Novel MSX1 frameshift causes autosomal-dominant oligodontia

Critical Considerations in Calling Disease-Causing EDAR Mutations in Nonsyndromic Oligodontia

Background/Objectives: Oligodontia, the absence of six or more teeth excluding third molars, is a rare genetic condition, unlike hypodontia (missing one or more teeth), which is a relatively common human disease. Methods: To identify the genetic etiology of nonsyndromic oligodontia (NSO) families, we performed mutational analysis and investigated the functional effects of identified EDAR mutations. Whole-exome sequencing was conducted on recruited families with NSO. Bioinformatic analysis identified mutations in oligodontia-causing candidate genes, which were confirmed by Sanger sequencing and segregation within families. The impact of EDAR mutations on the EDA signaling pathway was assessed using luciferase activity analysis. Results:EDAR mutations were identified in three NSO families. A homozygous missense EDAR mutation (NM_022336.4: c.319A>G p.(Met107Val)) was found in the singleton proband of family 1. The proband of family 2 carried compound heterozygous EDAR mutations: a maternal missense mutation (c.319A>G p.(Met107Val)) and a paternal missense variant (c.1270G>A p.(Val424Met)). The proband of family 3 had heterozygous EDAR mutations: a maternal missense mutation (c.389T>A p.(Ile130Asn)) and paternal intronic variants in cis (c.[357-4G>A;440+50C>T]). Luciferase assays confirmed reduced transcriptional activity for all identified missense mutations, while splicing assays revealed altered splicing patterns. Conclusions: In conclusion, recessive EDAR mutations, including novel ones, were identified in NSO families, and their pathological mechanism was explored through transcriptional activity measurements.

Palatal canine impaction is associated with craniofacial shape in humans

BACKGROUND/OBJECTIVES

It is unclear whether palatal canine impaction is related to genetic or local/environmental factors. If a genetic origin is assumed, then it could be expected that palatal canine impaction is associated with overall craniofacial development. Within this context, the aim of this study was to evaluate the craniofacial morphology of individuals with palatal canine impaction and compare it to a matched group of normal controls.

MATERIALS/METHODS

The sample for this investigation comprised 404 individuals (232 females and 172 males). Half of these individuals presented with unilateral or bilateral palatal canine impaction confirmed clinically and radiographically. The other half were matched for sex and age with the first half and comprised individuals without tooth impaction, apart from third molars. The shape of the craniofacial structures was outlined on calibrated cephalometric images through 15 curves and 127 landmarks (11 fixed and 116 semi-landmarks). Shape configurations were superimposed using Procrustes Superimposition and the resulting shape coordinates were reduced into principal components for all subsequent analyses. The effect of palatal canine impaction on craniofacial shape was assessed with regression models, separately in females and males. All statistical tests were performed assuming a type-1 error of 5%.

RESULTS

Individuals with palatally impacted canines appear to have a less convex face, a more brachyfacial skeletal pattern, and a sagittally extended premaxilla. In females effect sizes ranged between η2 = 0.136-0.397 (P < 0.05) and in males between η2 = 0.125-0.396 (P < 0.05, apart from the entire craniofacial configuration: P = 0.259).

LIMITATIONS

Palatal canine impaction was not confirmed through cone beam computer tomography images in all patients, however, in those cases, the treatment history confirmed the diagnosis.

CONCLUSIONS/IMPLICATIONS

Palatal canine impaction is related to a distinct craniofacial shape in females and males. These findings allow for speculation that palatal canine impaction is affected by genetic pathways involved in overall craniofacial development.

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.

Orodental malformations associated with human MSX1 sequence variants

BACKGROUND

MSX1 sequence variants have been known to cause human tooth agenesis (TA) with or without orofacial clefts. However, their roles during the whole processes of tooth development are not fully understood. This study aimed to characterize a 4-membered family with TA carrying a novel MSX1 pathogenic variant and investigate the disease mechanism.

METHODS

The authors conducted whole exome analysis to define the disease-causing sequence variant. They performed microcomputed tomography, morphometric analyses, transcriptome profiling, and molecular characterization to study the affected teeth and the gene variant.

RESULTS

The authors identified an MSX1 pathogenic variant, p.Glu232∗, in affected family members with TA and concomitant orodental anomalies, namely, prominent maxillary labial frenum, central incisor diastema, median maxillary anterior alveolar cleft, tooth fusion, mandibular molar dysmorphology, thin dentin layer, and slender dental roots. MSX1-defective teeth were not apparently microdontic but had thin dentin layers. The mandibular molars showed a homeotic transformation to maxillary counterparts. Genes involved in extracellular matrix organization and dentinogenesis, such as DMP1 and MMP20, were downregulated in dental pulp tissues of MSX1-defective teeth. The p.Glu232∗-truncated MSX1 properly localized to the nucleus but partially lost its transactivation ability. Analyzing reported cases indicated that truncation sequence variants within the homeobox domain of MSX1 caused a more severe TA phenotype than those outside of the homeobox domain, probably due to dominant negativity compared with haploinsufficiency.

CONCLUSIONS

This study provides in vivo evidence that MSX1 contributes to developmental processes of various orodental tissues in humans.

PRACTICAL IMPLICATIONS

Clinically, hypertrophic labial frenum, incisor diastema, and median maxillary anterior alveolar cleft might be considered diagnostic for MSX1-associated TA.

Dental abnormalities in rare genetic bone diseases: Literature review

Currently, over 500 rare genetic bone disorders are identified. These diseases are often accompanied by dental abnormalities, which are sometimes the first clue for an early diagnosis. However, not many dentists are sufficiently familiar with phenotypic abnormalities and treatment approaches when they encounter patients with rare diseases. Such patients often need dental treatment but have difficulties in finding a dentist who can treat them appropriately. Herein we focus on major dental phenotypes and summarize their potential causes and mechanisms, if known. We discuss representative diseases, dental treatments, and their effect on the oral health of patients and on oral health-related quality of life. This review can serve as a starting point for dentists to contribute to early diagnosis and further investigate the best treatment options for patients with rare disorders, with the goal of optimizing treatment outcomes.

