Relationship between P561T and C422F polymorphisms in growth hormone receptor gene and mandibular prognathism

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.

East Asian and Southern European craniofacial class III phenotype: two sides of the same coin?

OBJECTIVES

The skeletal class III phenotype is a heterogeneous condition in populations of different ethnicities. This study aimed to analyse the joint and ethnicity-specific clustering of morphological features in skeletal class III patients of Asian and European origins.

MATERIALS AND METHODS

This cross-sectional study involved South Korean and Spanish participants who fulfilled the cephalometric, clinical, and ethnic-related selection criteria. Radiographic records were standardised, calibrated, and measured. A total of 54 skeletal variables were selected for varimax factorial analysis (VFA). Subsequently, a cluster analysis (CA) was performed (mixed method: k-means and hierarchical clustering). Method error and precision were assessed using ICC, Student's t-test, and the Dahlberg formula.

RESULTS

A total of 285 Korean and Spanish participants with skeletal class III malocclusions were analysed. After performing VFA and CA, the joint sample revealed three global clusters, and ethnicity-specific analysis revealed four Korean and five Spanish clusters. Cluster_1_global was predominantly Spanish (79.2%) and male (83.01%) and was characterised by a predominantly mesobrachycephalic pattern and a larger cranial base, maxilla, and mandible. Cluster_2_global and Cluster_3_global were mainly South Korean (73.9% and 75.6%, respectively) and depicted opposite phenotypes of mandibular projection and craniofacial pattern.

CONCLUSIONS

A distinct distribution of Spanish and South Korean participants was observed in the global analysis. Interethnic and interethnic differences were observed, primarily in the cranial base and maxilla size, mandible projection, and craniofacial pattern.

CLINICAL RELEVANCE

Accurate phenotyping, reflecting the complexity of skeletal class III phenotype across diverse populations, is critical for improving diagnostic predictability and future personalised treatment protocols.

Effects of novel microimplant-assisted rapid palatal expanders manufactured by 3-dimensional printing technology: A finite element study

INTRODUCTION

The expansion effects of several new microimplant-assisted rapid palatal expanders (MARPEs) manufactured by 3-dimensional printing technology were evaluated by finite element analysis (FEA). The aim was to identify a novel MARPE suitable for treating maxillary transverse deficiency.

METHODS

The finite element model was established using MIMICS software (version 19.0; Materialise, Leuven, Belgium). First, the appropriate microimplant insertion characteristics were identified via FEA, and several MARPEs with the above insertion patterns were manufactured by 3-dimensional printing technology. Then, the stress distribution and displacement prediction of the 4 MARPEs and hyrax expander (model E) were evaluated via FEA: bone-borne (model A), bone-tooth-borne (model B), bone-mucous-borne (model C), bone-tooth-mucous-borne (model D).

RESULTS

Monocortical microimplants perpendicular to the cortical bone on the coronal plane resulted in better expansion effects. Compared with a conventional hyrax expander, the orthopedic expansion of each of the 4 MARPEs was far larger, the parallelism was greater, and the posterior teeth tipping rate was lower. Among them, the expansion effects of models C and D were the best; the von Mises peak values on the surfaces of the microimplants were smaller than those of models A and B.

CONCLUSIONS

This study may demonstrate that the 4 MARPEs obtained more advantageous orthopedic expansion effects than a hyrax expander. Models C and D obtained better biomechanical effects and had better primary stability. Overall, model D is the recommended expander for treating maxillary transverse deficiency because its structure acts like an implant guide and is beneficial for the accurate insertion of the microimplant.

Genetic Polymorphisms of Estrogen Receptors α and β are Associated with Craniofacial Measurements in Patients With Dentofacial Deformity

