A novel nonsense mutation in PAX9 is associated with marked variability in number of missing teeth

Genotypic and phenotypic correlations in tooth agenesis: insights from WNT10A and EDA mutations in syndromic and non-syndromic forms

Tooth agenesis (TA) occurs when tooth development is disrupted at the initiation stage. It can be classified into non-syndromic and syndromic forms (named NSTA and STA), depending on whether it is accompanied by abnormalities of other organs and systems. Genetic factors play a predominant role in the pathogenesis of tooth agenesis, with dozens of genes implicated in both forms. Several genes have been identified, mutations in which can lead to both forms of TA. Among these, WNT10A and EDA are frequently mutated genes in this context, representing extensively researched and documented genes in human non-syndromic selective agenesis of permanent teeth and their association with ectodermal dysplasia syndromes. In this review, we present an overview of the current knowledge regarding genes associated with NSTA and STA, focusing on the distribution and nature of WNT10A and EDA gene mutations. We also explore how these mutations relate to the condition's both forms, including their association with the number of missing permanent teeth.

Genotype-phenotype pattern analysis of pathogenic PAX9 variants in Chinese Han families with non-syndromic oligodontia

Background: Non-syndromic oligodontia is characterized by the absence of six or more permanent teeth, excluding third molars, and can have aesthetic, masticatory, and psychological consequences. Previous studies have shown that PAX9 is associated with autosomal dominant forms of oligodontia but the precise molecular mechanisms are still unknown.

Methods: Whole-exome and Sanger sequencing were performed on a cohort of approximately 28 probands with NSO, for mutation analysis. Bioinformatic analysis was performed on the potential variants. Immunofluorescence assay, western blotting, and qPCR were used to explore the preliminary functional impact of the variant PAX9 proteins. We reviewed PAX9-related NSO articles in PubMed to analyze the genotype-phenotype correlations.

Results: We identified three novel PAX9 variants in Chinese Han families: c.152G>T (p.Gly51Val), c.239delC (p.Thr82Profs*3), and c.409C>T (q.Gln137Ter). In addition, two previously reported missense variants were identified: c.140G>C (p.Arg47Pro) and c.146C>T (p.Ser49Leu) (reference sequence NM_006194.4). Structural modeling revealed that all missense variants were located in the highly conserved paired domain. The other variants led to premature termination of the protein, causing structural impairment of the PAX9 protein. Immunofluorescence assay showed abnormal subcellular localizations of the missense variants (R47P, S49L, and G51V). In human dental pulp stem cells, western blotting and qPCR showed decreased expression of PAX9 variants (c.140G>C, p.R47P, and c.152G>T, p.G51V) compared with the wild-type group at both the transcription and translation levels. A review of published papers identified 64 PAX9 variants related to NSO and found that the most dominant feature was the high incidence of missing upper second molars, first molars, second premolars, and lower second molars.

Conclusion: Three novel PAX9 variants were identified in Chinese Han families with NSO. These results extend the variant spectrum of PAX9 and provide a foundation for genetic diagnosis and counseling.

Novel PAX9 compound heterozygous variants in a Chinese family with non-syndromic oligodontia and genotype-phenotype analysis of PAX9 variants

OBJECTIVE

Studies have reported that >91.9% of non-syndromic tooth agenesis cases are caused by seven pathogenic genes. To report novel heterozygous PAX9 variants in a Chinese family with non-syndromic oligodontia and summarize the reported genotype-phenotype relationship of PAX9 variants.

METHODOLOGY

We recruited 28 patients with non-syndromic oligodontia who were admitted to the Hospital of Stomatology Hebei Medical University (China) from 2018 to 2021. Peripheral blood was collected from the probands and their core family members for whole-exome sequencing (WES) and variants were verified by Sanger sequencing. Bioinformatics tools were used to predict the pathogenicity of the variants. SWISS-MODEL homology modeling was used to analyze the three-dimensional structural changes of variant proteins. We also analyzed the genotype-phenotype relationships of PAX9 variants.

