Craniofacial syndromes and class III phenotype: common genotype fingerprints? A scoping review and meta-analysis.

Skeletal Class III (SCIII) is among the most challenging craniofacial dysmorphologies to treat. There is, however, a knowledge gap regarding which syndromes share this clinical phenotype. The aims of this study were to: (i) identify the syndromes affected by the SCIII phenotype; (ii) clarify the involvement of maxillary and/or mandibular structures; (iii) explore shared genetic/molecular mechanisms. A two-step strategy was designed: [Step#1] OMIM, MHDD, HPO, GeneReviews and MedGen databases were explored; [Step#2]: Syndromic conditions indexed in [Step#1] were explored in Medline, Pubmed, Scopus, Cochrane Library, WOS and OpenGrey. Eligibility criteria were defined. Individual studies were assessed for risk of bias using the New Ottawa Scale. For quantitative analysis, a meta-analysis was conducted. This scoping review is a hypothesis-generating research. Twenty-two studies met the eligibility criteria. Eight syndromes affected by the SCIII were targeted: Apert syndrome, Crouzon syndrome, achondroplasia, X-linked hypohidrotic ectodermal dysplasia (XLED), tricho-dento-osseous syndrome, cleidocranial dysplasia, Klinefelter and Down syndromes. Despite heterogeneity between studies [p < 0.05], overall effects showed that midface components were affected in Apert and Down Syndromes, lower face in Klinefelter Syndrome and midface and lower face components in XLED. Our review provides new evidence on the craniofacial characteristics of genetically confirmed syndromes exhibiting the SCIII phenotype. Four major regulatory pathways might have a modulatory effect on this phenotype. IMPACT: What does this review add to the existing literature? To date, there is no literature exploring which particular syndromes exhibit mandibular prognathism as a common trait. Through this research, it was possibly to identify the particular syndromes that share the skeletal Class III phenotype (mandibular prognathism) as a common trait highlighting the common genetic and molecular pathways between different syndromes acknowledging their impact in craniofacial development.

Skeletal Class III phenotype: Link between animal models and human genetics: A scoping review.

This study aimed to identify evidence from animal studies examining genetic variants underlying maxillomandibular discrepancies resulting in a skeletal Class III (SCIII) malocclusion phenotype. Following the Manual for Evidence Synthesis of the JBI and the PRISMA extension for scoping reviews, a participant, concept, context question was formulated and systematic searches were executed in the PubMed, Scopus, WOS, Scielo, Open Gray, and Mednar databases. Of the 779 identified studies, 13 met the selection criteria and were included in the data extraction. The SCIII malocclusion phenotype was described as mandibular prognathism in the Danio rerio, Dicentrarchus labrax, and Equus africanus asinus models; and as maxillary deficiency in the Felis silvestris catus, Canis familiaris, Salmo trutta, and Mus musculus models. The identified genetic variants highlight the significance of BMP and TGF-ß signaling. Their regulatory pathways and genetic interactions link them to cellular bone regulation events, particularly ossification regulation of postnatal cranial synchondroses. In conclusion, twenty genetic variants associated with the skeletal SCIII malocclusion phenotype were identified in animal models. Their interactions and regulatory pathways corroborate the role of these variants in bone growth, differentiation events, and ossification regulation of postnatal cranial synchondroses.

Genetic polymorphisms are involved in oral health-related quality of life in skeletal class III patients submitted to orthognathic surgery.

