Multivariate GWAS of Structural Dental Anomalies and Dental Caries in a Multi-Ethnic Cohort

Odontogenesis is a complex process, where disruption can result in dental anomalies and/or increase the risk of developing dental caries. Based on previous studies, certain dental anomalies tend to co-occur in patients, suggesting that these traits may share common genetic and etiological components. The main goal of this study was to implement a multivariate genome wide association study approach to identify genetic variants shared between correlated structural dental anomalies and dental caries. Our cohort (N = 3,579) was derived from the Pittsburgh Orofacial Clefts Study, where multiple dental traits were assessed in both the unaffected relatives of orofacial cleft (OFC) cases (n = 2,187) and unaffected controls (n = 1,392). We identified four multivariate patterns of correlated traits in this data: tooth agenesis, impaction, and rotation (AIR); enamel hypoplasia, displacement, and rotation (HDR); displacement, rotation, and mamelon (DRM); and dental caries, tooth agenesis and enamel hypoplasia (CAH). We analyzed each of these four models using genome-wide multivariate tests of association. No genome-wide statistically significant results were found, but we identified multiple suggestive association signals (P ≤ 10−5) near genes with known biological roles during tooth development, including ADAMTS9 and PRICKLE2 associated with AIR; GLIS3, WDR72, and ROR2 associated with HDR and DRM; ROBO2 associated with DRM; BMP7 associated with HDR; and ROBO1, SMAD2, and MSX2 associated with CAH. This is the first study to investigative genetic associations for multivariate patterns of correlated dental anomalies and dental caries. Further studies are needed to replicate these results in independent cohorts.

An in vitro and computational validation of a novel loss-of-functional mutation in PAX9 associated with non-syndromic tooth agenesis

Congenital tooth agenesis (CTA) is one of the most common craniofacial anomalies. Its frequency varies among different population depending upon the genetic heterogeneity. CTA could be of familial or sporadic and syndromic or non-syndromic. Five major genes are found to be associated with non-syndromic CTA namely, PAX9, MSX1, EDA1, AXIN2 and WNT10A. In this study, an India family with CTA was investigated and a novel c.336C>G variation was identified in the exon 3 of PAX9, leading to substitution of evolutionary conserved Cys with Trp at 112 amino acid position located at the functionally significant DNA binding paired domain region. Functional analysis revealed that p.Cys112Trp mutation did not prevent the nuclear localization although mutant protein had higher cytoplasmic retention. EMSA using e5 probe revealed that mutant protein was unable to bind with the paired-domain binding site. Subsequently, GST pull-down assay revealed lower binding activity of the mutant protein with its known interactor MSX1. Further RNA-sequencing of PAX9 over-expressed HEK293, identified two potential novel targets, WNT4 and WNT7b those are up-regulated by wild-type PAX9 but not by mutant. These in vitro results were consistent with the computational results. The in vitro and computational observations altogether suggest that c.336C>G (p.Cys112Trp) variation leads to loss-of-function of PAX9 leading to CTA in this family.

Prosthodontic Rehabilitation of Bilateral Maxillary Lateral Incisors Agenesis: A Case Report with One-Year Follow-Up

Globally, non-syndromic tooth agenesis is commonly seen in clinical practice. However, its management is often complex and requires a multidisciplinary team approach for the maximal outcome. While various treatment options are possible, considerations for the treatment are not only based on the dentofacial conditions but also cultural and social background and personal preference of the patient. Thus, patientcentred care approach should always be practised for an optimal outcome. In the present case, a patient with established craniofacial growth presenting with bilateral agenesis of maxillary lateral incisors and over-retained deciduous maxillary left canine sought for aesthetic improvements. The patient did not prefer any orthodontic treatment citing a prolonged treatment duration and sub-optimal motivation as a hindrance. Thus, a prosthodontic only approach was taken by providing a conventional cantilever bridge and ceramic veneers to achieve the aims of treatment. This article discusses the possible limitation of such prosthodontic only solution in managing tooth agenesis.

A novel mutation of SATB2 inhibits odontogenesis of human dental pulp stem cells through Wnt/β-catenin signaling pathway

Background SATB2-associated syndrome (SAS) is a multisystem disorder caused by mutation of human SATB2 gene. Tooth agenesis is one of the most common phenotypes observed in SAS. Our study aimed at identifying novel variant of SATB2 in a patient with SAS, and to investigate the cellular and molecular mechanism of tooth agenesis caused by SATB2 mutation. Methods We applied whole exome sequencing (WES) to identify the novel mutation of SATB2 in a Chinese patient with SAS. Construction and overexpression of wild-type and the mutant vector was performed, followed by functional analysis including flow cytometry assay, fluorescent immunocytochemistry, western blot, quantitative real-time PCR and Alizarin Red S staining to investigate its impact on hDPSCs and the underlying mechanisms. Results As a result, we identified a novel frameshift mutation of SATB2 (c. 376_378delinsTT) in a patient with SAS exhibiting tooth agenesis. Human DPSCs transfected with mutant SATB2 showed decreased cell proliferation and odontogenic differentiation capacity compared with hDPSCs transfected with wild-type SATB2 plasmid. Mechanistically, mutant SATB2 failed to translocate into nucleus and distributed in the cytoplasm, failing to activate Wnt/β-catenin signaling pathway, whereas the wild-type SATB2 translocated into the nucleus and upregulated the expression of active β-catenin. When we used Wnt inhibitor XAV939 to treat hDPSCs transfected with wild-type SATB2 plasmid, the increased odontogenic differentiation capacity was attenuated. Furthermore, we found that SATB2 mutation resulted in the upregulation of DKK1 and histone demethylase JHDM1D to inhibit Wnt/β-catenin signaling pathway. Conclusion We identified a novel frameshift mutation of SATB2 (c.376_378delinsTT, p.Leu126SerfsX6) in a Chinese patient with SATB2-associated syndrome (SAS) exhibiting tooth agenesis. Mechanistically, SATB2 regulated osteo/odontogenesis of human dental pulp stem cells through Wnt/β-catenin signaling pathway by regulating DKK1 and histone demethylase JHDM1D.