Occlusal characteristics in modern humans with tooth agenesis

Non-syndromic permanent tooth agenesis affects a significant proportion of the population, especially if third molars are considered. Although tooth agenesis has been linked to a smaller craniofacial size, reduced facial convexity and a shorter skeletal face, the occlusal characteristics of individuals with tooth agenesis remain largely unexplored. Therefore, this study investigated potential associations between tooth agenesis and metric occlusal traits in 806 individuals (491 with 4.1 missing teeth per subject, including third molars, and 315 without any tooth agenesis). Dentoskeletal morphology was defined through anatomical landmarks on pre-treatment cephalometric radiographs. Multivariate regression models, adjusted for sex and age, showed that tooth agenesis was significantly associated with a reduced overjet, an increased interincisal angle, and shorter upper and lower dental arch lengths, but not with overbite. Moreover, apart from reduced tooth length and dentoalveolar effects, as the number of missing teeth increased the upper front teeth were progressively retruded according to the craniofacial complex and to the face. Thus, tooth agenesis has a substantial influence on dental and occlusal characteristics, as well as on the sagittal position and inclination of anterior teeth. These findings emphasize the necessity for personalized, multidisciplinary approaches in individuals with multiple agenesis to successfully meet treatment goals.

Novel PAX9 Mutations Causing Isolated Oligodontia

Hypodontia, i.e., missing one or more teeth, is a relatively common human disease; however, oligodontia, i.e., missing six or more teeth, excluding the third molars, is a rare congenital disorder. Many genes have been shown to cause oligodontia in non-syndromic or syndromic conditions. In this study, we identified two novel PAX9 mutations in two non-syndromic oligodontia families. A mutational analysis identified a silent mutation (NM_006194.4: c.771G>A, p.(Gln257=)) in family 1 and a frameshift mutation caused by a single nucleotide duplication (c.637dup, p.(Asp213Glyfs*104)) in family 2. A minigene splicing assay revealed that the silent mutation resulted in aberrant pre-mRNA splicing instead of normal splicing. The altered splicing products are ones with an exon 4 deletion or using a cryptic 5' splicing site in exon 4. Mutational effects were further investigated using protein expression, luciferase activity assay and immunolocalization. We believe this study will not only expand the mutational spectrum of PAX9 mutations in oligodontia but also strengthen the diagnostic power related to the identified silent mutation.

Correlation of Dental Anomalies with Cleft Type and Gender in Non-Syndromic Oral Cleft Patients: A Cross-Sectional Study

To investigate the distribution of dental anomalies between non-syndromic orofacial cleft patients and their association with the cleft type and gender.

Retrospective cross-sectional study involving examination of intraoral dental records and radiographs.

300 non-syndromic orofacial cleft patients included (161 males and 139 females, mean age: 10.23 ± 2.3 years).

Variables analyzed: tooth agenesis, microdontia, and supernumerary teeth. Data analysis: Chi-square and Fisher's exact tests to investigate the correlation between dental anomalies, cleft type, and gender.

Agenesis occurred in 66% of the subjects, supernumerary teeth in 19.6%, and microdontia in 18.3%. In females with unilateral left cleft lip and palate (CLP), agenesis was significantly higher compared to males. Both genders presented significant agenesis of maxillary lateral incisors and right central incisor. Significant agenesis of central incisor, canine and second premolar on the upper left side and lower second premolars were observed only in males, with significant microdontia for maxillary lateral incisors and left central incisor. Significant agenesis of maxillary first premolars was seen only in females. Agenesis in maxillary quadrants was significant for patients with unilateral right and left CLP, and bilateral CLP. In mandibular quadrants, agenesis was substantially higher for patients with isolated CP.

Results suggest that tooth agenesis and microdontia might not be directly associated with the cleft area's anatomical irregularity but are affected by gender and other genetic factors that regulate the development of the anomaly and the orofacial clefting mutually.

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.

A Missense Mutation in the Collagen Triple Helix of EDA Is Associated with X-Linked Recessive Hypohidrotic Ectodermal Dysplasia in Fleckvieh Cattle

Mutations within the ectodysplasin A (EDA) gene have been associated with congenital hypotrichosis and anodontia (HAD/XHED) in humans, mice, dogs and cattle. We identified a three-generation family of Fleckvieh cattle with male calves exhibiting clinical and histopathological signs consistent with an X-linked recessive HAD (XHED). Whole genome and Sanger sequencing of cDNA showed a perfect association of the missense mutation g.85716041G>A (ss2019497443, rs1114816375) within the EDA gene with all three cases following an X-linked recessive inheritance, but normal EDAR and EDARADD. This mutation causes an exchange of glycine (G) with arginine (R) at amino acid position 227 (p.227G>R) in the second collagen triple helix repeat domain of EDA. The EDA variant was associated with a significant reduction and underdevelopment of hair follicles along with a reduced outgrowth of hairs, a complete loss of seromucous nasolabial and mucous tracheal and bronchial glands and a malformation of and reduction in number of teeth. Thermostability of EDA G227R was reduced, consistent with a relatively mild hair and tooth phenotype. However, incisors and canines were more severely affected in one of the calves, which correlated with the presence of a homozygous missense mutation of RNF111 (g.51306765T>G), a putative candidate gene possibly associated with tooth number in EDA-deficient Fleckvieh calves.

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 genetic basis of hypodontia in dental development

Dental agenesis is one of the most common developmental anomalies in humans, characterised by the developmental absence of one or more teeth. It can present as an isolated condition (non-syndromic hypodontia) or associated with a syndrome (syndromic hypodontia). This paper aims to review the genetic basis of hypodontia with reference to aetiology, classification and the subsequent clinical features.Significant progress has been made to identify the developmental basis of tooth formation, though there is still a lack of knowledge within the literature of the aetiological basis of inherited tooth loss.Gene anomalies or mutations in WNT10A, MSX1, PAX9, AXIN2 and EDA appear to be most critical during tooth development, leading to various forms of tooth agenesis.

