title: ITGB6 loss-of-function mutations cause autosomal recessive amelogenesis imperfecta.
abstract: Integrins are cell-surface adhesion receptors that bind to extracellular matrices (ECM) and mediate cell-ECM interactions. Some integrins are known to play critical roles in dental enamel formation. We recruited two Hispanic families with generalized hypoplastic amelogenesis imperfecta (AI). Analysis of whole-exome sequences identified three integrin beta 6 (ITGB6) mutations responsible for their enamel malformations. The female proband of Family 1 was a compound heterozygote with an ITGB6 transition mutation in Exon 4 (g.4545G > A c.427G > A p.Ala143Thr) and an ITGB6 transversion mutation in Exon 6 (g.27415T > A c.825T > A p.His275Gln). The male proband of Family 2 was homozygous for an ITGB6 transition mutation in Exon 11 (g.73664C > T c.1846C > T p.Arg616*) and hemizygous for a transition mutation in Exon 6 of Nance-Horan Syndrome (NHS Xp22.13; g.355444T > C c.1697T > C p.Met566Thr). These are the first disease-causing ITGB6 mutations to be reported. Immunohistochemistry of mouse mandibular incisors localized ITGB6 to the distal membrane of differentiating ameloblasts and pre-ameloblasts, and then ITGB6 appeared to be internalized by secretory stage ameloblasts. ITGB6 expression was strongest in the maturation stage and its localization was associated with ameloblast modulation. Our findings demonstrate that early and late amelogenesis depend upon cell-matrix interactions. Our approach (from knockout mouse phenotype to human disease) demonstrates the power of mouse reverse genetics in mutational analysis of human genetic disorders and attests to the need for a careful dental phenotyping in large-scale knockout mouse projects.
authors.affiliation: Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, 1210 Eisenhower Place, Ann Arbor, MI 48108, USA.
authors.forename: Shih-Kai
authors.initials: SK
authors.lastname: Wang
authors.forename: Murim
authors.initials: M
authors.lastname: Choi
authors.forename: Amelia S
authors.initials: AS
authors.lastname: Richardson
authors.forename: Bryan M
authors.initials: BM
authors.lastname: Reid
authors.forename: Brent P
authors.initials: BP
authors.lastname: Lin
authors.forename: Susan J
authors.initials: SJ
authors.lastname: Wang
authors.forename: Jung-Wook
authors.initials: JW
authors.lastname: Kim
authors.forename: James P
authors.initials: JP
authors.lastname: Simmer
authors.forename: Jan C-C
authors.initials: JC
authors.lastname: Hu
mesh_terms: D000565:Ameloblasts / Q000378:metabolism / Q000473:pathology; D000567:Amelogenesis Imperfecta / Q000235:genetics* / Q000378:metabolism / Q000473:pathology*; D000595:Amino Acid Sequence; D000818:Animals; D002386:Cataract / Q000151:congenital* / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D002648:Child; D003743:Dental Enamel / Q000378:metabolism / Q000473:pathology; D005260:Female; D005808:Genes, Recessive; D040181:Genetic Diseases, X-Linked / Q000235:genetics* / Q000378:metabolism / Q000473:pathology*; D006579:Heterozygote; D006720:Homozygote; D006801:Humans; D007124:Immunoenzyme Techniques; D039641:Integrin beta Chains / Q000235:genetics* / Q000378:metabolism; D008297:Male; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics*; D010375:Pedigree; D010641:Phenotype; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D014071:Tooth Abnormalities / Q000235:genetics* / Q000378:metabolism / Q000473:pathology*
chemical_list: D039641:Integrin beta Chains; D012333:RNA, Messenger; C072170:integrin beta6