AMELX gene association to early childhood caries in south-Indian children: a case-control study

PURPOSE

Genetic variants of AMELX gene can affect the protein content, organization of enamel prisms, microstructure and microhardness of the enamel, thus altering the caries susceptibility. The present study aims to assess the association between polymorphisms rs17878486, rs5934997, and rs5933871 of AMELX gene and Early Childhood Caries (ECC).

MATERIALS AND METHODS

This case-control study was conducted on 200 participants, aged 3-6 years, with 100 controls and 100 children with ECC. A questionnaire was used to collect demographic data, birth-weight, type of delivery, oral hygiene practices, feeding history and 24-h diet diary. DNA was isolated from blood and subjected to PCR followed by Sanger sequencing.

RESULTS

The CC genotype of rs17878486 showed an OR of 1.93 (0.34-10.81; P = 0.73). In a recessive model, the CC genotype of rs17878486 reported an OR of 2.04 (0.36-11.40; P = 0.68); rs5593871 reported an OR of 1.00 (0.31-3.21). Statistically significant differences (P ≤ 0.05) between genotype and allele frequencies of rs17878486, rs5934997, and rs5933871 were not observed between children with ECC and the controls.

CONCLUSION

Polymorphisms of AMELX gene did not show a significant association with ECC in this population. However, documentation of genetic data in a global context of ECC may be essential for the future.

Association between polymorphisms of immune response genes and early childhood caries - systematic review, gene-based, gene cluster, and meta-analysis

BACKGROUND

Early childhood caries is a significant public health concern affecting about 600 million children globally. The etiology of early childhood caries can be explained as an interplay between genetic and environmental factors. Single nucleotide polymorphisms are the most common variations in the human genome. Genetic variations of immune response genes can modify the defense response of the host, and alter the susceptibility to bacterial colonization of the oral cavity and early childhood caries. The aim of this systematic review is to identify genetic variants of immune response genes associated with early childhood caries.

RESULTS

A total of 7124 articles were identified by conducting an elaborate search across various electronic databases and genome-wide association studies databases. Subsequent to exclusion at various stages, fifteen articles qualified to be included into the present review. Risk of bias assessment was done with the Q-genie tool. Quantitative synthesis revealed that the odds ratio for TT and CC genotypes of rs11362 was 1.07 (0.67-1.71) and 1.16 (0.84-1.60), respectively. Gene-based analysis revealed a statistically significant association between variants of tumor necrosis factor-alpha gene and T-cell receptor alpha variable 4 locus with early childhood caries. Gene clustering showed the presence of three functional clusters. To comprehend the protein-protein interaction, the bioinformatic tool of "Search Tools for the Retrieval of Interacting Genes and Proteins" was used. Among the biological processes and the reactome pathways, complement activation through the lectin pathway showed the highest strength of association with early childhood caries. To understand the interaction and functionality of the genes, "gene function prediction using Multiple Association Network Integration Algorithm" was used, which revealed that the genes were linked by physical interaction (39.34%) and through co-expression (34.88%).

CONCLUSIONS

Genotype TT of rs7217186 of arachidonate 15-lipoxygenase gene was a risk factor for early childhood caries. Multiple genetic variants of T-cell receptor alpha variable 4 locus and tumor necrosis factor-alpha gene were associated with increased susceptibility to early childhood caries. Polymorphisms of genes regulating the lectin pathway of complement activation can modify the susceptibility to early childhood caries.

Evaluation of telomerase expression in chronic periodontitis

BACKGROUND

Human telomerase is a multi subunit ribonucleoprotein enzyme concerned with telomeric lengthening and homeostasis in man. This enzyme has been found to be elevated in inflammatory conditions like rheumatoid arthritis and silica injury lung. Since chronic periodontitis is also an inflammatory condition where immune cells and cytokines mediate tissue destruction, we set out to evaluate telomerase in gingival tissue samples from healthy subjects and chronic periodontitis patients by reverse transcriptase polymerase chain reaction.

MATERIALS AND METHODS

Gingival biopsies were obtained from eight healthy subjects and eight chronic periodontitis patients. Reverse transcriptase polymerase chain reaction (RTPCR) was carried out to evaluate telomerase gene expression in the samples.

RESULTS

None of the healthy gingival tissue samples expressed the telomerase gene while all the chronic periodontitis samples expressed it. The severe chronic periodontitis samples expressed the gene more intensely than the moderate chronic periodontitis samples.

CONCLUSION

Various mechanisms have been explained to account for telomerase elevation in chronic periodontitis .This study helps us understand the role of telomerase in the pathogenesis of periodontal disease. It could be concluded that telomerase could be used as a marker to assess the severity of inflammation in chronic periodontitis.

