Targeted next-generation sequencing (NGS) analysis of mutations in nonsyndromic tooth agenesis candidate genes : Analysis of a Turkish cohort

Exonic and Intronic WNT10A Variants Isolated from Korean Children with Non-Syndromic Tooth Agenesis

Background/Objectives: Tooth agenesis (TA) is a developmental anomaly prevalent in humans. It is particularly significant in children and adolescents because it is related to esthetic, physiological, and functional problems, including malocclusion, periodontal damage, and insufficient alveolar growth. WNT10A mutations have been identified as the main genetic alterations associated with tooth agenesis. Most previous studies have investigated WNT10A mutations in patients with tooth agenesis using single nucleotide polymorphism (SNP) arrays or exome sequencing. In this study, we conducted a comprehensive profiling of mutations within the exons and introns of WNT10A in Korean patients with non-syndromic tooth agenesis. Methods: Saliva samples were collected from Korean children and adolescents with non-syndromic tooth agenesis. Tagmentation-based sequencing was conducted to acquire mutation information for all exonic and intronic bases of the WNT10A gene. Results: Mutations were detected exclusively in the patient samples: 629C>G and 1100C>T in exon 1, 1977T>C in intron 1, 10256C>T and 10382G>A in exon 3, and 15953G>A in intron 4. Additional mutations were also observed at high ratios in the patient samples. Conclusions: The mutations identified in this study differ from previous findings. These results may provide useful information for understanding the pathogenicity of WNT10A mutations in Korean patients with tooth agenesis and support future diagnostic and therapeutic approaches.

Novel MSX1 Gene Variants in Chinese Children with Non-Syndromic Tooth Agenesis: A Clinical and Genetic Analysis

BACKGROUND

Tooth agenesis is the most frequently occurring genetic developmental anomaly in clinical dentistry. The MSX1 gene, essential for tooth development, has been associated with non-syndromic tooth agenesis. This study aims to identify novel MSX1 variants associated with this condition and to understand their impact on tooth development.

METHODS

This study involved the genetic analysis of two children presenting with non-syndromic tooth agenesis. Conservation analysis and 3D structural modeling were conducted to assess the pathogenicity of these variants. Additionally, a review of 108 patients with known MSX1 variants was performed to identify patterns of tooth agenesis.

RESULTS

We discovered two novel MSX1 variants, c.823 T>G and c.890 A>G, located in the second exon of the MSX1 gene. The identified MSX1 variants, c.823 T>G and c.890 A>G, were predicted to be pathogenic. Conservation analysis showed that the impacted amino acids are highly conserved across species, and 3D structural analysis indicated potential disruptions to protein function. Among the 108 patients reviewed, a consistent pattern of tooth agenesis was observed, with the most frequently missing teeth being the maxillary second premolars, the mandibular second premolars, and the maxillary first premolars.

CONCLUSIONS

This research broadens the known range of MSX1 gene variants and deepens our comprehension of the genetic foundations of non-syndromic tooth agenesis. The findings provide valuable insights for genetic counseling and future research into tooth development, emphasizing the importance of MSX1 in dental anomalies.

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.

Identification of novel candidate genes associated with non-syndromic tooth agenesis in Mongolian families

OBJECTIVES

This study aimed to identify genetic variants associated with non-syndromic tooth agenesis (TA) in nine families from Mongolia using whole-exome sequencing (WES) and bioinformatics analysis.

MATERIAL AND METHODS

The study enrolled 41 participants, including three inherited and six non-inherited families. WES analysis was performed on 14 saliva samples from individuals with non-syndromic TA. The potential candidate genes were identified through variant filtering and segregation analysis. The filtered variants were then analyzed in silico mutation impact analysis.

RESULTS

WES analysis identified 21 variants associated with TA, and 5 of these variants met all filtering criteria. These variants were located in the exome region of MAST4, ITGA6, PITX2, CACNA1S, and CDON genes. The variant in PITX2 was found in eight participants from inherited and non-inherited families, while the MAST4 variant was identified in 6 participants from inherited families.

CONCLUSIONS

The study identified various genetic variant candidates associated with TA in different family groups, with PITX2 being the most commonly identified. Our findings suggest that MAST4 may also be a novel candidate gene for TA due to its association with the Wnt signaling pathway. Additionally, we found that five candidate genes related to focal adhesion and calcium channel complex were significant and essential in tooth development.