OBJECTIVE: This study aimed to evaluate whether sex and genetic polymorphisms impact the oral health-related quality of life (OHRQoL) preoperatively and the difference between preoperative and postoperative OHRQoL in skeletal Class III patients submitted to orthognathic surgery. MATERIALS AND METHODS: This longitudinal study consisted of ninety-nine patients with skeletal Class III malocclusion who required orthognathic surgery. The Oral Health Impact Profile-14 (OHIP-14) is a questionnaire used to assess the OHRQoL with a 5-point Likert-type scale, covering seven domains related to physical and psychosocial factors. The questionnaire was applied in the preoperative and postoperative periods, and the difference scores were calculated to assess the OHRQoL after orthognathic surgery. The DNA was extracted from oral mucosa cells to evaluate genetic polymorphisms in ANKK1, DRD2, ESR1, and ESR2 through real-time PCR. RESULTS: There was an improvement in all OHRQoL domains following orthognathic surgery (p < 0.05). In the preoperative evaluation, women presented worse OHRQoL (p < 0.05) than men. There was no statistical difference between sex and the OHRQoL after surgery (p > 0.05). When evaluating the polymorphisms and preoperative OHIP-14 scores, CT genotype patients for rs1800497 (ANKK1) had a worse perception of the physical pain domain than CC genotype (p = 0.026), and CC genotype patients for rs1256049 (ESR2) had a worse perception of the functional limitation domain than CT genotype (p = 0.002). In the analysis between polymorphisms and postoperative and preoperative difference scores, CT genotype patients for rs1256049 (ESR2) had a greater improvement in the perception of the physical pain domain than the CC genotype (p = 0.031). In rs6275 and rs6276 (DRD2), patients with the CC genotype worsened the perception of the functional limitation domain than the TT genotype (p = 0.045), and AA genotype patients worsened the perception of the functional limitation domain than GG genotype (p = 0.048) after surgery, respectively. In addition, patients with the CT genotype for rs1800497 (ANKK1) had a greater improvement of OHRQoL perception in the total scale than the TT genotype (p = 0.018), and CT genotype patients had a greater improvement in the perception of function limitation domain than TT genotype (p = 0.017). CONCLUSION: Women have a worse perception of OHRQoL in the preoperative period of orthognathic surgery. Furthermore, polymorphisms in the ANKK1, DRD2, and ESR2 genes could be involved with OHRQoL in the preoperative period and following orthognathic surgery. CLINICAL RELEVANCE: The knowledge of the genetic background concerning OHRQoL in skeletal class III patients would aid in clinical practice to screen for associated genetic factors and prevent OHRQoL deterioration, especially after orthognathic surgery, considering that patients' genetic profiles would soon be available.

Dissecting the Complexity of Skeletal-Malocclusion-Associated Phenotypes: Mouse for the Rescue.

Skeletal deformities and malocclusions being heterogeneous traits, affect populations worldwide, resulting in compromised esthetics and function and reduced quality of life. Skeletal Class III prevalence is the least common of all angle malocclusion classes, with a frequency of 7.2%, while Class II prevalence is approximately 27% on average, varying in different countries and between ethnic groups. Orthodontic malocclusions and skeletal deformities have multiple etiologies, often affected and underlined by environmental, genetic and social aspects. Here, we have conducted a comprehensive search throughout the published data until the time of writing this review for already reported quantitative trait loci (QTL) and genes associated with the development of skeletal deformation-associated phenotypes in different mouse models. Our search has found 72 significant QTL associated with the size of the mandible, the character, shape, centroid size and facial shape in mouse models. We propose that using the collaborative cross (CC), a highly diverse mouse reference genetic population, may offer a novel venue for identifying genetic factors as a cause for skeletal deformations, which may help to better understand Class III malocclusion-associated phenotype development in mice, which can be subsequently translated to humans. We suggest that by performing a genome-wide association study (GWAS), an epigenetics-wide association study (EWAS), RNAseq analysis, integrating GWAS and expression quantitative trait loci (eQTL), micro and small RNA, and long noncoding RNA analysis in tissues associated with skeletal deformation and Class III malocclusion characterization/phenotypes, including mandibular basic bone, gum, and jaw, in the CC mouse population, we expect to better identify genetic factors and better understand the development of this disease.

Genetic architecture of non-syndromic skeletal class III malocclusion.

Non-syndromic skeletal Class III malocclusion is a major craniofacial disorder characterized by genetic and environmental factors. Patients with severe skeletal Class III malocclusion require orthognathic surgery to obtain aesthetic facial appearance and functional occlusion. Recent studies have demonstrated that susceptible chromosomal regions and genetic variants of candidate genes play important roles in the etiology of skeletal Class III malocclusion. Here, we provide a comprehensive review of our current understanding of the genetic factors that affect non-syndromic skeletal Class III malocclusion, including the patterns of inheritance and multiple genetic approaches. We then summarize the functional studies on related loci and genes using cell biology and animal models, which will help to implement individualized therapeutic interventions.

Influence of COL2A1-G1405S polymorphism on mandibular skeletal malocclusions: A genetic association study and in silico analysis.

