Association of the C677T and A1298C polymorphisms of methylenetetrahydrofolate reductase gene with schizophrenia: association is significant in men but not in women

Association between variants of MTHFR genes and psychiatric disorders: A meta-analysis

Background

Psychiatric disorders have seriously affected human life, one of the risk genes related to psychosis is the methylenetetrahydrofolatereductase (MTHFR) gene. This gene has a potential role in psychiatric disorders. Therefore, a meta-analysis is conducted to investigate the correlations between two prevalent MTHFR single nucleotide polymorphisms (SNPs), MTHFR C677T, A1298C, severe psychological disorders (schizophrenia, major depression, bipolar disorder).

Methods

A total of 81 published studies were screened and selected by a search of electronic databases up to April 2022. Odds ratios (ORs) with 95% confidence intervals (CIs) were used to assess the association between MTHFR polymorphism and psychiatric disorders susceptibility by using random effect models.

Results

We found that MTHFR C677T polymorphism is significantly related to schizophrenia and major depression in the overall population. MTHFR C677T has been linked to an increased risk of bipolar disorder in the recessive model (TT vs. CT + CC). Ethnic subgroup analysis shows that schizophrenia and major depression significantly correlate with MTHFR C677T and A1298C in Asian populations but not Caucasians. Besides, schizophrenia is correlated substantially with MTHFR C677T in the African population. However, the MTHFR A1298C polymorphism is only marginally linked to major depression.

Conclusion

Findings of the current study revealed that MTHFR may contribute to the common pathogenesis of psychiatric diseases and that its variants may be essential in controlling the expression of psychosis-related genes. This study could help the researchers and health specialists in the early diagnosis and treatment of psychiatric disorders.

Association between MTHFR (677C>T and 1298A>C) polymorphisms and psychiatric disorder: A meta-analysis

Recent studies showed that genetic polymorphism of 5,10-methylenetetrahydrofolate reductase (MTHFR) is related to attention-deficit hyperactivity disorder (ADHD), bipolar disorder (BD) and schizophrenia (SCZ). However, no consistent conclusion has been determined. This meta-analysis aims to interrogate the relationship between MTHFR gene polymorphisms (677C>T and 1298A>C) and the occurrence of ADHD, BD and SCZ. We retrieved case-control studies that met the inclusion criteria from the PubMed database. Associations between MTHFR polymorphisms (677C>T and 1298A>C) and ADHD, BD and SCZ were measured by means of odds ratios (ORs) using a random effects model and 95% confidence intervals (CIs). Additionally, sensitivity analysis and publication bias were performed. After inclusion criteria were met, a total of five studies with ADHD including 434 cases and 670 controls, 18 studies with BD including 4167 cases and 5901 controls and 44 studies with SCZ including 16,098 cases and 19913 controls were finally included in our meta-analysis. Overall, our meta-analytical results provided evidence that the MTHFR 677C>T was associated with occurrence of BD and SCZ, while the 1298A>C polymorphism was related to ADHD and BD, and additionally the sensitivity analysis indicated these results were stable and reliable. This may provide useful information for relevant studies on the etiology of psychiatric disorders.

Pharmacodynamic Gene Testing in Prader-Willi Syndrome

Prader-Willi syndrome (PWS) is a rare genetic disorder with a complex neurobehavioral phenotype associated with considerable psychiatric co-morbidity. This clinical case series, for the first time, describes the distribution and frequency of polymorphisms of pharmacodynamic genes (serotonin transporter, serotonin 2A and 2C receptors, catechol-o-methyltransferase, adrenergic receptor 2A, methylene tetrahydrofolate reductase, and human leucocytic antigens) across the two major molecular classes of PWS in a cohort of 33 referred patients who met medical criteria for testing. When results were pooled across PWS genetic subtypes, genotypic and allelic frequencies did not differ from normative population data. However, when the genetic subtype of PWS was examined, there were differences observed across all genes tested that may affect response to psychotropic medication. Due to small sample size, no statistical significance was found, but results suggest that pharmacodynamic gene testing should be considered before initiating pharmacotherapy in PWS. Larger scale studies are warranted.

