Polymorphisms located in the region containing BHMT and BHMT2 genes as maternal protective factors for orofacial clefts

Combined Analysis of Expression Profiles in a Mouse Model and Patients Identified BHMT2 as a New Regulator of Lipid Metabolism in Metabolic-Associated Fatty Liver Disease

Metabolic associated fatty liver disease (MAFLD) is associated with obesity, type 2 diabetes mellitus, and other metabolic syndromes. Farnesoid X receptor (FXR, NR1H4) plays a prominent role in hepatic lipid metabolism. This study combined the expression of liver genes in FXR knockout (KO) mice and MAFLD patients to identify new pathogenic pathways for MAFLD based on genome-wide transcriptional profiling. In addition, the roles of new target genes in the MAFLD pathogenic pathway were also explored. Two groups of differentially expressed genes were obtained from FXR-KO mice and MAFLD patients by transcriptional analysis of liver tissue samples. The similarities and differences between the two groups of differentially expressed genes were analyzed to identify novel pathogenic pathways and target genes. After the integration analysis of differentially expressed genes, we identified 134 overlapping genes, many of which have been reported to play an important role in lipid metabolism. Our unique analysis method of comparing differential gene expression between FXR-KO mice and patients with MAFLD is useful to identify target genes and pathways that may be strongly implicated in the pathogenesis of MAFLD. The overlapping genes with high specificity were screened using the Gene Expression Omnibus (GEO) database. Through comparison and analysis with the GEO database, we determined that BHMT2 and PKLR could be highly correlated with MAFLD. Clinical data analysis and RNA interference testing in vitro confirmed that BHMT2 may a new regulator of lipid metabolism in MAFLD pathogenesis. These results may provide new ideas for understanding the pathogenesis of MAFLD and thus provide new targets for the treatment of MAFLD.

Interaction analysis of gene variants related to one-carbon metabolism with chronic hepatitis B infection in Chinese patients

BACKGROUND

The risk of chronic hepatitis B (CHB) infection is influenced by aberrant DNA methylation and altered nucleotide synthesis and repair, possibly caused by polymorphic variants in one-carbon metabolism genes. In the present study, we investigated the relationship between polymorphisms belonging to the one-carbon metabolic pathway and CHB infection.

METHODS

A case-control study using 230 CHB patients and 234 unrelated healthy controls was carried out to assess the genetic association of 24 single nucleotide polymorphisins (SNPs) determined by mass spectrometry.

RESULTS

Three SNPs, comprising rs10717122 and rs2229717 in serine hydroxymethyltransferase1/2 (SHMT2) and rs585800 in betaine-homocysteine S-methyltransferase (BHMT), were associated with the risk of CHB. Patients with DEL allele, DEL.DEL and DEL.T genotypes of rs10717122 had a 1.40-, 2.00- and 1.83-fold increased risk for CHB, respectively. Cases inheriting TA genotype of rs585800 had a 2.19-fold risk for CHB infection. The T allele of rs2229717 was less represented in the CHB cases (odds ratio = 0.66, 95% confidence interval = 0.48-0.92). The T allele of rs2229717 was less in patients with a low hepatitis B virus-DNA level compared to the control group (odds ratio = 0.49, 95% confidence interval = 0.25-0.97) and TT genotype of rs2229717 had a significant correlation with hepatitis B surface antigen level (p = 0.0195). Further gene-gene interaction analysis showed that subjects carrying the rs10717122 DEL.DEL/DEL.T and rs585800 TT/TA genotypes had a 2.74-fold increased risk of CHB.

CONCLUSIONS

The results of the present study suggest that rs10717122, rs585800 and rs2229717 and gene-gene interactions of rs10717122 and rs585800 affect the outcome of CHB infection, at the same time as indicating their usefulness as a predictive and diagnostic biomarker of CHB infection.