OBJECTIVE: The current study aimed to assess the association between collagen type II alpha 1 chain (COL2A1) single nucleotide polymorphism (SNP: rs2070739; C>T; G1405S) and mandibular skeletal malocclusions in the population of Mazandaran (North Iran). DESIGN: During 13 months, 102 control samples, 81 samples with skeletal Class III malocclusion contributed by mandibular prognathism and 82 samples with skeletal Class II malocclusion contributed by mandibular retrognathism were screened. Cephalometric analysis was performed to determine the type of abnormalities. COL2A1-G1405S genotyping was performed using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method. The HOPE tool was used to investigate the effect of COL2A1-G1405S on the three-dimensional structure of protein. RESULTS: Results showed that there is no significant correlation between genotypes and alleles related to COL2A1-G1405S and mandibular prognathism (CT genotype: p-value= 0.210; T allele: p-value= 0.222). On the other hand, an association was observed between COL2A1-G1405S and mandibular retrognathism (CT genotype: p-value= 0.008; T allele: p-value= 0.011). The outputs of the HOPE tool also showed that COL2A1-G1405S can disrupt the NC1 domain of the protein. CONCLUSIONS: Here, we provide evidence that COL2A1-G1405S polymorphism may have positive correlation with the risk of skeletal Class II malocclusion contributed by mandibular retrognathism in the population of Mazandaran. Given that the COL2A1-G1405S occurs in NC1 domain, it is possible that this domain plays an important role in signaling pathways related to ossification. So, we suggest that the study of COL2A1 SNPs can help researchers understand the significant role of this collagen in mandibular skeletal malocclusions.

Genetic effect of single nucleotide polymorphisms in growth hormone receptor gene on the risk of non-syndromic mandibular prognathism in the Korean population.

OBJECTIVES: To evaluate the association of three single-nucleotide polymorphisms (SNPs) of growth hormone receptor (GHR) gene with mandibular prognathism (MP) and relationships between mandibular morphology and GHR gene SNPs in the Korean population. MATERIALS AND METHODS: A total of 325 subjects were divided into two groups based on sagittal maxillomandibular relationship by the lateral cephalography: the MP and control groups. From the SNPs in the GHR gene, three SNPs (rs6180, rs6182 and rs6184) were selected. SNP genotyping was performed using direct sequencing. The craniofacial measurements of lateral cephalography were analysed. RESULTS: We found a lack of association between GHR and MP. However, in the analysis according to the values of cephalometric measurements, rs6180 was significantly associated with ANB, SNB, effective mandibular length and SNMP in females. Additionally, rs6182 and rs6184 were significantly associated with ramal height in males. CONCLUSION: Growth hormone receptor SNPs may affect not only the sagittal development of mandible but also the vertical development of ramal height, and GHR SNPs may gender-differently influence mandibular morphology. This finding supports that the GHR might be susceptible on mandibular morphogenesis in the Korean population.

Genetic factors contributing to skeletal class III malocclusion: a systematic review and meta-analysis.

OBJECTIVES: The present systematic review aims to report and critically assess the findings of the available scientific evidence from genetic association studies examining the genetic variants underlying skeletal class III malocclusion and its sub-phenotypes. MATERIAL AND METHODS: A pre-piloted protocol was registered and followed. The PubMed, Scopus, WOS, Cochrane Library, Gray Open literature, and CADTH databases were explored for genetic association studies following PICOS-based selection criteria. The research was reported in accordance with PRISMA statement and HuGE guidelines. The Q-genie tool was applied to assess the quality of genetic studies. Meta-analysis of genetic association studies was done by means of Meta-Genyo tool. RESULTS: A total of 8258 articles were retrieved, of which 22 were selected for in-depth analysis. Most of the studies did not differentiate between sub-phenotypes, and the cohorts were heterogeneous regarding ethnicity. Four to five principal components of class III malocclusion explained the phenotypic variation, and gene variants at MYO1H(rs10850110), BMP3(rs1390319), GHR (rs2973015,rs6184, rs2973015), FGF7(rs372127537), FGF10(rs593307), and SNAI3(rs4287555) (p < .05) explained most of the variation across the studies, associated to vertical, horizontal, or combined skeletal discrepancies. Meta-analysis results identified a statistically significant association between risk of class III malocclusion of A allele of the FBN3 rs7351083 [OR 2.13; 95% CI 1.1-4.1; p 0.02; recessive model]. CONCLUSION: Skeletal class III is a polygenic trait substantially modulated by ethnicity. A multicentric approach should be considered in future studies to increase sample sizes, applying multivariate analysis such as PCA and cluster analysis to characterize existing sub-phenotypes warranting a deeper analysis of genetic variants contributing to skeletal class III craniofacial disharmony. CLINICAL RELEVANCE: Grasping the underlying mechanisms of this pathology is critical for a fuller understanding of its etiology, allowing generation of preventive strategies, new individualized therapeutic approaches and more accurate treatment planification strategies.

Potential interactions among single nucleotide polymorphisms in bone- and cartilage-related genes in skeletal malocclusions.