Distribution of 1298A > C polymorphism of methylenetetrahydrofolate reductase gene in patients with bipolar disorder and schizophrenia

We investigated the genotype frequency of methylenetetrahydrofolate reductase (MTHFR) 1298A > C polymorphism in the group of patients with bipolar disorder type I (BDI) (n = 200) and schizophrenia (n = 200) and in the control group (n = 300). Odds ratio (OR) for patients with BD and schizophrenia in 1298CC homozygous state was 3.768 (95% CI = 1.752–8.104); P = 0.0003; (P = 0.0006 after Bonferroni correction) and 2.694; (95% CI = 1.207–6.013); P = 0.0123 (P = 0.0246 after Bonferroni correction), respectively. The stratification of patients based on gender revealed significant association of 1298CC genotype with female patients only with BDI (OR = 7.293; 95% CI = 2.017–26.363; P = 0.0005).

Our results confirm association of BD and schizophrenia with the 1p36.3 MTHFR locus and with the methyl group transfer using folate-dependent one-carbon pathway.

Female gender specific association of the Reelin (RELN) gene rs7341475 variant with schizophrenia

RELN gene encodes a large extracellular matrix protein which is critical for neuronal migration, cell positioning and cell-cell interactions. It also controls the synaptic plasticity of neurons for initiation and maintenance of long term potentiation. The aim of this study is to investigate the association of RELN rs7341475 variant with schizophrenia. Genomic DNA isolation was performed from 105 schizophrenic patients and 137 healthy controls to determine RELN rs7341475 genotypes. Genotype and allele frequencies were determined by a polymerase chain reaction-restriction fragment length polymorphism method developed in our laboratory. Statistical analysis was performed using χ² test. The frequencies for G allele were 79.5% in cases and 81.0% in controls, for A allele 20.5% in cases and 19.0% in controls in the overall population. The genotype frequencies of the RELN gene rs7341475 variant were GG; 63.8%, GA; 31.4% and AA; 4.8% in cases, GG; 63.5%, GA; 35.0% and AA; 1.5% in controls in the overall population. There was no statistically significant association between the rs7341475 variant of RELN gene and schizophrenia in the overall population (χ² = 2.473, p = 0.290). In the gender specific analysis, female gender specific association was only found. The RELN rs7341475 variant GG genotype was significantly associated with schizophrenia (p = 0.034, OR 2.760, 95% CI 1.058-7.197) and A allele was protective against schizophrenia (p = 0.034, OR 0.362, 95% CI 0.139-0.945). All cases and controls were in Hardy-Weinberg equilibrium (p > 0.05). Population size can be increased to improve the statistical power. Moreover, other RELN gene variants which are especially involved in neuronal migration and epigenetic regulation may be analyzed for revealing the complex genetic architecture of schizophrenia. In conclusion, there was only association between the RELN rs7341475 variant and schizophrenia in the female gender in a Turkish population.

Haplotypic and Genotypic Association of Catechol-O-Methyltransferase rs4680 and rs4818 Polymorphisms and Treatment Resistance in Schizophrenia

Treatment-resistant schizophrenia (TRS) continues to be a challenge. It was related to different factors, including alterations in the activity of brain dopaminergic system, which could be influenced by the dopamine-degrading enzyme, catechol-O-methyltransferase (COMT). Variants of the COMT gene have been extensively studied as risk factors for schizophrenia; however, their association with TRS has been poorly investigated. The aim of the present study was to determine the haplotypic and genotypic association of COMT rs4680 and rs4818 polymorphisms with the presence of TRS. Overall, 931 Caucasian patients diagnosed with schizophrenia (386 females and 545 males) were included, while 270 participants met the criteria for TRS. In males, no significant haplotypic and genotypic associations between COMT rs4680 and rs4818 polymorphisms and TRS were detected. However, genotypic analyses demonstrated higher frequency of COMT rs4680 AA genotype carriers compared to G-allele carriers (p = 0.033) and higher frequency of COMT rs4818 CC genotype carriers than G-allele carriers (p = 0.014) in females with TRS. Haplotype analyses confirmed that the presence of the G allele in females was associated with lower risk of TRS. In women with TRS, the high activity G-G/G-G haplotype was rare, while carriers of other haplotypes were overrepresented (p = 0.009). Such associations of COMT rs4680 and rs4818 high-activity (G variants), as well as G-G/G-G haplotype, with the lower risk of TRS in females, but not in males, suggest significant, but sex-specific influence of COMT variants on the development of treatment-resistance in patients with schizophrenia. However, due to relatively low number of females, those findings require replication in a larger sample.