PAX9 mutations and genetic synergism in familial tooth agenesis

Familial tooth agenesis (FTA) is one of the most common craniofacial anomalies in humans. Loss-of-function mutations in PAX9 and WNT10A have been known to cause FTA with various expressivity. In this study, we identified five FTA kindreds with novel PAX9 disease-causing mutations: p.(Glu7Lys), p.(Val83Leu), p.(Pro118Ser), p.(Ser197Argfs*23), and c.771+4A>G. Concomitant PAX9 and WNT10A pathogenic variants found in two probands with severe phenotypes suggested an effect of mutational synergism. All overexpressed PAX9s showed proper nuclear localization, excepting the p.(Pro118Ser) mutant. Various missense mutations caused differential loss of PAX9 transcriptional ability. PAX9 overexpression in dental pulp cells upregulated LEF1 and AXIN2 expression, indicating a positive regulatory role for PAX9 in canonical Wnt signaling. Analyzing 176 cases with 63 different mutations, we observed a distinct pattern of tooth agenesis for PAX9-associated FTA: Maxillary teeth are in general more frequently affected than mandibular ones. Along with all second molars, maxillary bicuspids and first molars are mostly involved, while maxillary lateral incisors and mandibular bicuspids are relatively less affected. Genotypically, missense mutations are associated with fewer missing teeth than frameshift and nonsense variants. This study significantly expands the phenotypic and genotypic spectrums of PAX9-associated disorders and reveals a molecular mechanism of genetic synergism underlying FTA variable expressivity.

Advances in tooth agenesis and tooth regeneration

The lack of treatment options for congenital (0.1%) and partial (10%) tooth anomalies highlights the need to develop innovative strategies. Over two decades of dedicated research have led to breakthroughs in the treatment of congenital and acquired tooth loss. We revealed that by inactivating USAG-1, congenital tooth agenesis can be successfully ameliorated during early tooth development and that the inactivation promotes late-stage tooth morphogenesis in double knockout mice. Furthermore, Anti- USAG-1 antibody treatment in mice is effective in tooth regeneration and can be a breakthrough in treating tooth anomalies in humans. With approximately 0.1% of the population suffering from congenital tooth agenesis and 10% of children worldwide suffering from partial tooth loss, early diagnosis will improve outcomes and the quality of life of patients. Understanding the role of pathogenic USAG-1 variants, their interacting gene partners, and their protein functions will help develop critical biomarkers. Advances in next-generation sequencing, mass spectrometry, and imaging technologies will assist in developing companion and predictive biomarkers to help identify patients who will benefit from tooth regeneration.

Msx1 is essential for proper rostral tip formation of the mouse mandible

The right and left mandibular processes derived from the first branchial arch grow toward the midline and fuse to create the rostral tip region of the mandible during mandibular development. Severe and mild cases of failure in this process results in rare median cleft of the lower lip and cleft chin, respectively. The detailed molecular mechanisms of mandibular tip formation are unknown. We hypothesize that the Msx1 gene is involved in mandibular tip development, because Msx1 has a central role in other craniofacial morphogenesis processes, such as teeth and the secondary palate development. Normal Msx1 expression was observed in the rostral end of the developing mandible; however, a reduced expression of Msx1 was observed in the soft tissue of the mandibular tip than in the lower incisor bud region. The rostral tip of the right and left mandibular processes was unfused in both control and Msx1-null (Msx1^-/-) mice at embryonic day (E) 12.5; however, a complete fusion of these processes was observed at E13.5 in the control. The fused processes exhibited a conical shape in the control, whereas the same region remained bifurcated in Msx1^-/-. This phenotype occurred with 100% penetrance and was not restored at subsequent stages of development. Furthermore, Meckel's cartilage in addition to the outline surface soft tissues was also unfused and bifurcated in Msx1^-/- from E14.5 onward. The expression of phosho-Smad1/5, which is a mediator of bone morphogenetic protein (Bmp) signaling, was downregulated in the mandibular tip of Msx1^-/- at E12.5 and E13.5, probably due to the downregulated Bmp4 expression in the neighboring lower incisor bud. Cell proliferation was significantly reduced in the midline region of the mandibular tip in Msx1^-/- at the same developmental stages in which downregulation of pSmad was observed. Our results indicate that Msx1 is indispensable for proper mandibular tip development.

The Human Genetics of Dental Anomalies

The development of tooth is a highly complex procedure and mastered by specific genetic programs. Genetic alterations, environmental factors, and developmental timing can disturb the execution of these programs, and result in various dental anomalies like hypodontia/oligodontia, and supernumerary teeth, which are commonly seen in our clinical practice. Advances in molecular research enabled the identification of various genes involved in the pathogenesis of dental anomalies. In the near future, it will help provide a more accurate diagnosis and biological-based treatment for these anomalies. In this article, we present the molecular phenomenon of tooth development and the genetics of various dental anomalies.

Detection of a rare AXIN2 variant in an Iranian family with hypodontia and oligodontia

Background. Hypodontia, or the absence of one or more teeth during tooth formation, is a highly prevalent dental anomaly. Nevertheless, the main causes are still unknown. Mutations in PAX9, MSX1, WNT10A, and AXIN2 genes are most commonly associated with non-syndromic tooth agenesis in the literature. This study investigated these candidate genes in an Iranian family with non-syndromic hypodontia and oligodontia. Methods. Peripheral blood samples of the proband and her family members were collected, and DNA extractions using the salting-out method were carried out. In addition, polymerase chain reaction (PCR) and Sanger sequencing for candidate genes were performed. Results. A missense variant (rs4904210) was identified in the PAX9 gene, with one heterozygous missense variant (rs2240308) and one stop-gained variant (rs121908568) in the AXIN2 gene. Conclusion. By surveying similar studies and analyzing the variant in bioinformatics websites, we concluded that the heterozygous stop-gained variant rs121908568 in exon 8 of the AXIN2 gene could be responsible for tooth agenesis in the Iranian population.

Maxillofacial morphological characteristics in growing orthodontic patients with non-syndromic oligodontia

OBJECTIVE

Patients with oligodontia frequently show different types of malocclusions. However, how oligodontia affects the maxillofacial growth remains uncertain. This study aimed to investigate the maxillofacial morphological characteristics in growing patients with oligodontia.

SETTING AND SAMPLE POPULATION

The study subjects included 33 Japanese children with non-syndromic oligodontia (14 boys and 19 girls; mean age: 10.2 years) who visited the orthodontic clinic of Fukuoka Dental College Medical and Dental Hospital from 1999 to 2019.