Dentofacial deformities are characterized by abnormalities in craniofacial development that affects the individual's skeletal and occlusion, often causing functional and esthetic problems. In literature, there is an involvement of polymorphisms in estrogen receptor 1 (ESR1) and estrogen receptor 2 (ESR2) genes in craniofacial measurements. The aim of this study was to evaluate a possible association between polymorphisms in ESR1 (rs2234693 and rs9340799) and ESR2 (rs1256049 and rs4986938) genes with cephalometric measurements in individuals with dentofacial deformities. This cross-sectional study was performed with 158 individuals in the preoperative period of orthognathic surgery. The cephalometric measurements obtained through lateral cephalogram using Dolphin Imaging software. For genetic analysis, the DNA extracted from epithelial cells of the oral mucosa and were genotyped using the real-time polymerase chain reaction. The data found submitted to statistical analysis, through the Kolmogorov-Smirnov, Mann-Whitney, and Kruskal-Wallis tests, using the IBM SPSS software version 24.0. Considered a significance level of 0.05. We found association between polymorphisms and cephalometric measurements just in the female sex. The polymorphisms ESR1/rs9340799 ( P= 0.003), ESR1/rs2234693 ( P= 0.026), and ESR2/rs1256049 ( P= 0.046) were associated with the upper gonial angle (Ar-Go-N). The polymorphism ESR2/rs1256049 was also associated with the facial axis-rickets (NBa-PtGn) ( P= 0.004), anterior cranial base (SN) ( P= 0.036), and Y-axis (SGn-SN) ( P= 0.031).

The association of polymorphisms in BMP2/MYO1H and skeletal Class II div.1 maxillary and mandibular dimensions. A preliminary ‘report

Introduction

The genetic impact directly or indirectly predefines maxillofacial dimensions, potentially leading to an inappropriate relationship of the jaws and subsequently skeletal malocclusion. Previous studies focused mainly on genetic polymorphisms and class III malocclusion. This study was set out to investigate the association between genetic polymorphisms in two genes BMP2 (rs235768) and MYO1H (rs11066446) with Class II division 1 malocclusion, skeletal variation in vertical plane, and maxillary and mandibular jaws length.

Subjects and methods

Sixty patients classified as Skeletal Class I (n = 30) and Class II division 1 (n = 30) were recruited. DNA was extracted from saliva and analyzed by Sanger sequencing. Lateral cephalometric radiographs were measured for the anterio-posterior relationship of maxillary and mandibular arch using digital tracing. Hardy-Weinberg equilibrium analysis of genotype frequencies was performed using Chi-square test to compare genotype distribution among groups and multiple logistic regression analysis adjusted by gender was also performed.

Results

The rs235768 polymorphism in BMP2 was associated with hypodivergent face, increased maxillary length, and decreased mandibular length. Meanwhile, the rs11066446 polymorphism in MYO1H was associated with decreased mandibular length. New polymorphism was identified in MYO1H (rs10850090) in association with decreased mandibular length.

Conclusion

A potential association between polymorpisms in BMP2 rs235768 and MOY1H rs11066446 and rs10850090 and Class II division 1 skeletal malocclusion related phenotypes exists, however, the degree of it has to be further investigated and yet to be discovered.

Polymorphism analysis of myosin 1H (G/A) and P561T (C/A) genes on class I, class II, and class III malocclusion

CONTEXT:

Besides environmental factors, genetic factors play an important role in the etiology of malocclusion. Polymorphisms of the Myosin 1H gene in orofacial muscle fibers are thought to influence the growth and development of the mandible. Growth hormone receptors are present on the growth of cartilage, especially the condyle of the mandible. The polymorphisms of the growth hormone receptor have an effect on the growth and development of the mandible. The potential of the Myosin 1H and P561T genes as bioindicators in aiding diagnosis of malocclusion is quite good based on the available literature. However, until now there has been no research that has observed genetic analysis on polymorphism-based malocclusion of the Myosin 1H and P561T genes in the Indonesian population.

AIMS:

To determine the relationship between polymorphisms of Myosin 1H and P561T genes, towards the growth and development of the mandible in malocclusion cases.

SETTINGS AND DESIGN:

Subjects were patients aged 17--45 years old with skeletal malocclusions who were undergoing or were about to undergo orthodontic treatment at RSGM-FKG UI (Universitas Indonesia's Dental Hospital), with 50 people in each group.

METHODS AND MATERIAL:

Malocclusions were determined based on radiographic analysis of the initial cephalometry using the Stainer method. DNA samples were extracted from buccal swabs and blood cells in Class I and II malocclusion while nail clippings and hair follicles extracts were used in Class III malocclusion. DNA sequence amplification was carried out using Polymerase Chain Reaction, while Genetic Polymorphism Analysis of Myosin 1H and P561T genes was performed with Restriction Fragment Length Polymorphism.

STATISTICAL ANALYSIS USED:

Pearson Chi-Square was used to analyze the Myosin 1H gene, while the Fisher Exact Test was used to analyze the P561T gene.