RESULTS

We identified novel compound heterozygous PAX9 variants (reference sequence NM_001372076.1) in a Chinese family with non-syndromic oligodontia: a new missense variant c.1010C>A (p.T337K) in exon 4 and a new frameshift variant c.330_331insGT (p.D113Afs*9) in exon 2, which was identified as the pathogenic variant in this family. This discovery expands the known variant spectrum of PAX9; then, we summarized the phenotypes of non-syndromic oligodontia with PAX9 variants.

CONCLUSION

We found that PAX9 variants commonly lead to loss of the second molars.

Mutations in COL1A1/A2 and CREB3L1 are associated with oligodontia in osteogenesis imperfecta

Background

Osteogenesis imperfecta (OI) is a heterogeneous connective tissue disorder characterized by an increased tendency for fractures throughout life. Autosomal dominant (AD) mutations in COL1A1 and COL1A2 are causative in approximately 85% of cases. In recent years, recessive variants in genes involved in collagen processing have been found. Hypodontia (< 6 missing permanent teeth) and oligodontia (≥ 6 missing permanent teeth) have previously been reported in individuals with OI. The aim of the present cross-sectional study was to investigate whether children and adolescents with OI and oligodontia and hypodontia also present with variants in other genes with potential effects on tooth development. The cohort comprised 10 individuals (7.7–19.9 years of age) with known COL1A1/A2 variants who we clinically and radiographically examined and further genetically evaluated by whole-genome sequencing. All study participants were treated at the Astrid Lindgren Children’s Hospital at Karolinska University Hospital, Stockholm (Sweden’s national multidisciplinary pediatric OI team). We evaluated a panel of genes that were associated with nonsyndromic and syndromic hypodontia or oligodontia as well as that had been found to be involved in tooth development in animal models.

Results

We detected a homozygous nonsense variant in CREB3L1, p.Tyr428*, c.1284C > A in one boy previously diagnosed with OI type III. COL1A1 and COL1A2 were the only two genes among 9 individuals which carried a pathogenic mutation. We found rare variants with unknown significance in several other genes related to tooth development.

Conclusions

Our findings suggest that mutations in COL1A1, COL1A2, and CREB3L1 may cause hypodontia and oligodontia in OI. The findings cannot exclude additive effects from other modifying or interacting genes that may contribute to the severity of the expressed phenotype. Larger cohorts and further functional studies are needed.

Orthodontic management of patients with congenitally missing permanent teeth

Dental agenesis is one of the most common developmental anomalies in humans. It occurs as part of a genetic syndrome or as an isolated sporadic or familial finding. Third molars, second mandibular premolars and maxillary lateral incisors are the most frequently targeted teeth of the permanent dentition. Clinically, patients with congenitally missing permanent teeth seeking treatment present with unesthetic diastemas, midline deviation and tilting of adjacent teeth in the edentulous areas. The impact of tooth agenesis reflects on esthetics, function, psychological and social well-being of the individuals affected. Orthodontics can contribute to the treatment plan selected by rearranging the present teeth so as to open spaces for prosthetic restorations or close spaces by reshaping teeth if needed. Following orthodontic space opening/maintaining, the usual alternatives involve single implants, two-(cantilever) or full coverage(cantilever) prostheses. Less frequently, the treatment modality of autotransplantation is proposed with a good esthetic result but feasible only in young patients where the roots of the premolars are still developing. In orthodontic space closure, treatment is accomplished sooner without waiting for the completion of growth of the patient. Depending on various factors such as the malocclusion, the dento-skeletal profile, the smile line, the space requirements, the teeth missing, the periodontal issues, the age of the patient and any financial issues, the clinician will determine the most appropriate treatment approach. The final esthetic and functional result should resemble an intact natural dentition.