Association study of methylenetetrahydrofolate reductase genetic polymorphism 677C>T with schizophrenia in hospitalized patients in population of European Russia

The purpose of the research was to investigate the association of methylenetetrahydrofolate reductase (hereinafter MTHFR) genetic polymorphism 677C>T with schizophrenia in the Russian population in comparison with the control group of healthy blood donors. Also some characteristics of schizophrenia were examined in patients with/without defective T-allele of MTHFR677C>T polymorphism. 500 patients with schizophrenia and 499 blood donors were examined for T-allele carriage of polymorphism MTHFR677C>T by PCR method. 150 archival medical records were studied (in the first patients included in the study). The carriage of T-allele of genetic polymorphism MTHFR677C>T was significantly more common in patients than in healthy donors: 255/500 versus 219/499 (p=0,0287, χ2=4,79; OR=1,33, 95%CI [1037; 1707]). The number of patients with chronic type of schizophrenia onset was significantly more among T-allele carriers (n=77) than among normal CC-genotype carriers (n=73): р=0.038. The number of "incapacitated" persons in the group of patients with defective T-allele (n=77) was significantly higher than in patients with normal genotype (n=73, p=0.0439; OR=2.878, 95%CI=1.111-7.456). The results suggest that T-allele of genetic polymorphism MTHFR677C>T in the population of European Russia may increase the risk of developing schizophrenia and its unfavorable prognosis, which requires further investigation.

Nicotinamide-N-Methyltransferase gene rs694539 variant and migraine risk

Background

Migraine is a common neurovascular disorder affecting 10 to 20 % of the world population usually subdivided into migraine with auro (MA) and migraine without auro (MO). Homocysteine is involved in the pathophysiology of a number of neurological disorders. Elevated levels of homocysteine in the plasma is produced by the MTHFR gene rs 1801133 and rs 1801131 variants as well as the NNMT gene rs 694539 variant.

Methods

With the polymerase chain reaction-restriction fragment length polymorphism method developed recently in our laboratory, we were able to show an association between the NNMT gene rs694539 variant and migraine for the first time.

Results

Here we report the association of the Nicotinamide-N-methyltransferase gene (NNMT) rs694539 variant with migraine in a case–control study of 433 patients with migraine and 229 healthy controls (χ2 = 6.076, P = 0.048). After stratification, we were able only to show an association between the NNMT gene rs694539 variant and female patients with migraine on the genotype and allelic levels. However there was no association in male patients with migraine (χ2 = 1.054, P = 0.590).

Conclusions

Consequently our results clearly indicate that the NNMT gene rs694539 variant is a genetic risk factor for migraine.

Role of MTHFR C677T gene polymorphism in the susceptibility of schizophrenia: An updated meta-analysis

Methylenetetrahydrofolate reductase (MTHFR) is the key enzyme of folate/homocysteine metabolic pathway. C677T polymorphism of MTHFR gene was reported as risk factor for congenital defects, metabolic and neuropsychiatric disorders. Numerous case-control studies investigated C677T polymorphism as risk factor for schizophrenia but results of these studies were contradictory. To draw a conclusion, a meta-analysis of all available case-control studies was performed. PubMed, Google Scholar, Springer Link and Elsevier databases were searched for eligible case-control studies. Pooled odds ratio with 95%CI was used as an association measure and all statistical analyses were performed by Open Meta-Analyst and MIX software. Total 38 studies with 10,069 cases and 13,372 controls were included in the present meta-analysis. Results of meta-analysis showed significant associated between C677T polymorphism and risk of schizophrenia (ORTvsC=1.18, 95%CI=1.10-1.27, p=<0.001; ORCTvsCC=1.10, 95%CI=1.04-1.17, p=<0.001; ORTTvsCC=1.40, 95%CI=1.20-1.64, p=<0.001; ORTT+CTvsCC=1.19, 95%CI=1.09-1.30, p=<0.001). We also performed subgroup and sensitivity analyses. Subgroup analysis was done according to ethnicity and significant association was found between C677T polymorphism and risk of schizophrenia in all three ethnic populations-African (OR=2.51; 95%CI=1.86-3.40; p=<0.001), Asian (OR=1.21; 95%CI=1.10-1.33; p=<0.001) and Caucasian (OR=1.07; 95%CI=1.01-1.14; p=0.01). In conclusion the results of the present meta-analysis suggested that the MTHFR C677T polymorphism is a risk factor for schizophrenia.

