Biomedical subjects

Anne Parle-McDermott

Publications and source records attributed to Anne Parle-McDermott.

14 recordsLinked to original sources

PubMed2006

The MTHFR 1298CC and 677TT genotypes have opposite associations with red cell folate levels.

Individuals homozygous for the thermolabile variant (677TT) of methylenetetrahydrofolate reductase exhibit reduced folate status as evidenced by a drop in the biomarker red cell folate (RCF) compared to those who carry at least one 677C allele. We now report that a different polymorphism in the same enzyme, namely 1298A>C, is associated with increased RCF levels. Thus, these two common polymorphisms change a metabolic phenotype in opposite directions suggesting that their cancer protective associations are by different mechanisms.

Biomarkers↗

PubMed2006

Confirmation of the R653Q polymorphism of the trifunctional C1-synthase enzyme as a maternal risk for neural tube defects in the Irish population.

The risk of neural tube defects (NTDs) is known to have a significant genetic component that could act through either the NTD patient and/or maternal genotype. The success of folic acid supplementation in NTD prevention has focused attention on polymorphisms within folate-related genes. We previously identified the 1958G>A (R653Q) polymorphism of the trifunctional enzyme MTHFD1 (methylenetetrahydrofolate-dehydrogenase, methenyltetrahydrofolate-cyclohydrolase, formyltetrahydrofolate synthetase; often referred to as 'C1 synthase') as a maternal risk for NTDs, but this association remains to be verified in a separate study to rule out a chance finding. To exclude this possibility, we genotyped an independent sample of mothers with a history of an NTD-affected pregnancy derived from the same Irish population. In this sample there was a significant excess of 1958AA homozygote mothers of NTD cases (n=245) compared to controls (n=770). The direction and magnitude of risk (odds ratio 1.49 (1.07-2.09), P=0.019) is consistent with our earlier finding. Sequencing of the MTHFD1 gene revealed that this association is not being driven by another common variant within the coding region. We have established that the MTHFD1 1958G>A polymorphism has a significant role in influencing a mother's risk of having an NTD-affected pregnancy in the Irish population.

Amino Acid Substitution↗

PubMed2005

Reduced folate carrier polymorphisms and neural tube defect risk.

The reduced folate carrier (RFCI) is essential for folate transport into cells. Low folate is an important cause of neural tube defects (NTDs), and a single-nucleotide polymorphism (H27R) (80G-->A) in the RFCI gene has been reported to be a NTD risk factor. We investigated H27R and a 61 bp tandem repeat polymorphism as potential risk factors for NTDs, using a large homogeneous Irish population by case/control comparison, log-linear analysis, and transmission disequilibrium testing. No association was found between NTDs and H27R in mothers [p = 0.23, odds ratio (OR) 0.87, 95% confidence interval (CI) 0.69-1.09], fathers (p = 0.11, OR 0.83, 95% CI 0.66-1.04), or cases (p = 0.36, OR 0.9, 95% CI 0.72-1.12) when compared to controls or through log-linear modeling for dominant or recessive effects or with the transmission disequilibrium test for preferential allele transmission. Using log-linear models, a significant protective case effect was seen for the 61 bp polymorphism (p = 0.0039, OR 0.21, 95% CI 0.05-0.85). When analyzed by genotype, individuals homozygous for a single copy of the 61 bp sequence were underrepresented in cases as compared to controls, although these results did not reach statistical significance (p = 0.081, OR 0.5, 95% CI 0.23-1.09, goodness of fit p = 0.42). We compared the frequencies of H27R and the 61 bp polymorphism in African-Americans and American-Caucasians. The frequencies of H27R polymorphism differed significantly between the two populations (p = 0.0001). This large study does not confirm previous reports that H27R is a risk factor for NTDs. The previously unstudied 61 bp tandem repeat, however, has a possible protective NTD effect in our Irish population. This requires confirmation in other studies.

