Genetic and Morphological Variation in Hypodontia of Maxillary Lateral Incisors.

(1) Background: Hypodontia has a multifactorial aetiology, in which genetic factors are a major component. Associated with this congenital absence, the formed teeth may show differences in size and shape, which may vary with the specific genetic variants and with the location of the missing teeth. The aims of the present study were to investigate a specific variant of MSX1, derive morphometric tooth measurements in a sample of patients with isolated maxillary lateral incisor agenesis and matched controls, and model the findings. (2) Methods: Genotyping of the MSX1 rs8670 genetic variant and morphometric measurements with a 2D image analysis method were performed for 26 hypodontia patients and 26 matched controls. (3) Results: The risk of upper lateral incisor agenesis was 6.9 times higher when the T allele was present. The morphometric parameters showed significant differences between hypodontia patients and controls and between the unilateral and bilateral agenesis cases. The most affected crown dimension in the hypodontia patients was the bucco-lingual dimension. In crown shape there was significant variation the Carabelli trait in upper first molars. (4) Conclusions: The MSX1 rs8670 variant was associated with variations in morphological outcomes. The new findings for compensatory interactions between the maxillary incisors indicate that epigenetic and environmental factors interact with this genetic variant. A single-level directional complex interactive network model incorporates the variations seen in this study.

A novel mutation in the WNT6 gene of congenital tooth agenesis / 口腔疾病防治

Objective @#This article explores the relationship between congenital tooth agenesis and related gene mutations, providing a reference for early diagnosis of the disease.@*Methods @# Clinical and radiographic examinations of a rare case of congenital tooth agenesis were conducted to evaluate the abnormal morphology and quantity of the teeth, as well as the overall health of the patient. Bidirectional sequencing of the PAX9 and MSX1 genes and whole-exome sequencing were conducted to identify potential genetic abnormalities. Sanger sequencing of the newly discovered mutation site was performed on the proband's son. Subsequently, the impacts of the mutations were evaluated through computational tools and a cell-based gene transfection assay. @*Results @#This is a rare case of tooth agenesis characterized by a congenitally missing first molar, a second molar with one single root and a supernumerary second premolar in the right mandibular dentition. The c.717 C>C/T in PAX9 is synonymous. The c.119C>G in MSX1 is a missense mutation predicted to be “benign” by Polyphen. Through whole-exome sequencing, we found a novel mutation, c.637-7 C>A in intron 3 of the WNT6 gene, which is predicted by MAXENT to influence the splicing of mRNA. Both the proband and his son carry this mutation. A cell-based gene transfection assay demonstrated that it did not alter the mRNA splicing of WNT6. @* Conclusion @#The interaction between single nucleotide polymorphisms may contribute to congenital tooth agenesis.

Disorders of sex development in Wolf-Hirschhorn syndrome: a genotype-phenotype correlation and MSX1 as candidate gene.

BACKGROUND: Wolf-Hirschhorn (WHS) is a set of congenital physical anomalies and mental retardation associated with a partial deletion of the short arm of chromosome 4. To establish a genotype-phenotype correlation; we carried out a molecular cytogenetic analysis on two Tunisian WHS patients. Patient 1 was a boy of 1-year-old, presented a typical WHS phenotype while patient 2, is a boy of 2 days presented an hypospadias, a micropenis and a cryptorchidie in addition to the typical WHS phenotype. Both the array comparative genomic hybridization and fluorescence in situ hybridization techniques were used. RESULTS: Results of the analysis showed that patient 2 had a greater deletion size (4.8 Mb) of chromosome 4 than patient 1 (3.4 Mb). Here, we notice that the larger the deletion, the more genes are likely to be involved, and the more severe the phenotype is likely to be. If we analyze the uncommon deleted region between patient1 and patient 2 we found that the Muscle Segment Homeobox (MSX1) gene is included in this region. MSX1 is a critical transcriptional repressor factor, expressed in the ventral side of the developing anterior pituitary and implicated in gonadotrope differentiation. Msx1 acts as a negative regulatory pituitary development by repressing the gonadotropin releasing hormone (GnRH) genes during embryogenesis. We hypothesized that the deletion of MSX1 in our patient may deregulate the androgen synthesis. CONCLUSION: Based on the MSX1 gene function, its absence might be indirectly responsible for the hypospadias phenotype by contributing to the spatiotemporal regulation of GnRH transcription during development.

