Phenotype-genotype correlations of facial width and height proportions in patients with Class II malocclusion

Association between Taql polymorphism of vitamin D receptor gene and vertical growth of the mandible: A cross-sectional study

Objective

To determine whether the gonial angle on digital panoramic radiographs is associated with vitamin D receptor (VDR) Taql polymorphism.

Methods

Genomic DNA samples were collected from the buccal mucosa of patients aged 26-43 years. TaqMan assay for single nucleotide polymorphism genotyping was used to detect the genotype of Taql polymorphism. The gonial angle was measured bilaterally on panoramic radiography. The normal gonial angle was fixed as 121.8°, and it represented the cutoff value for the high gonial angle (HGA) and low gonial angle (LGA) groups. Various genetic models were analyzed, namely dominant (homozygous [AA] vs. heterozygous [AG] + polymorphic [GG]), recessive (AA + AG vs. GG), and additive (AA + GG vs. AG), using the chi-squared test.

Results

The reliability of the gonial angle measurement was analyzed using a random sample (26%) of the tests, with the intra-examiner correlation showing an intra-class correlation coefficient of 0.99. The frequencies of the AA, AG, and GG genotypes of rs731236 polymorphism were 40.5%, 41.9%, and 17.6% in the HGA group and 21.8%, 51.0%, and 27.2% in the LGA group, respectively (P = 0.042). A statistically significant difference was observed in the allele frequencies between the two groups (P = 0.011). Moreover, a significant correlation was observed in the dominant genetic model.

Conclusions

Taql polymorphism in the VDR gene plays a critical role in the vertical growth of the mandible and decreased gonial angle.

Facial Analysis for Gender Affirmation/Gender-Related Facial Analysis

There are anthropometric differences between the bony and integumentary facial features of male and female individuals. When compared to males, female faces in general are more heart-shaped, with a shorter and smoother forehead, a smaller more defined nose, and a tapered chin.

Hmga2 deficiency is associated with allometric growth retardation, infertility, and behavioral abnormalities in mice

The high mobility group AT-hook 2 (HMGA2) protein works as an architectural regulator by binding AT-rich DNA sequences to induce conformational changes affecting transcription. Genomic deletions disrupting HMGA2 coding sequences and flanking noncoding sequences cause dwarfism in mice and rabbits. Here, CRISPR/Cas9 was used in mice to generate an Hmga2 null allele that specifically disrupts only the coding sequence. The loss of one or both alleles of Hmga2 resulted in reduced body size of 20% and 60%, respectively, compared to wild-type littermates as well as an allometric reduction in skull length in Hmga2-/- mice. Both male and female Hmga2-/- mice are infertile, whereas Hmga2+/- mice are fertile. Examination of reproductive tissues of Hmga2-/- males revealed a significantly reduced size of testis, epididymis, and seminal vesicle compared to controls, and 70% of knock-out males showed externalized penis, but no cryptorchidism was observed. Sperm analyses revealed severe oligospermia in mutant males and slightly decreased sperm viability, increased DNA damage but normal sperm chromatin compaction. Testis histology surprisingly revealed a normal seminiferous epithelium, despite the significant reduction in testis size. In addition, Hmga2-/- mice showed a significantly reduced exploratory behavior. In summary, the phenotypic effects in mouse using targeted mutagenesis confirmed that Hmga2 is affecting prenatal and postnatal growth regulation, male reproductive tissue development, and presents the first indication that Hmga2 function is required for normal mouse behavior. No specific effect, despite an allometric reduction, on craniofacial development was noted in contrast to previous reports of an altered craniofacial development in mice and rabbits carrying deletions of both coding and noncoding sequences at the 5' part of Hmga2.

Systematic review on the genetic factors associated with skeletal Class II malocclusion

AIM

The aim of this study is to review studies evaluating the role of genetics in skeletal class II malocclusion.

OBJECTIVE

To assess the scientific evidence associating the role of genes in skeletal class II malocclusion. Materials and Methods: A complete search across the electronic database through PubMed, Cochrane, LILACS, BMC and manual hand search of orthodontic journals were done till May 2019. The keywords for the search included: "Genetics", "class II malocclusion", "maxillary prognathism", "mandibular retrognathism".

DATA COLLECTION AND ANALYSIS

Studies were selected based on PRISMA guidelines.

RESULTS

Articles were selected based on the inclusion and exclusion criteria. A total of 11 cross-sectional studies satisfied the inclusion criteria and were analyzed for the role of genes in skeletal class II malocclusion. Almost all the studies except for one revealed a positive correlation of genes with skeletal class II malocclusion.

CONCLUSIONS

Out of the 11 studies included, a positive correlation of the genes with the skeletal II malocclusion was found in 10 studies. Genes FGFR2, MSX1, MATN1, MYOH1, ACTN3, GHR, KAT6B, HDAC4, AJUBA were found to be positively linked to skeletal class II malocclusion.

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.

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.