OBJECTIVE: To investigate SNPs in bone- and cartilage-related genes and their interaction in the aetiology of sagittal and vertical skeletal malocclusions. SETTINGS AND SAMPLE POPULATION: This study included 143 patients and classified as follows: skeletal class I (n = 77), class II (n = 47) and class III (n = 19); maxillary retrusion (n = 39), protrusion (n = 52) and well-positioned maxilla (n = 52); mandibular retrognathism (n = 50), prognathism (n = 50) and well-positioned mandible (n = 43); normofacial (n = 72), dolichofacial (n = 55) and brachyfacial (n = 16). MATERIALS AND METHODS: Steiner's ANB, SNA, SNB angles and Ricketts' NBa-PtGn angle were measured to determine the skeletal malocclusion and the vertical pattern. Nine SNPs in BMP2, BMP4, SMAD6, RUNX2, WNT3A and WNT11 were genotyped. Chi-squared test was used to compare genotypes among the groups. Multifactor dimensionality reduction (MDR) and binary logistic regression analysis, both using gender and age as co-variables, were also used. We performed Bonferroni correction for multiple testing. RESULTS: Significant associations at P < .05 were observed for SNPs rs1005464 (P = .042) and rs235768 (P = .021) in BMP2 with mandibular retrognathism and for rs59983488 (RUNX2) with maxillary protrusion (P = .04) as well as for rs708111 (WNT3A) with skeletal class III (P = .02; dominant model), rs1533767 (WNT11) with a brachyfacial skeletal pattern (P = .01, OR = 0.10; dominant model) and for rs3934908 (SMAD6) with prognathism (P = .02; recessive model). After the Bonferroni correction, none of the SNPs remained associated. The MDR predicted some interaction for skeletal class II, dolichofacial and brachyfacial phenotypes. CONCLUSION: Our results suggest that SNPs in BMP2, BMP4, SMAD6, RUNX2, WNT3A and WNT11 could be involved in the aetiology of sagittal and vertical malocclusions.

Koolen-de Vries syndrome in the first adulthood patient of Southern India ancestry.

Koolen-de Vries syndrome (KdVS, MIM#610443) is a rare malformation condition mainly characterized by cognitive impairment in association with craniofacial and visceral anomalies. The core phenotype is caused by mutations in the chromatin remodeler KANSL1 (MSL1V1, KIAA1267, KAT8 Regulatory NSL Complex Subunit 1, MIM#612452), which maps to 17q21.31 critical genomic region (Koolen et al., Nature Genetics 2012;44:639-641). Considering its molecular basis, KdVS is included in the group of Developmental Disorders of Chromatin Remodeling (DDCRs), also termed chromatinopathies. We describe the first KdVS patient of Southern India ethnicity, harboring the typical de novo 17q21.31 microdeletion, including KANSL1. Observed facial features and congenital anomalies are in line with the already reported KdVS phenotype, suggesting that phenotypic features are consistent across different ethnicities.

O fenótipo radiográfico da maxila na maloclusão Classe III / The radiographic phenotype of the maxilla in Class III malocclusion

A maloclusão Classe III apresenta diversidade fenotípica que se expressa por retrusão esquelética da maxila, protrusão esquelética da mandíbula ou combinação de ambas. A literatura evidencia que a maxila apresenta alteração, em 49,6% dos casos da maloclusão Classe III. Objetiva-se investigar e reconhecer características fenotípicas da maxila nesta maloclusão, utilizadandose duas casuísticas: a primeira, integrada por 195 indivíduos, oriundos de 8 famílias, com alta prevalência das características craniofaciais da Classe III, (86 afetados e 109 não afetados). A segunda, constituída por 47 indivíduos, sendo 28 com maloclusão Classe III de Angle e 19 com maloclusão Classe I. Os projetos foram submetidos e aprovados no Comitê de Ética em Pesquisa junto ao Hospital Universitário Clementino Fraga Filho. O mesmo operador (L.T.V) realizou a análise de todas as radiografias e tomografias. Medidas lineares e angulares foram avaliadas, para identificar as dimensões da maxila. Os resultados foram analisados estatisticamente: na amostra 2D por Shapiro-Wilk, após comprovada distribuição não normal, o teste selecionado foi teste de Mann-Whitney para comparação intergrupos e entre gêneros. Enquanto a amostra 3D foi submetida ao teste Kolmogorov-Smirnov e mediante a distribuição normal dos dados foi realizado teste t e Correlação de Pearson. Os resultados evidenciaram significante envolvimento na anatomia dos processos alveolares, mostrando-se distintos entre indivíduos Classe III e Classe I, quanto à altura, largura e espessura, assim como alteração do fenótipo nos indivíduos afetados em comparação aos não afetados, em algumas dimensões das estruturas e na localização espacial, com ênfase na deficiência anteroposterior maxilar. Concluiuse que existem variações anatômicas em diferentes partes da maxila, entre os grupos, entretanto a localização espacial da mesma, no sentido anteroposterior, foi determinante na configuração fenotípica da maloclusão Classe III esquelética. (AU)