MATERIALS AND METHODS

Cephalometric analyses were performed, and the variables measured in each subject were converted into Z scores in relation to the mean and standard deviation of the Japanese norms matched for growth stage. The one-sample t-test or Wilcoxon signed-rank test was performed to compare the mean scores in the patients with oligodontia with those of the Japanese norms.

RESULTS

Compared with the Japanese norms, patients with oligodontia showed a smaller convexity and larger A-B plane and SNB angles. The Frankfort-mandibular plane and gonial angles were smaller, whereas the height of the ramus was larger. The vertical height of the alveolar bone in the maxillary and mandibular incisors and molar areas was smaller in patients with oligodontia.

CONCLUSIONS

Patients with oligodontia showed Class III skeletal tendency with mandibular prognathism and flattened mandibular plane with a smaller gonial angle. These maxillofacial morphological features can be induced by a deficiency in the vertical growth of the alveolar bone in the maxillary and mandibular molar areas due to the lack of tooth germs.

Research algorithm for the detection of genetic patterns and phenotypic variety of non-syndromic dental agenesis

Introduction: Dental agenesis (DA), brings together the anodontia, oligodontia, hypodontia, characterized by a deficit in the development of a variable number of teeth. The objectives of the study were to illustrate the phenotypic variability of non-syndromic DA, to identify cases of DA with hereditary genetic transmission, and establish the mode of DA genetic pattern in these cases, together with the determination of DA prevalence in the population group study. Patients, Materials and Methods: The cross-sectional observational study was performed on a mixed population group, consisting of 861 Caucasian patients, between January 2018–December 2019. The clinical evaluation protocol of patients with DA, used to illustrate their phenotype, included the following stages: oral examination, photographic examination, and radiological examination. The evaluation protocol specific to the family genetic study of patients with DA, involved the following three stages: family survey, construction of the family tree and analysis of the pedigree structure. Results: The prevalence of DA in the population group was 2.78%. Regarding the phenotype, DA mainly affected the upper arch (50% of cases); bilateral DA had a significantly increased incidence (83.33% of cases) compared to unilateral form; in most cases (75%), a patient lacked one to two teeth, the lack of two teeth being the most common form (83.33% of cases); the upper lateral incisors were the teeth most frequently involved in DA (31.11% of the total missing teeth). Regarding the family genetic study, hereditary DA with autosomal dominant inheritance was present in 37.50% of cases. In the other cases (62.50%), isolated, sporadic forms of DA were registered, suggesting a spontaneous de novo mutation or a disorder of odontogenesis of a non-genetic nature. Conclusions: We consider that this study is of interest for current scientific research with applicability in dental medicine, by bringing actual information on the prevalence of non-syndromic DA in South-East Romania, the variety of phenotypic spectrum of DA for this geographic area, and the role of heredity in the DA genetic determinism in the studied population.

Consecutive tooth agenesis patterns in non-syndromic oligodontia

Agenesis of two or more consecutive adjacent permanent teeth (consecutive tooth agenesis, CTA) is a serious manifestation of oligodontia requiring long-term, multi-disciplinary treatment. Therefore, the present study investigated the characteristics of the CTA pattern in orthodontic patients with non-syndromic oligodontia. Using panoramic radiographs, the number of agenetic permanent teeth excluding third molars in non-syndromic orthodontic patients was evaluated, and patients with six or more agenetic teeth (oligodontia group, n = 97) and with one to five agenetic teeth (hypodontia group, n = 107) were selected. The numbers of CTA including third molars in each quadrant and in each patient were compared between the groups. Each quadrant with CTA of patients was categorized into one of the following four types: (I) involves anterior teeth only; (II) involves posterior teeth only; (IIIA) includes anterior and posterior teeth; and (IIIB) separate in the anterior and posterior teeth. CTA in at least one quadrant was found in 91.8 and 4.7% of patients in the oligodontia and hypodontia groups, respectively. The highest frequency CTA patterns included agenesis of the first and second premolars and of the second and third molars in the oligodontia and hypodontia groups, respectively. In the oligodontia group, type IIIA was significantly more frequent in the maxillary than in the mandibular quadrant. Most oligodontia patients who visit orthodontic clinics have CTA. A rare but severe CTA pattern that continues from the anterior to posterior segments is more frequent in the maxillary than in the mandibular quadrant.

Association of Polymorphic and Haplotype Variants of the MSX1 Gene and the Impacted Teeth Phenomenon

It is known that genetic factors determine odontogenesis; furthermore, studies have revealed that various genes in humans can regulate the development of different types and generations of teeth. In this study it has been assumed that tooth impaction—at least to some extent—also depends on the presence of specific genetic markers, especially allelic variants of the MSX1 gene. The primary objective of the study was to evaluate the suitability of selected molecular markers located within the MSX1 gene for the determination of the risk of tooth impaction in particular patients. The study participants were divided into two groups: (1) the study group—at least one secondary tooth was impacted in the jaws; (2) the control group—no impacted tooth in the jaws. Real-Time PCR and TaqMan probes were used to detect selected polymorphisms in the analyzed genes. Two single nucleotide polymorphisms of MSX1 were analyzed. After the two subgroups of patients were distinguished in the study group based on the number of impacted teeth, statistically significant differences in the frequency of genotypes described for rs12532 in the MSX1 gene were found.

Novel MSX1 variants identified in families with nonsyndromic oligodontia

The goal of this study was to identify MSX1 gene variants in multiple Chinese families with nonsyndromic oligodontia and analyse the functional influence of these variants. Whole-exome sequencing (WES) and Sanger sequencing were performed to identify the causal gene variants in five families with nonsyndromic oligodontia, and a series of bioinformatics databases were used for variant confirmation and functional prediction. Phenotypic characterization of the members of these families was described, and an in vitro analysis was performed for functional evaluation. Five novel MSX1 heterozygous variants were identified: three missense variants [c.662A>C (p.Q221P), c.670C>T (p.R224C), and c.809C>T (p.S270L)], one nonsense variant [c.364G>T (p.G122*)], and one frameshift variant [c.277delG (p.A93Rfs*67)]. Preliminary in vitro studies demonstrated that the subcellular localization of MSX1 was abnormal with the p.Q221P, p.R224C, p.G122*, and p.A93Rfs*67 variants compared to the wild type. Three variants (p.Q221P, p.G122*, and p.A93Rfs*67) were classified as pathogenic or likely pathogenic, while p.S270L and p.R224C were of uncertain significance in the current data. Moreover, we summarized and analysed the MSX1-related tooth agenesis positions and found that the type and variant locus were not related to the severity of tooth loss. Our results expand the variant spectrum of nonsyndromic oligodontia and provide valuable information for genetic counselling.