Dental and craniofacial features associated with GNAS loss of function mutations

BACKGROUND

Pseudohypoparathyroidism (PHP, OMIM #103580) is a very rare disease (incidence 0.3-1/100,000). Heterozygous inactivating mutations involving the maternal GNAS exons 1-13 that encodes the alpha subunit of the stimulatory G protein (Gsα) cause inactivating parathyroid hormone (PTH)/PTHrP signalling disorder type 2 (iPPSD2 or PHP type 1A), which is characterized by Albright hereditary osteodystrophy and resistance to multiple hormones that act through the Gsα signalling pathway (including PTH, thyroid-stimulating hormone, and α-melanocyte-stimulating hormone). To date, little information is available on craniofacial features in patients with PHP. The small number of patients studied in previous reports as well as the lack of molecular characterization of the patients may have precluded the detection of specific orofacial manifestations in the different PHP subtypes.

MATERIALS/METHODS

We conducted a systematic analysis of dental and craniofacial features in 19 patients with iPPSD2 and maternal GNAS inactivating mutations to assess the frequency and specificity of the anomalies.

RESULTS

Facial examinations showed reduced vertical, sagittal, and transverse development of the mid-facial structures. Intraoral and radiographic examinations revealed that 89 per cent of the patients had at least one dental anomaly, including tooth submergence leading to severe infraocclusion in 83 per cent of cases. Craniofacial analysis of lateral cephalometric radiographs also showed a significant alteration in the development of the cranial base and maxillary and mandibular structures in these patients.

CONCLUSIONS

Patients with iPPSD2 and maternal GNAS mutations had specific craniofacial alterations and dental abnormalities. These specific defects should be assessed in order to provide appropriate dental and orthodontic care to these patients. (clinical trial registration: 1920371 v 0, French Nationale Data Processing and Liberties Commission - CNIL).

The ADAMTS9 gene is associated with mandibular retrusion in a Chinese population

OBJECTIVE

Many studies suggest that genetics plays an important role in mandibular retrusion. In this study, we hypothesized that single nucleotide polymorphisms (SNPs) of ADAMTS9 gene is associated with mandibular retrusion in a Han Chinese population.

METHODS

Saliva samples from 60 patients undergoing orthodontic for correction of malocclusion were collected. 130 SNPs genotyping of ADAMTS9 was used to asses the association of polymorphisms with the mandibular retrusion. The general linear model using age,gender and ANB as covariates weighed the relationship between SNP and mandibular retrusion. Additionally we leveraged the generalized multifactor dimensionality reduction (GMDR) method to investigate SNP-SNP interactions. The significance level was set at P < 0.05 in this study.

RESULTS

The general linear model results showed that four SNPs (rs1014640,rs7648540,rs75839462 and rs4605539) in the ADAMTS9 gene may be related to the occurrence of mandibular retrusion,even after Bonferroni correction. In addition, we further found that the interaction between the ADAMTS9 rs75839462 and ADAMTS9 rs80118777 promoted the occurrence of mandibular retrusion.

CONCLUSION

Our finding suggest that the ADAMTS9 gene may cause mandibular retrsusion independently and through SNP-SNP interactions.

HMGA Genes and Proteins in Development and Evolution

HMGA (high mobility group A) (HMGA1 and HMGA2) are small non-histone proteins that can bind DNA and modify chromatin state, thus modulating the accessibility of regulatory factors to the DNA and contributing to the overall panorama of gene expression tuning. In general, they are abundantly expressed during embryogenesis, but are downregulated in the adult differentiated tissues. In the present review, we summarize some aspects of their role during development, also dealing with relevant studies that have shed light on their functioning in cell biology and with emerging possible involvement of HMGA1 and HMGA2 in evolutionary biology.

Assessment of knowledge of oral cancer in dentists in the Los Ríos Region, Chile, in 2017

The alteration of the vertical dimension can deteriorate the facial harmony, and it can be measured through objective and subjective methods, although many of which are not reliable. Objective: Relate the anthropometric fingers length with the measurement of the vertical occlusal dimension (VOD). Material and Methods: Cross-sectional, observational study that included 114 students from the School of Dentistry with class I malocclusion and complete dentition. The VOD was evaluated as the measurement between the subnasal points and the mental point; anthropometric measures included the length of the fingers (from the most mesial fold to the most distal edge) and the distance projected between the thumb and the index finger. Results: The average VOD was 64.03±5.15mm. A correlation was found between the VOD and the index finger length (p<0.01, r=0.29), between the VOD and middle finger length (p<0.01, r=0.31) and correlation between the VOD and the length of the little finger (p<0.05, r=0.23). No correlation was found between the VOD and the ring finger lengths (p= 0.051) or thumb (p=0.12). Conclusions: The anthropometric measurements of the index finger, middle finger, little finger and the projection of the thumb on the index finger correlated with the length of the vertical occlusal dimension.

