Association of Dental Caries in Primary Teeth With HLA Class II Gene Among Syrian Children

Background and objectives Numerous studies have shown that there is evidence that genetic factors contribute in different ways to the occurrence of caries lesions, and the multiple differences in the human leucocytes antigen (HLA) gene patterns play an important role in the body's immune response. Therefore, this study aimed to evaluate the association between some HLA class II alleles (HLA-DR4, HLA-DQ2, HLA-DQ4) and early childhood caries (ECC) occurrence in Syrian children. Materials and methods The study included 80 children aged three to six, divided into two groups: Group 1 (n = 40) being severe early childhood caries (S-ECC) children (deft ≥ 10) and Group 2 (n = 40) being free caries children (deft = 0). The genomic DNAs were extracted and collected by taking a buccal swab using a sterile metal strip and were amplified by polymerase chain reaction-single specific primer (PCR-SSP) and then HLA-typing was performed for all alleles. Results There were no statistically significant differences in the frequency of occurrence of S-ECC, HLA-DR4, and HLA-DQ2 alleles (p = 0.626, 0.256 respectively), while the incidence of S-ECC was associated with the DQ4 allele (p = 0.012). Conclusion HLA class II molecules may play a crucial role in predisposing to ECC, since positive HLA-DQ4 may enhance the chance of developing ECC. However, no association were found between (HLA-DR4 and HLA-DQ2) and ECC.

Genetic Aspects of Dental Erosive Wear and Dental Caries

Objectives

The present review aims to give an overview of the literature focusing on novel genetic aspects of dental erosion and dental caries. Once the tooth erupts into the oral cavity, the regenerative capability of enamel is fundamentally limited due to the loss of dental epithelium during eruption. The susceptibility or resistance to dental erosion and caries is presumably a result of environmental, phenotypic, and/or genetic influence. Even though it is evident that individuals frequently exposing their teeth to acid and sugar are at high risk of developing dental erosion and caries, the findings exclusively based on these factors are elusive. Data resources and study selection. The present review was based on data collected from the National Library of Medicine database with different combinations of the following terms: "tooth," "dental," "dentin," "enamel," "erosion," "erosive wear," "caries," "decay," "gene," and "genetic." A total of forty-six studies met the inclusion criteria. Data were extracted by one reviewer and verified by another.

Conclusion

The high prevalence of erosion and caries among certain groups, and observations that not all individuals appearing to be at risk develop these lesions, has sparked research on identifying genetic effects to these conditions. A connection of genome-wide and candidate gene studies has increased considerably in the literature. This review reveals largely varying success among studies, demonstrating the difficulties of developing the study with adequate sample sizes and durable phenotype definitions that permit enough statistical power to identify genetic contributors.

Genes and SNPs in the pathway of immune response and caries risk: a systematic review and meta-analysis

The aim of this systematic review and meta-analysis was to pool the data on Single Nucleotide Polymorphisms (SNPs) in immune response genes associated with dental caries. Nineteen studies were included in the review and 18 in the meta-analysis. Twenty-two SNPs were evaluated, which are linked to six different genes (MBL2, LFT, MASP2, DEFB1, FCN2 and MUC5B). Most SNPs (81.8%) are related to the possible functional impact on protein coding. The MBL2 gene was associated with caries experience in the analysis of the homozygote (OR = 2.12 CI95%[1.12-3.99]) and heterozygote (OR = 2.22 CI95%[1.44-3.44]) genotypes. The MUC5B gene was associated according to an analysis of the heterozygous genotype (OR = 1.83 CI95%[1.08-3.09]). Thus, SNPs related to immune response genes are linked to the phenotype of caries experience. Although the meta-analysis showed that the genes MBL2 and MUC5B were associated with caries, these results should be interpreted with caution due to the quality of the evidence.

Association between HLA-DRB1* allele polymorphism and caries susceptibility in Han Chinese children and adolescents in the Xinjiang Uygur Autonomous Region

OBJECTIVE

The rate of caries and the mean number of decayed, missing, or filled teeth were reported to be significantly higher in children in the Xinjiang Uygur Autonomous Region than in children in eastern China. Little is known regarding the genetic basis of caries among residents of the Xinjiang Uygur Autonomous Region. This study investigated the association between HLA-DRB1 alleles and caries susceptibility in Han Chinese children and adolescents in the Xinjiang Uygur Autonomous Region.