Association of Nicotinamide-N-Methyltransferase Gene rs694539 Variant with Epilepsy

Here, we report the association of the rs694539 variant of nicotinamide-N-methyltransferase gene with epilepsy in a case-control study of 215 patients with epilepsy and 239 healthy controls (χ (2) = 11.641, P = 0.003). The individuals with the GG genotype revealed protection against epilepsy (χ (2) = 5.866, P = 0.015, OR = 0.623, 95 % CI = 0.425-0.915), whereas the individuals with the AA genotype showed statistically significant increased risk for epilepsy (χ (2) = 8.676, P = 0.003, OR = 5.479, 95 % CI = 1.553-19.337). In addition, the G allele was protective against epilepsy (χ (2) = 8.676, P = 0.003, OR = 0.183, 95 % CI = 0.052-0.644); on the contrary, the A allele was a genetic risk factor for epilepsy (χ (2) = 5.866, P = 0.015, OR = 1.604, 95 % CI = 1.093-2.354). Stratification analysis revealed that the association was statistically significant in male patients with epilepsy (χ (2) = 6.682, P = 0.035). However, the statistical power was only 0.33 in female patients with epilepsy (χ (2) = 5.275, P = 0.072). This finding, for the first time, suggests the involvement of the NNMT gene rs694539 variant in the etiology of epilepsy.

Evaluation of an association between plasma total homocysteine and schizophrenia by a Mendelian randomization analysis

BACKGROUND

The results of meta-analyses conducted by previous association studies between total homocysteine and schizophrenia suggest that an elevated total homocysteine level is a risk factor for schizophrenia. However, observational studies have potential limitations, such as confounding and reverse causation. In the present study, we evaluated a causal relationship between plasma total homocysteine and schizophrenia by conducting a Mendelian randomization analysis.

METHODS

We used the MTHFR C677T polymorphism as an instrumental variable, which affects the plasma total homocysteine levels. To calculate the risk estimate for the association of this single nucleotide polymorphism (SNP) with schizophrenia, we conducted a meta-analysis of case-control studies that comprise a total of 11,042 patients with schizophrenia and 14,557 control subjects. We obtained an estimate for the association of this SNP with the plasma total homocysteine levels from a meta-analysis of genome-wide association studies comprising 44,147 individuals.

RESULTS

By combining these two estimates, we demonstrated a significant effect of the plasma total homocysteine on schizophrenia risk, representing an OR of 2.15 (95 % CI = 1.39-3.32; p = 5.3 x 10(-4)) for schizophrenia per 1-SD increase in the natural log-transformed plasma total homocysteine levels.

CONCLUSIONS

We provided evidence of a causal relationship between the plasma total homocysteine and schizophrenia, and this result will add insight into the pathology and treatment of schizophrenia.

Methylenetetrahydrofolate reductase (MTHFR) polymorphism susceptibility to schizophrenia and bipolar disorder: an updated meta-analysis

Previous studies examining the possible role of the methylenetetrahydrofolate reductase (MTHFR) polymorphisms in the development of schizophrenia (SZ) and bipolar disorder (BPD) have provided inconclusive findings, this meta-analysis was therefore designed to get a more reliable assessment. A total of 38 articles were identified through a search of electronic databases, up to 27 February 2014. Odds ratios (ORs) with 95% confidence interval (CIs) were calculated using random effects models. Meta-analysis showed that MTHFR C677T was significantly associated with SZ, the highest OR was found for the recessive model (for TT vs. CT + CC: OR = 1.34, 95% CI: 1.18-1.53); a marginal association of MTHFR C677T with increased risk of BPD has also been found for the recessive model (OR = 1.26, 95% CI: 1.00-1.59). Subgroup analysis by ethnicity indicated that the significant association with SZ and BPD existed among Asian and African populations, but not for the white. MTHFR A1298C was significant associated with SZ, the highest OR for the dominant model (OR = 1.13, 95% CI: 1.03-1.24). Subgroup analysis indicated a significant association with SZ existed in Asian populations, not among the white populations and no significant association was detected between the MTHFR A1298C and BPD in all groups. We conclude that MTHFR polymorphism is associated with SZ and BPD among Asian, African populations, but not the white.