The role of PAX9 promoter gene polymorphisms in causing hypodontia: a study in the Jordanian population

Background

The congenital absence of one or few teeth, hypodontia, is considered one of the utmost dental ageneses in human beings. Several genes have been shown to be involved in the development of hypodontia such as paired box gene 9 (PAX9). The expression of PAX9 is controlled by several polymorphic elements in the promoter region of the gene on 14q13.3 locus. The aim of this study was to find any association between PAX9 c.-912T>C (rs2073247) and c.-1031G>A (rs2073244) promoter polymorphisms and the development of hypodontia among the Jordanian population.

Methods

Genotyping of the polymorphisms in 72 unrelated subjects with hypodontia was performed using PCR-restriction fragment length polymorphism (RFLP) technique and compared with that of 72 normal healthy unrelated control individuals.

Results

The hypodontia group had a significantly higher -1031GG genotype (P<0.01) and a significantly lower -912TC genotype (P<0.01) compared with the control group. The results suggest that the transcriptional activity of PAX9 gene is affected by polymorphisms in the promoter region of this gene and is associated with hypodontia phenotype.

Conclusion

The rs2073247) and rs2073244 promoter polymorphisms of PAX9 might play a role in the development of hypodontia in the Jordanian population.

Hypodontia: An Update on Its Etiology, Classification, and Clinical Management

Hypodontia, or tooth agenesis, is the most prevalent craniofacial malformation in humans. It may occur as part of a recognised genetic syndrome or as a nonsyndromic isolated trait. Excluding third molars, the reported prevalence of hypodontia ranges from 1.6 to 6.9%, depending on the population studied. Most affected individuals lack only one or two teeth, with permanent second premolars and upper lateral incisors the most likely to be missing. Both environmental and genetic factors are involved in the aetiology of hypodontia, with the latter playing a more significant role. Hypodontia individuals often present a significant clinical challenge for orthodontists because, in a number of cases, the treatment time is prolonged and the treatment outcome may be compromised. Hence, the identification of genetic and environmental factors may be particularly useful in the early prediction of this condition and the development of prevention strategies and novel treatments in the future.

Nonsyndromic oligodontia : Does the Tooth Agenesis Code (TAC) enable prediction of the causative mutation?

OBJECTIVES

The literature suggests an association between phenotype and causative mutation in nonsyndromic oligodontia. Thus, the present study was designed to verify this hypothesis in a consecutive cohort of patients.

METHODS

All patients with nonsyndromic oligodontia who had been treated at the study center (Department of Orthodontics, University of Giessen, Germany) over the period 1986-2013 were contacted. Candidates were included only if at least one more family member had hypo- or oligodontia (i.e., without regard to the number of congenitally missing teeth). A total of 20 patients were included. After evaluating the dental status of each participant, the Tooth Agenesis Code (TAC) was applied. On this basis, a tentative diagnosis was made to predict which gene (MSX1, AXIN2, EDA, or PAX9) was likely to show mutation. Afterwards this hypothesis was confirmed or rejected by analyzing a saliva sample for mutation of the predicted gene. If confirmed, any available family members were also genetically analyzed.

RESULTS

Based on their TAC scores and sums, gene mutations were predicted for MXS1 in 11, AXIN2 in 3, EDA in 6, and PAX9 in none of the patients. The evaluation of MSX1 yielded variants in 4 of 11 cases, all of which were classified as nonpathogenic since they were not considered as functional mutations. The evaluation of EDA yielded a pathogenic exon-7 mutation in 2 of 6 patients, both being brothers with different TAC scores; the same mutation, which represents a novel missense mutation, was also found in other members of the same family. The evaluation of AXIN2 yielded variants in 3 of 3 cases, all of which were classified as nonpathogenic.

CONCLUSIONS

Our findings obtained in consecutive patients with nonsyndromic oligodontia did not reveal any clinically relevant associations between oligodontia phenotype (based on TAC) and causative mutations for nonsyndromic oligodontia.