METHODS

HLA-DRB1 allele frequency was assessed in DNA samples from buccal swabs of 42 patients with caries and 123 healthy control participants using a polymerase chain reaction method with sequence-specific primers. The chi-squared test or Fisher's exact test, followed by Bonferroni correction, was used to calculate differences in allele frequencies between groups.

RESULTS

Compared with the healthy controls, the allele frequency of HLA-DRB1*13 was significantly higher in patients with caries in the Xinjiang Uygur Autonomous Region (35.71% vs. 18.70%). The allele frequency of HLA-DRB1*09 was significantly lower in patients with caries than in healthy controls (4.76% vs. 25.20%).

CONCLUSIONS

HLA-DRB1*13 alleles could confer greater caries susceptibility, whereas HLA-DRB1*09 could be protective against caries pathogenesis, in Han Chinese children in the Xinjiang Uygur Autonomous Region.

Dental caries: Genetic and protein interactions

OBJECTIVE

To present a genetic and protein interaction analysis associated with dental caries.

MATERIAL AND METHODS

The first step was to conduct a systematic literature review (SLR) through an electronic database search. Case-controls that reported associations between genes and dental caries were the main type of study design used as inclusion criteria, retrieved from the PubMed and the Virtual Health Library databases, comprising the chronological range from 1982 to 2017. The SLR was guided by PRISMA protocol and the methodological quality of the studies was established through Newcastle-Ottawa Scale (NOS). In the second step, the String Protein Interaction (SPI) approach was used to analyze protein interaction (by esyN software) and also the Ingenuity Pathway Analysis (IPA) to check biological pathways associated with dental caries genes.

RESULTS

A total of 51 articles were included to perform this SLR, describing a number of 27 genes associated with dental caries development. At the genetic level, 23 genes have at least one other gene with which they interact. The genes TUFT1, VDR, TFIP11, LTF, HLA-DRB1, MMP2, MMP3 and MUC5B were shown to be connected in interactive networks by at least 10 other genes.

CONCLUSION

It is essential to apprehend the multifactorial pattern of inheritance in human disease. This study presents pathways which may be directly correlated with several dental caries phenotype and this contributes to a better understanding of this disease, opening up a wider range of biotechnology options for its effective control in the future.

Host genetics role in the pathogenesis of periodontal disease and caries

BACKGROUND

This study aimed to produce the latest summary of the evidence for association of host genetic variants contributing to both periodontal diseases and caries.

MATERIALS AND METHODS

Two systematic searches of the literature were conducted in Ovid Medline, Embase, LILACS and Cochrane Library for large candidate gene studies (CGS), systematic reviews and genome-wide association studies reporting data on host genetic variants and presence of periodontal disease and caries.

RESULTS

A total of 124 studies were included in the review (59 for the periodontitis outcome and 65 for the caries outcome), from an initial search of 15,487 titles. Gene variants associated with periodontitis were categorized based on strength of evidence and then compared with gene variants associated with caries. Several gene variants showed moderate to strong evidence of association with periodontitis, although none of them had also been associated with the caries trait.

CONCLUSIONS

Despite some potential aetiopathogenic similarities between periodontitis and caries, no genetic variants to date have clearly been associated with both diseases. Further studies or comparisons across studies with large sample size and clear phenotype definition could shed light into possible shared genetic risk factors for caries and periodontitis.

