PAX6 polymorphisms in 20 Chinese children with supernumerary teeth in the maxillary incisor area

Prevalence, clinical characteristics, and 3-dimensional radiographic analysis of supernumerary teeth in Guangzhou, China: a retrospective study

OBJECTIVE

The aim was to investigate the prevalence and clinical and 3-dimensional (3D) radiographic characteristics of supernumerary teeth (ST) in a paediatric dental population. The factors associated with ST eruption potential were analysed, and the optimal extraction time for nonerupted ST was discussed.

METHODS

A retrospective study was performed in a 13,336-participant baseline population aged 3-12 years for whom panoramic radiographs had been obtained in the hospital from 2019 to 2021. The medical records and radiographic data were reviewed to identify patients with ST. Both the demographic variables and ST characteristics were recorded and analysed .

RESULTS

In total, 890 patients with 1,180 ST were screened from the 13,336 baseline population. The ratio of males (679) to females (211) was approximately 3.2:1. Generally, ST occurred singularly and were frequently found in the maxilla (98.1%). A total of 40.8% of ST were erupted, and the 6-year-old age group presented the highest eruption rate (57.8%). The eruption rate of ST was highly negatively correlated with age. A total of 598 patients additionally underwent cone- beam computed tomography (CBCT). According to the CBCT images, the majority of ST were conical, normally oriented, palatally situated, nonerupted and symptomatic. The most common ST-associated complication was failed eruption of adjacent teeth. In addition, symptomatic ST were more common in the 7- to 8- and 9- to 10-year-old age groups. The eruption rate of ST was 25.3% among the patients who had undergone CBCT. A normal orientation and the labial position were significant protective factors for ST eruption, with odds ratios (ORs) of 0.004 (0.000-0.046) and 0.086 (0.007-1.002), respectively. Age and the palatal position were significant risk factors, with ORs of 1.193 (1.065-1.337) and 2.352 (1.377-4.02), respectively.

CONCLUSIONS

This study provides a detailed analysis of ST characteristics in 3-12 year old children. Age as well as the position and orientation of ST were reliable predictors of the ST eruption. An age of 6 years old may be the optimal time for extraction of nonerupted ST to maximize the utilization of eruption potential and reduce the incidence of ST-associated complications.

Identification of a novel missense mutation in non-syndromic familial multiple supernumerary teeth

OBJECTIVE

This study intended to evaluate the involvement of genetic factors in the etiology of non-syndromic multiple supernumerary teeth.

DESIGN

We filtered the single nucleotide polymorphisms (SNPs) of the proband and his mother with similar phenotypes through whole-genome sequencing (WGS). By integrating multiple databases related to human genome mutations and disease information for mutation annotation, we excluded the SNPs of people without supernumerary teeth. Subsequently, the bioinformatics analysis tools (Sorting Intolerant From Tolerant (SIFT) < 0.05, Polymorphism Phenotyping (PolyPhen) > 0.90) were used to screen out the most correlated SNPs of the disease, besides, Gene Ontology (GO) analysis (P<0.05, FDR<0.05) and Sanger sequencing was applied to further verify the candidate pathogenic mutation point.

RESULTS

A novel heterozygous variant in fer-1 like family member 6 (FER1L6) gene likely denoted pathogenicity in non-syndromic familial multiple supernumerary teeth. We identified a cohort of 3499 non-synonymous SNPs (nsSNPs), and only 142 nsSNPs with the score of SIFT < 0.05 and PolyPhen > 0.90 were retained. Then we got 54 nsSNPs from 31 candidate genes through GO analysis. Sanger sequencing revealed a missense variant in exon 31 of the FER1L6 gene, causing a transition from guanine to adenine in position 1447 of protein kinase C conserved region 2.

CONCLUSIONS

We identified a novel heterozygous chromosome 8q24.13 mutation of FER1L6, which was a new mutation site identified in non-syndromic familial multiple supernumerary teeth through genetic analysis of a Chinese family.