Mutations in the MSX1 gene in Turkish children with non-syndromic tooth agenesis and other dental anomalies

Aim:

To search for mutations on the MSX1 gene and to present a genetic basis for non-syndromic tooth agenesis in conjunction with dental anomalies in a Turkish population.

Materials and Methods:

The patients included in this study were otherwise healthy, with ages ranging from seven to eighteen years. Eighty-two of them had one to six teeth missing (Group I) and 26 had more than six teeth missing (Group II), except for the third molars,. The missing teeth and dental anomalies were examined clinically and radiographically. The MSX1 gene was sequenced from the blood samples of patients who consented to the study.

Results:

Mutations or polymorphisms on the MSX1 gene were identified in six patients. Taurodontism was seen in patients from both groups I and II. The nucleotide changes were identified by mutation screening.

Conclusions:

Performing family studies, screening other candidate genes, and investigation of interactions between genes will provide a basis for better analysis of tooth agenesis models and their association with other dental anomalies.

Clinical and genetic analysis of a nonsyndromic oligodontia in a child

The etiology of tooth agenesis may be related to several factors, among them, the genetic alterations that play a fundamental role in the development of this dental anomaly, so that knowledge about it helps the clinician to have a greater understanding of their patients. Thus, the aim of this study was to report the case of a nonsyndromic child, with tooth agenesis of one premolar, three first permanent molars, and all second permanent molars. In addition, a genetic research between polymorphic variants in genes MMP3 and BMP2 was performed in order to observe the association between changes in these genes and congenital tooth absences. For this purpose, DNA from child was extracted and polymorphisms were investigated. It was clinically and radiographically observed that this was a case of oligodontia, in which the authors suggested an association between the polymorphisms found and tooth agenesis diagnosed in that child.

Exclusion of PAX9 and MSX1 mutation in six families affected by tooth agenesis. A genetic study and literature review

OBJECTIVE

In the present study, it is describe the phenotypical analysis and the mutational screening, for genes PAX9 and MSX1, of six families affected by severe forms of tooth agenesis associated with other dental anomalies and systemic entities.

STUDY DESIGN

Six families affected by severe tooth agenesis associated with other dental anomalies and systemic entities were included. Oral exploration, radiological examination, medical antecedents consideration and mutational screening for PAX9 and MSX1 were carried out.

RESULTS

No mutations were discovered despite the fact that numerous teeth were missing. An important phenotypical variability was observed within the probands, not being possible to establish a parallelism with the patterns associated to previously described PAX9 and MSX1 mutations. CONCLUSIONS; These results bring us to conclude that probably other genes can determine phenotypical patterns of dental agenesis in the families studied, different than the ones described in the mutations of PAX9 and MSX1. Moreover, epigenetic factors can be involved, as those that can reduce gene dosage and other post-transcriptional modulation agents, causing dental agenesis associated or not with systemic anomalies.

Genetic background of nonsyndromic oligodontia: a systematic review and meta-analysis

OBJECTIVES

The goal of this work was to identify all known gene mutations that have been associated with the development of nonsyndromic oligodontia.

METHODS

A systematic literature search was performed electronically in two databases (PubMed, Medpilot) supplemented by a hand search. Articles published up to March 2012 were considered. Search terms were combined as follows: oligodontia and genes, oligodontia and mutations, tooth agenesis and genes, and tooth agenesis and mutations. A meta-analysis of the data was conducted based on the Tooth Agenesis Code (TAC).

RESULTS

Seven genes are currently known to have a potential for causing nonsyndromic oligodontia. All these genes vary both in terms of number of identified mutations and in terms of number of documented patients: 33 mutations and 93 patients are on record for PAX9, 10 mutations and 51 patients for EDA, 12 mutations and 33 patients for MSX1, 6 mutations and 17 patients for AXIN2, and 1 mutation in 1 patient for EDARADD, NEMO, and KRT17 each. A total TAC score of 250 was found to have cutoff properties, as 100% of MSX1 and 80% of EDA patients exhibited TAC ≤ 250, whereas 96.9% of PAX9 and 90% of AXIN2 patients exhibited TAC >250. Furthermore, 94.3% of EDA patients but only 28.6% of MSX1 patients exhibited odd-numbered TAC scores in at least one quadrant, and 72.7% of PAX9 but none of the AXIN2 patients were found to show TAC scores of 112 in at least one quadrant.