RESULTS:

A relationship between Myosin 1H gene polymorphism and Class I, II, and III skeletal malocclusion was found. There was no correlation between P561T gene polymorphism and Class I, II, and III skeletal malocclusion.

CONCLUSIONS:

Myosin 1H gene polymorphism is one of the risk factors for Class I, II, and III malocclusion. Extraction of DNA from hair follicles gave good results in terms of DNA quality and was a relatively easier sampling method compared to blood cell purification and buccal swabs.

Analysis of MYO1H Gene Polymorphism in Skeletal Class-III Malocclusion Due to Mandibular Prognathism

Background  Mandibular prognathism (MP) is a craniofacial deformity resulting from the combined effects of environmental and genetic factors. Although various linkage and genome-wide association studies for mandibular prognathism have identified multiple strongly associated regions and genes, the causal genes and variants responsible for the deformity remained ambiguous.

Aim  This research work was aimed to study the association between polymorphism rs10850110 of the MYO1H gene and skeletal class-III malocclusion in our local population.

Materials and Methods  Thirty patients with skeletal class III due to mandibular prognathism in the study group and 30 patients with skeletal class I in the control group were selected for this study. These patients were from both sexes and above age 10 years. Based on the cephalometric values, patients were categorized into study and control groups. SNB (angle between sella, nasion and point B at nasion) greater than 82 degrees with an ANB (angle between point A, nasion and point B at nasion) of less than 0 degrees in the study group and ANB (angle between point A, nasion and point B at nasion) of 2 to 4 degrees in the control group were categorized. The polymorphism (rs10850110) of the MYO1H gene was genotyped using polymerase chain reaction and restriction fragment length polymorphism. Associations were tested with SNP exact test using SNPstats software.

Results  The single-nucleotide polymorphism rs10850110 showed a statistically significant association with mandibular prognathism. The G allele of marker rs10850110 (5′ of myosin1H - MYO1H ) was overrepresented when compared with the “A” allele in mandibular prognathism cases ( p  < 0.0001), and this was very significant.

Conclusion  These results suggest that the rs10850110 polymorphism of the MYO1H gene is associated with an increased risk for mandibular prognathism.

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.

Evaluation of Mandibular Growth and Symmetry in Child with Congenital Zygomatic-Coronoid Ankylosis

Ankyloses in the area of the temporomandibular joint (TMJ) are mentioned as a potential etiological factor of mandibular growth disorders and facial asymmetry. The aim of this case study was to evaluate the changes in the mandible of a child with zygomatic-coronoid ankylosis during the first five years of life, in which two adhesion release procedures were performed. The adopted symmetrical approach is based on the assumption of symmetry of the structure of the stomatognathic system in relation to the sagittal median plane. However, the assessment of pathological changes in the structure of the skeletal system was performed using an asymmetrical approach. Computed tomography techniques and a system of computer-aided diagnosis (CAD) were used in the case study. During the child’s growth, linear and angular measurements were made thrice (at the age of 16, 25 and 54 months). The degree of asymmetry was estimated in the measurements made on the right and left sides of the three-dimensional mandible. Unilateral congenital hypoplasia of the articular process and zygomatic-coronoid adhesion caused asymmetrical growth of the mandible in the child along with shortening of the mandibular branch and body on the damaged side and a visible difference in the size of the mandibular angles. Removal of the adhesions during surgical procedures made it possible to reduce the asymmetry of the mandible and catch-up growth, although at the age of five, the mandible was still smaller than the mandible in healthy peers. It was shown that the early adhesion release procedures supported by the CAD analysis enabled the restoration of mandibular symmetry.

The Role of GH/IGF Axis in Dento-Alveolar Complex from Development to Aging and Therapeutics: A Narrative Review