MSX1 gene polymorphisms in Mexican patients with non-syndromic cleft lip/palate.

OBJECTIVE: Non-syndromic cleft lip/palate malformation (CL/P) is one of the most common birth defects in humans and has a complex etiology involving genetic and environmental factors. Mutations in the MSX1 gene are critical during craniofacial development. The purpose of this study was to investigate the contribution of MSX1 gene polymorphisms to the risk of developing CL/P in a sample of Mexican patients. METHODS: The sample consisted of 282 subjects (69 cases and 213 relatives). Four single-nucleotide polymorphisms (SNP1, P147Q, SNP5 and P278S) were tested for association with CL/P in triad and case-pseudo-control analyses. Polymorphism typing was performed by restriction fragment length polymorphism and dot-blot techniques. Allele and genotype frequencies were calculated between patients and pseudo-controls and compared using the Chi square test with Yates correction. Odds ratios and 95% confidence intervals were obtained using SPSS software (v19). Triad analysis was also performed using the program HAPLIN (v5.3). RESULTS: In the cases and pseudo-controls, an association was found between CL/P and the SNP1-G allele (P = 0.031) and the SNP1-G/G genotype (P = 0.032), a polymorphism located near MSX1. Triad analysis showed a tendency toward CL/P susceptibility for the genotype SNP1-G/G (P = 0.075) and an association between CL/P and the haplotype GCTC (P = 0.037). No associated haplotype was found in the cases and pseudo-controls. Two partial haplotypes, GT (SNP1-SNP5) (P = 0.032) and GC (SNP1-P278S) (P = 0.033), were associated with susceptibility in the heterozygous and homozygous types, respectively. In contrast, haplotype AT (SNP1-SNP5) was associated with protection (P = 0.012) in the homozygous type. CONCLUSIONS: The results of this study suggest an association between CL/P susceptibility and SNP1, located near the MSX1 gene, in the Mexican population.

The Gene Network Underlying Hypodontia.

Mammalian tooth development is a precise and complicated procedure. Several signaling pathways, such as nuclear factor (NF)-κB and WNT, are key regulators of tooth development. Any disturbance of these signaling pathways can potentially affect or block normal tooth development, and presently, there are more than 150 syndromes and 80 genes known to be related to tooth agenesis. Clarifying the interaction and crosstalk among these genes will provide important information regarding the mechanisms underlying missing teeth. In the current review, we summarize recently published findings on genes related to isolated and syndromic tooth agenesis; most of these genes function as positive regulators of cell proliferation or negative regulators of cell differentiation and apoptosis. Furthermore, we explore the corresponding networks involving these genes in addition to their implications for the clinical management of tooth agenesis. We conclude that this requires further study to improve patients' quality of life in the future.

Análisis mutacional del gen MSX1 en pacientes con FLPNS e hipodoncia / Mutation analysis of MSX1 gene in patients with NSCLP and hypodontia