Functional study of novel PAX9 variants: The paired domain and non-syndromic oligodontia

OBJECTIVES

To investigate pathogenic variants of the paired box 9 (PAX9) gene in patients with non-syndromic oligodontia, and the functional impact of these variants.

SUBJECTS AND METHODS

Whole exome sequencing and Sanger sequencing were utilized to detect gene variants in a cohort of 80 patients diagnosed with non-syndromic oligodontia. Bioinformatic and conformational analyses, fluorescence microscopy and luciferase reporter assay were employed to explore the functional impact.

RESULTS

We identified three novel variants in the PAX9, including two frameshift variants (c.211_212insA; p.I71Nfs*246 and c.236_237insAC; p.T80Lfs*6), and one missense variant (c.229C > G; p.R77G). Familial co-segregation verified an autosomal-dominant inheritance pattern. Conformational analyses revealed that the variants resided in the paired domain, and could cause corresponding structural impairment of the PAX9 protein. Fluorescence microscopy showed abnormal subcellular localizations of frameshift variants, and luciferase assay showed impaired downstream transactivation activities of the bone morphogenetic protein 4 (BMP4) gene in all variants.

CONCLUSIONS

Our findings broaden the spectrum of PAX9 variants in patients with non-syndromic oligodontia and support that paired domain structural impairment and the dominant-negative effect are likely the underlying mechanisms of PAX9-related non-syndromic oligodontia. Our findings will facilitate genetic diagnosis and counselling, and help lay the foundation for precise oral health therapies.

Patterns of dental anomalies in patients with nonsyndromic oral cleft

Aim: To characterize the patterns of dental anomalies (DA) in the mixed and permanent dentitions of patients with nonsyndromic oral cleft (NSOC). Methods: This cross-sectional, observational, case-control study included 173 patients, 61 with mixed dentition (NSOC=29 and control=32) and 112 with permanent dentition (NSOC=57 and control=55). All subjected were submitted to clinical and radiographic examination. Dental anomalies of eruption, number, size and shape outside the cleft area were considered. Results: Although there was no statistical significance among patients with mixed dentition, dental agenesis was the anomaly more common in this group. In patients with permanent dentition, a higher prevalence of DA in NSOC group compared to control group was observed (p=0.02). Gyroversion and dental agenesis were the DA more frequently observed in the permanent dentition and the second premolar was the tooth more affected (p=0.003). Mandible and the left side were more involved, and dental agenesis was more frequently found in patients with unilateral cleft lip with or without cleft palate (NSCL±P). Conclusion: Our findings show a higher frequency of DA in NSOCs than in the control group in patients with permanent dentition, mainly due to a higher occurrence of agenesis of second premolars in patients with unilateral NSCL±P.

Craniofacial shape differs in patients with tooth agenesis: geometric morphometric analysis

Aim

To evaluate the shape of the craniofacial complex in patients with tooth agenesis and compare it to matched controls.

Subjects and methods

The sample comprised 456 patients that were allocated to three groups: the agenesis group of 100 patients with at least one missing tooth, excluding third molars, the third molar agenesis group (3dMAG; one to four missing third molars) of 52 patients and the control group (CG) of 304 patients with no missing teeth. The main craniofacial structures depicted on lateral cephalograms were digitized and traced with 15 curves and 127 landmarks. These landmarks were subjected to Procrustes superimposition and principal component analysis in order to describe shape variability of the cranial base, maxilla and mandible, as well as of the whole craniofacial complex. For statistical analysis, permutation tests were used (10 000 permutations without replacement).

Results

Approximately half of the sample's variability was described by the first three principal components. Comparisons within the whole sample revealed sexual dimorphism of the craniofacial complex and its structures (P < 0.01). Differences between the agenesis group and matched controls were found in the shape of all craniofacial structures except for the cranial base (P < 0.05). Specifically, patients with agenesis presented with Class III tendency and hypodivergent skeletal pattern. However, the comparison between the 3dMAG and matched CG revealed no differences.

Conclusion

The shape of the craniofacial complex differs in patients with tooth agenesis suggesting that common factors are implicated in tooth development and craniofacial morphology.

Next generation sequencing reveals a novel nonsense mutation in MSX1 gene related to oligodontia

Tooth agenesis is one of the most common craniofacial disorders in humans. More than 350 genes have been associated with teeth development. In this study, we enrolled 60 child patients (age 13 to 17) with various types of tooth agenesis. Whole gene sequences of PAX9, MSX1, AXIN2, EDA, EDAR and WNT10a genes were sequenced by next generation sequencing on the Illumina MiSeq platform. We found previously undescribed heterozygous nonsense mutation g.8177G>T (c.610G>T) in MSX1 gene in one child. Mutation was verified by Sanger sequencing. Sequencing analysis was performed in other family members of the affected child. All family members carrying g.8177G>T mutation suffered from oligodontia (missing more than 6 teeth excluding third molars). Mutation g.8177G>T leads to a stop codon (p.E204X) and premature termination of Msx1 protein translation. Based on previous in vitro experiments on mutation disrupting function of Msx1 homeodomain, we assume that the heterozygous g.8177G>T nonsense mutation affects the amount and function of Msx1 protein and leads to tooth agenesis.

A novel mutation of MSX1 in oligodontia inhibits odontogenesis of dental pulp stem cells via the ERK pathway

BACKGROUND

Tooth agenesis, one of the most common developmental anomalies, can affect the function and esthetics of patients. The aim of the present study was to identify genetic clues for familial tooth agenesis and explore the underlying mechanisms, focusing on the role of human dental pulp stem cells (hDPSCs).