The GH/IGF axis is a major regulator of bone formation and resorption and is essential to the achievement of normal skeleton growth and homeostasis. Beyond its key role in bone physiology, the GH/IGF axis has also major pleiotropic endocrine and autocrine/paracrine effects on mineralized tissues throughout life. This article aims to review the literature on GH, IGFs, IGF binding proteins, and their respective receptors in dental tissues, both epithelium (enamel) and mesenchyme (dentin, pulp, and tooth-supporting periodontium). The present review re-examines and refines the expression of the elements of the GH/IGF axis in oral tissues and their in vivo and in vitro mechanisms of action in different mineralizing cell types of the dento-alveolar complex including ameloblasts, odontoblasts, pulp cells, cementoblasts, periodontal ligament cells, and jaw osteoblasts focusing on cell-specific activities. Together, these data emphasize the determinant role of the GH/IGF axis in physiological and pathological development, morphometry, and aging of the teeth, the periodontium, and oral bones in humans, rodents, and other vertebrates. These advancements in oral biology have elicited an enormous interest among investigators to translate the fundamental discoveries on the GH/IGF axis into innovative strategies for targeted oral tissue therapies with local treatments, associated or not with materials, for orthodontics and the repair and regeneration of the dento-alveolar complex and oral bones.

Methods in Genetic Analysis for Evaluation Mandibular Shape and Size Variations in Human Mandible

ABSTRACT

The human mandible has been investigated from both clinical and evolutionary perspectives. Recent advances in genome science have identified the genetic regulation of human mandibular shape and size. Identification of genes that regulate mandibular shape and size would not only enhance our understanding of the mechanisms of mandibular growth and development but also help define a strategy to prevent mandibular dysplasia. This review provides a comprehensive summary of why and how the mandible was evaluated in the human mandible genome study. The variation in human mandibular shape and size has been progressively clarified, not only by focusing on the mandible alone but also by using extremely diverse approaches. The methods of data acquisition for evaluating human mandibular shape and size variation are well established. Furthermore, this review explains how to proceed with future research.

Craniofacial growth predictors for class II and III malocclusions: A systematic review

OBJECTIVE

To evaluate the validity of craniofacial growth predictors in class II and III malocclusion.

MATERIAL AND METHODS

An electronic search was conducted until August 2020 in PubMed, Cochrane Library, Embase, EBSCOhost, ScienceDirect, Scopus, Bireme, Lilacs and Scielo including all languages. The articles were selected and analyzed by two authors independently and the selected studies was assessed using the 14-item Quality Assessment Tool for Diagnostic Accuracy Studies (QUADAS-2). The quality of evidence and strength of recommendation was assessed by the GRADE tool.

RESULTS

In a selection process of two phases, 10 articles were included. The studies were grouped according to malocclusion growth predictor in (1) class II (n = 4); (2) class III (n = 5) and (3) class II and III (n = 1). The predictors were mainly based on data extracted from cephalometries and characterized by: equations, structural analysis, techniques and computer programs among others. The analyzed studies were methodologically heterogeneous and had low to moderate quality. For class II malocclusion, the predictors proposed in the studies with the best methodological quality were based on mathematical models and the Fishman system of maturation assessment. For class III malocclusion, the Fishman system could provide adequate growth prediction for short- and long-term.

CONCLUSIONS

Because of the heterogeneity of the design, methodology and the quality of the articles reviewed, it is not possible to establish only a growth prediction system for class II and III malocclusion. High-quality cohort studies are needed, well defined data extraction from cephalometries, radiographies and clinical characteristics are required to design a reliable predictor.

Genetics of Dentofacial and Orthodontic Abnormalities

The development of craniofacial complex and dental structures is a complex and delicate process guided by specific genetic mechanisms. Genetic and environmental factors can influence the execution of these mechanisms and result in abnormalities. An insight into the mechanisms and genes involved in the development of orofacial and dental structures has gradually gained by pedigree analysis of families and twin studies as well as experimental studies on vertebrate models. The development of novel treatment techniques depends on in-depth knowledge of the various molecular or cellular processes and genes involved in the development of the orofacial complex. This review article focuses on the role of genes in the development of nonsyndromic orofacial, dentofacial variations, malocclusions, excluding cleft lip palate, and the advancements in the field of molecular genetics and its application to obtain better treatment outcomes.

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.

GHR and IGF2R genes may contribute to normal variations in craniofacial dimensions: Insights from an admixed population

INTRODUCTION

This study aimed to determine whether single nucleotide polymorphisms in the growth hormone receptor (GHR) and insulin-like growth factor 2 receptor (IGF2R) genes are associated with different craniofacial phenotypes.