Genetic Polymorphisms in DEFB1 and miRNA202 Are Involved in Salivary Human β-Defensin 1 Levels and Caries Experience in Children

The antimicrobial peptides human β-defensins (hBDs) are encoded by β-defensin genes (DEFBs) and are possibly involved in caries susceptibility. In this study we aimed (1) to investigate the relationship between salivary hBDs and caries and (2) to evaluate the association of genetic polymorphisms in DEFB1 and microRNA202 (miRNA202) with salivary levels of hBDs and caries experience. Two data sets were available for this study, totalizing 678 Brazilian children. Dental examination and saliva collection were performed in all included children. The salivary level for hDB1, hBD2, and hBD4 was assessed by ELISA sandwich technique in 168 children. The DNA was extracted from saliva, and polymorphisms in DEFB1 and miRNA202 were analyzed by real-time PCR. Statistical analysis was performed to investigate the associations between caries experience, hBD salivary level, genotype, and allele distribution, with an alpha of 0.05. The hBD1 level was significantly higher in caries-free children (p < 0.0001). The miRNA202 was associated with a lower level of salivary hBD1 (p < 0.05). Also, the polymorphic distribution of miRNA202 was associated with caries (p = 0.006). The polymorphisms in DEFB1 were not associated with hBD salivary level and caries experience (p > 0.05). In conclusion, our results indicate that genetic polymorphism in miRNA202 is involved in hBD1 salivary level as well as caries experience in children.

Genetic Association of MMP10, MMP14, and MMP16 with Dental Caries

Matrix metalloproteinases (MMPs), which degrade extracellular proteins as part of a variety of physiological processes, and their inhibitors have been implicated in the dental caries process. Here we investigated 28 genetic variants spanning the MMP10, MMP14, and MMP16 genes to detect association with dental caries experience in 13 age- and race-stratified (n = 3,587) samples from 6 parent studies. Analyses were performed separately for each sample, and results were combined across samples by meta-analysis. Two SNPs (rs2046315 and rs10429371) upstream of MMP16 were significantly associated with caries in an individual sample of white adults and via meta-analysis across 8 adult samples after gene-wise adjustment for multiple comparisons. Noteworthy is SNP rs2046315 (p = 8.14 × 10⁻⁸) association with caries in white adults. This SNP was originally nominated in a genome-wide-association study (GWAS) of dental caries in a sample of white adults and yielded associations in a subsequent GWAS of surface level caries in white adults as well. Therefore, in our study, we were able to recapture the association between rs2046315 and dental caries in white adults. Although we did not strengthen evidence that MMPs 10, 14, and 16 influence caries risk, MMP16 is still a likely candidate gene to pursue.

HLA Typing and Celiac Disease in Moroccans

Genetic and environmental factors are responsible for differences in the prevalence of some diseases across countries. Human leukocyte antigen (HLA) allele frequencies in North African populations show some differences in their distribution compared to Europeans, Mediterraneans, and sub-Saharans, and some specific alleles and haplotypes could be clinically relevant. Celiac disease (CD) has been fast increasing in prevalence in North Africa; but few immunogenetic data are available for this area, in which a high prevalence of the disease has been described. In this report, we assess and discuss results of HLA class II (HLA-DQA1/DQB1/DRB1) typing in Moroccan patients with CD and compare them with a control population from Morocco—genetically well characterized—and with other North African, Mediterranean, and European populations. The classical HLA-DQ associations were confirmed in Moroccans with CD. The high frequency of DQ2.5 homozygosity (45.2%) found in Moroccans with CD was noteworthy as compared with other populations (23%–32%). The genetic risk gradient for CD, identified by previous studies, has been confirmed in Moroccans with some differences, mainly concerning DQ8 genotypes. This study provides the immunogenetic framework of CD in Moroccans and confirms the need to learn more about associations with additional HLA and non-HLA genetic factors.

Association of MBL2 Gene Polymorphism with Dental Caries in Saudi Children

The high prevalence of dental caries in children worldwide is a major oral health problem which requires early intervention. Dental caries is mainly caused by the action of acids produced by bacteria in addition to many other factors. Recent genetic studies have reported that a number of genes are associated with the susceptibility to dental caries. The majority of these genes are associated with inflammation, increased susceptibility to infection, and dentine matrix formation. Using the TaqMan assay and direct DNA sequencing, the prevalence of 6 single-nucleotide polymorphisms (SNPs) in MMP9, MBL2, MMP2, and TIMP2 genes was determined in 102 children with caries and in 100 age-matched caries-free controls. Out of the 6 SNPs tested in the 4 selected genes, only rs11003125 in the MBL2 gene was shown to be associated with a high prevalence of caries in our cohort. In addition, haplotype analysis of the 6 SNPs tested revealed that certain haplotypes, namely GT of rs11003125G and rs7501477T and GT of rs7096206G and rs7501477T, were found to be associated with a high prevalence of dental caries in our cohort, while haplotype AG of rs17576A and rs7501477G was found to have a protective effect against dental caries. In conclusion, the data indicate that rs11003125 in the MBL2 gene was shown to be associated with a high prevalence of caries in our cohort, and 2 haplotypes are also involved in the increased susceptibility to dental caries.