Class III malocclusion presents phenotypic diversity that is expressed by skeletal retrusion of the maxilla, skeletal protrusion of the mandible or a combination of both. The literature shows that the maxilla presents some kind of alterations, in 49.6% of Class III malocclusion cases. The aim of this study was to recognize phenotypic characteristics of the maxilla in subjects with Class III expression, two samples were used: the first, comprising 195 subjects, from 8 families, with high prevalence of the Class III craniofacial characteristics (86 affected and 109 unaffected). The second, consisting of 47 subjects, 19 with Class I malocclusion and 28 with Angle Class III malocclusion. This study was approved by Comitê de Ética em Pesquisa in Hospital Universitário Clementino Fraga Filho. The same operator (L.T.V) performed the analysis of all radiographs and conebeam computed tomography. Linear and angular measurements were evaluated to identify the dimensions of the maxilla. The results were analyzed statistically: in the 2D sample, Shapiro-Wilk and Kolmogorov-Smirnov, after proven non-normal distribution the selected test was the Mann-Whitney test for intergroup and gender comparison. While a 3D sample was submitted to Shapiro-Wilk and KolmogorovSmirnov, provided the normal data distribution, the t test and Pearson's correlation were performed. The results showed a significant involvement in the anatomy of the alveolar processes, showing a difference between Class III and Class I individuals, as for height, width and thickness, as well as alteration of the phenotype in the affected individuals compared to the unaffected ones, in some dimensions of the structures and in the spatial location, with emphasis on the anteroposterior deficiency. It was concluded that there are anatomical variations in different parts of the maxilla, between the groups, however its spatial location, in the anteroposterior direction, characterized the phenotypic configuration of skeletal Class III malocclusion. (AU)

Is the "Habsburg jaw" related to inbreeding?

Background: The "Habsburg jaw" has long been associated with inbreeding due to the high prevalence of consanguineous marriages in the Habsburg dynasty. However, it is thought that mandibular prognathism (MP) is under the influence of a dominant major gene.Aim: To investigate the relationship between the "Habsburg jaw" and the pedigree-based inbreeding coefficient (F) as a relative measure of genome homozygosity.Subjects and methods: The degree of MP and maxillary deficiency (MD) of 15 members of the Habsburg dynasty was quantified through the clinical analysis of 18 dysmorphic features diagnosed from 66 portraits.Results: A statistically significant correlation (r = 0.711, p = 0.003) between MP and MD was observed among individuals. Only MP showed a statistically significant positive regression on F as evidenced from univariate analysis (b = 6.36 ± 3.34, p = 0.040) and multivariate analysis (PCA) performed from single dysmorphic features (b = 14.10 ± 6.62, p = 0.027, for the first PC).Conclusion: Both MP and MD are generally involved in the "Habsburg jaw." The results showed a greater sensitivity to inbreeding for the lower third of the face and suggest a positive association between the "Habsburg jaw" and homozygosity and therefore a basically recessive inheritance pattern.

Association of the P561T and C422F polymorphisms of the growth hormone receptor gene with facial dimensions / Asociación de los polimorfismos P561T y C422F del gen receptor de la hormona del crecimiento con dimensiones faciales

Background: Growth hormone plays a significant role in determining craniofacial morphology. Mutations of its receptor gene might be associated with mandibular prognathism (MP). Purpose: The aim of the current study was to evaluate growth hormone receptor (GHR) gene polymorphisms in relation to facial dimensions. Material and Method: The study enrolled 65 participants with class III profile in MP group and 60 orthognathic control participants. Genomic DNA was extracted from a blood sample from the patients and the P561T and C422F polymorphisms of GHR gene were screened by PCR-RFLP method followed by Sanger sequencing of randomly selected samples to validate the genotyping results. Chi square was used to compare distribution of polymorphism in MP and control groups (p<0.05). Results: Heterozygous P561T mutation was found in 10.77% and 8.33% of MP and control groups, respectively (p=0.644) while none of the subjects had the C422F mutation. Sanger sequencing confirmed the genotyping results from the PCR-RFLP method. P561T polymorphism was significantly associated with ramus and lower facial height in MP patients and with ramus height in orthognathic patients (p<0.05). Conclusion: The results indicate that the P561T polymorphism of the GHR gene is associated with the vertical dimension of the mandible in an Iranian population.