METHODS

A total of 596 orthodontic and 98 orthognathic patients from 4 cities in Brazil were included for analyses. Angular and linear cephalometric measurements were obtained, and phenotype characterizations were performed. Genomic DNA was collected from buccal cells and single nucleotide polymorphisms in GHR (rs2910875, rs2973015, rs1509460) and IGF2R (rs2277071, rs6909681, rs6920141) were genotyped by polymerase chain reactions using TaqMan assay. Genotype-phenotype associations were assessed in the total sample (statistical significance was set at P <8.333 × 10^-3) and by a meta-analytic approach implemented to calculate the single effect size measurement for the different cohorts.

RESULTS

Rare homozygotes for the GHR rs2973015 showed increased measurements for the lower anterior facial height (ANS-Me) and mandibular sagittal lengths (Co-Gn and Go-Pg). In contrast, common homozygotes for the IGF2R rs6920141 presented reduced measurements for these dimensions (ANS-Me and Go-Pg). Furthermore, the less common homozygotes for IGF2R rs2277071 had reduced maxillary sagittal length (Ptm'-A'). The meta-analytical approach replicated the associations of rs2973015 with ANS-Me, rs2277071 with Ptm'-A', and rs6920141 with Go-Pg.

CONCLUSIONS

Our results provide further evidence that GHR contributes to the determination of mandibular morphology. In addition, we report that IGF2R is a possible gene associated with variations in craniofacial dimensions. Applying meta-analytical approaches to genetic variation data originating from likely underpowered samples may provide additional insight regarding genotype and/or phenotype associations.

Orthodontics and Genetics

Introduction:

Genetics has been suggested as an explanation for the etiology of malocclusions, although some questions, due to the perception that genetic inheritance is tied to a monogenic or Mendelian form of inheritance.

Objective:

This paper describes the inheritance of malocclusions, highlighting the areas of knowledge where research has explored mechanisms that explain deviations in patterns of craniofacial growth.

Conclusion:

Malocclusions have a complex or multifactorial pattern of inheritance, where more than one gene is involved in the development of the phenotype. There is also the possibility that the environment influences malocclusions.

Possible association between craniofacial dimensions and genetic markers in ESR1 and ESR2

OBJECTIVE

To investigate the association of genetic markers in ESR1 and ESR2 with craniofacial measurements.

DESIGN

Cross-sectional study.

SETTING

School of Dentistry of Ribeirão Preto, University of São Paulo.

PARTICIPANTS

A total of 146 biologically unrelated, self-reported Caucasian Brazilians with no syndromic conditions were included.

METHODS

Sagittal and vertical measurements (ANB, S-N, Ptm'-A', Co-Gn, Go-Pg, N-Me, ANS-Me, S-Go and Co-Go) from lateral cephalograms were examined for craniofacial evaluation. DNA was extracted from saliva and genetic markers in ESR1 (rs2234693 and rs9340799) and in ESR2 (rs1256049 and rs4986938) were analysed by real-time polymerase chain reaction. Hardy-Weinberg equilibrium was evaluated using the Chi-square test within each marker. The associations between craniofacial dimensions and genotypes were analysed by linear regression and adjusted by sex and age. The established alpha was 5%.

RESULTS

Individuals carrying CC in ESR1 rs2234693 had a decrease of -3.146 mm in ANS-Me (P = 0.044). In addition, rs4986938 in ESR2 was associated with S-N measurement (P = 0.009/ ß = -3.465). This marker was also associated with Go-Pg measurement, in which the CC genotype had a decrease of -3.925 mm in the length of the mandibular body (P = 0.043).

CONCLUSION

The present study suggests that in ESR1 and ESR2 are markers for variations in the craniofacial dimensions. However, further research should confirm the results.

Association analysis between rs6184 and rs6180 polymorphisms of growth hormone receptor gene regarding skeletal-facial profile in a Colombian population

Background/Objective

There is strong evidence that genetic factors may affect the craniofacial morphology. This study aimed to examine the association between the rs6184 and rs6180 polymorphic variants of the growth hormone receptor (GHR) gene and skeletal-facial profile in a Colombian population.

Subjects/Methods

Saliva samples from 306 individuals ranging in age from 15 to 53 (mean 24.33) years were collected. Cephalometric parameters were used to categorize the participants as Class I, Class II, or Class III skeletal-facial profile. The polymerase chain reaction-restriction fragment length polymorphism method was used to identify genotypes of the rs6184 and rs6180 single nucleotide polymorphisms (SNPs). The association of polymorphisms with the skeletal-facial profile was assessed separately and adjusted for confounding using a multivariate binary logistic regression model, alongside with analysis of linkage disequilibrium and haplotype associations.