Association of nicotinamide-N-methyltransferase (NNMT) gene rs694539 variant with bipolar disorder

Here we report the association of the rs694539 variant of nicotinamide-N-methyltransferase gene with bipolar disorder in a case-control study of 95 bipolar disorder patients and 201 healthy controls (χ(2)=13.382, P=0.001). With the polymerase chain reaction restriction fragment length polymorphism method we developed we were able to show the association for the first time. This new finding may provide evidence to understand the mechanism of the disease.

Association of MTHFR C677T polymorphism with schizophrenia and its effect on episodic memory and gray matter density in patients

Growing evidence suggests that the methylenetetrahydrofolate reductase (MTHFR) may play a role in the pathogenesis of schizophrenia. Recent studies suggested that the MTHFR 677T, as a risk allele, has an impact on brain activation and memory function in schizophrenia patients. To confirm further the association between this functional polymorphism and schizophrenia, we detected genotypes of MTHFR C677T polymorphism in 1002 schizophrenic patients and 1036 controls of Chinese Han population, by using direct DNA sequencing method. To explore further effects of MTHFR C677T polymorphism on memory and brain function in schizophrenia, 33 schizophrenia patients and 29 healthy participants were selected from above samples to be assessed with MRI scanning and episodic memory (EM) examination. The case-control association study results showed that the MTHFR C677T was associated with schizophrenia (χ(2)=14.11, P=1.74 × 10(-4), OR=0.79; 95% CI=0.70-0.89). We also found that the MTHFR 677T allele had a load-dependent effect on EM in schizophrenic patients, but not in healthy control participants. Further analysis on gray matter density (GMD) revealed significant diagnostic effects in bilateral frontal cortices, bilateral insula, left medial temporal cortex and bilateral occipital cortices, effects of MTHFR genotype in the right insula, right inferior frontal gyrus, right rolandic opercula, right parahippocampal gyrus and right medial temporal pole, and effects of genotype-diagnosis interaction in the right temporal gyrus. Our findings suggested that the MTHFR 677T allele might have effect on risk of schizophrenia, memory impairment and GMD changes in patients.

Association between MTHFR C677T and A1298C, and MTRR A66G polymorphisms and susceptibility to schizophrenia in a Syrian study cohort

The folate-homocystiene metabolic pathway has been shown to be involved in the susceptibility for developing schizophrenia by several studies. In the present study we investigated the role of three common polymorphisms of the folate-homocysteine metabolic pathway in an Arab population from Syria consisting of 85 schizophrenic patients and 126 healthy controls. The studied polymorphisms included the MTHFR C677T and A1298C, and MTRR A66G, all of which result into amino acid changes, and were previously shown to yield decreased enzymatic activity and alter plasma homocysteine concentration. While MTHFR C677T and A1298C polymorphisms were not previously studied in an Arab population with respect to the susceptibility for developing schizophrenia, the MTRR A66G was not previously investigated in any population around the world. Our results indicated a strong association between MTHFR A1298C and schizophrenia. The variant C allele frequency was significantly higher in the patients group (40% vs 29.4%, OR=1.6, 95% CI (1.06-2.41), p=0.023). A statistically significant association was found for MTHFR 677TT genotype under the recessive model in the male patients subgroup (OR=2.6, 95% CI (1.04-6.5), p=0.036), and MTHFR 677CT genotype under the overdominant model in the total patients group (OR=0.52 95% CI (0.29-0.92), p=0.024). No statistically significant association was found for MTRR A66G polymorphism on an individual basis. However, a borderline association was found for the CC/GG (C677T/A66G) compound genotype (OR=2.24, 95% CI (0.97-5.15), p=0.053). Our results support the hypothesis of association between schizophrenia and folate-homocystiene metabolic pathway genes.

Gender-specific association of methylenetetrahydrofolate reductase gene polymorphisms with sporadic amyotrophic lateral sclerosis