Antecedentes: La hormona del crecimiento desempeña un papel importante en la determinación de la morfología craneofacial. Las mutaciones de su gen receptor podrían estar asociadas con el prognatismo mandibular (PM). Propósito: El objetivo del presente estudio fue evaluar dos polimorfismos del gen del receptor de la hormona del crecimiento (RHC) en relación con las dimensiones faciales. Materiales y Métodos: El estudio incluyó a 65 participantes con perfil de clase III en el grupo MP y 60 participantes de control ortognático. El ADN genómico se extrajo de una muestra de sangre de los pacientes y los polimorfismos P561T y C422F del gen RHC se seleccionaron mediante el método PCR-RFLP seguido de la secuenciación por Sanger de muestras seleccionadas al azar para validar los resultados del genotipo por RFLP. El test chi cuadrado se utilizó para comparar la distribución del polimorfismo en el grupo MP y grupo control (p<0.05). Resultados: Se encontró mutación heterocigota P561T en 10.77% y 8.33% de los grupos PM y control, respectivamente (p=0.644) mientras que ninguno de los sujetos tenía la mutación C422F. La secuenciación de Sanger confirmó los resultados de genotipado por el método PCR-RFLP. El polimorfismo P561T se asoció significativamente con la rama y la altura facial más baja en pacientes con PM y con la altura de la rama en pacientes ortognáticos (p<0.05). Conclusión: Los resultados indican que el polimorfismo P561T del gen RHC está asociado con la dimensión vertical de la mandíbula en una población iraní.

Three novel genes tied to mandibular prognathism in eastern Mediterranean families.

INTRODUCTION: Mandibular prognathism (MP) is subject to major polygenic influence and segregates within families in autosomal dominance with variable expressivity and incomplete penetrance. We aimed to identify the inheritance pattern and genes and loci involved in the development of MP in Mediterranean families and to evaluate the dentoskeletal characteristics of affected individuals. METHODS: Fifty-one eastern Mediterranean families with individuals affected by MP were identified. Data and biospecimens were collected from 14 of the families, including clinical examination, lateral cephalography (on subjects with Class III malocclusion), and 5 mL blood drawn from consenting affected and nonaffected relatives. Next-generation sequencing (NGS) was performed on 8 families (7 Lebanese, 1 Lebanese/Syrian), including large numbers of affected individuals over many generations and severe conditions, with the use of whole-exome sequencing. RESULTS: Most pedigrees suggested autosomal-dominant inheritance with an equal number of affected male and female individuals. Affected individuals had macrognathic and prognathic mandibles with dentoalveolar compensation. Genetic screening did not correspond with previously reported MP-linked genes, but yielded 3 novel genes (C1orf167, NBPF8, NBPF9) on chromosome 1 potentially responsible for mandibular development and macrognathism. CONCLUSIONS: In this first genetic study with the use of NGS on the largest reported number of families with MP, novel genes (C1orf167, NBPF8, NBPF9) were associated with familial MP in the eastern Mediterranean population.

ADAMTSL1 and mandibular prognathism.

Mandibular prognathism is characterized by a prognathic or prominent mandible. The objective of this study was to find the gene responsible for mandibular prognathism. Whole exome sequencing analysis of a Thai family (family 1) identified the ADAMTSL1 c.176C>A variant as the potential defect. We cross-checked our exome data of 215 people for rare variants in ADAMTSL1 and found that the c.670C>G variant was associated with mandibular prognathism in families 2 and 4. Mutation analysis of ADAMTSL1 in 79 unrelated patients revealed the c.670C>G variant was also found in family 3. We hypothesize that mutations in ADAMTSL1 cause failure to cleave aggrecan in the condylar cartilage, and that leads to overgrowth of the mandible. Adamtsl1 is strongly expressed in the condensed mesenchymal cells of the mouse condyle, but not at the cartilage of the long bones. This explains why the patients with ADAMTSL1 mutations had abnormal mandibles but normal long bones. This is the first report that mutations in ADAMTSL1 are responsible for the pathogenesis of mandibular prognathism.