CONCLUSION

In order of decreasing frequency, PAX9, EDA, MSX1, AXIN2, EDARADD, NEMO, and KRT17 are the seven genes currently known to have a potential for causing nonsyndromic oligodontia. TAC scores enabled us to identify an association between oligodontia phenotypes and genotypes in the patients covered by this meta-analysis.

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

OBJECTIVE

To investigate the association between the risk of tooth agenesis and single-nucleotide polymorphisms (SNPs) of MSX1 and PAX9 genes in nonsyndromic cleft patients.

MATERIALS AND METHODS

The subjects were 126 Korean nonsyndromic cleft patients. Tooth agenesis type (TAT) was classified as none (0); cleft area (1); cleft area + other area (2); and other area (3) based on agenesis of the maxillary lateral incisor (MXLI) and another tooth within or outside the cleft area. TAT was further grouped into two subcategories (0 and 1) and four subcategories (0, 1, 2, and 3). Three SNPs of MSX1 and 10 SNPs of PAX9 were investigated using Fisher's exact test and logistic regression analysis.

RESULTS

Although the association between genotype distribution of PAX9-rs7142363 and TAT was significant (P < .05 in four subcategories), genotypic odds ratios (GORs) of SNPs in each TAT were not meaningful. However, for MSX1-rs12532 and PAX9-rs2073247, associations between genotypic distribution and TAT were significant (P < .01 in four subcategories and P < .05 in two subcategories; P < .01 in two subcategories, respectively). In cleft area, GORs of MXLI agenesis in genotypes GA of MSX1-rs12532 and CT of PAX9-rs2073247 were increased by 3.14-fold and 4.15-fold compared with genotype GG of MSX1-rs12532 and CC of PAX9-rs2073247, respectively (P <. 01; P < .05). In cleft area + other area, the GOR of agenesis of MXLI and another tooth in genotype AA of MSX1-rs12532 was increased by fivefold compared with genotype GG (P < .05).

CONCLUSION

Genetic disturbances of MSX1 and PAX9 genes are associated with tooth agenesis within and outside the cleft area.

Novel PAX9 and COL1A2 missense mutations causing tooth agenesis and OI/DGI without skeletal abnormalities

Inherited dentin defects are classified into three types of dentinogenesis imperfecta (DGI) and two types of dentin dysplasia (DD). The genetic etiology of DD-I is unknown. Defects in dentin sialophosphoprotein (DSPP) cause DD type II and DGI types II and III. DGI type I is the oral manifestation of osteogenesis imperfecta (OI), a systemic disease typically caused by defects in COL1A1 or COL1A2. Mutations in MSX1, PAX9, AXIN2, EDA and WNT10A can cause non-syndromic familial tooth agenesis. In this study a simplex pattern of clinical dentinogenesis imperfecta juxtaposed with a dominant pattern of hypodontia (mild tooth agenesis) was evaluated, and available family members were recruited. Mutational analyses of the candidate genes for DGI and hypodontia were performed and the results validated. A spontaneous novel mutation in COL1A2 (c.1171G>A; p.Gly391Ser) causing only dentin defects and a novel mutation in PAX9 (c.43T>A; p.Phe15Ile) causing hypodontia were identified and correlated with the phenotypic presentations in the family. Bone radiographs of the proband's dominant leg and foot were within normal limits. We conclude that when no DSPP mutation is identified in clinically determined isolated DGI cases, COL1A1 and COL1A2 should be considered as candidate genes. PAX9 mutation p.Phe15Ile within the N-terminal β-hairpin structure of the PAX9 paired domain causes tooth agenesis.