METHODS

We applied Sanger sequencing to identify the cause of oligodontia in a Chinese family. DNA transfection and functional analysis in DPSCs was also performed to explore the impact of the identified mutation on this phenotype.

RESULTS

In this study, a novel frameshift mutation, the twenty-nucleotide deletion (c.128_147del20, p.Met43Serfsx125), in exon1 of MSX1 was detected in a Chinese family causing autosomal dominant nonsyndromic oligodontia. The mutation cosegregated with the tooth agenesis phenotype in this family. DPSCs transfected with mutant MSX1 plasmid showed decreased capacity of osteo/odontogenic differentiation with a lower expression level of dentin sialophosphoprotein (DSPP) and bone sialoprotein (BSP) compared with those transfected with control MSX1 plasmid. Mechanically, control MSX1 showed nuclear localization while the mutant MSX1 inhibited its nuclear translocation and localized on the cytoplasm to inhibit ERK phosphorylation. Furthermore, we inhibited the ERK pathway using ERK inhibitor (U0126) treatment in control MSX1-transfected DPSCs which could downregulate mineralized nodule formation and the expression of odontogenic genes.

CONCLUSION

We demonstrated a novel MSX1 mutation causing familial nonsyndromic oligodontia and mechanically MSX1 regulates odontogenesis through the ERK signaling pathway in human dental pulp stem cells.

A cross-sectional analysis of the prevalence of tooth agenesis and structural dental anomalies in association with cleft type in non-syndromic oral cleft patients

Background

The aim of this study was to investigate the prevalence of tooth agenesis, microdontia, and tooth malformation among non-syndromic oral cleft patients and their potential association with cleft type and gender.

Methods

Intraoral records and radiographs of 154 patients (97 males and 57 females) were examined. The variables assessed were tooth agenesis, microdontia, dental malformations, and cleft types. The statistics included chi-square and Fisher’s exact tests as well as logistic regression to assess any mutual effects of gender and cleft type on the dental variables.

Results

Tooth agenesis occurred in 50% of the sample and microdontia in 18%. Non-statistically significant odds ratios for the association of gender and cleft type with tooth agenesis were obtained. Tooth agenesis was substantially higher at the unilateral right CL + P and the bilateral CL + P in quadrant 1 and at the unilateral left CL + P and bilateral CL + P in quadrant 2. It was also higher, at the isolated cleft palate (CP) in quadrants 3 and 4. These results were attributed to teeth 22 (31.8%) and 12 (21.6%) in the maxilla and to teeth 35 (6.1%) and 45 (5.4%) in the mandible. In unilateral CL + P patients, the cleft quadrant that presented tooth agenesis was associated with the side of the cleft.

Conclusions

Interdisciplinary treatment of the oral cleft patients should take into consideration the high prevalence of tooth agenesis and their association with the different cleft types. The most frequently affected teeth by cleft are by far the upper lateral incisors. Results indicate that tooth agenesis appears to be a genetically controlled anomaly related to the orofacial cleft development through various genetic links and not caused by the cleft disruptive process.

Bilateral Second Premolars Agenesia Together with a Unilateral Canine Radiculomegaly

Congenitally missing teeth is a common feature for the third molars. However, missing teeth, macrodontia and radiculomegaly occurring in a single patient is very rare. This article describes a case of agenesis of mandibular second premolars, radiculomegaly with dilacerations of a canine tooth together with elongated roots of other canines. All these features had been discerned through diagnostic radiographs taken during a routine treatment planning.

Novel human mutation and CRISPR/Cas genome-edited mice reveal the importance of C-terminal domain of MSX1 in tooth and palate development

Several mutations, located mainly in the MSX1 homeodomain, have been identified in non-syndromic tooth agenesis predominantly affecting premolars and third molars. We identified a novel frameshift mutation of the highly conserved C-terminal domain of MSX1, known as Msx homology domain 6 (MH6), in a Japanese family with non-syndromic tooth agenesis. To investigate the importance of MH6 in tooth development, Msx1 was targeted in mice with CRISPR/Cas system. Although heterozygous MH6 disruption did not alter craniofacial development, homozygous mice exhibited agenesis of lower incisors with or without cleft palate at E16.5. In addition, agenesis of the upper third molars and the lower second and third molars were observed in 4-week-old mutant mice. Although the upper second molars were present, they were abnormally small. These results suggest that the C-terminal domain of MSX1 is important for tooth and palate development, and demonstrate that that CRISPR/Cas system can be used as a tool to assess causality of human disorders in vivo and to study the importance of conserved domains in genes.

Prevalence of delayed tooth development and its relation to tooth agenesis in Korean children

OBJECTIVE

The aim of this study was to investigate the epidemiology of delayed tooth development (DTD) and the link between DTD and tooth agenesis (TA).

DESIGN

The dental maturity of all of the developing permanent teeth of 4611 children (2417 males and 2194 females) was evaluated from panoramic radiographs. The prevalence of DTD and TA was analyzed, and gender difference for DTS and TA was investigated. The correlation of DTD and TA was investigated in intra-fields and inter-fields.

RESULTS

The total prevalence of DTD among the 4611 children was 3.40%. The maxillary second premolar was the most frequently delayed tooth (1.02%), followed by the maxillary second molar (0.88%) and the mandibular second premolar (0.74%). DTD significantly correlated with TA in both intra-fields and inter-fields (p<0.05).

CONCLUSIONS

The field of delayed development exhibited a significant correlation with that of TA.