Black or African American↗

PubMed2005

Screening for new MTHFR polymorphisms and NTD risk.

The enzyme, 5,10-methylenetetrahydrofolate reductase (MTHFR) plays a key role in cellular folate metabolism. The A222V (677C->T) polymorphism is a confirmed neural tube defect (NTD) risk factor within Irish and other populations. To search for other unknown single nucleotide polymorphisms (SNPs) that might play a role in the etiology of NTDs, we examined the entire MTHFR coding region in healthy individuals (n = 100). SNPs were identified using sequencing and database analysis and allele frequencies were determined in our Irish population. We identified P39P (116C->T; T allele frequency 0.13) and previously reported R594Q (1793G->A; Q allele frequency 0.07). We screened a large ethnically homogeneous Irish NTD cohort (n>1,300) for P39P and R594Q. A possible association between NTD cases and P39P (P = 0.034) was found but this was not confirmed by transmission disequilibrium testing. R594Q also showed some evidence of a NTD case association (P = 0.07). Further analysis indicated these observations are due to linkage disequilibrium with A222V (677C->T), and therefore these new SNPs are unlikely to be independent risk factors for NTDs. As rates of NTDs differ between ethnic groups, we examined allele and genotype frequencies of P39P and R594Q within African-American and American-Caucasian populations. This is the first NTD association study of both R594Q and the novel P39P. The association with NTD risk reported for these SNPs is driven by the linkage disequilibrium with the A222V (677C->T) NTD risk factor.

Base Sequence↗

PubMed2005

Analysis of methionine synthase reductase polymorphisms for neural tube defects risk association.

Methionine synthase reductase (MTRR) regenerates methylated cobalamin levels from the oxidised cob(II)alamin form and in so doing plays a crucial role in maintaining the active state of methionine synthase (MTR). MTR is an essential enzyme catalyzing the conversion of homocysteine to methionine. Single nucleotide polymorphisms (SNPs) within the MTRR gene may potentially compromise MTR activity leading to elevated homocysteine levels, a known risk factor for neural tube defects (NTDs). We studied the MTRR polymorphisms I22M (66A-->G), S175L (524C-->T), and K350R (1049A-->G) as potential NTD risk factors in a large homogeneous Irish NTD population. Degree of risk was assessed via case/control comparison, log-linear analysis, and transmission disequilibrium testing. No association was found between NTDs and I22M in mothers (p = 0.16, OR1.14 [0.95-1.38], n = 447) or cases (p = 0.13, OR1.15 [0.96-1.38], n = 470) compared to controls (n = 476). A dominant I22M paternal effect was found through case/control comparison and log-linear modelling (p = 0.019) (goodness-of-fit p=0.91, OR 1.46 [1.10-1.93], n = 423). No significant NTD association was found with S175L or K350R in cases or their parents and no interactions were observed between these polymorphisms and the D919G variant of MTR or the A222V variant of 5,10-methylenetetrahydrofolate reductase (MTHFR). We also compared the frequencies of I22M, S175L, and K350R in African-Americans versus American-Caucasians. The frequencies of I22M and K350R differed significantly between the two groups (p = 0.0005 and p = 0.0001, respectively). Our findings do not support an important role for these MTRR variants in NTDs.

5,10-Methylenetetrahydrofolate Reductase (FADH2)↗

PubMed2005

MTHFD1 R653Q polymorphism is a maternal genetic risk factor for severe abruptio placentae.