Results

Although individuals carrying the CA genotype of the rs6184 SNP showed both significantly decreased values for ANB angle and increased measures concerning mandibular body length and mandibular length, no significant differences amongst genotype groups of rs6180 SNP were observed. Moreover, chi-square test and logistic regression analysis revealed that the CA genotype of rs6184 SNP and the A-A haplotype were highly associated with Class III skeletal-facial profile.

Conclusions

Although these results do not support that rs6180 SNP could be identified as a predictor for skeletal-facial profile, they suggest that the allele A of rs6184 SNP alone or in combination with other SNPs in the GHR gene yields significant horizontal and longitudinal variations of the mandibular morphology and might be a strong/independent prognostic indicator for Class III skeletal-facial profile in the present population.

Systematic review of hormonal and genetic factors involved in the nonsyndromic disorders of the lower jaw

Mandibular disorders are among the most common birth defects in humans, yet the etiological factors are largely unknown. Most of the neonates affected by mandibular abnormalities have a sequence of secondary anomalies, including airway obstruction and feeding problems, that reduce the quality of life. In the event of lacking corrective surgeries, patients with mandibular congenital disorders suffer from additional lifelong problems such as sleep apnea and temporomandibular disorders, among others. The goal of this systematic review is to gather evidence on hormonal and genetic factors that are involved in signaling pathways and interactions that are potentially associated with the nonsyndromic mandibular disorders. We found that members of FGF and BMP pathways, including FGF8/10, FGFR2/3, BMP2/4/7, BMPR1A, ACVR1, and ACVR2A/B, have a prominent number of gene-gene interactions among all identified genes in this review. Gene ontology of the 154 genes showed that the functional gene sets are involved in all aspects of cellular processes and organogenesis. Some of the genes identified by the genome-wide association studies of common mandibular disorders are involved in skeletal formation and growth retardation based on animal models, suggesting a potential direct role as genetic risk factors in the common complex jaw disorders. Developmental Dynamics 248:162-172, 2019. © 2018 Wiley Periodicals, Inc.

Subclustering in Skeletal Class III Phenotypes of Different Ethnic Origins: A Systematic Review

OBJECTIVE

We aimed to systematically review articles investigating the efficiency of the clustering of skeletal class III malocclusion phenotypic subtypes of different ethnic origins as a diagnostic tool.

METHODS

The review protocol was structured in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement and registered in Prospero (CRD42016053865). A survey of articles published up to March 2018 investigating the identification of different subgroups of skeletal class III malocclusion via cluster analysis was performed using 11 electronic databases. Any type of study design that addressed the classification of subclusters of class III malocclusion was considered. The Newcastle-Ottawa scale for cohort and cross-sectional (modified) studies was used for quality assessment.

RESULTS

The final selection included 7 studies that met all the criteria for eligibility (% overall agreement 0.889, free marginal kappa 0.778). All studies identified at least 3 different types of class III clusters (ranging from 3 to 14 clusters; the total variation of the prevalence of each cluster ranged from 0.2% to 36.0%). The main shared variables used to describe the more prevalent clusters in the studies included were vertical measurements (Ar-Go-Me: 117.51°-135.8°); sagittal measurements: maxilla (SNA: 75.3°-82.95°), mandible (SNB: 77.03°-85.0°). With regard to ethnicity, a mean number of 8.5 and 3.5 clusters of class III were retrieved for Asian and Caucasian population, respectively.

CONCLUSIONS

The total number of clusters identified varied from 3 to 14 to explain all the variability in the phenotype class III malocclusions. Although each extreme may be too simple or complex to facilitate an exhaustive but useful classification for clinical use, a classification system including 4 to 7 clusters may prove to be efficient for clinical use in conjunction with complete and meticulous subgrouping.

CLINICAL SIGNIFICANCE

The identification and description of a subclustering classification system may constitute an additional step toward more precise orthodontic/orthopedic diagnosis and treatment of skeletal class III malocclusion.