CLINICAL RELEVANCE

Identifying new pathogenic genes associated with TA can improve our understanding of the molecular mechanisms underlying the disease, leading to better diagnosis, prevention, and treatment. Early detection of TA based on biomarkers can improve dental management and facilitate orthodontic and prosthetic treatment.

Phenotypic characteristics of taurodontism and a novel WNT10A variant in non-syndromic oligodontia family

OBJECTIVE

Variants in wingless-type MMTV integration site family member 10A (WNT10A) have been proposed to be the most common cause of non-syndromic oligodontia (NSO). The goal of the present study was to identify the novel WNT10A variants in Chinese families with NSO.

DESIGN

Clinical data were collected from 39 families with oligodontia admitted to the Hospital of Stomatology Hebei Medical University (China) from 2016 to 2022. Whole-exome sequencing (WES) and Sanger sequencing were performed to identify WNT10A variants in three families with non-syndromic oligodontia. Amino acid conservation analysis and protein conformational analysis were conducted for the WNT10A variant. Genotype-phenotype analysis was performed on the previously reported WNT10A variants related to NSO.

RESULTS

We found a novel heterozygous WNT10A variant c.1127 G>A (p.Cys376Tyr) and two reported heterozygous variants c.460 C>A (p.Leu154Met) and c.511 C>T (p.Arg171Cys). Structural modeling showed that the novel WNT10A variant was located in a highly conserved domain, which led to structural damage of WNT10A protein. In addition, we found that the phenotype of the WNT10A variants affected the maxillary second premolars, followed by the mandibular second premolars, and rarely affected the maxillary central incisor. Herein, it is the first time to report that NSO patients with WNT10A monoallele mutation carry taurodontism phenotype and 6.1% prevalence of taurodontism in WNT10A-related NSO patients.

CONCLUSIONS

Our results demonstrated that the novel variant c.1127 G>A (p.Cys376Tyr) of WNT10A causes NSO. The present study expanded the known variation spectrum of WNT10A and provided valuable information for genetic counseling of families.

Novel LRP6 Mutations Causing Non-Syndromic Oligodontia

The process of tooth formation is a series of reciprocal interactions between the ectoderm and mesoderm, and it is believed that many genetic factors are involved in this complex process. More than a dozen genes have been identified in non-syndromic tooth agenesis; however, the genetic etiology underlying tooth agenesis is not fully understood yet. In this study, we identified two novel LRP6 mutations in two non-syndromic oligodontia families. Both probands had 16 and 17 missing teeth in their permanent dentition. Mutational analysis identified a de novo frameshift mutation by a 1-bp insertion in exon 9 (NM_002336.2: c.1870dupA, p.(Met624Asnfs*29)) and a splicing donor site mutation in intron 8 (c.1762+2T>C). An in vitro splicing assay confirmed the deletion of exon 8, and the deletion would result in a frameshift. Due to the premature termination codons introduced by the frameshift, both mutant transcripts would be degraded by nonsense-mediated mRNA decay, resulting in haploinsufficiency.

Synergistic Mutations of LRP6 and WNT10A in Familial Tooth Agenesis

Familial tooth agenesis (FTA), distinguished by developmental failure of selected teeth, is one of the most prevalent craniofacial anomalies in humans. Mutations in genes involved in WNT/β-catenin signaling, including AXIN2 WNT10A, WNT10B, LRP6, and KREMEN1, are known to cause FTA. However, mutational interactions among these genes have not been fully explored. In this study, we characterized four FTA kindreds with LRP6 pathogenic mutations: p.(Gln1252*), p.(Met168Arg), p.(Ala754Pro), and p.(Asn1075Ser). The three missense mutations were predicted to cause structural destabilization of the LRP6 protein. Two probands carrying both an LRP6 mutant allele and a WNT10A variant exhibited more severe phenotypes, suggesting mutational synergism or digenic inheritance. Biallelic LRP6 mutations in a patient with many missing teeth further supported the dose-dependence of LRP6-associated FTA. Analysis of 21 FTA cases with 15 different LRP6 loss-of-function mutations revealed high heterogeneity of disease severity and a distinctive pattern of missing teeth, with maxillary canines being frequently affected. We hypothesized that various combinations of sequence variants in WNT-related genes can modulate WNT signaling activities during tooth development and cause a wide spectrum of tooth agenesis severity, which highlights the importance of exome/genome analysis for the genetic diagnosis of FTA in this era of precision medicine.