neuropeptide Y