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.

Effect of Tooth Agenesis on Mandibular Morphology and Position

Congenital missing teeth (OMIM #106600) is the most common dental abnormality. The aim of the study was to evaluate the effects of tooth agenesis on the total mandibular length, length of the mandibular body and alveolar process, and the mandibular anteroposterior position. The material was obtained from the Department of Orthodontics, Medical University of Warsaw. The study group included 116 patients aged 9–18 years with a congenital absence of at least two permanent tooth buds in the maxilla and/or mandible (mean: 6.2 teeth missing/patient). All patients were Caucasians: 68 (59%) females and 48 (41%) males. The control group included 115 patients without tooth agenesis matched with the age and gender of the study group. A cephalometric analysis was performed, and it was focused on assessing anteroposterior mandibular measurements. This assessment was based on 17 measurements (12 linear and 5 angular). Statistical analysis of the cephalometric measurements between the study group and the control group showed significant changes regarding selected mandibular measurements. Tooth agenesis does not affect the total length of the mandible and the length of the mandibular body, but it might reduce the length of the mandibular arch length and result in a more retrusive mandibular position.

Rare phenotype: Hand preaxial polydactyly associated with LRP6-related tooth agenesis in humans

Low-density lipoprotein receptor-related protein 6 (LRP6) is a pathogenic gene of selective tooth agenesis-7 (OMIM#616724). Although the malformation of the digits and fore- and hindlimbs has been reported in Lrp6-deficient mice, it has been rarely discovered in humans with LRP6 mutations. Here, we demonstrate an unreported autosomal dominant LRP6 heterozygous mutation (c.2840 T > C;p.Met947Thr) in a tooth agenesis family with hand polydactyly, and another unreported autosomal dominant LRP6 heterozygous mutation (c.1154 G > C;p.Arg385Pro) in a non-syndromic tooth agenesis family. Bioinformatic prediction demonstrated the deleterious effects of the mutations, and LRP6 structure changes suggested the corresponding functional impairments. Analysis on the pattern of LRP6-related tooth agenesis demonstrated the maxillary lateral incisor was the most affected. Our study report that LRP6 mutation might be associated with hand preaxial polydactyly in humans, which broaden the phenotypic spectrum of LRP6-related disorders, and provide valuable information on the characteristics of LRP6-related tooth agenesis.

Prevalence of Dental Number Anomalies Among A Group of Turkish Children

Summary Background/Aim: The study aimed to evaluate the prevalence and distribution of congenital dental number anomalies in the permanent dentition among a group of Turkish children in the Inner Aegean Region of Turkey. Material and Methods: A total of 5377 patients aged 7–9 who visited our clinic for the first time between September 2018 and September 2019 were investigated. The children were examined for tooth agenesis and supernumerary teeth using panoramic radiographs taken for various reasons and clinical records reviewed. Dental number anomalies were evaluated according to gender and localization. Descriptive and comparative statistical analyses were performed using the SPSS package software program Version 23. Results: For the study, the data of 1987 patients (947 female, 1040 male) were examined. The tooth agenesis was found in 109 patients (5.5%), the supernumerary teeth were found in 24 patients (1.2%). The prevalence of tooth agenesis was 5% in males, 6% in females. There was no statistical difference between genders (p>0.05). The distribution of tooth agenesis according to jaws and sides by gender was not statistically different (p>0.05). The most commonly missing teeth were mandibular left second premolar (37.6% of patients) and mandibular right second premolar (33% of patients). According to types of teeth and gender, molar tooth agenesis was seen more common in females than males (p<0.05), there was no significant difference in other types of teeth by gender. The prevalence of supernumerary teeth were 1.9% in males, 0.4% in females and the difference between genders was found to be statistically significant (p<0.05). All the supernumerary teeth were located in the anterior maxilla, and half of them were mesiodens. Conclusions: Early diagnosis and appropriate treatment choice are very important managing complications associated with congenital dental number anomalies and for differential diagnosis of characteristic syndromes.

Developmental Anomalies of Teeth – A cross-sectional study

Background: This study was conducted to find out prevalence of tooth developmental anomalies and tooth agenesis syndrome in patients of Fariyal Dental College Lahore visiting the out-door department during the year 2017. Objective: The objective of this study was to conduct a retrospective examination of prevalence of developmental tooth anomalies and tooth agenesis syndrome .The relationship of age and gender was also focused. Methods: All patients of Fariyal Dental College Lahore visiting the out-patient department during the year 2017 were observed and analyzed. The documents scrutinized for this purpose were hospital history charts including patient’s biodata, family history and oral examination details. Results: Out of 160 total cases, 10 cases were of tooth developmental anomalies and 7 cases were of tooth agenesis syndrome were observed. Conclusion: There are 6% cases of developmental anomalies and 4% cases of tooth agenesis were found. Both findings are quite significant in the given number of patients. Keywords: Fariyal Dental College, Tooth Developmental Anomalies, Tooth agenesis.