Mutation analysis by direct and whole exome sequencing in familial and sporadic tooth agenesis

Dental agenesis is one of the most common congenital craniofacial abnormalities. Dental agenesis can be classified, relative to the number of missing teeth (excluding third molars), as hypodontia (1 to 5 missing teeth), oligodontia (6 or more missing teeth), or anodontia (lack of all teeth). Tooth agenesis may occur either in association with genetic syndromes, based on the presence of other inherited abnormalities, or as a non-syndromic trait, with both familiar and sporadic cases reported. In this study, we enrolled 16 individuals affected by tooth agenesis, prevalently hypodontia, and we carried out direct Sanger sequencing of paired box 9 (PAX9) and Msh homeobox 1 (MSX1) genes in 9 subjects. Since no mutations were identified, we performed whole exome sequencing (WES) in the members of 5 families to identify causative gene mutations either novel or previously described. Three individuals carried a known homozygous disease mutation in the Wnt family member 10A (WNT10A) gene (rs121908120). Interestingly, two of these individuals were siblings and also carried a heterozygous functional variant in EDAR-associated death domain (EDARADD) (rs114632254), another disease causing gene, generating a combination of genetic variants never described until now. The analysis of exome sequencing data in the members of other 3 families highlighted new candidate genes potentially involved in tooth agenesis and considered suitable for future studies. Overall, our study confirmed the major role played by WNT10A in tooth agenesis and the genetic heterogeneity of this disease. Moreover, as more genes are shown to be involved in tooth agenesis, WES analysis may be an effective approach to search for genetic variants in familiar or sporadic tooth agenesis, at least in more severe clinical manifestations.

A novel MSX1 intronic mutation associated with autosomal dominant non-syndromic oligodontia in a large Chinese family pedigree

BACKGROUND

Tooth agenesis is a common developmental dental anomaly. The aim of the study was to identify the causal genetic mutation in a four-generation Chinese family affected with non-syndromic autosomal dominant tooth agenesis.

METHODS

Genome-wide scanning was performed using the Illumina Linkage-12 array. Genotyping of short tandem repeat markers was used to finely map the causative locus. Haplotype analysis and Sanger sequencing was performed to precisely locate the position and nature of the gene defect.

RESULTS

Clinical examination of the available 23 family members showed variable tooth agenesis in 10 subjects, ranging from oligodontia to mild hypodontia. Genome-wide scanning and haplotype analyses identified the 4p16.1-p16.3 region with a maximum multi-point LOD score of 3.50, which overlapped with the MSX1 gene. A single heterozygous point mutation IVS1-5 G>A in the MSX1 gene was exclusively detected in the 10 family members affected with tooth agenesis. Sequencing of MSX1 cDNA revealed that the intronic mutation did not affect the normal splicing pattern of the pre-mRNA. However, real-time qPCR analysis of lymphocyte RNA showed that the level of MSX1 mRNA was significantly decreased in individuals heterozygous for the mutation.

CONCLUSIONS

We identified and characterized a novel intronic mutation in the MSX1 gene in a large Chinese pedigree, adding to the small repertoire of MSX1 mutations associated with autosomal dominant tooth agenesis. We hypothesize that the variable degree of tooth agenesis observed in each affected individual may be due to sub-optimal levels of MSX1 expression during critical stages tooth development.

MSX1 mutations and associated disease phenotypes: genotype-phenotype relations

The Msx1 transcription factor is involved in multiple epithelial-mesenchymal interactions during vertebrate embryogenesis. It has pleiotropic effects in several tissues. In humans, MSX1 variants have been related to tooth agenesis, orofacial clefting, and nail dysplasia. We correlate all MSX1 disease causing variants to phenotypic features to shed light on this hitherto unclear association. MSX1 truncations cause more severe phenotypes than in-frame variants. Mutations in the homeodomain always cause tooth agenesis with or without other phenotypes while mutations outside the homeodomain are mostly associated with non-syndromic orofacial clefts. Downstream effects can be further explored by the edgetic perturbation model. This information provides new insights for genetic diagnosis and for further functional analysis of MSX1 variants.

An aberrant splice acceptor site due to a novel intronic nucleotide substitution in MSX1 gene is the cause of congenital tooth agenesis in a Japanese family

Congenital tooth agenesis is caused by mutations in the MSX1, PAX9, WNT10A, or AXIN2 genes. Here, we report a Japanese family with nonsyndromic tooth agenesis caused by a novel nucleotide substitution in the intronic region between exons 1 and 2 of the MSX1 gene. Because the mutation is located 9 bp before exon 2 (c.452-9G>A), we speculated that the nucleotide substitution would generate an abnormal splice site. Using cDNA analysis of an immortalized patient blood cell, we confirmed that an additional 7-nucleotide sequence was inserted at the splice junction between exons 1 and 2 (c.451_452insCCCTCAG). The consequent frameshift generated a homeodomain-truncated MSX1 (p.R151fsX20). We then studied the subcellular localization of truncated MSX1 protein in COS cells, and observed that it had a whole cell distribution more than a nuclear localization, compared to that of wild-type protein. This result suggests a deletion of the nuclear localization signal, which is mapped to the MSX1 homeodomain. These results indicate that this novel intronic nucleotide substitution is the cause of tooth agenesis in this family. To date, most MSX1 variants isolated from patients with tooth agenesis involve single amino acid substitutions in the highly conserved homeodomain or deletion mutants caused by frameshift or nonsense mutations. We here report a rare case of an intronic mutation of the MSX1 gene responsible for human tooth agenesis. In addition, the missing tooth patterns were slightly but significantly different between an affected monozygotic twin pair of this family, showing that epigenetic or environmental factors also affect the phenotypic variations of missing teeth among patients with nonsyndromic tooth agenesis caused by an MSX1 haploinsufficiency.

A novel frameshift MSX1 mutation in a Saudi family with autosomal dominant premolar and third molar agenesis

OBJECTIVES

In this study, the aim was to investigate a consanguineous Saudi family with non-syndromic premolars and third molars agenesis and to identify the causal mutation(s) using whole exome sequencing.

DESIGN

Family phenotype and family pedigree were constructed from clinical and radiographic examinations. Whole exome sequencing was performed in two affected members of the Saudi family using the SureSelect Human all Exon 50 Mb kit (Agilent Technologies, Inc., Santa Clara, CA) and then sequenced on an Illumina HiSeq. SNP and indel calling were performed using samtools version 0.18 and were annotated using the software ANNOVAR.

RESULTS

The family pedigree showed that the inheritance was autosomal dominant. Whole exome sequencing revealed that the affected members in this family were heterozygous with a novel frameshift mutation in exon 2 of the MSX1 gene, (NM_002448:c.750_751insACCGGCTGCC, p.F251PfsX92).

CONCLUSIONS

The novel MSX1 frameshift mutation was linked to a family with moderate to severe tooth agenesis phenotype affecting second premolars and third molars in both arches. This expands the genotype-phenotype of MSX1 associated conditions.