Genetic polymorphisms in MTR are associated with non-syndromic congenital heart disease from a family-based case-control study in the Chinese population

Genetic polymorphisms of folate pathway genes have been reported to be associated with congenital heart diseases (CHDs); however, the results remain conflicting. We conducted a family-based case-control study, which included160 CHD case-parent triads and 208 control-parent triads to explore the association of 18 genetic variants of seven folate metabolism-related genes with the risk of CHDs. The MTR C allele of rs1770449 (OR = 1.961, 95%CI: 1.379–2.788) and the MTR A allele of rs1050993 (OR = 1.994, 95%CI: 1.401–2.839) in infants were associated with an increased risk of CHDs. Over-transmission of SNPs rs1770449 and rs1050993 and haplotype CAA (rs1770449-rs1805087-rs1050993) in MTR were detected in total CHDs. The above mentioned associations of MTR with CHDs were also observed in septal defects and conotruncal heart defects subgroups. Without maternal periconceptional folate intake, the risk of CHDs among women carrying the rs1770449 “CT or CC” genotype or the rs1050993 “AG or AA” genotype in MTR was 3.262(95%CI: 1.656–6.429) or 3.263(95%CI: 1.656–6.429) times greater than the aOR in women carrying wild genotype, respectively. Our study suggests that MTR polymorphisms (rs1770449 and rs1050993) may be associated with the risk of CHDs and modify the relation between maternal folate intake and CHDs.

Importance of polymorphic variants of phosphatidylethanolamine N-methyltransferase (PEMT) gene in the etiology of intrauterine fetal death in the Polish population

OBJECTIVES

Intrauterine fetal death (IUFD) is a multifactorial disorder and one of the most severe obstetrical complications. Our primary aim was to study the possible associations between polymorphic variants of the PEMT gene and IUFD in the Polish population.

STUDY DESIGN

The case-control study involved 76 mothers with IUFD occurrence and 215 mothers of healthy children. Genetic analysis of the four single nucleotide polymorphisms in the PEMT gene (rs4646406, rs4244593, rs897453 and rs12325817) was performed with the PCR/RFLP method.

RESULTS

Three oef the analyzed PEMT polymorphisms (rs4646406, rs4244593, and rs8974) were significantly associated with IUFD in the Polish population. Among them, PEMT variant rs4244593 was associated with increased risk of IUFD in three genetic inheritance models. Results were statistically significant even after applying Bonferroni correction for multiple comparisons (p < 0.0125). The distribution of all haplotypes except TAGC was not different between cases and controls, however, after applying permutation test, none of the haplotypes showed a relation with IUFD.

CONCLUSIONS

The present findings indicate that PEMT polymorphisms may be associated with the susceptibility to IUFD in the Polish population.

PEMT rs12325817 and PCYT1A rs7639752 polymorphisms are associated with betaine but not choline concentrations in pregnant women

Maternal metabolism during gestation may depend on nutrient intake but also on polymorphism of genes encoding enzymes involved in metabolism of different nutrients. Data on choline or carnitine metabolism in pregnant women are scarce. We hypothesized that (1) choline intake in Polish pregnant women is inadequate and (2) choline and carnitine metabolism would differ by genotype and nutritional status of pregnant women. One hundred three healthy Polish women aged 18 to 44 years in the third trimester of pregnancy were enrolled in the study. The average choline, folate, and carnitine intakes were 365 ± 14 mg/d, 1089 ± 859 μg, and 132 ± 8 mg/d, respectively. Most women did not achieve an adequate intake of choline. Average choline, betaine, trimethylamine oxide, l-carnitine, and acetylcarnitine concentrations were 10.64 ± 3.30 μmol/L, 14.43 ± 4.01 μmol/L, 2.01 ± 1.24 μmol/L, 12.73 ± 5.41 μmol/L, and 6.79 ± 3.82 μmol/L, respectively. Approximately 15% lower betaine concentrations were observed in the GG homozygotes of PEMT rs12325817 and in the GG homozygotes of PCYT1A rs7639752 than in the respective minor allele carriers. Birth weight was higher in the G allele homozygotes of the CHDH rs2289205 than in the minor allele carriers: GG: 3398 ± 64 g; GA+AA: 3193 ± 76 g. Our study shows that choline intake in Polish pregnant women is inadequate and that polymorphisms of PEMT rs12325817 and PCYT1A rs7639752 are associated with betaine but not choline concentrations.