Lack of association between PAX6/SOSTDC1/FAM20B gene polymorphisms and mesiodens

Background

The purpose of this study was to analyze the association between the genetic polymorphism of genes (PAX6, SOSTDC1and FAM20B) and the susceptibility to mesiodens.

Methods

This study was carried out on 50 patients with mesiodens and 50 controls. The family history of each patient with mesiodens were recorded. Genomic DNA was extracted from saliva samples, and single nucleotide polymorphisms were detected in all exons and exon/intron boundaries of PAX6, SOSTDC1 and FAM20B using Sanger sequencing. The data were analyzed using pearson chi-square test with theoretical frequency ≥ 5. For theoretical frequency less than 5 but at least 1 (≤20% cell), the data were analyzed by continuity correction. For the rest, Fisher’s Exact test was used. A P-value< 0.05 was considered statistically significant. The Odds ratio (OR) and confidence intervals (CI) were recorded.

Results

Three polymorphisms were detected in PAX6. Two polymorphisms were detected in SOSTDC1. Twenty-nine polymorphisms were detected in FAM20B. Although, the T allele of FAM20B (rs3766626) appears to be associated with mesiodens (P = 0.051), there were no significant differences of PAX6/SOSTDC1/FAM20B gene polymorphisms between the two groups. The T allele of FAM20B (rs3766626) was associated with susceptibility to two mesiodens (P < 0.001; OR = 8.333; CI = 2.516–27.600).

Conclusions

Lack of association between PAX6/SOSTDC1/FAM20B gene polymorphisms and mesiodens in the population studied was detected. Further studies with large samples on T allele of FAM20B (rs3766626) are needed.

Electronic supplementary material

The online version of this article (10.1186/s12903-019-0788-3) contains supplementary material, which is available to authorized users.

The epidemiology of supernumerary teeth and the associated molecular mechanism

Supernumerary teeth are common clinical dental anomalies. Although various studies have provided abundant information regarding genes and signaling pathways involved in tooth morphogenesis, which include Wnt, FGF, BMP, and Shh, the molecular mechanism of tooth formation, especially for supernumerary teeth, is still unclear. In the population, some cases of supernumerary teeth are sporadic, while others are syndrome-related with familial hereditary. The prompt and accurate diagnosis of syndrome related supernumerary teeth is quite important for some distinctive disorders. Mice are the most commonly used model system for investigating supernumerary teeth. The upregulation of Wnt and Shh signaling in the dental epithelium results in the formation of multiple supernumerary teeth in mice. Understanding the molecular mechanism of supernumerary teeth is also a component of understanding tooth formation in general and provides clinical guidance for early diagnosis and treatment in the future.

Genetic alterations in mesiodens as revealed by targeted next-generation sequencing and gene co-occurrence network analysis

OBJECTIVE

Mesiodens is the most common type of supernumerary tooth which includes a population prevalence of 0.15%-1.9%. Alongside evidence that the condition is heritable, mutations in single genes have been reported in few human supernumerary tooth cases. Gene sequencing methods in tradition way are time-consuming and labor-intensive, whereas next-generation sequencing and bioinformatics are cost-effective for large samples and target sizes.

MATERIALS AND METHODS

We describe the application of a targeted next-generation sequencing (NGS) and bioinformatics approach to samples from 17 mesiodens patients. Subjects were diagnosed on the basis of panoramic radiograph. A total of 101 candidate genes which were captured custom genes were sequenced on the Illumina HiSeq 2500. Multistep bioinformatics processing was performed including variant identification, base calling, and in silico analysis of putative disease-causing variants.

RESULTS

Targeted capture identified 88 non-synonymous, rare, exonic variants involving 42 of the 101 candidate genes. Moreover, we investigated gene co-occurrence relationships between the genomic alterations and identified 88 significant relationships among 18 most recurrent driver alterations.

CONCLUSION

Our search for co-occurring genetic alterations revealed that such alterations interact cooperatively to drive mesiodens. We discovered a gene co-occurrence network in mesiodens patients with functionally enriched gene groups in the sonic hedgehog (SHH), bone morphogenetic proteins (BMP), and wingless integrated (WNT) signaling pathways.