title: Comparison of Iroquois gene expression in limbs/fins of vertebrate embryos.
abstract: In Drosophila, Iroquois (Irx) genes have various functions including the specification of the identity of wing veins. Vertebrate Iroquois (Irx) genes have been reported to be expressed in the developing digits of mouse limbs. Here we carry out a phylogenetic analysis of vertebrate Irx genes and compare expression in developing limbs of mouse, chick and human embryos and in zebrafish pectoral fin buds. We confirm that the six Irx gene families in vertebrates are well defined and that Clusters A and B are duplicates; in contrast, Irx1 and 3, Irx2 and 5, and Irx4 and 6 are paralogs. All Irx genes in mouse and chick are expressed in developing limbs. Detailed comparison of the expression patterns in mouse and chick shows that expression patterns of genes in the same cluster are generally similar but paralogous genes have different expression patterns. Mouse and chick Irx1 are expressed in digit condensations, whereas mouse and chick Irx6 are expressed interdigitally. The timing of Irx1 expression in individual digits in mouse and chick is different. Irx1 is also expressed in digit condensations in developing human limbs, thus showing conservation of expression of this gene in higher vertebrates. In zebrafish, Irx genes of all but six of the families are expressed in early stage pectoral fin buds but not at later stages, suggesting that these genes are not involved in patterning distal structures in zebrafish fins.
authors.affiliation: Department of Biology & Biochemistry, University of Bath, Somerset, UK.
authors.forename: Laura A
authors.initials: LA
authors.lastname: McDonald
authors.forename: Dianne
authors.initials: D
authors.lastname: Gerrelli
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Fok
authors.forename: Laurence D
authors.initials: LD
authors.lastname: Hurst
authors.forename: Cheryll
authors.initials: C
authors.lastname: Tickle
mesh_terms: D000818:Animals; D002642:Chick Embryo; D047108:Embryonic Development / Q000235:genetics*; D005121:Extremities / Q000196:embryology; D015870:Gene Expression; D018507:Gene Expression Regulation, Developmental; D018398:Homeodomain Proteins / Q000235:genetics*; D006801:Humans; D051379:Mice; D010802:Phylogeny; D014714:Vertebrates / Q000235:genetics; D015027:Zebrafish / Q000196:embryology / Q000235:genetics*
chemical_list: D018398:Homeodomain Proteins
references.citation: BMC Evol Biol. 2009 Apr 15;9:74
references.pmid: 19368711
references.citation: Dev Cell. 2008 Apr;14(4):624-32
references.pmid: 18410737
references.citation: Genome Res. 2005 Aug;15(8):1061-72
references.pmid: 16024824
references.citation: Dev Genes Evol. 2004 Jun;214(6):277-84
references.pmid: 15064948
references.citation: Genes Dev. 1999 Jul 1;13(13):1754-61
references.pmid: 10398687
references.citation: J Comp Neurol. 2005 Nov 21;492(3):289-302
references.pmid: 16217788
references.citation: Dev Dyn. 1992 Dec;195(4):231-72
references.pmid: 1304821
references.citation: J Histochem Cytochem. 2001 Jan;49(1):1-8
references.pmid: 11118473
references.citation: Mech Dev. 2001 Sep;107(1-2):169-74
references.pmid: 11520674
references.citation: Nature. 2009 Jun 18;459(7249):940-4
references.pmid: 19536256
references.citation: Cell. 1996 Apr 5;85(1):95-105
references.pmid: 8620542
references.citation: Mech Dev. 2001 Aug;106(1-2):159-62
references.pmid: 11472848
references.citation: Gene Expr Patterns. 2004 Dec;5(2):279-84
references.pmid: 15567726
references.citation: Methods Enzymol. 1993;225:361-73
references.pmid: 8231863
references.citation: Development. 1996 May;122(5):1449-66
references.pmid: 8625833
references.citation: Genes Dev. 2004 Oct 1;18(19):2404-17
references.pmid: 15371327
references.citation: Mech Dev. 2001 May;103(1-2):193-5
references.pmid: 11335133
references.citation: Bioinformatics. 2001 Aug;17(8):754-5
references.pmid: 11524383
references.citation: Nucleic Acids Res. 2006 Mar 23;34(6):1692-9
references.pmid: 16556910
references.citation: Dev Biol. 1999 May 1;209(1):11-27
references.pmid: 10208739
references.citation: Dev Dyn. 1995 Jul;203(3):253-310
references.pmid: 8589427
references.citation: Genome Res. 2000 Oct;10(10):1453-62
references.pmid: 11042145
references.citation: Dev Genes Evol. 2004 Jun;214(6):267-76
references.pmid: 15133664
references.citation: Hum Mol Genet. 1998 May;7(5):813-22
references.pmid: 9536085
references.citation: Nucleic Acids Res. 2007 Jul;35(Web Server issue):W645-8
references.pmid: 17526519
references.citation: Dev Biol. 2008 Oct 1;322(1):220-33
references.pmid: 18638469
references.citation: Nucleic Acids Res. 1994 Jun 25;22(12):2360-5
references.pmid: 8036164
references.citation: Development. 2004 Jul;131(13):3121-31
references.pmid: 15175248
references.citation: Development. 2001 Aug;128(15):2847-55
references.pmid: 11532909
references.citation: J Exp Zool B Mol Dev Evol. 2005 May 15;304(3):206-19
references.pmid: 15880771
references.citation: Int J Dev Biol. 1990 Sep;34(3):323-36
references.pmid: 1702679
references.citation: Cytogenet Cell Genet. 2001;92(3-4):320-5
references.pmid: 11435706
references.citation: Nature. 1995 Jun 22;375(6533):678-81
references.pmid: 7791900
references.citation: Hum Mol Genet. 2000 Jan 22;9(2):165-73
references.pmid: 10607827