Longer (TA)n repeat but not A49T and V89L polymorphisms in SRD5A2 gene may confer prostate cancer risk in South Indian men

Testosterone is converted to 5 alpha-dihydrotestosterone (DHT) by 5 alpha-reductase enzyme, which is encoded by the SRD5A2 gene. DHT is the main androgen responsible for prostate growth. We have analyzed the complete coding region of the SRD5A2 gene in 87 histologically confirmed prostate cancer (PC) patients, 40 benign prostatic hyperplasia (BPH) cases, and 96 control samples from southern parts of India. The study revealed the A49T site to be monomorphic, the V89L site to be highly polymorphic, and the (TA)(n) repeat site to be polymorphic with only 2 alleles in our populations. The distribution of V89L alleles between PC cases and controls was not significantly different; however, (TA)(9) alleles distributed differently between the 2 groups. BPH cases exhibited alleles similar to controls at all polymorphic sites. The sequencing of the whole coding region did not reveal any other known or novel polymorphism in this gene. Our study emphasizes that the (TA)(9) allele might confer certain PC risk but that A49T and V89L polymorphisms do not confer PC risk in South Indian men.

XRCC1 and XPD gene polymorphisms in a South Indian population

DNA repair systems play an important role in maintaining the integrity of the human genome. Deficiency in the repair capacity due to either mutations or inherited polymorphisms in DNA repair genes may contribute to variations in the DNA repair capacity and subsequently susceptibility to cancer. The interindividual variability as well as ethnic differences in DNA repair polymorphisms, stress the importance to establish genotype profiles unique to a population. Hence the present study aimed to determine the frequencies of XRCC1 and XPD gene polymorphisms in 255 healthy random unrelated individuals from South India. DNA was isolated from the peripheral blood sample of these individuals and the XRCC1 and XPD genotypes were determined by PCR- RFLP with Msp1 and Pst1 enzymes respectively. The XRCC1 genotype frequencies revealed 36% Arg/Arg, 47% Arg/Gln and 17% Gln/Gln with Gln allele frequency of 0.41. Analysis of XPD genotypes revealed 51% Lys/Lys, 41% Lys/Gln and 8% Gln/Gln with Gln allele frequency of 0.29. No significant difference in the distribution of genotypes was seen based on gender. Comparison of the frequencies of XRCC1 and XPD polymorphisms observed in the present study with other populations revealed a distinctive nature of the South Indian population. An understanding of DNA repair gene polymorphisms might not only enable risk assessment of humans exposed to environmental carcinogens but also response to therapy, which target the DNA repair pathway.

Cytochrome p4501A1 gene variants as susceptibility marker for prostate cancer

CYP1A1 activates environmental procarcinogens and catalyzes oxidative metabolism of estrogens and is likely to play an important role in the etiology of prostate cancer. To evaluate this phenomenon, the association between two single nucleotide polymorphisms (A to G transition in exon7 leading to amino acid substitution Ile462Val and T3801C at 3'UTR) of CYP1A1 gene in prostate cancer were analyzed in a case-control study of 100 individuals in South Indian population. The estimated relative risk was significantly high for individuals with w1/m1 genotype at 3'UTR of CYP1A1 gene (OR-4.64; 95%CI = 1.51-14.86; P < 0.01) whereas the CYP1A1 Ile/Val genotype (w2/m2) on exon 7 was found to be associated with a decreased risk for prostate cancer (OR-0.17; 95%CI = 0.02-0.89; P=0.03). A Stratified analysis of the genotypes with age of onset and tumor grade showed the w1/m1 genotype to be significantly associated with an early age of onset; however the tumor grades did not have significant association with the variant genotypes. Thus the present study indicates that individuals with the variant w1/m1 genotype exhibit an increased risk while those with w2/m2 genotype exhibit a decreased risk for prostate cancer.

Molecular diversity of HLA-A*19 group of alleles in south Indian population

To determine the genetic diversity of the human leucocyte antigen (HLA)-A*19 group of alleles in the south Indian Tamil population, we studied 100 random healthy unrelated individuals. The frequency of HLA-A*19 was 37% with A*33 (45.9%), A*32 (29.7%), A*31 (16.2%), A*30 (5.4%), A*29 (2.7%) and A*74 (0%). The frequency distribution of the HLA-A*19 alleles was distinct and revealed marked similarities and variations with other populations.

Polymorphisms at GSTM1 and GSTP1 gene loci and risk of prostate cancer in a South Indian population

Inter-individual differences in cancer susceptibility may be mediated in part through polymorphic variability in the bioactivation and detoxification of carcinogens. The glutathione S-transferases (GSTs), which are active in detoxification of wide variety of carcinogens, have been consistently implicated as cancer susceptibility genes in this context. We here assessed the association of GSTM1 and GSTP1 polymorphisms with susceptibility to prostate cancer in a case-control study of 75 patients and 100 age-matched controls in a South Indian population. The GSTM1 null polymorphism was detected by PCR and the GSTP1 Ile105Val polymorphism by PCR-RFLP using peripheral blood DNA. There was no significant link between the null genotype of GSTM1 and risk of prostate cancer (OR-1.79; 95% CI-0.78-4.11; P-0.18). However, the GSTP1 Ile/Val genotype was significantly associated with a decreased risk for prostate cancer (OR-0.36; 95% CI-0.18-0.73; P<0.001). Analysis of the variant GSTM1 and GSTP1 genotypes in combination did not reveal any significant difference between cases and controls, even with a stratified analysis tumor grades. Thus our study indicates that the GSTP1 Ile/Val genotype may decrease risk of prostate cancer in the South Indian population.