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.

Isolated oligodontia in monozygotic twins

This case report defines a case of isolated oligodontia of 9 and 10 permanent teeth in 9-year-old monozygotic twin sisters and gives information about the possible genetic and environmental etiology, related dental anomalies and treatment options. The twins have a negative family history of hypodontia and oligodontia in their parents, as well as their paternal and maternal grandmothers and first cousins. No other dental anomalies could be detected in either of the twins. With the occurrence of similarly located tooth agenesis, except for one tooth, in monozygotic twins, one may consider the influence of genetic and/or environmental factors in their etiology. Hereditary relationships associated with oligodontia could help the clinicians to predict the possibility of its occurrence in other family members and in the next generations. However, clinicians should consider oligodontia when it is not hereditary.

A novel non-stop mutation in MSX1 causing autosomal dominant non-syndromic oligodontia

Oligodontia, which is the congenital absence of six or more permanent teeth, excluding the third molars, may contribute to masticatory dysfunction, speech alteration, aesthetic problems and malocclusion. Msh homeobox 1 (MSX1) was the first gene identified as causing non-syndromic oligodontia. In this study, we identified a novel heterozygous non-stop mutation (c.910_911dupTA, p.*304Tyrext*48) in MSX1 in a Chinese family with autosomal dominant non-syndromic oligodontia. This novel mutation substitutes the stop codon with a tyrosine residue, potentially adding 48 amino acids to the C-terminus of MSX1. Further in vitro study found that mutant MSX1 could be expressed but had lost its ability to enter the nucleus. This is the first report indicating that a non-stop mutation in MSX1 is responsible for oligodontia. This study broadens the mutation spectrum for MSX1 and provides a new way to clarify the mechanism of MSX1 in tooth agenesis.

Absence of multiple premolars and ankylosis of deciduous molar with cant of the occlusal plane treated using skeletal anchorage

Ankylosis and the absence of premolars are two relatively common conditions encountered in the field of orthodontics. However, the absence of multiple premolars, particularly two adjacent premolars, along with ankylosis of deciduous teeth, is unusual. Herein, we present a case report and discuss some aspects related to these abnormalities. A 15-year-old boy was missing the upper right first and second premolars and the lower right and left second premolars. In addition, the deciduous lower left second molar was ankylosed and in infraocclusion, causing canting of the occlusal plane. The patient was treated with a mini-implant to correct the Class II malocclusion on the left side and a miniplate to correct the cant of the occlusal plan. After treatment, the upper right space was kept closed, with the canine in contact with the first molar, and the lower left space was opened to an implant-prosthetic rehabilitation.

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.

Oligodontia and curly hair occur with ectodysplasin-a mutations

Oligodontia is the developmental absence of more than 5 permanent teeth except for the third molar. Familial oligodontia can occur as an isolated form or as part of a genetic syndrome. Mutations in the MSX1, PAX9, AXIN2, EDA, and WNT10A genes have been identified in familial non-syndromic oligodontia. Ectodermal dysplasia is a group of syndromes involving abnormalities of the ectodermal structures and is comprised of more than 150 different forms. Mutations in the ectodysplasin-A (EDA) gene have been associated with X-linked hypohidrotic ectodermal dysplasia, and partial disruption of the EDA signaling pathway has been shown to cause an isolated form of oligodontia. We identified 2 X-linked oligodontia families and performed mutational analysis of the EDA gene. The mutational analysis revealed 2 novel EDA mutations: c.866G>T, p.Arg289Leu and c.1135T>G, p.Phe379Val (reference sequence NM_001399.4). These mutations were perfectly segregated with oligodontia and curly hair within each family and were not found in the 150 control X-chromosomes with the same ethnic background and in the exome variant server. This study broadens the mutational spectrum of the EDA gene and the understanding of X-linked oligodontia with curly hair.

Nonsyndromic familial oligodontia with multiple dens invaginatus: a case report of an unusual case

Oligodontia is a rare dental anomaly with a prevalence of 0.3% in permanent teeth and much less frequency in the primary dentition. Familial oligodontia represents an absence of varying numbers of primary and/or secondary teeth as an isolated trait. It is a complex and multifactorial condition. Many explanations—evolutionary, genetic, and environmental—have been proposed as the etiology. Simultaneous with oligodontia are often the different positional changes of the existing teeth, their morphology, size, and growth disturbances of the maxillofacial skeleton. Early recognition is vital to provide adequate treatment and prevent squeal. Multidisciplinary referral or consultation is thus important in treatment planning to improve function and esthetics. The present paper reports a rare case of familial oligodontia associated with multiple dense invaginatus and microdontia.

Mutational analysis of AXIN2, MSX1, and PAX9 in two Mexican oligodontia families

The genes for axin inhibition protein 2 (AXIN2), msh homeobox 1 (MSX1), and paired box gene 9 (PAX9) are involved in tooth root formation and tooth development. Mutations of the AXIN2, MSX1, and PAX9 genes are associated with non-syndromic oligodontia. In this study, we investigated phenotype and AXIN2, MSX1, and PAX9 gene variations in two Mexican families with non-syndromic oligodontia. Individuals from two families underwent clinical examinations, including an intra-oral examination and panoramic radiograph. Retrospective data were reviewed, and peripheral blood samples were collected. The exons and exon-intronic boundaries of the AXIN2, MSX1, and PAX9 genes were sequenced and analyzed. Protein and messenger RNA structures were predicted using bioinformative software programs. Clinical and oral examinations revealed isolated non-syndromic oligodontia in the two Mexican families. The average number of missing teeth was 12. The sequence analysis of exons and exon-intronic regions of AXIN2, MSX1, and PAX9 revealed 11 single-nucleotide polymorphisms (SNPs), including seven in AXIN2, two in MSX1, and three in PAX9. One novel SNP of MSX1, c.476T>G (Leu159Arg), was found in all of the studied patients in the families. MSX1 Leu159Arg and PAX9 Ala240Pro change protein and messenger RNA structures. Our findings suggested that a combined reduction of MSX1 and PAX9 gene dosages increased the risk for oligodontia in the Mexican families, as in vivo investigation has indicated that interaction between Msx1 and Pax9 is required for tooth development.