Associação dos genes EPB41, COL2A1, MYO1H e TBX3 com a maloclusão de Classe III em famílias brasileiras evidenciando a contribuição da maxila / Association of EPB41, COL2A1, MYO1H and TBX3 genes with Class III malocclusion in Brazilian families evidencing the Maxilla contribution

O objetivo dos autores foi testar, em famílias brasileiras, quatro polimorfismos de Nucleotídeo Único (SNPs) nos genes EPB41(2 SNPs), COL2A1 e MYO1H previamente relacionados ao aumento de risco para desenvolvimento da maloclusão de Classe III em outras populações, e um SNP no gene TBX3 sem nenhuma associação prévia com esta condição. O estudo baseou-se em amostras de DNA e radiografias cefalométricas laterais de indivíduos pertencentes a oito famílias do município de Imbituba (SC) com diagnóstico de maloclusão de Classe III (ANB≤0 ou Wits≤-4), em pelo menos duas gerações. O Teste de Desequilíbrio de Transmissão (TDT) foi empregado para testar a associação alélica e haplotípica entre os cinco SNPs e quatro grupos de x fenótipos relacionados a maloclusão de Classe III: GMx- grupo com comprometimento exclusivamente maxilar, GMd- grupo com apenas alterações mandibulares, GComb- grupo com alterações na maxila e mandíbula simultaneamente e GIII- grupo que continha todos os indivíduos Classe III da amostra. O gene TBX3 foi estatisticamente associado ao aumento de risco para a maloclusão de Classe III no grupo GIII (p=0,03), e o gene EPB41 no grupo GMx (p=0,02). A combinação haplotípica (G-G-A) dos genes COL2A1/MYO1H/TBX3 mostrou-se estatisticamente significativa no grupo GIII (p=0,04), assim como a (A-A) do gene EPB41 e a (G-A) dos genes COL2A1/TBX3 no grupo GMx (p=0,01 e p=0,04 respectivamente). Já a combinação (A-G) dos genes COL2A1/TBX3 parece reduzir significativamente o risco para a maloclusão de Classe III no grupo GIII (p=0,04) e GComb (p=0,03). O grupo GMd não apresentou associação significativa em nenhum dos testes realizados. Frente a evidência de associação genética com o fenótipo GMx, o qual raramente é considerado nas investigações genéticas de maloclusão de Classe III, foi desenvolvida revisão sistemática, com o intuito de verificar o percentual de contribuição da maxila e da mandíbula nesta maloclusão. Concluiu-se que a deficiência de maxila isolada foi responsável por 22,8% dos casos de maloclusão de Classe III classificados, e em 34,2% dos casos apareceu associada simultaneamente a alterações mandibulares. Portanto 57% dos casos de maloclusão de Classe III classificados apresentaram algum grau de envolvimento da maxila, confirmando sua importância neste traço e defendendo sua inclusão nas pesquisas genéticas sobre o tema. (AU)

The authors aimed to test in Brazilian families four Single Nucleotide Polymorphisms (SNPs) in genes EPB41(2 SNPs), COL2A1, MYO1H previously related to increased risk for Class III malocclusion development in other ethnicities, in addition, one SNP in TBX3 gene without any previous association with this condition was tested. The study was based on DNA samples and lateral cephalometric radiographs of individuals belonging to eight families from Imbituba county (SC) that presented Class III malocclusion diagnosis (ANB≤0 ou Wits≤-4), in at least, two generations. The Transmission Disequilibrium Test (TDT) was used to perform allelic and haplotypic association between five SNPs and four phenotypic groups related to Class III malocclusion: CMx- group xii with exclusive maxillary involvement, GMd- group with only mandibular problems, GComb- maxillary and mandibular commitment simultaneously and GIII- group containing all Class III individuals of the sample. The TBX3 gene was statistically associated with increased risk for Class III malocclusion in group GIII (p = 0.03), and gene EPB41 in group GMx (p = 0.02). The haplotypic combination (G-G-A) from COL2A1/MYO1H/TBX3 genes was statistically significant in group GIII (p = 0.04), as well as (A-A) from EPB41 gene and (G-A) from COL2A1/TBX3 genes in group GMx (p = 0.01 and p = 0.04 respectively). The combination (A-G) from COL2A1/TBX3 genes seemed to reduce significantly the risk of Class III malocclusion development in GIII (p = 0.04) and GComb (p = 0.03). The GMd group didn't presented significant association with any performed tests. Faced with evidence of genetic association with GMx phenotype, which is rarely considered in genetics investigations of Class III malocclusion, a systematic review was settled with purpose of verifying the maxilla and mandible contribution amount in this malocclusion in adults. It was concluded that maxilla deficiency was responsible for 22,8% of cases of Class III malocclusion by itself, and in 34,2% of cases it was associated simultaneously with mandibular problems. Therefore 57% of the Class III malocclusion classified cases demonstrated some degree of maxilla involvement, reinforcing its importance in this trait and supporting its inclusion in genetic research about this topic. (AU)

Genome-wide association study for mandibular prognathism using microsatellite and pooled DNA method.

