Novel nonsense mutation in MSX1 causes tooth agenesis with cleft lip in a Chinese family

Abstract

Tooth agenesis is one of the most common developmental disorders in humans. Previous studies have attributed non-syndromic tooth agenesis to mutations in several genes, including MSX1, PAX9, EDA, and AXIN2. In this study, we investigated a Chinese family with tooth agenesis combined with cleft lip. Genomic DNA was isolated from blood samples of all available family members. Candidate genes MSX1 and PAX9 were amplified by the PCR and directly sequenced. A novel heterozygous mutation at c.C565T, exon 2 of MSX1, was identified in affected members. To analyze the effect of the nonsense mutation on MSX1 expression, vectors containing wild-type and mutated MSX1 were constructed and transfected into COS7 cell lines. Real-time PCR showed that the mRNA expression of the mutated MSX1 was dramatically reduced compared with that of the wild-type MSX1. Our findings suggest that the nonsense mutation in MSX1 might have resulted in rapid degradation of the mutated transcript and caused the phenotype of tooth agenesis with cleft lip in the Chinese family.

MSX1 mutations and associated disease phenotypes: genotype-phenotype relations

“…Functional analyses of the mutant proteins suggest that haploinsufficiency of MSX1 underlies this phenotype. 16,38 Mutant proteins were predicted to either exhibit reduced stability or to have reduced DNA binding capacity, or to have reduced capability to interact with their cognate protein factors. As a result, the function of MSX1 as a transcriptional repressor can be greatly impaired.…”

“…9 Up to now, two reports propose MSX1 as a candidate gene for tooth agenesis combined with orofacial clefting. 16,41 FROM GENOTYPE TO PHENOTYPE Overview of human MSX1 mutations Since the first MSX1 variant was identified in a pedigree with tooth agenesis, 8 several additional pathogenic variants have been discovered. To analyze the MSX1 mutations, we retrieved all MSX1 variants from HGMD (Human Gene Mutation Database) Professional up to the 30th of June, 2015.…”

“…38 Msx1 mutations mostly function in a dose-sensitive manner but because truncating mutations often lead to complete loss of function or to abnormal mRNA and/or protein expression they result in more disabled Msx1 proteins than in case of in-frame mutations. 16 Secondly, in order to analyse the relation between the TA phenotype severity to the mutations in as much detail as possible, we refined the phenotypes by introducing 6 subcategories with increasing (average) number of TA (Table 4). This way we could cover the spectrum of dental phenotype severity from agenesis of 1 -4 teeth towards agenesis of 17-20 teeth in the permanent dentition (except for the wisdom teeth).…”

“…[13][14][15] In a previous study we identified a novel MSX1 mutation causing tooth agenesis with cleft lip, further confirming that different MSX1 mutations may cause different phenotypes. 16 This review reveals a strong correlation between observed phenotypes and the location in the MSX1 protein structure of the disease causing mutations. Mutations in the structural part, which disturb DNA binding of the homeodomain (HD), preferentially cause tooth agenesis with or without other phenotypes, while variants in the natively unfolded N-terminal part of the protein generally cause ns OFC.…”

Associations between the risk of tooth agenesis and single-nucleotide polymorphisms of MSX1 and PAX9 genes in nonsyndromic cleft patients

“…[15][16][17][18][19] To date, only a few studies have addressed the genetic basis of oral cleft with or without tooth agenesis in humans. [20][21][22] Van den Boogaard et al 20 and Liang et al 21 suggested that tooth agenesis and oral cleft were associated with nonsense mutations of MSX1, such as Ser104stop in exon 1 in a Dutch family and Q189X in exon 2 in a Chinese family, respectively. However, Liang et al 21 also reported that sequence analysis of PAX9 did not reveal mutation in any of the affected individuals studied.…”