title: Organization of mouse Iroquois homeobox genes in two clusters suggests a conserved regulation and function in vertebrate development.
abstract: Iroquois proteins comprise a conserved family of homeodomain-containing transcription factors involved in patterning and regionalization of embryonic tissues in both vertebrates and invertebrates. Earlier studies identified four murine Iroquois (Irx) genes. Here we report the isolation of two additional members of the murine gene family, Irx5 and Irx6. Phylogenetic analysis of the Irx gene family revealed distinct clades for fly and vertebrate genes, and vertebrate members themselves were classified into three pairs of cognate genes. Mapping of the murine Irx genes identified two gene clusters located on mouse chromosomes 8 and 13, respectively. Each gene cluster is represented by three Irx genes whose relative positions within both clusters are strictly conserved. Combined results from phylogenetic, linkage, and physical mapping studies provide evidence for the evolution of two Irx gene clusters by duplication of a larger chromosomal region and dispersion to two chromosomal locations. The maintenance of two cognate Irx gene clusters during vertebrate evolution suggests that their genomic organization is important for the regulation, expression, and function of Irx genes during embryonic development.
authors.affiliation: Entwicklungs- und Molekularbiologie der Tiere, Heinrich-Heine-Universität, 40225 Düsseldorf, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Peters
authors.forename: R
authors.initials: R
authors.lastname: Dildrop
authors.forename: K
authors.initials: K
authors.lastname: Ausmeier
authors.forename: U
authors.initials: U
authors.lastname: Rüther
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002645:Chickens; D017124:Conserved Sequence; D004330:Drosophila; D020224:Expressed Sequence Tags; D020440:Gene Duplication; D018507:Gene Expression Regulation, Developmental / Q000235:genetics / Q000502:physiology; D005801:Genes, Homeobox / Q000502:physiology*; D018398:Homeodomain Proteins / Q000235:genetics* / Q000502:physiology; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D005810:Multigene Family; D010802:Phylogeny; D051381:Rats; D014157:Transcription Factors / Q000235:genetics* / Q000502:physiology; D014981:Xenopus; D015027:Zebrafish; D029961:Zebrafish Proteins
chemical_list: D018398:Homeodomain Proteins; C501600:IRX5 protein, human; C501604:IRX6 protein, human; C501601:Irx5 protein, mouse; C501605:Irx6 protein, mouse; D014157:Transcription Factors; D029961:Zebrafish Proteins; C501593:irx1a protein, zebrafish; C501602:irx5a protein, zebrafish