Aquaporin 5 Interacts with Fluoride and Possibly Protects against Caries

Aquaporins (AQP) are water channel proteins and the genes coding for AQP2, AQP5, and AQP6 are clustered in 12q13. Since AQP5 is expressed in serous acinar cells of salivary glands, we investigated its involvement in caries. DNA samples from 1,383 individuals from six groups were studied. Genotypes of eight single nucleotide polymorphisms covering the aquaporin locus were tested for association with caries experience. Interaction with genes involved in enamel formation was tested. The association between enamel microhardness at baseline, after creation of artificial caries lesion, and after exposure to fluoride and the genetic markers in AQP5 was tested. Finally, AQP5 expression in human whole saliva, after exposure to fluoride in a mammary gland cell line, which is known to express AQP5, and in Wistar rats was also verified. Nominal associations were found between caries experience and markers in the AQP5 locus. Since these associations suggested that AQP5 may be inhibited by levels of fluoride in the drinking water that cause fluorosis, we showed that fluoride levels above optimal levels change AQP5 expression in humans, cell lines, and rats. We have shown that AQP5 is involved in the pathogenesis of caries and likely interacts with fluoride.

Association of sweet taste receptor gene polymorphisms with dental caries experience in school children

Sweet taste is a powerful factor influencing food acceptance. The peripheral taste response to sugar is mediated by the TAS1R2/TAS1R3 taste receptors. The aim of the study was to determine the relationship between TAS1R2 (rs35874116 or rs9701796) and/or TAS1R3 (rs307355) single nucleotide polymorphisms with dental caries experience in schoolchildren. A total of 184 schoolchildren aged between 7 and 12 years (101 girls, 83 boys) were included in the study. Genomic DNA was extracted from saliva samples and the genotypes were identified by qPCR. The genotype frequencies were as follows: 6.6% for homozygous wild type, 41.8% for heterozygous and 51.6% for homozygous polymorphic genotype carriers of TAS1R2 gene rs35874116; 27.8% for heterozygous and 72.2% for homozygous polymorphic genotype carriers of TAS1R2 gene rs9701796, and 83.1% for homozygous wild type and 16.9% for heterozygous genotype carriers of TAS1R3 gene rs307355 polymorphism. A significant association was observed between total caries experience (dft + DMFT - decayed filled primary teeth + decayed, missing and filled permanent teeth) and TAS1R2 rs35874116 (p = 0.008) and TAS1R3 rs307355 (p = 0.04) gene polymorphisms but not for TAS1R2 gene rs9701796 polymorphism. TAS1R3 gene rs307355 polymorphism has been found to be an independent risk factor for dental caries experience by logistic regression analysis and to have increased the risk of caries. Moderate caries experience (4-7 caries) was found to be associated with TAS1R3 rs307355 heterozygous genotype, whereas high-risk caries experience (>8 caries) was found to be associated with TAS1R2 rs35874116 homozygous polymorphic genotype.

World perspective and celiac disease epidemiology

In Europe and the USA, the mean frequency of celiac disease (CD) in the general population is approximately 1%, with some regional differences, the reasons for which remain elusive. A similar disease prevalence has been found in other countries mostly populated by individuals of European origin, e.g. Australia and Argentina. In Western countries, a true rise in overall CD prevalence of CD has been documented. CD is a common disorder in North Africa, the Middle East and India; however, the diagnostic rate is low in these countries due to low availability of diagnostic facilities and poor disease awareness. The highest CD prevalence in the world (5.6%) has been described in an African population originally living in Western Sahara, the Saharawi, of Arab-Berber origin. The reasons for this high CD frequency are unclear but could be primarily related to recent dietary changes and genetic factors, given the high level of consanguinity of this population. Further studies are needed to quantify the incidence of the celiac condition in apparently 'celiac-free' areas such as Sub-Saharan Africa and the Far East. In many developing countries, the frequency of CD is likely to increase in the near future given the diffuse tendency to adopt Western, gluten-rich dietary patterns. As most cases currently escape diagnosis all over the world, an effort should be made to increase the awareness of CD polymorphism. A cost-effective case-finding policy and new strategies of mass CD screening could significantly reduce the morbidity and mortality associated with untreated disease. The current high prevalence of CD is just the last link in a chain of events started about 10,000 years ago after wheat domestication and diffusion from the Middle East. We hypothesize different mechanisms to explain the so-called evolutionary celiac paradox of co-localization of gluten consumption and HLA CD-predisposing genotypes.