GWAS reveals loci associated with velopharyngeal dysfunction

Velopharyngeal dysfunction (VPD) occurs when the muscular soft palate (velum) and lateral pharyngeal walls are physically unable to separate the oral and nasal cavities during speech production leading to hypernasality and abnormal speech reduction. Because VPD is often associated with overt or submucous cleft palate, it could be present as a subclinical phenotype in families with a history of orofacial clefting. A key assumption to this model is that the overt and subclinical manifestations of the orofacial cleft phenotype exist on a continuum and therefore share common etiological factors. We performed a genome-wide association study in 976 unaffected relatives of isolated CP probands, 54 of whom had VPD. Five loci were significantly (p < 5 × 10^-8) associated with VPD: 3q29, 9p21.1, 12q21.31, 16p12.3 and 16p13.3. An additional 15 loci showing suggestive evidence of association with VPD were observed. Several genes known to be involved in orofacial clefting and craniofacial development are located in these regions, such as TFRC, PCYT1A, BNC2 and FREM1. Although further research is necessary, this could be an indication for a potential shared genetic architecture between VPD and cleft palate, and supporting the hypothesis that VPD is a subclinical phenotype of orofacial clefting.

Evidence of interaction between genes in the folate/homocysteine metabolic pathway in controlling risk of non-syndromic oral cleft

OBJECTIVE

Little consistent evidence is available for the association between the risk of non-syndromic cleft lip with or without cleft palate (NSCL/P) and any of the individual genes in the folate/homocysteine metabolic pathway. We investigated the genes in the folate pathway to further clarify its potential influence on the risk of NSCL/P considering gene-gene (G×G) interaction.

SUBJECTS AND METHODS

We selected markers in 18 genes from the pathway and applied Cordell's method to test for G×G interaction using 1,908 NSCL/P case-parent trios ascertained in an international consortium where a genomewide association study (GWAS) of oral clefts was conducted.

RESULTS

We found intriguing signals among Asian and European ancestry groups for G×G interaction between markers in betaine-homocysteine methyltransferase gene (BHMT/BHMT2) and dimethylglycine dehydrogenase gene (DMGDH) attaining genomewide significance. In the pooled data, the top significant interaction was found between rs13158309 (BHMT) and rs10514154 (DMGDH, p = 1.45 × 10^-12 ).

CONCLUSIONS

Our study illustrated the importance of taking into account potential G×G interaction for genetic association analysis in NSCL/P, and this study suggested both BHMT/BHMT2 and DMGDH should be considered as candidate genes for NSCL/P in future studies.

Sequence variation in folate pathway genes and risks of human cleft lip with or without cleft palate

In an effort to comprehensively interrogate genetic variation in the folate pathway for risk of cleft lip with or without cleft palate (CLP), we evaluated 504 common and rare variants in 35 folate-related genes in a panel of 330 infants with CLP and 367 non-malformed controls. Odds ratios (OR) with 95% confidence intervals were computed for common genotypes. A Case-Control Difference metric was calculated for rare variants to highlight differentially occurring alleles. Interactions between variants and a maternal folate intake variable were also evaluated. In gene-only results, significant odds ratios were observed for multiple variants in the BHMT/BHMT2/DMGDH gene cluster, particularly in Hispanic infants. Also in this cluster, rare variant analysis highlighted a substantial case-control difference in BHMT rs60340837 (synonymous Y284Y). In Hispanics, the ALDH1L1 I812V variant (rs4646750) was the most significant risk allele: OR = 3.8 (95%CI = 1.6-9.2) when heterozygous. In non-Hispanic white infants, we observed significant risk for AHCYL2 rs1095423 (homozygous OR = 3.0, 95%CI 1.1-7.8) and the 68 bp CBS insertion (c.844ins68; heterozygous OR = 2.4, 95%CI = 1.1-5.3). Rare variant analysis in this group revealed case-control differences in MTRR and several other methionine cycle genes, a process implicated previously in clefting risk. In women with low folate intake specifically, increased risks were observed for CBS rs2851391 (OR = 3.6, 95%CI = 1.3-9.6) and the R259P nonsynonymous variant of TCN2 (rs1801198; OR = 2.8, 95%CI = 1.2-6.3). This comprehensive study provides further direction on candidate loci to help disentangle the folate-related developmental phenomena in human clefting risk. © 2016 Wiley Periodicals, Inc.