Non-surgical treatment of transverse deficiency in adults using Microimplant-assisted Rapid Palatal Expansion (MARPE)

INTRODUCTION

Maxillary transverse deficiency is a highly prevalent malocclusion present in all age groups, from primary to permanent dentition. If not treated on time, it can aggravate and evolve to a more complex malocclusion, hindering facial growth and development. Aside from the occlusal consequences, the deficiency can bring about serious respiratory problems as well, due to the consequent nasal constriction usually associated. In growing patients, this condition can be easily handled with a conventional rapid palatal expansion. However, mature patients are frequently subjected to a more invasive procedure, the surgically-assisted rapid palatal expansion (SARPE). More recently, researches have demonstrated that it is possible to expand the maxilla in grown patients without performing osteotomies, but using microimplants anchorage instead. This novel technique is called microimplant-assisted rapid palatal expansion (MARPE).

OBJECTIVE

The aim of the present article was to demonstrate and discuss a MARPE technique developed by Dr. Won Moon and colleagues at University of California - Los Angeles (UCLA).

METHODS

All laboratory and clinical steps needed for its correct execution are thoroughly described. For better comprehension, a mature patient case is reported, detailing all the treatment progress and results obtained.

CONCLUSION

It was concluded that the demonstrated technique could be an interesting alternative to SARPE in the majority of non-growing patients with maxillary transverse deficiency. The present patient showed important occlusal and respiratory benefits following the procedure, without requiring any surgical intervention.

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 Etiology in Nonsyndromic Mandibular Prognathism

Mandibular prognathism (MP) is considered to be a cranial-facial disorder resulting from the interaction between genes and environment. Recent studies have demonstrated that susceptible chromosomal regions and candidate genes may be responsible for MP. In this study, the authors present current views on the effect of genetic components in nonsystematic mandibular prognathism, in order to clarify the genetic etiology of MP. Data source were Electronic databases, manual searching, and reference lists checking, up to April 2016. Study selection, level of evidence assessment, and data extraction were done by 2 individuals in duplicate. Ninety-one studies were retrieved in initial electronic and manual search, and based on the established inclusion and exclusion criteria, 15 were selected for the review. In result, loci 1p36, 1q32.2, 1p22.3, 4p16.1, 6q25, 19p13, 14q24.3, 14q31.1, and 14q31.2 were thought to harbor genes that confer susceptibility to MP. Genes Matrilin-1, ADAMTS1, COL2A1, and EPB41 seemed to be strongly associated with MP while gene of growth hormone receptor was in dispute. Genetic components appeared to be associated with MP. However, in view of the variety of populations and results in related publications, further studies are necessary to clarify the genetic etiology of MP.

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 A<G) (P <0.01; odds ratio, 7.44 [4.02-13.77]) was associated with an increased risk for the mandibular prognathism phenotype. These results were confirmed by PC analysis, which showed 4 PCs representing the sample variations (PC1, 37.24%; PC2, 20.02%; PC3, 12.18%; and PC4, 11.40%), and PC1 was associated with MYO1H (P <0.001). We also found by PC analysis associations between MYO1H (P <0.001) and GHR (rs2973015 A>G) (P = 0.001) with PC2 and between FGF10 (rs593307 A<G) (P = 0.001) with PC4.

CONCLUSIONS

Polymorphism in MYO1H could be used as a marker for genetic susceptibility to Class III malocclusion with mandibular prognathism, and polymorphisms in GHR and FGF were associated with maxillomandibular discrepancies. This study may contribute to improved diagnosis and further research assessing possible differences in treatment responses based on genetic polymorphisms.

Correlation between facial morphology and gene polymorphisms in the Uygur youth population

Human facial morphology varies considerably among individuals and can be influenced by gene polymorphisms. We explored the effects of single nucleotide polymorphisms (SNPs) on facial features in the Uygur youth population of the Kashi area in Xinjiang, China. Saliva samples were collected from 578 volunteers, and 10 SNPs previously associated with variations in facial physiognomy were genotyped. In parallel, 3D images of the subjects’ faces were obtained using grating facial scanning technology. After delimitation of 15 salient landmarks, the correlation between SNPs and the distances between facial landmark pairs was assessed. Analysis of variance revealed that ENPP1 rs7754561 polymorphism was significantly associated with RAla-RLipCn and RLipCn-Sbn linear distances (p = 0.044 and p = 0.012, respectively) as well as RLipCn-Stm curve distance (p = 0.042). The GHR rs6180 polymorphism correlated with RLipCn-Stm linear distance (p = 0.04), while the GHR rs6184 polymorphism correlated with RLipCn-ULipP curve distance (p = 0.047). The FGFR1 rs4647905 polymorphism was associated with LLipCn-Nsn linear distance (p = 0.042). These results reveal that ENPP1 and FGFR1 influence lower anterior face height, the distance from the upper lip to the nasal floor, and lip shape. FGFR1 also influences the lower anterior face height, while GHR is associated with the length and width of the lip.

