Novel EDAR mutation in tooth agenesis and variable associated features

Characterization of novel MSX1 variants causally associated with non-syndromic oligodontia in Chinese families

BACKGROUND

MSX1 (OMIM #142983) is crucial to normal dental development, and variants in MSX1 are associated with dental anomalies. The objective of this study was to characterize the pathogenicity of novel MSX1 variants in Chinese families with non-syndromic oligodontia (NSO).

METHODS

Genomic DNA was extracted from individuals representing 35 families with non-syndromic oligodontia and was analyzed by Sanger sequencing and whole-exome sequencing. Pathogenic variants were screened via analyses involving PolyPhen-2, Sorting-Intolerant from Tolerant, and MutationTaster, and conservative analysis of variants. Patterns of MSX1-related NSO were analyzed. MSX1 structural changes suggested functional consequences in vitro.

RESULTS

Three previously unreported MSX1 heterozygous variants were identified: one insertion variant (c.576_577insTAG; p.Gln193*) and two missense variants (c. 871T>C; p.Tyr291His and c. 644A>C; p.Gln215Pro). Immunofluorescence analysis revealed abnormal subcellular localization of the p.Gln193* MSX1 variant. In addition, we found that these MSX1 variants likely lead to the loss of second premolars.

CONCLUSION

Three novel MSX1 variants were identified in Chinese Han families with NSO, expanding the MSX1 variant spectrum and presenting a genetic origin for the pathogenesis detected in patients and their families.

MSX1 involved selective tooth agenesis and abnormal labial frenum, pedigree, and retrospective study

OBJECTIVE

Muscle segment homeobox gene 1 (MSX1) is widely expressed in craniofacial development and tooth formation. The aim of this study was to report a novel MSX1 mutation in a Chinese family with selective tooth agenesis and abnormal median maxillary labial frenum (MMLF).

MATERIALS AND METHODS

Mutation analysis was carried out by whole exome sequencing. The pMD18-T vector was used to verify the mutations. PubMed and Human Gene Mutation Database were searched to analyze the relationship between the mutations in MSX1 and related phenotypes.

RESULTS

A novel heterozygous mutation (c.75delG) in MSX1 was detected in the proband and her mother. They presented as oligodontia and lower attached hypertrophy median maxillary labial frenum. 60 MSX1 mutations from 39 reports did not declare malformed MMLF except our cases. Meanwhile, we found that the types and sites of MSX1 mutations may affect the selectivity of tooth agenesis and orofacial cleft.

CONCLUSION

This study suggests malformed MMLF as a new phenotype of MSX1 mutation and a specific relationship between MSX1 genotype and phenotype.

The EDA/EDAR/NF-κB pathway in non-syndromic tooth agenesis: A genetic perspective

Non-syndromic tooth agenesis (NSTA) is one of the most common dental developmental malformations affected by genetic factors predominantly. Among all 36 candidate genes reported in NSTA individuals, EDA, EDAR, and EDARADD play essential roles in ectodermal organ development. As members of the EDA/EDAR/NF-κB signaling pathway, mutations in these genes have been implicated in the pathogenesis of NSTA, as well as hypohidrotic ectodermal dysplasia (HED), a rare genetic disorder that affects multiple ectodermal structures, including teeth. This review provides an overview of the current knowledge on the genetic basis of NSTA, with a focus on the pathogenic effects of the EDA/EDAR/NF-κB signaling pathway and the role of EDA, EDAR, and EDARADD mutations in developmental tooth defects. We also discuss the phenotypic overlap and genetic differences between NSTA and HED. Ultimately, this review highlights the importance of genetic analysis in diagnosing and managing NSTA and related ectodermal disorders, and the need for ongoing research to improve our understanding of these conditions.

A novel EDAR variant identified in non-syndromic tooth agenesis: Insights from molecular dynamics

OBJECTIVE

This study aims to investigate a novel pathogenic variant in a Chinese family of non-syndromic tooth agenesis (NSTA) and study the impact of the variant on related protein and pathway.