Testing Allele Transmission of an SNP Set Using a Family-Based Generalized Genetic Random Field Method

Family-based association studies are commonly used in genetic research because they can be robust to population stratification (PS). Recent advances in high-throughput genotyping technologies have produced a massive amount of genomic data in family-based studies. However, current family-based association tests are mainly focused on evaluating individual variants one at a time. In this article, we introduce a family-based generalized genetic random field (FB-GGRF) method to test the joint association between a set of autosomal SNPs (i.e., single-nucleotide polymorphisms) and disease phenotypes. The proposed method is a natural extension of a recently developed GGRF method for population-based case-control studies. It models offspring genotypes conditional on parental genotypes, and, thus, is robust to PS. Through simulations, we presented that under various disease scenarios the FB-GGRF has improved power over a commonly used family-based sequence kernel association test (FB-SKAT). Further, similar to GGRF, the proposed FB-GGRF method is asymptotically well-behaved, and does not require empirical adjustment of the type I error rates. We illustrate the proposed method using a study of congenital heart defects with family trios from the National Birth Defects Prevention Study (NBDPS).

DNA Methylation in Newborns and Maternal Smoking in Pregnancy: Genome-wide Consortium Meta-analysis

Epigenetic modifications, including DNA methylation, represent a potential mechanism for environmental impacts on human disease. Maternal smoking in pregnancy remains an important public health problem that impacts child health in a myriad of ways and has potential lifelong consequences. The mechanisms are largely unknown, but epigenetics most likely plays a role. We formed the Pregnancy And Childhood Epigenetics (PACE) consortium and meta-analyzed, across 13 cohorts (n = 6,685), the association between maternal smoking in pregnancy and newborn blood DNA methylation at over 450,000 CpG sites (CpGs) by using the Illumina 450K BeadChip. Over 6,000 CpGs were differentially methylated in relation to maternal smoking at genome-wide statistical significance (false discovery rate, 5%), including 2,965 CpGs corresponding to 2,017 genes not previously related to smoking and methylation in either newborns or adults. Several genes are relevant to diseases that can be caused by maternal smoking (e.g., orofacial clefts and asthma) or adult smoking (e.g., certain cancers). A number of differentially methylated CpGs were associated with gene expression. We observed enrichment in pathways and processes critical to development. In older children (5 cohorts, n = 3,187), 100% of CpGs gave at least nominal levels of significance, far more than expected by chance (p value < 2.2 × 10(-16)). Results were robust to different normalization methods used across studies and cell type adjustment. In this large scale meta-analysis of methylation data, we identified numerous loci involved in response to maternal smoking in pregnancy with persistence into later childhood and provide insights into mechanisms underlying effects of this important exposure.

A Three-Way Interaction among Maternal and Fetal Variants Contributing to Congenital Heart Defects

Congenital heart defects (CHDs) develop through a complex interplay between genetic variants, epigenetic modifications, and maternal environmental exposures. Genetic studies of CHDs have commonly tested single genetic variants for association with CHDs. Less attention has been given to complex gene-by-gene and gene-by-environment interactions. In this study, we applied a recently developed likelihood-ratio Mann-Whitney (LRMW) method to detect joint actions among maternal variants, fetal variants, and maternal environmental exposures, allowing for high-order statistical interactions. All subjects are participants from the National Birth Defect Prevention Study, including 623 mother-offspring pairs with CHD-affected pregnancies and 875 mother-offspring pairs with unaffected pregnancies. Each individual has 872 single nucleotide polymorphisms encoding for critical enzymes in the homocysteine, folate, and trans-sulfuration pathways. By using the LRMW method, three variants (fetal rs625879, maternal rs2169650, and maternal rs8177441) were identified with a joint association to CHD risk (nominal P-value = 1.13e-07). These three variants are located within genes BHMT2, GSTP1, and GPX3, respectively. Further examination indicated that maternal SNP rs2169650 may interact with both fetal SNP rs625879 and maternal SNP rs8177441. Our findings suggest that the risk of CHD may be influenced by both the intragenerational interaction within the maternal genome and the intergenerational interaction between maternal and fetal genomes.