Linear and Volumetric Mandibular Asymmetries in Adult Patients With Different Skeletal Classes and Vertical Patterns: A Cone-Beam Computed Tomography Study

This study aimed to quantify the height of the mandibular condyle and ramus, condylar volume, and the asymmetry index in adult patients of different sex, skeletal class and vertical pattern using Cone-Beam Computed Tomography (CBCT), and to determine whether there were differences between these groups. The study used CBCT scans of 159 patients with a mean age of 32.32 ± 8.31 years. InVivoDental® software was used to perform both linear (condylar, ramal, and total height) and condylar volume measurements. Linear and volumetric asymmetries were calculated. There were not significant differences between right and left sides. The mean value obtained for condyle height was 7.27 mm, ramus height 42.3 mm, total height 49.6 mm and condyle volume 1907.1 mm3, with significant differences between men and women. Significantly higher values were found for condylar volume in hypodivergent patterns (p = 0.001) and for the asymmetry index of the condylar volume in Class II patients (p < 0.05). The prevalence of relevant asymmetry was high for condyle height and volume (73.1% y 75.6% respectively). Higher height and volume values were found among men, Class III, and hypodivergent patients. Linear and volumetric asymmetries were more prevalent among men, Class III and hyperdivergent patterns.

Candidate gene analyses of 3-dimensional dentoalveolar phenotypes in subjects with malocclusion

INTRODUCTION

Genetic studies of malocclusion etiology have identified 4 deleterious mutations in genes DUSP6,ARHGAP21, FGF23, and ADAMTS1 in familial Class III cases. Although these variants may have large impacts on Class III phenotypic expression, their low frequency (<1%) makes them unlikely to explain most malocclusions. Thus, much of the genetic variation underlying the dentofacial phenotypic variation associated with malocclusion remains unknown. In this study, we evaluated associations between common genetic variations in craniofacial candidate genes and 3-dimensional dentoalveolar phenotypes in patients with malocclusion.

METHODS

Pretreatment dental casts or cone-beam computed tomographic images from 300 healthy subjects were digitized with 48 landmarks. The 3-dimensional coordinate data were submitted to a geometric morphometric approach along with principal component analysis to generate continuous phenotypes including symmetric and asymmetric components of dentoalveolar shape variation, fluctuating asymmetry, and size. The subjects were genotyped for 222 single-nucleotide polymorphisms in 82 genes/loci, and phenotpye-genotype associations were tested via multivariate linear regression.

RESULTS

Principal component analysis of symmetric variation identified 4 components that explained 68% of the total variance and depicted anteroposterior, vertical, and transverse dentoalveolar discrepancies. Suggestive associations (P < 0.05) were identified with PITX2, SNAI3, 11q22.2-q22.3, 4p16.1, ISL1, and FGF8. Principal component analysis for asymmetric variations identified 4 components that explained 51% of the total variations and captured left-to-right discrepancies resulting in midline deviations, unilateral crossbites, and ectopic eruptions. Suggestive associations were found with TBX1AJUBA, SNAI3SATB2, TP63, and 1p22.1. Fluctuating asymmetry was associated with BMP3 and LATS1. Associations for SATB2 and BMP3 with asymmetric variations remained significant after the Bonferroni correction (P <0.00022). Suggestive associations were found for centroid size, a proxy for dentoalveolar size variation with 4p16.1 and SNAI1.

CONCLUSIONS

Specific genetic pathways associated with 3-dimensional dentoalveolar phenotypic variation in malocclusions were identified.

Genomewide Association Study of African Children Identifies Association of SCHIP1 and PDE8A with Facial Size and Shape

The human face is a complex assemblage of highly variable yet clearly heritable anatomic structures that together make each of us unique, distinguishable, and recognizable. Relatively little is known about the genetic underpinnings of normal human facial variation. To address this, we carried out a large genomewide association study and two independent replication studies of Bantu African children and adolescents from Mwanza, Tanzania, a region that is both genetically and environmentally relatively homogeneous. We tested for genetic association of facial shape and size phenotypes derived from 3D imaging and automated landmarking of standard facial morphometric points. SNPs within genes SCHIP1 and PDE8A were associated with measures of facial size in both the GWAS and replication cohorts and passed a stringent genomewide significance threshold adjusted for multiple testing of 34 correlated traits. For both SCHIP1 and PDE8A, we demonstrated clear expression in the developing mouse face by both whole-mount in situ hybridization and RNA-seq, supporting their involvement in facial morphogenesis. Ten additional loci demonstrated suggestive association with various measures of facial shape. Our findings, which differ from those in previous studies of European-derived whites, augment understanding of the genetic basis of normal facial development, and provide insights relevant to both human disease and forensics.

The human face is made up of distinct yet related anatomic structures that together make both individuals and families recognizable. It is clear there is a strong genetic component to the human face, and though the genetics of the face have been studied for several years, there are relatively few genes known to impact normal human facial development and facial shape. We report here a large-scale human genetic study in which we successfully identify and replicate genetic markers associated with normal facial variation using advanced 3D facial imaging in African children. We identified two significant replicated genes associated with measures of human facial size, SCHIP1 and PDE8A, demonstrated their clear expression in the developing face in the mouse, and identified 10 additional candidate genetic loci for human facial shape. Gene discovery for human facial development is an important first step for both diagnosing and treating craniofacial syndromes and for developing forensic modeling of the human face.