Co-localization of gluten consumption and HLA-DQ2 and -DQ8 genotypes, a clue to the history of celiac disease

Celiac disease is an immune-mediated disorder triggered by gluten in genetically susceptible persons. Despite its detrimental effects on human health, it has not disappeared over time. The current evolutionary theory is that celiac disease is more common in areas reached later by agricultural revolution than in countries that started consumption of wheat earlier, due to negative selection caused by celiac disease. We reviewed data on worldwide prevalence of celiac disease, wheat consumption, and frequencies of HLA-celiac-disease-predisposing-genotypes to investigate their mutual relationship. Studies assessing prevalence of celiac disease were identified through a MEDLINE search. Wheat consumption and frequencies of HLA-DQ2-DQ8 were obtained from Food and Agriculture Organization of the United Nations and allelefrequencies.net database. Correlations between celiac disease, wheat consumption, and HLA were analyzed by linear regression. We observed a significant correlation between wheat consumption and HLA DQ2 (p=0.01) and the sum of DQ2 and DQ8 (p=0.01) frequencies. Wheat consumption and HLA-DQ2 tend to co-localize in different continents. The correlation between the prevalence of celiac disease and either DQ2 and/or DQ8, or the product of DQ2+DQ8*wheat consumption was not statistically significant. Co-localization of gluten consumption and HLA-celiac-disease-predisposing-genotypes can be explained by positive selection of HLA-DQ2 genes in wheat-consuming areas, and "demic diffusion" of Middle East farmers into Europe.

Caries: review of human genetics research

The NIH Consensus Development Program released a statement in 2001 (http://consensus.nih.gov/2001/2001DentalCaries115html.htm) and listed six major clinical caries research directions. One of these directions was the need for genetic studies to identify genes and genetic markers of diagnostic, prognostic and therapeutic value. This last decade has seen a steep increase in studies investigating the presence of genetic factors influencing individual susceptibility to caries. This review revisits recent caries human genetic studies and provides a perspective for future studies in order to fulfil their promise of revolutionizing our understanding of and the standard of care for the most prevalent bacteria-mediated non-contagious disease in the world.

Genetic Association of MPPED2 and ACTN2 with Dental Caries

The first genome-wide association study of dental caries focused on primary teeth in children aged 3 to 12 yr and nominated several novel genes: ACTN2, EDARADD, EPHA7, LPO, MPPED2, MTR, and ZMPSTE24. Here we interrogated 156 single-nucleotide polymorphisms (SNPs) within these candidate genes for evidence of association with dental caries experience in 13 race- and age-stratified samples from 6 independent studies (n = 3600). Analysis was performed separately for each sample, and results were combined across samples via meta-analysis. MPPED2 was significantly associated with caries via meta-analysis across the 5 childhood samples, with 4 SNPs showing significant associations after gene-wise adjustment for multiple comparisons (p < .0026). These results corroborate the previous genome-wide association study, although the functional role of MPPED2 in caries etiology remains unknown. ACTN2 also showed significant association via meta-analysis across childhood samples (p = .0014). Moreover, in adults, genetic association was observed for ACTN2 SNPs in individual samples (p < .0025), but no single SNP was significant via meta-analysis across all 8 adult samples. Given its compelling biological role in organizing ameloblasts during amelogenesis, this study strengthens the hypothesis that ACTN2 influences caries risk. Results for the other candidate genes neither proved nor precluded their associations with dental caries.