This study examined the relationship between folate/homocysteine-related genetic polymorphisms: MTHFD1 1958G --> A (R653Q), MTHFR 677C --> T (A222V), MTHFR 1298A --> C (E429A), and risk of severe abruptio placentae. We genotyped 62 women with a pregnancy history complicated by severe abruptio placentae and 184 control pregnancies. Analysis of the MTHFD1 1958G --> A (R653Q) polymorphism showed increased frequency of the 'QQ' homozygote genotype in pregnancies affected by severe abruptio placentae compared to control pregnancies (odds ratio 2.85 (1.47-5.53), P = 0.002). In contrast to previous reports, the MTHFR polymorphisms 677C --> T (A222V) and 1298A --> C (E429A) were not associated with abruptio placentae risk in our cohort, when analyzed either independently or in combination. We conclude that women who are 'QQ' homozygote for the MTHFD1 1258G --> A (R653Q) polymorphism are almost three times more likely to develop severe abruptio placentae during their pregnancy than women who are 'RQ' or 'RR.'

Abruptio Placentae↗

PubMed2005

Evaluation of transcobalamin II polymorphisms as neural tube defect risk factors in an Irish population.

BACKGROUND: Decreased maternal folate levels are associated with having a child with a neural tube defect (NTD), and periconceptual folic acid supplementation reduces this risk by >50%. Vitamin B(12) (as methylcobalamin) is a cofactor for methionine synthase, an enzyme that plays a key role in folate metabolism. Alterations in vitamin B(12) metabolism may influence the development of NTDs. Low levels of maternal plasma vitamin B(12) and reduced binding of vitamin B(12) by transcobalamin II (TCII) are independent risk factors for NTDs. TCII levels are altered in the amniotic fluid of pregnancies affected by NTDs. Given this evidence, inherited variants in genes involved in vitamin B(12) trafficking such as TCII are candidate NTD risk factors. METHODS: We used case/control and family-based association methods to investigate whether six common polymorphisms in the TCII gene influence NTD risk. TCII genotypes were determined for more than 300 Irish NTD families and a comparable number of Irish controls. RESULTS: Allele and genotype frequencies for each polymorphism did not differ between family members and controls. CONCLUSIONS: These six TCII polymorphisms do not strongly influence NTD risk in the Irish population. The Supplementary Material for this article can be found on the Birth Defects Research (Part A) website: http://www.mrw.interscience.wiley.com/suppmat/1542-0752/suppmat/2005/73/v73.4.swanson.html

Alleles↗

PubMed2005

A polymorphism in the MTHFD1 gene increases a mother's risk of having an unexplained second trimester pregnancy loss.

Low maternal folate or vitamin B12 status has been implicated in numerous pregnancy complications including spontaneous abortion. The primary aim of this study was to test a polymorphism within the trifunctional folate enzyme MTHFD1 (5,10-methylenetetrahydrofolate dehydrogenase, 5,10-methenyltetrahydrofolate cyclohydrolase, 10-formyltetrahydrofolate synthetase) for an association with a mother's risk of having an unexplained second trimester pregnancy loss. We genotyped 125 women who had at least one unexplained spontaneous abortion or intrauterine fetal death between 13 and 26 weeks gestation and 625 control women with no history of prior pregnancy loss. Our study is the first to identify an association between the MTHFD1 1958G-->A (R653Q) polymorphism and the maternal risk of having an unexplained second trimester pregnancy loss. Women who are MTHFD1 1958AA homozygous have a 1.64-fold increased risk of having an unexplained second trimester loss compared to women who are MTHFD1 1958AG or 1958GG [OR 1.64 (1.05-2.57), P = 0.03]. It has been reported that polymorphisms in 5,10-methylenetetrahydrofolate reductase (MTHFR), 677C-->T (A222V), transcobalamin II (TCII), 776C-->G (P259R), are associated with pregnancy loss. Both variants were tested in this study. Neither showed evidence of significantly affecting the maternal risk of having a second trimester pregnancy loss. In conclusion, the MTHFD1 1958AA genotype may be an important maternal risk factor to consider during pregnancy.

Aborted Fetus↗

PubMed2003

Analysis of the MTHFR 1298A-->C and 677C-->T polymorphisms as risk factors for neural tube defects.