TGFB3 and BMP4 polymorphism are associated with isolated tooth agenesis

OBJECTIVE

To evaluate the association of the polymorphisms in the TGFB3 gene (rs2268626) and the BMP4 gene (rs17563) with isolated human tooth agenesis.

MATERIALS AND METHODS

One hundred and seventy-five unrelated individuals (125 control individuals without tooth agenesis and 50 cases with tooth agenesis) were evaluated using a case-control design. The participants of the study were recruited through the Dental School of the Federal University of Rio de Janeiro, Brazil. Genotyping of the selected polymorphisms for TGFB3 (48 individuals with tooth agenesis and 125 control cases) and BMP4 (46 individuals with tooth agenesis and 88 control cases) were carried out by real-time PCR using the Taqman assay method from a genomic DNA isolated from buccal epithelial cells of all individuals.

RESULTS

Significant statistical differences were found for genotype frequencies between tooth agenesis and TGFB3 control samples (p = 0.026). In addition, significant differences were also observed for allele and genotype frequencies between unilateral tooth agenesis and TGFB3 control samples (p = 0.014 and 0.004 for allele and genotype frequencies, respectively). For BMP4, genotype distribution had a statistically significant difference between groups (p = 0.047). The GG genotype of BMP4 was more frequent in individuals with three or more missing teeth than in the control group (p < 0.0001).

CONCLUSIONS

These results indicate that polymorphisms in the TGFB3 gene and in BMP4 genes contribute to tooth agenesis. Nonetheless, the extents to which this polymorphism may actually contribute to the tooth agenesis status should be clarified.

A novel nonsense mutation in PAX9 is associated with sporadic hypodontia

The most important events during the regulation of tooth development were inductive interactions between the epithelial and mesenchymal tissues. The expression of Pax9 had been shown to specifically mark the mesenchymal regions at the prospective sites of all teeth prior to any morphological manifestations. Here, we investigated the PAX9 gene as a candidate gene for hypodontia in five unrelated Chinese patients with tooth agenesis. Direct sequencing and restriction enzyme analysis revealed a novel heterozygous mutation c.480C>G (p.160Tyr>X, Y160X) in a patient who was missing 20 permanent teeth (the third molars excluded) and 6 primary teeth. The mutation was a nonsense mutation, leading to a premature stop codon in exon 2 of PAX9 gene. PCR analysis of complementary DNA from cultured lymphocytes of the affected individual could not indicate the complete degradation of the mutated transcript. Promoter reporter assays revealed reduced transcriptional activity of the mutated PAX9 protein suggesting that the severe phenotype may result from haploinsufficiency of PAX9. In another patient with 15 missing permanent teeth (the third molars excluded), we found the c.219insG mutation previously reported by Stockton.

Sequence analysis of PAX9, MSX1 and AXIN2 genes in a Chinese oligodontia family

OBJECTIVES

The goal of our research was to look into the clinical traits and genetic mutations in nonsyndromic oligodontia in a Chinese family and to gain insight into the role of mutations of PAX9, MSX1 and AXIN2 in oligodontia phenotypes.

MATERIALS AND METHODS

6 subjects from a family underwent complete oral examination, including panoramic radiographs. Retrospective data were reviewed and blood samples were collected. PCR primers for PAX9, MSX1, and AXIN2 were designed through the Oligo Primer Analysis Software. PCR products were purified and sequenced using the BigDye Terminator Kit and analysed by the 3730 DNA Analyzer.

RESULTS

The proband missed 4 permanent canines, 2 permanent maxillary lateral incisors, 2 permanent mandibular lateral incisors, and 2 permanent mandibular central incisors, whilst his maternal grandfather lacked only 2 permanent mandibular central incisors. Moreover, the size of some permanent teeth appeared smaller than normal values of crown width of Chinese people. Oligodontia and abnormalities of teeth were not present in other family members. Radiographic examination showed that the proband and the rest of family members retained all germs of the third molars. There was one known mutation A240P (rs4904210) of PAX9 in the coding region in the proband and the maternal family members (II-2, II-3, and II-4), which possibly contributed to structural and functional changes of proteins. No mutations were identified in MSX1 and AXIN2.