DESIGN

One NSTA family was collected. Whole exome sequencing and Sanger sequencing were performed on the proband with NSTA and his 5 family members. The pathogenic influence of the mutant is evaluated by bioinformatics analyses including evolutionary conservation analysis and secondary structure prediction. Molecular dynamics (MD) simulations and binding free energy calculations were then performed to explore changes in the tertiary structure and binding ability of the protein.

RESULTS

We found a novel missense ectodysplasin A receptor (EDAR) variant (c .1292 T > G; p.Ile431Arg) in all affected family members. The results of bioinformatics analyses revealed that the EDAR had harmful changes after mutation. MD simulations and the binding free energy calculations results showed that the mutant EDAR protein and EDAR/ectodysplasin-A receptor-associated adapter (EDARADD) complex displayed tertiary structural change, and EDAR possessed a lower affinity to EDARADD after mutation.

CONCLUSIONS

We found a novel EDAR variant (c.1292 T > G; p.Ile431Arg) in one NSTA family, which affects the binding of EDAR and EDARADD.

Association between superior labial frenum and maxillary midline diastema - a systematic review

BACKGROUND

Pediatric otolaryngologists have seen an increased focus on upper lip frenum as a possible culprit for feeding difficulties and the development of maxillary midline diastema (MMD). This increase may be encouraged by parents' exposure to medical advice over the internet about breastfeeding and potential long-term aesthetic concerns for their children. Subsequently, there has been increased pressure on pediatric otolaryngologists to perform superior labial frenectomies. There has been a reported 10-fold increase in frenectomies since the year 2000. However, there is no consensus within the literature regarding the benefit of superior labial frenectomy in preventing midline diastema.

OBJECTIVE

To provide physicians and parents with the most updated information by systematically reviewing the available literature for the association between superior labial frenum and midline diastema.

METHODS

A literature search was performed in MEDLINE (PubMed), EMBASE, Web of Science, the Cochrane Library and Dental and Oral Sciences Source (DOSS). Using the Covidence platform, a systematic review was conducted. The initial 314 articles identified underwent systematic review and 11 studies were included in the final review.

RESULTS/DISCUSSION

Available data, primarily from the dental literature, showed that two subtypes of frenum: papillary and papillary penetrating frenum, are associated with maxillary midline diastema. Superior labial frenectomy should be delayed until permanent lateral incisors have erupted, as this can spontaneously close the physiological MMD. Current literature recommends against frenectomy before addressing the diastema with orthodontics, which helps to prevent diastema relapse. It is also imperative to rule out other odontogenic and oral cavity causes of diastema, such as thumb sucking, dental agenesis, and other causes. Online information may not always be fully representative and should be interpreted in the full context of the patient's medical history before referral for surgical intervention.

A novel EDAR missense mutation identified by whole-exome sequencing with non-syndromic tooth agenesis in a Chinese family

Background

Causative variants in genes of the EDA/EDAR/NF‐κB pathway, such as EDA and EDARADD, have been widely identified in patients with non‐syndromic tooth agenesis (NSTA). However, few cases of NSTA are due to ectodysplasin‐A receptor (EDAR) variants. In this study, we investigated NSTA‐associated variants in Chinese families.

Methods

Peripheral blood samples were collected from the family members of 24 individuals with NSTA for DNA extraction. The coding region of the EDA gene of the 24 probands was amplified by PCR and sequenced to investigate new variants. Whole‐exome sequencing and Sanger sequencing were then performed for probands without EDA variants detected by PCR.

Results

A novel missense variant EDAR c.338G>A (p.(Cys113Tyr)) was identified in one family. In addition, three known EDA variants (c.865C>T, c.866G>A, and c.1013C>T) were identified in three families. Genotype–phenotype correlation analysis of EDAR gene mutation showed that NSTA patients were most likely to lose the maxillary lateral incisors and the maxillary central incisors were the least affected. The phenotype of mutations at codon 289 of EDA in NSTA affected patients was characterized by lateral incisors loss, rarely affecting the maxillary first molars.

Conclusion

A novel EDAR missense variant c.338G>A (p.(Cys113Tyr)) was identified in a family with NSTA, extending the mutation spectrum of the EDAR gene. Genotype–phenotype correlation analyses of EDAR and EDA mutations could help to improve disease status prediction in NSTA families.