The thermolabile variant (677TT) of methylenetetrahydrofolate reductase (MTHFR) is a known risk factor for neural tube defects (NTDs). The relationship between a second MTHFR polymorphism (1298A-->C) and NTD risk has been inconsistent between studies. We genotyped 276 complete NTD triads (mother, father and child affected with an NTD) and 256 controls for MTHFR 1298A-->C. Our findings do not support a role for the 1298A-->C polymorphism in NTDs (OR 0.85 (95% CI 0.49-1.47), p= 0.55), nor do we observe a combined effect with the 677C-->T polymorphism.

Case-Control Studies↗

PubMed2003

Polymorphisms within the vitamin B12 dependent methylmalonyl-coA mutase are not risk factors for neural tube defects.

Methionine synthase and methylmalonyl-CoA mutase (mutase) are the only two known vitamin B(12) (B(12)) dependent enzymes in humans. A lower level of B(12) has been shown to be an independent maternal risk factor for neural tube defects (NTDs) prompting an investigation of common genetic variants within B(12) dependent enzymes. To investigate the role of methylmalonyl-CoA mutase variants we studied 279 complete NTD triads (NTD affected case and both parents) and 256 controls. Based on case-control and family based (transmission disequilibrium test) analyses we did not find an association between the mutase single nucleotide polymorphisms (SNPs) K212K (636A-->G), H532R (1595A-->G) and V671I (2011G-->A) and NTDs. However, there was a significant difference in the frequencies of these polymorphisms between a group of African Americans and American Caucasians (K212K, P=0.002; H532R, P</=0.001; V671I, P=0.006). In conclusion, common variants in the mutase gene do not appear to be risk factors for NTDs but their allele frequencies are significantly different between ethnic groups.

Case-Control Studies↗

PubMed2003

Analysis of the human folate receptor beta gene for an association with neural tube defects.

The folate receptor beta (FRbeta) gene encodes a receptor that binds and transports 5-methyltetrahydrofolate. FRbeta polymorphisms may potentially alter folate delivery and are likely candidates for an association with neural tube defect (NTD) risk. To look for association between FRbeta polymorphisms we studied NTD-affected children and their parents (254 triads) recruited throughout Ireland and a control population of 296 pregnant women who did not give birth to an NTD-affected child. Five potential single nucleotide polymorphisms (SNPs) were examined. These were located within the coding, intronic and 3(')-untranslated regions of the FRbeta gene. Four of these SNPs were not found to be variable within our Irish cohort. SNP rs651646 (A-->T), located upstream of exon 2 within an intronic region, is polymorphic and is thus a marker for an FRbeta NTD association study. The frequency of the SNP rs651646 "A" allele was not significantly different in cases (odds ratio [OR] 1.07, 95% CI. 0.84-1.36; P=0.60), their mothers (odds ratio [OR] 1.09, 95% CI. 0.86-1.38; P=0.51) or fathers (odds ratio [OR] 1.09, 95% CI. 0.86-1.38; P=0.50) when compared to controls. Comparisons of allele transmission from 255 informative heterozygous parents of NTD cases showed no preferential transmission of either the A or T alleles (A: 50.2%, n=128; T: 49.8%, n=127; P=1.00, McNemar chi(2) 0.0). We also measured allele frequencies in a sample of American-Caucasians and African-Americans. Highly significant allele frequency differences were observed between populations. In conclusion, SNP rs651646 within the FRbeta gene is polymorphic but is not associated with neural tube defects within the Irish population.

3' Untranslated Regions↗

PubMed2002

A polymorphism, R653Q, in the trifunctional enzyme methylenetetrahydrofolate dehydrogenase/methenyltetrahydrofolate cyclohydrolase/formyltetrahydrofolate synthetase is a maternal genetic risk factor for neural tube defects: report of the Birth Defects Research Group.