CONCLUSIONS

Our findings may imply that the PAX9 A240P mutation is a risk factor for oligodontia in the Chinese population. A240P is likely to be a genetic cause of oligodontia though previous literature suggested it as a polymorphism only.

A novel g.-1258G>A mutation in a conserved putative regulatory element of PAX9 is associated with autosomal dominant molar hypodontia

Mutations in the transcription factor PAX9 which plays a critical role in the switching of odontogenic potential from the epithelium to the mesenchyme during tooth development cause autosomal dominant non-syndromic hypodontia primarily affecting molars. Linkage analysis on a family segregating autosomal dominant molar hypodontia with markers flanking and within PAX9 yielded a maximum multipoint LOD score of 3.6. No sequence variants were detected in the coding or 5'- and 3'-untranslated regions (UTRs) of PAX9. However, we identified a novel g.-1258G>A sequence variant in all affected individuals of the family but not in the unaffected family members or in 3088 control chromosomes. This mutation is within a putative 5'-regulatory sequence upstream of PAX9 highly conserved in primates, somewhat conserved in ungulates and carnivores but not conserved in rodents. Bioinformatics analysis of the sequence determined that there was no abolition or creation of a putative binding site for known transcription factors. Based on our previous findings that haploinsufficiency for PAX9 leads to hypodontia, we postulate that the g.-1258G>A variant reduces the expression of PAX9 which underlies the hypodontia phenotype in this family.

Deletion of PAX9 and oligodontia: a third family and review of the literature

OBJECTIVE

This study was conducted to report a family affected by benign hereditary chorea in which a large deletion including TTF1, PAX9, and other genes was identified and results in oligodontia.

METHODS

Clinical and radiological studies of the two affected members (mother and daughter) were used to describe the oligodontia present in both of them.

RESULTS

The missing teeth in both patients are described in detail, and these data are compared with the dental anomalies observed in the only two other families with deletions of PAX9 and with the data available for 12 previously reported families carrying different types of PAX9 mutations.

CONCLUSIONS

There is a clinical relevance for recognizing such families, and offering available therapies since childhood is stressed. Some genotype-phenotype correlations between PAX9 mutations and dental anomalies can be drawn.

Identification of a novel missense mutation of MSX1 gene in Chinese family with autosomal-dominant oligodontia

OBJECTIVES

Oligodontia is defined as the congenital absence of 6 or more permanent teeth excluding the third molar. The occurrence of non-syndromic still remains poorly understood, but in recent years some cases have been reported where mutations or polymorphisms of PAX9 and MSX1 had been associated with non-syndromic oligodontia. The objective of the present work was to study the phenotype and genotype of three generations of a Han Chinese family affected by non-syndromic autosomal-dominant oligodontia.

DESIGN

We examined all individuals of the oligodontia family by clinical and radiographic examinations. Based on clinical manifestations, candidate genes MSX1 and PAX9 were picked up to analyse and screen mutations.

RESULTS

Dental evaluation showed that the most commonly missing teeth are the mandibular second premolars, followed by the maxillary second premolars and maxillary lateral incisors, and subsequently the maxillary first premolars. The probability of missing a particular type of tooth is not always bilaterally symmetrical, and differences exist between maxilla and mandible. PCR-SSCP analysis and DNA sequencing revealed a novel missense mutation c.662C>A in a highly conserved homeobox sequence of MSX1 and a known polymorphisms c.347C>G.

CONCLUSION

Our finding suggests the missense transversion (c.662C>A) and the polymorphisms (c.347C>G) may be responsible for oligodontia phenotype in this Chinese family.