INTRODUCTION: The purpose of this study was to extend an association study from chromosome 1 to the whole genome (genome-wide association study) to find susceptibility loci of mandibular prognathism. METHODS: Two hundred forty patients diagnosed with mandibular prognathism and 360 healthy controls of Japanese descent were recruited. The typing of microsatellites covering the whole genome was conducted using a pooled DNA method. Upon completion of the first and second screenings with pooled DNA, the positive microsatellite markers from both the first and second typings were retyped using individual-subject DNA samples to confirm the significance of allele frequency. RESULTS: Six microsatellites (D1S0411i, D1S1358i, D3S0810i, D6S0827i, D7S0133i, and D15S0154i) showed differences between allele frequencies of the subjects and controls at P <0.001. D1S0411i, D1S1358i, D3S0810i, D6S0827i, D7S0133i, and D15S0154i were located on chromosomes 1p22.3, 1q32.2, 3q23, 6q23.2, 7q11.22, and 15q22.22, respectively. SSX2IP, PLXNA2, RASA2, TCF21, CALN1, and RORA were suggested as candidate genes. CONCLUSIONS: The genome-wide association study using microsatellites suggested that 6 loci (1p22.3, 1q32.2, 3q23, 6q23.2, 7q11.22, and 15q22.22) were susceptibility regions of mandibular prognathism. The locus 1p22.3 was supported by a previous linkage analysis, and the other 5 were novel loci.

A genetic heritage; the same yet different: A comparative study in twins.

Since the 19th century, and in every field of medicine, monozygotic twins have been studied to assess the involvement of genetic and environmental factors in phenotypic expression. The phenotype/genotype relationship remains the leading problem in contemporary biology. In dentofacial orthopedics, this relationship is of relevance in the three-dimensional approach to the face, in both diagnosis and treatment. The present study of two monozygotic twins presenting skeletal class III malocclusions which were genetic yet different is a clear illustration of the interaction of genotype and epigenetic factors with environmental influences. We will demonstrate that treatment can reduce phenotypic differences.

Genetic Factors Involved in Mandibular Prognathism.

Mandibular prognathism is defined as an abnormal forward projection of the mandible beyond the standard relation to the cranial base and it is usually categorized as both a skeletal Class III pattern and Angle Class III malocclusion. The etiology of mandibular prognathism is still uncertain, with various genetic, epigenetic, and environmental factors possibly involved. However, many reports on its coexistence in both twins and segregation in families suggest the importance of genetic influences. A multifactorial and polygenic background with a threshold for expression or an autosomal dominant mode with incomplete penetrance and variable expressivity are the most probable inheritance patterns. Linkage analyses have, thus far, shown the statistical significance of such loci as 1p22.1, 1p22.3, 1p32.2, 1p36, 3q26.2, 4p16.1, 6q25, 11q22, 12pter-p12.3, 12q13.13, 12q23, 12q24.11, 14q24.3 to 31.2, and 19p13.2. The following appear among candidate genes: MATN1, EPB41, growth hormone receptor, COL2A1, COL1A1, MYO1H, DUSP6, ARHGAP21, ADAMTS1, FGF23, FGFR2, TBX5, ALPL, HSPG2, EVC, EVC2, the HoxC gene cluster, insulin-like growth factor 1, PLXNA2, SSX2IP, TGFB3, LTBP2, MMP13/CLG3, KRT7, and FBN3. On the other hand, MYH1, MYH2, MYH3, MYH7, MYH8, FOXO3, NFATC1, PTGS2, KAT6B, HDAC4, and RUNX2 expression is suspected to be involved in the epigenetic regulations behind the mandibular prognathism phenotype.

Genetic polymorphisms underlying the skeletal Class III phenotype.

INTRODUCTION: Our goal was to verify the association between candidate polymorphisms and skeletal Class III malocclusion in a well-characterized homogeneous sample set. METHODS: Thirty-five single-nucleotide polymorphisms were studied from 10 candidate loci in 54 Class III subjects and 120 controls. Skeletal Class III characteristics included ANB angle less than 0°, SNB angle greater than 83° (mandibular prognathism), SNA angle less than 79° (maxillary deficiency), Class III molar relationship, and negative overjet. Inclusion criteria for the controls were ANB angle between 0° and 4°, Class I molar relationship, and normal overjet. Chi-square and Fisher exact tests and principal component (PC) analysis were used to determine overrepresentation of marker alleles with alpha of 0.05. Odds ratios and 95% confidence intervals were calculated. RESULTS: MYO1H (rs10850110 AG) (P = 0.001) with PC2 and between FGF10 (rs593307 A