Women who take folic acid periconceptionally reduce their risk of having a child with a neural tube defect (NTD) by >50%. A variant form of methylenetetrahydrofolate reductase (MTHFR) (677C-->T) is a known risk factor for NTDs, but the prevalence of the risk genotype explains only a small portion of the protective effect of folic acid. This has prompted the search for additional NTD-associated variants in folate-metabolism enzymes. We have analyzed five potential single-nucleotide polymorphisms (SNPs) in the cytoplasmic, nicotinamide adenine dinucleotide phosphate-dependent, trifunctional enzyme methylenetetrahydrofolate dehydrogenase/methenyltetrahydrofolate cyclohydrolase/formyltetrahydrofolate synthetase (MTHFD1) for an association with NTDs in the Irish population. One SNP, R653Q, in this gene appears to be associated with NTD risk. We observed an excess of the MTHFD1 "Q" allele in the mothers of children with NTD, compared with control individuals. This excess was driven by the overrepresentation of QQ homozygotes in the mothers of children with NTD compared with control individuals (odds ratio 1.52 [95% confidence interval 1.16-1.99], P=.003). We conclude that genetic variation in the MTHFD1 gene is associated with an increase in the genetically determined risk that a woman will bear a child with NTD and that the gene may be associated with decreased embryo survival.

Aminohydrolases↗

PubMed2002

Gene expression differences between the microsatellite instability (MIN) and chromosomal instability (CIN) phenotypes in colorectal cancer revealed by high-density cDNA array hybridization.

Two distinct pathways of tumorigenesis exist in sporadic colorectal cancer. The microsatellite instability pathway (MIN), which is characterized by widespread microsatellite instability due to aberrant mismatch repair machinery, accounts for 15% of all sporadic colorectal cancers. The chromosomal instability (CIN) phenotype, which accounts for 85% of sporadic colorectal cancers, is characterized by gross chromosomal lesions but the underlying mechanism remains unclear. We have addressed differences in gene expression between the MIN and CIN colorectal cancer phenotypes in vitro by the use of high density cDNA filters to compare gene expression patterns between MIN and CIN colorectal cancer cell-lines yielding a panel of 73 consistently differentially expressed genes. Nine of these genes were subjected to confirmatory analysis by independent methods, of which six were confirmed as being differentially expressed; PLK, RanBP2 and CCNA2 were overexpressed in CIN lines while BTF3, H2AZ and PTPD1 were overexpressed in MIN lines. These six genes are involved in diverse processes, such as maintenance of chromatin architecture, DNA-damage checkpoint and cell cycle regulation, which may contribute to the CIN and MIN phenotypes.

Adenocarcinoma↗

PubMed2002

MTRR and MTHFR polymorphism: link to Down syndrome?

Polymorphisms in genes encoding the folate metabolizing enzymes methylenetetrahydrofolate reductase (MTHFR C677T) and methionine synthase reductase (MTRR A66G) have been linked to the etiology of Down syndrome. We examined the prevalence of these variant genotypes in mothers who had given birth to a child with Down syndrome (n = 48) and in control mothers (n = 192), and investigated the biochemical factors influenced by the presence of MTRR A66G and MTHFR C677T. The frequency of the MTRR variant genotypes (AG, GG) was significantly higher in mothers of children with Down syndrome compared to controls (P = 0.0028). MTHFR C677T genotype frequencies were not significantly altered in mothers of children with Down syndrome (P = 0.74). However, mothers who had a MTHFR CT or TT genotype and a MTRR GG genotype had a 2.98-fold increased risk of having a child with Down syndrome (P = 0.02). The MTRR polymorphism did not increase plasma homocysteine. Higher homocysteine was found with the presence of the MTHFR T allele. In conclusion, MTRR A66G is significantly more common in mothers of children with Down syndrome but does not appear to increase the risk for Down syndrome by changing homocysteine metabolism. Women who have both the MTRR and MTHFR variant genotypes are also at increased risk of producing offspring with Down syndrome.

Alleles↗