Multi-dimensional prioritization of dental caries candidate genes and its enriched dense network modules

A number of genetic studies have suggested numerous susceptibility genes for dental caries over the past decade with few definite conclusions. The rapid accumulation of relevant information, along with the complex architecture of the disease, provides a challenging but also unique opportunity to review and integrate the heterogeneous data for follow-up validation and exploration. In this study, we collected and curated candidate genes from four major categories: association studies, linkage scans, gene expression analyses, and literature mining. Candidate genes were prioritized according to the magnitude of evidence related to dental caries. We then searched for dense modules enriched with the prioritized candidate genes through their protein-protein interactions (PPIs). We identified 23 modules comprising of 53 genes. Functional analyses of these 53 genes revealed three major clusters: cytokine network relevant genes, matrix metalloproteinases (MMPs) family, and transforming growth factor-beta (TGF-β) family, all of which have been previously implicated to play important roles in tooth development and carious lesions. Through our extensive data collection and an integrative application of gene prioritization and PPI network analyses, we built a dental caries-specific sub-network for the first time. Our study provided insights into the molecular mechanisms underlying dental caries. The framework we proposed in this work can be applied to other complex diseases.

Total IgA and IgA reactivity to antigen I/II epitopes in HLA-DRB1*04 positive subjects

Bacterial adherence to the acquired dental pellicle, important in dental caries (caries), is mediated by receptor-adhesins such as salivary agglutinin binding to Streptococcus mutans antigen I/II (I/II). Ten selected I/II epitopes were chosen to determine their reactivity to human salivary IgA. Previous studies suggested that a specific HLA biomarker group (HLA-DRB1*04) may have differential influence of immune responses to I/II. However, it was not known whether secretory IgA (SIgA) responses to the selected epitopes from HLA-DRB1*04 positive subjects were different compared to controls, or across other caries-related factors such as total IgA (TIgA). Thirty-two total subjects were matched according to HLA type, gender, ethnicity and age. HLA genotyping, oral bacterial, immunoglobulin and antibody analyses were performed. A large observed difference emerged with regard to the natural immune reservoir of TIgA in HLA-DRB1*04 positive subjects, specifically, a 27.6% reduction compared to controls. In contrast to all other epitopes studied, HLA-DRB1*04 positive subjects also exhibited reduced reactivity to I/II epitope 834-853. HLA-DRB1*04 positive subjects exhibited lower specific SIgA activity/TIgA to 834-853 and also a lower specific reactivity to 834-853/whole cell S. mutans UA159. Furthermore, HLA-DRB1*04 positive subjects exhibited lower responses to I/II in its entirety. The large observed difference in TIgA and the 834-853 reactivity pattern across multiple measures suggest potentially important connections pertaining to the link between HLA-DRB1*04 and caries.

Association signals unveiled by a comprehensive gene set enrichment analysis of dental caries genome-wide association studies

Gene set-based analysis of genome-wide association study (GWAS) data has recently emerged as a useful approach to examine the joint effects of multiple risk loci in complex human diseases or phenotypes. Dental caries is a common, chronic, and complex disease leading to a decrease in quality of life worldwide. In this study, we applied the approaches of gene set enrichment analysis to a major dental caries GWAS dataset, which consists of 537 cases and 605 controls. Using four complementary gene set analysis methods, we analyzed 1331 Gene Ontology (GO) terms collected from the Molecular Signatures Database (MSigDB). Setting false discovery rate (FDR) threshold as 0.05, we identified 13 significantly associated GO terms. Additionally, 17 terms were further included as marginally associated because they were top ranked by each method, although their FDR is higher than 0.05. In total, we identified 30 promising GO terms, including ‘Sphingoid metabolic process,’ ‘Ubiquitin protein ligase activity,’ ‘Regulation of cytokine secretion,’ and ‘Ceramide metabolic process.’ These GO terms encompass broad functions that potentially interact and contribute to the oral immune response related to caries development, which have not been reported in the standard single marker based analysis. Collectively, our gene set enrichment analysis provided complementary insights into the molecular mechanisms and polygenic interactions in dental caries, revealing promising association signals that could not be detected through single marker analysis of GWAS data.