Gene Expression Profiling in Mouse Embryonic Stem Cells Reveals Glycogen Synthase Kinase-3-Dependent Targets of Phosphatidylinositol 3-Kinase and Wnt/β-Catenin Signaling Pathways

Glycogen synthase kinase-3 (Gsk-3) activity is an important regulator of numerous signal transduction pathways. Gsk-3 activity is the sum of two largely redundant proteins, Gsk-3α and Gsk-3β, and in general, Gsk-3 is a negative regulator of cellular signaling. Genetic deletion of both Gsk-3α and Gsk-3β in mouse embryonic stem cells (ESCs) has previously been shown to lead to the constitutive activation of the Wnt/β-catenin signaling pathway. However, in addition to Wnt signaling, all Gsk-3-regulated pathways, such as insulin signaling, are also affected simultaneously in Gsk-3α(-) (/) (-); Gsk-3β(-) (/) (-)ESCs. In an effort to better understand how specific signaling pathways contribute to the global pattern of gene expression in Gsk-3α(-) (/) (-); Gsk-3β(-) (/) (-)ESCs, we compared the gene expression profiles in Gsk-3α(-) (/) (-); Gsk-3β(-) (/) (-) ESCs to mouse ESCs in which either Wnt/β-catenin signaling or phosphatidylinositol 3-kinase (PI3K)-dependent insulin signaling are constitutively active. Our results show that Wnt signaling has a greater effect on up-regulated genes in the Gsk-3α(-) (/) (-); Gsk-3β(-) (/) (-)ESCs, whereas PI3K-dependent insulin signaling is more responsible for the down-regulation of genes in the same cells. These data show the importance of Gsk-3 activity on gene expression in mouse ESCs, and that these effects are due to the combined effects of multiple signaling pathways.

The human flavoproteome

Vitamin B2 (riboflavin) is an essential dietary compound used for the enzymatic biosynthesis of FMN and FAD. The human genome contains 90 genes encoding for flavin-dependent proteins, six for riboflavin uptake and transformation into the active coenzymes FMN and FAD as well as two for the reduction to the dihydroflavin form. Flavoproteins utilize either FMN (16%) or FAD (84%) while five human flavoenzymes have a requirement for both FMN and FAD. The majority of flavin-dependent enzymes catalyze oxidation-reduction processes in primary metabolic pathways such as the citric acid cycle, β-oxidation and degradation of amino acids. Ten flavoproteins occur as isozymes and assume special functions in the human organism. Two thirds of flavin-dependent proteins are associated with disorders caused by allelic variants affecting protein function. Flavin-dependent proteins also play an important role in the biosynthesis of other essential cofactors and hormones such as coenzyme A, coenzyme Q, heme, pyridoxal 5'-phosphate, steroids and thyroxine. Moreover, they are important for the regulation of folate metabolites by using tetrahydrofolate as cosubstrate in choline degradation, reduction of N-5.10-methylenetetrahydrofolate to N-5-methyltetrahydrofolate and maintenance of the catalytically competent form of methionine synthase. These flavoenzymes are discussed in detail to highlight their role in health and disease.

A case-parent triad assessment of folate metabolic genes and the risk of childhood acute lymphoblastic leukemia

PURPOSE

We conducted a case-parent triad study evaluating the role of maternal and offspring genotypes in the folate metabolic pathway on childhood acute lymphoblastic leukemia (ALL) risk.

METHODS

Childhood ALL case-parent triads (n = 120) were recruited from Texas Children's Hospital. DNA samples were genotyped using the Sequenom iPLEX MassARRAY for 68 tagSNPs in six folate metabolic pathway genes (MTHFR, MTRR, MTR, DHFR, BHMT, and TYMS). Log-linear modeling was used to examine the associations between maternal and offspring genotypes and ALL.