Introducción. La etiología de la hendidura labio-palatina es compleja e involucra factores genéticos y ambientales. Además de la hendidura, numerosos estudios han reportado la presencia de anomalías dentales en asociación con varias formas de hendidura labial,palatina o ambas; entre estas anomalías se ha encontrado la prevalencia de agenesia dental. La idea de que los mismos factores etiológicos que causan la formación de la hendidura afectan el desarrollo de la dentición, es apoyada por varios autores que proponen al genMSX1 como candidato para estos dos fenotipos. Una mutación nonsense (Ser104stop) en el exon 1 del gen MSX1 se encontró en una familia danesa, en la que unos miembros presentaban agenesia dental o hendidura palatina y otros presentaban las dos entidadesasociadas. A pesar de que se han realizado varios estudios sobre anomalías dentales en pacientes con hendidura labio-palatina y existen estudios que confirman a MSX1 como ungen candidato tanto para hipodoncia como para hendiduras oro-faciales, la interpretación de los resultados ha sido muy compleja. Objetivo. Determinar la presencia de la mutación reportada en pacientes colombianos con hendidura labio-palatina e hipodoncia. Materiales y métodos. Se analizaron 30 pacientes, 22 con hendidura labio-palatina y 8 sólo con hipodoncia, y 60 controles sanos, mediante exámenes clínicos y radiográficos; se les tomaron muestras de sangre por venopunción, se extrajo el ADN y se realizó amplificación por la técnica de PCR del exón 1. Posteriormente, se llevó a cabo un análisis de restricción. Resultados. De los pacientes con hendidura labio-palatina, 16 presentaron agenesias dentalesfuera y dentro del área de hendidura, la mayoría fueron laterales y premolares superiores. La mayoría de los pacientes con hipodoncia únicamente, presentaron ausencias de incisivos. Además, presentaron otras anomalías dentarias, como micrognatismo, dientes supernumerarios y prognatismo mandibular...

Introduction: The etiology of non-syndromic cleft lip palate is complex and involves genetic and environmental factors. Additional to the fissure itself, numerous studies have reported the presence of dental anomalies with various forms of cleft lip, cleft palate or both. The prevalence of dental agenesis has been found within these anomalies. The idea that the same etiology factors which cause the formation of the cleft affect the dental development is supported by various authors who propose the MSX1 gene to be the candidate for these two phenotypes. A nonsense mutation in the exon 1 of the MSX1 gene was found in a Danish family in which one of the members presented dental agenesis and/or cleft palate and others presented both entities. Although various studies have been associated reported with respect to dental anomalies in patients with nonsyndromic cleft lip palate and there are studies which confirm MSX1 as a candidate gene for hypodontia and orofacial fissures, the interpretation of the results has been very complex.Objective: To determine the presence of the mutation reported in Colombian patients with nonsyndromic cleft lip palate and hypodontia. Materials and methods: 30 patients, 22 with non-syndromic cleft lip palate and 8 with only hypodontia and 60 healthy patients were clinically and radiographically analyzed. Blood samples were taken through venopunction, the DNA was extracted and the PCR technique was utilized. Afterwords, the restriction analysiswas carried out...

Characteristics of MSX1 gene in Korean nonsyndromic cleft lip and palate individuals / 대한치과교정학회지

OBJECTIVE: This study was performed to identify the characteristics of the MSX1 gene (locus chromosome 4p16) in Korean nonsyndromic cleft lip and palate (CL/P), which is assumed to be a major candidate gene acting as a causal factor in nonsyndromic CL/P and missing teeth. METHODS: The 36 individuals (23 males and 13 females) who had visited the department of orthodontics at from 1998 to 2002 and who had nonsyndromic CL/P were included in the study. Using a PCR-based assay, the MSX1 gene was amplified, sequenced, and searched for inferred protein products (Reference: Homo sapiens MSX1, accession number AF426432 and NP_002439). The common single nucleotide polymorphisms were observed. RESULTS: In exon 1, nucleotide "A" of the 253 basepair (bp) region was substituted for "G", and in the 255 bp region, nucleotide "G" was inserted. In exon 2, nucleotide "C" of the 11 bp region was substituted for "A", and "T" or "G" was inserted into the 351 bp region whereas "T" or "A" was inserted into the 352 bp region. In protein analysis, "Thr85Ala" missense mutation was found. The "Thr85Ala" missense mutation in this study is different from those of studies using subjects of other races. CONCLUSIONS: The results suggest that there is specific mutation of MSX1 in Korean and it plays an important role in Korean nonsyndromic CL/P. However, any distinct genetic polymorphisms between CL/P with missing teeth in the cleft region and CL/P without missing teeth could not be found.