title: Aryl hydrocarbon receptor nuclear translocator 2 (ARNT2): structure, gene mapping, polymorphisms, and candidate evaluation for human orofacial clefts.
abstract: BACKGROUND
  Nonsyndromic orofacial clefts have an estimated incidence of 1/1000 live births. Population genetic and embryologic studies suggest that cleft palate only (CPO) may be a distinct clinical entity from cleft lip with or without cleft palate (CL/P). Both CPO and CL/P are thought to be multifactorial in etiology, with evidence indicating that genetic, environmental, and developmental determinants may all play a role. The ARNT2 gene localizes to a conserved linkage group on mouse chromosome 7 that is syntenic with human chromosome 15q23-25. This chromosomal region was previously identified as a teratogen-induced clefting susceptibility locus in a genome-wide scan of AXB and BXA recombinant inbred mice. Arnt2 is expressed in the first branchial arch in mice. The teratogen 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) acts through the aryl hydrocarbon receptor (Ahr) pathway to produce dose-dependent CPO and thymic wasting in mice exposed in utero. Arnt2 and Ahr proteins dimerize in vitro. TCDD exposure is also associated with orofacial clefting in children of parents involved in agricultural work.
  
  
  METHODS
  To determine whether ARNT2 influences human craniofacial development, we identified the human ARNT2 gene and conducted genomic structural analysis. Mutational screening was performed in infants with nonsyndromic CPO or CL/P who were identified by the Iowa Birth Defects Registry.
  
  
  RESULTS
  A common amino acid polymorphism was detected but, no obvious disease-causing mutations were detected by SSCP analysis. The microsatellite marker, GATA89D04 (D15S823) was identified within intron 11 of the human ARNT2 gene, and linkage disequilibrium of nonsyndromic CPO and CL/P parent-infant trios was conducted.
  
  
  CONCLUSIONS
  No association was demonstrated with CPO (n = 45) and CL/P (n = 37). Teratology 66:85-90, 2002.
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, University of Iowa, Iowa City, Iowa 52242, USA.
authors.forename: Lon L
authors.initials: LL
authors.lastname: Barrow
authors.forename: Mary E
authors.initials: ME
authors.lastname: Wines
authors.forename: Paul A
authors.initials: PA
authors.lastname: Romitti
authors.forename: Bernadette C
authors.initials: BC
authors.lastname: Holdener
authors.forename: Jeffrey C
authors.initials: JC
authors.lastname: Murray
mesh_terms: D000818:Animals; D051784:Aryl Hydrocarbon Receptor Nuclear Translocator; D051792:Basic Helix-Loop-Helix Proteins; D015152:Blotting, Northern; D002874:Chromosome Mapping; D002971:Cleft Lip / Q000235:genetics*; D002972:Cleft Palate / Q000235:genetics*; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000032:analysis; D006801:Humans; D007223:Infant; D015810:Linkage Disequilibrium; D051379:Mice; D009154:Mutation; D016133:Polymerase Chain Reaction; D011110:Polymorphism, Genetic; D018807:Polymorphism, Single-Stranded Conformational; D018336:Receptors, Aryl Hydrocarbon / Q000235:genetics* / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism
chemical_list: D051784:Aryl Hydrocarbon Receptor Nuclear Translocator; D051792:Basic Helix-Loop-Helix Proteins; D018076:DNA, Complementary; D018336:Receptors, Aryl Hydrocarbon; D014157:Transcription Factors; C490989:ARNT2 protein, human; C099817:Arnt2 protein, mouse