RESULTS

After controlling for the false discovery rate (<0.1), there were 20 significant maternal effects in the following genes: BHMT (n = 3), MTR (n = 12), and TYMS (n = 5). For instance, maternal genotypes for BHMT rs558133 (relative risk [RR] = 0.51, 95 % confidence interval [CI]: 0.30-0.87, p = 0.008, Q = 0.08) and MTR rs2282369 (RR = 0.46, 95 % CI: 0.27-0.80, p = 0.004, Q = 0.08) were associated with ALL. There were no significant offspring effects after controlling for the false discovery rate.

CONCLUSIONS

This is one of the few studies conducted to evaluate maternal genetic effects in the context of childhood ALL risk. Furthermore, we employed a family-based design that is less susceptible to population stratification bias in the estimation of maternal genetic effects. Our findings suggest that maternal genetic variation in the folate metabolic pathway is relevant in the etiology of childhood ALL. The observed maternal genetic effects support the need for continued research of how the uterine environment may influence risk of ALL.

Association between genetic variants in DNA and histone methylation and telomere length

Telomere length, a biomarker of aging and age-related diseases, exhibits wide variation between individuals. Common genetic variation may explain some of the individual differences in telomere length. To date, however, only a few genetic variants have been identified in the previous genome-wide association studies. As emerging data suggest epigenetic regulation of telomere length, we investigated 72 single nucleotide polymorphisms (SNPs) in 46 genes that involve DNA and histone methylation as well as telomerase and telomere-binding proteins and DNA damage response. Genotyping and quantification of telomere length were performed in blood samples from 989 non-Hispanic white participants of the Sister Study, a prospective cohort of women aged 35-74 years. The association of each SNP with logarithmically-transformed relative telomere length was estimated using multivariate linear regression. Six SNPs were associated with relative telomere length in blood cells with p-values<0.05 (uncorrected for multiple comparisons). The minor alleles of BHMT rs3733890 G>A (p = 0.041), MTRR rs2966952 C>T (p = 0.002) and EHMT2 rs558702 G>A (p = 0.008) were associated with shorter telomeres, while minor alleles of ATM rs1801516 G>A (p = 0.031), MTR rs1805087 A>G (p = 0.038) and PRMT8 rs12299470 G>A (p = 0.019) were associated with longer telomeres. Five of these SNPs are located in genes coding for proteins involved in DNA and histone methylation. Our results are consistent with recent findings that chromatin structure is epigenetically regulated and may influence the genomic integrity of telomeric region and telomere length maintenance. Larger studies with greater coverage of the genes implicated in DNA methylation and histone modifications are warranted to replicate these findings.

Analysis of genetic interactions involving maternal and offspring genotypes at different Loci: power simulation and application to testicular cancer

The analyses of genetic interaction between maternal and offspring genotypes are usually conducted considering a single locus. Here, we propose testing maternal × offspring (M×O) and maternal × maternal (M×M) genotype interactions involving two unlinked loci. We reformulate the log-linear approach of analyzing cases and their parents (family trios) to accommodate two loci, fit fuller models to avoid confounding in a first analysis step and propose that the model be reduced to the most prominent effects in a second step. We conduct extensive simulations to assess the validity and power of this approach under various model assumptions. We show that the approach is valid and has good power to detect M×O and M×M interactions. For example, the power to detect a dominant interaction relative risk of 1.5 (both M×O and M×M) is 70% with 300 trios and approaches 100% with 1,000 trios. Unlike the main effects, M×O and M×M interactions are conditionally independent of mating types, and consequently, their power is not affected by missing paternal genotypes. When applied to single-locus M×O interaction, our method is as powerful as other existing methods. Applying the method to testicular cancer, we found a nominally significant M×M interaction between single nucleotide polymorphisms from C-Kit Ligand (KITLG) and Sex Hormone Binding Globulin (SHBG) using 210 families (relative risk 2.2, P = 0.03). This finding supports a role of maternal hormones in offspring testicular cancer and warrants confirmation in a larger dataset.

