title: Enamel malformations associated with a defined dentin sialophosphoprotein mutation in two families.
abstract: Dentin sialophosphoprotein (DSPP) mutations cause dentin dysplasia type II (DD-II) and dentinogenesis imperfecta types II and III (DGI-II and DGI-III, respectively). We identified two kindreds with DGI-II who exhibited vertical bands of hypoplastic enamel. Both families had a previously reported DSPP mutation that segregated with the disease phenotype. Oral photographs and dental radiographs of four affected and one unaffected participant in one family and of the proband in the second family were used to document the dental phenotypes. We aligned the 33 unique allelic DSPP sequences showing variable patterns of insertions and deletions (indels), generated a merged dentin phosphoprotein (DPP) sequence that includes sequences from all DSPP length haplotypes, and mapped the known DSPP mutations in this context. Analyses of the DSPP sequence changes and their probable effects on protein expression, as well as published findings of the dental phenotype in Dspp null mice, support the hypothesis that all DSPP mutations cause pathology through dominant-negative effects. Noting that Dspp is transiently expressed by mouse pre-ameloblasts during formation of the dentino-enamel junction, we hypothesize that DSPP dominant-negative effects potentially cause cellular pathology in pre-ameloblasts that, in turn, causes enamel defects. We conclude that enamel defects can be part of the dental phenotype caused by DSPP mutations, although DSPP is not critical for dental enamel formation.
authors.affiliation: Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, Ann Arbor, MI 48108, USA.
authors.forename: Shih-Kai
authors.initials: SK
authors.lastname: Wang
authors.forename: Hui-Chen
authors.initials: HC
authors.lastname: Chan
authors.forename: Sudha
authors.initials: S
authors.lastname: Rajderkar
authors.forename: Rachel N
authors.initials: RN
authors.lastname: Milkovich
authors.forename: Karen A
authors.initials: KA
authors.lastname: Uston
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: D000293:Adolescent; D000565:Ameloblasts / Q000378:metabolism / Q000473:pathology; D000595:Amino Acid Sequence; D004252:DNA Mutational Analysis; D003744:Dental Enamel Hypoplasia / Q000235:genetics*; D003805:Dentin Dysplasia / Q000235:genetics*; D003811:Dentinogenesis Imperfecta / Q000235:genetics*; D016326:Extracellular Matrix Proteins / Q000235:genetics* / Q000502:physiology*; D005260:Female; D005799:Genes, Dominant; D005838:Genotype; D006239:Haplotypes; D006801:Humans; D008297:Male; D008969:Molecular Sequence Data; D009154:Mutation; D010375:Pedigree; D010641:Phenotype; D010750:Phosphoproteins / Q000235:genetics* / Q000502:physiology*; D012795:Sialoglycoproteins / Q000235:genetics* / Q000502:physiology*; D000099311:Dentin Sialophosphoprotein
chemical_list: D016326:Extracellular Matrix Proteins; D010750:Phosphoproteins; D012795:Sialoglycoproteins; D000099311:Dentin Sialophosphoprotein