Review of the Genetic Basis of Jaw Malformations

Genetic etiologies for congenital anomalies of the facial skeleton, namely, the maxilla and mandible, are important to understand and recognize. Malocclusions occur when there exist any significant deviation from what is considered a normal relationship between the upper jaw (maxilla) and the lower jaw (mandible). They may be the result of anomalies of the teeth alone, the bones alone, or both. A number of genes play a role in the facial skeletal development and are regulated by a host of additional regulatory molecules. As such, numerous craniofacial syndromes specifically affect the development of the jaws. The following review discusses several genetic anomalies that specifically affect the bones of the craniofacial skeleton and lead to malocclusion.

Genome-Wide Association Study Reveals Multiple Loci Influencing Normal Human Facial Morphology

Numerous lines of evidence point to a genetic basis for facial morphology in humans, yet little is known about how specific genetic variants relate to the phenotypic expression of many common facial features. We conducted genome-wide association meta-analyses of 20 quantitative facial measurements derived from the 3D surface images of 3118 healthy individuals of European ancestry belonging to two US cohorts. Analyses were performed on just under one million genotyped SNPs (Illumina OmniExpress+Exome v1.2 array) imputed to the 1000 Genomes reference panel (Phase 3). We observed genome-wide significant associations (p < 5 x 10⁻⁸) for cranial base width at 14q21.1 and 20q12, intercanthal width at 1p13.3 and Xq13.2, nasal width at 20p11.22, nasal ala length at 14q11.2, and upper facial depth at 11q22.1. Several genes in the associated regions are known to play roles in craniofacial development or in syndromes affecting the face: MAFB, PAX9, MIPOL1, ALX3, HDAC8, and PAX1. We also tested genotype-phenotype associations reported in two previous genome-wide studies and found evidence of replication for nasal ala length and SNPs in CACNA2D3 and PRDM16. These results provide further evidence that common variants in regions harboring genes of known craniofacial function contribute to normal variation in human facial features. Improved understanding of the genes associated with facial morphology in healthy individuals can provide insights into the pathways and mechanisms controlling normal and abnormal facial morphogenesis.

There is a great deal of evidence that genes influence facial appearance. This is perhaps most apparent when we look at our own families, since we are more likely to share facial features in common with our close relatives than with unrelated individuals. Nevertheless, little is known about how variation in specific regions of the genome relates to the kinds of distinguishing facial characteristics that give us our unique identities, e.g., the size and shape of our nose or how far apart our eyes are spaced. In this paper, we investigate this question by examining the association between genetic variants across the whole genome and a set of measurements designed to capture key aspects of facial form. We found evidence of genetic associations involving measures of eye, nose, and facial breadth. In several cases, implicated regions contained genes known to play roles in embryonic face formation or in syndromes in which the face is affected. Our ability to connect specific genetic variants to ubiquitous facial traits can inform our understanding of normal and abnormal craniofacial development, provide potential predictive models of evolutionary changes in human facial features, and improve our ability to create forensic facial reconstructions from DNA.

Growth hormone receptor gene variant and three-dimensional mandibular morphology

OBJECTIVE

To examine the relationship between three-dimensional mandibular morphology and growth hormone receptor (GHR) gene variants in a healthy Japanese population.

MATERIALS AND METHODS

The subjects, who were unrelated Japanese orthodontic patients, consisted of 64 men and 114 women. Using the Taqman genotyping assay, GHR gene rs6184 and rs6180 variants were detected in genomic DNA extracted from saliva. Mandibular volume and length were measured from cone-beam computed tomography images that were analyzed using Analyze image-processing software. The relationship between GHR gene variants and three-dimensional mandibular morphology was statistically examined.

RESULTS

Statistical significance for the relationship between the distance between the left and right coronoid processes and rs6180 was noted (P < .05).

CONCLUSION

Our results indicate that the GHR variant rs6180 is associated with the distance between the left and right coronoid process in the Japanese subjects.