Polymorphisms in genes involved in folate metabolism and orofacial clefts

BACKGROUND

Orofacial clefts (OFCs) are one of the most common birth defects in humans. Maternal use of folate antagonists including dihydrofolate reductase inhibitors has been associated with a higher risk of OFCs thus suggesting that folate-related metabolism and associated genes may be involved in pathogenesis of OFC. The association between folate intake and risk of OFCs however is inconsistent.

OBJECTIVE

To review the published evidence that polymorphisms in genes that affect folate metabolism are associated with an increased risk of OFCs.

METHODS

We reviewed articles published up until October 2010, on polymorphisms of genes related to folate and homocysteine metabolism and their associations with OFCs. Articles were identified via Medline searches.

CONCLUSIONS

No consistent evidence emerged of a strong association between risk of OFCs and any known gene related to folate metabolism. Further, recent genome-wide association studies have not identified associations between OFCs and folate-related genes. Further studies are warranted to determine whether gene-environment interactions, including gene-nutrient interactions and epigenetic modifications of genes affect the risk of OFCs.

Polymorphic variants of genes involved in homocysteine metabolism in celiac disease

Celiac disease (CD) is a polygenic chronic enteropathy conferring an increased risk for various nutrient deficiency states. Hyperhomocysteinemia is a frequent finding in CD and may be related to the development of venous thrombosis, cardiovascular disease, and stroke in untreated CD patients. Recently, a possible excess in the frequency of the MTHFR c.677C>T (rs1801133) gene variant in CD patients was reported. The purpose of this study was to determine if there exist differences in the distribution of polymorphic variants of genes involved in homocysteine/methyl group metabolism between CD patients and the general population. A set of 10 gene polymorphisms (MTHFR rs1801133, MTR rs1805087, MTHFD1 rs2236225, MTRR rs1801394, CBS 844ins68, BHMT1 rs7356530 and rs3733890, BHMT2 rs526264 and rs625879, and TCN2 rs1801198) was tested in 134 patients with CD and 160 matched healthy controls. The frequency of the MTR rs1805087 GG genotype in CD patients was lower than in controls (0.01 and 0.06, respectively), although statistical significance was not achieved (P = 0.06). For the other analyzed polymorphisms, there was no evidence of difference in both allelic and genotypic distribution between cases and controls. The exhaustive Multifactor Dimensionality Reduction analysis revealed no combination of interactive polymorphisms predicting the incidence of CD. In contrast to the well-documented clinical observations of increased risks of vascular disease in patients with longstanding untreated CD, in our group of patients no significant association with CD was found for all tested polymorphic variants of genes involved in homocysteine metabolism. These findings should be replicated in studies with a larger sample size.

Polymorphisms in CHDH gene and the risk of tooth agenesis

BACKGROUND

Tooth agenesis is one of the most common anomalies of human dentition and is due to a complex and not fully elucidated etiology. The purpose of this study was to evaluate the possibility that polymorphic variants of genes encoding the main folate and choline metabolism enzymes might be associated with the risk of hypodontia in the Polish population.

METHODS AND RESULTS

We analyzed 21 polymorphisms of 13 candidate genes and found that single nucleotide polymorphisms (SNPs) in the CHDH gene are significantly correlated with the risk of dental agenesis. The strongest association was found for the SNP located in the intronic sequence of CHDH. Individuals carrying one copy of the rs6445606 C allele had an over two-fold decreased risk of having hypodontia (odds ratio [OR]CTvsTT=0.434; 95% confidence interval [CI], 0.2724-0.6915; p=0.0004; pcorr=0.0084). A reduced risk of tooth agenesis was also observed in individuals with one or two copies of the rs6445606 C allele compared to T allele carriers (ORCT+CCvsTT=0.524; 95% CI, 0.3386-0.8097; p=0.0035; pcorr=0.0735). Moreover, the gene-gene interaction analysis revealed a significant epistatic interaction between CHDH (rs6445606) and PLD2 (rs3764897) in the susceptibility to hypodontia (p=0.004).

CONCLUSION

Our study identified CHDH and PLD2 as novel candidate genes, the nucleotide variants of which could be associated with the risk of tooth agenesis.