Studies have revealed that elevated homocysteine levels can cause damage to motor neurons through multiple neurotoxic mechanisms, thus leading to the pathogenesis of amyotrophic lateral sclerosis (ALS). One way by which homocysteine levels are increased in the body is the consequence of methylenetetrahydrofolate reductase (MTHFR) gene polymorphisms. Therefore, to address this question, we studied the MTHFR C677T and A1298C polymorphisms in 437 sporadic ALS (SALS) and 439 healthy controls to learn whether they were associated with SALS. The overall SALS were not associated with MTHFR C677T and A1298C polymorphisms (χ(2)=1.378; p=0.502; χ(2)=1.304; p=0.521, respectively). However, when we stratified results in terms of gender, we found that the MTHFR C677T polymorphism (χ(2)=6.376; p=0.041), T677T genotype (χ(2)=5.508; p=0.019; odds ratio [OR]=2.561; 95% confidence interval [CI]=1.142-5.744), C677C/A1298A (χ(2)=5.216; p=0.022; OR=0.424, 95% CI=0.199-0.900), and T677T/A1298A (χ(2)=6.639; p=0.010; OR=2.900; 95% CI=1.252-6.717) compound genotypes were associated with SALS in female patients only. Moreover, stratification of SALS according to the onset of disease indicated that there was no association between MTHFR C677T (χ(2)=1.565; p=0.457; A1298C χ(2)=3.461; p=0.177) polymorphisms and overall spinal onset SALS. Further stratification analysis according to gender revealed that there was a remarkable association between MTHFR C677T (χ(2)=9.728, p=0.008), T677T genotype (χ(2)=7.820; p=0.005; OR=3.126; 95% CI=1.361-7.178) and T allele (χ(2)=5.000; p=0.025; OR=1.711; 95% CI=1.067-2.745), and T677T/A1298A compound genotype (χ(2)=9.108; p=0.003; OR=3.540; 95% CI=1.494-8.387) and spinal onset female SALS only. Likewise, there was also association between MTHFR A1298C polymorphism (χ(2)=5.946; p=0.051) and the C1298C genotype (χ(2)=5.282; p=0.022; OR=2.524; 95% CI=1.125-5.658), and the C677T/C1298C compound genotype (χ(2)=7.155; p=0.007; OR=1.045; 95% CI=0.983-1.112) and bulbar onset SALS only in women. In conclusion, the evidence we provide here clearly shows that MTHFR C677T and A1298C polymorphisms are genetic risk factors for SALS in women in a gender-specific manner whether they are of spinal or bulbar onset.

Meta-analysis of MTHFR gene variants in schizophrenia, bipolar disorder and unipolar depressive disorder: evidence for a common genetic vulnerability?

Past analyses examining the relationship between genetic variation in the 5, 10-methylenetetrahydrofolate reductase (MTHFR) gene and psychiatric disorders have provided mixed and largely inconclusive findings. MTHFR is involved in the one-carbon metabolic pathway which is essential for DNA biosynthesis and the epigenetic process of DNA methylation. We conducted a meta-analysis of all published case-control studies investigating associations between two common MTHFR single nucleotide polymorphisms (SNPs), MTHFR C677T (sample size 29,502) and A1298C (sample size 7934), and the major psychiatric disorders (i) schizophrenia (SZ), (ii) bipolar disorder (BPD), and (iii) unipolar depressive disorder (UDD). In order to examine possible shared genetic vulnerability, we also tested for associations between MTHFR and all of these major psychiatric disorders (SZ, BPD and UDD) combined. MTHFR C677T was significantly associated with all of the combined psychiatric disorders (SZ, BPD and UDD); random effects odds ratio (OR)=1.26 for TT versus CC genotype carriers; confidence interval (CI) 1.09-1.46); meta-regression did not suggest moderating effects of psychiatric diagnosis, sex, ethnic group or year of publication. Although MTHFR A1298C was not significantly associated with the combination of major psychiatric disorders, nor with SZ, there was evidence for diagnostic moderation indicating a significant association with BPD (random effects OR=2.03 for AA versus CC genotype carriers, CI: 1.07-3.86). Meta-analysis on UDD was not possible due to the small number of studies available. This study provides evidence for shared genetic vulnerability for SZ, BPD and UDD mediated by MTHFR 677TT genotype, which is in line with epigenetic involvement in the pathophysiology of these psychiatric disorders.

No association of functional polymorphisms in methlylenetetrahydrofolate reductase and the risk and minor physical anomalies of schizophrenia in Korean population

Methylenetetrahydrofolate reductase (MTHFR), a critical enzyme in folate metabolism, plays an important role in DNA methylation. It has been suggested that abnormal DNA methylation contributes to the pathogenesis of schizophrenia and congenital anomalies. The previous findings regarding the genetic relationship between MTHFR and schizophrenia are controversial. This study investigated the association of the two functional polymorphisms of MTHFR, C677T and A1298C, with the risk for schizophrenia. Furthermore, we conducted an updated meta-analysis on the two polymorphisms. In addition, we investigated the relationship between the polymorphisms and minor physical anomaly (MPA), which may represent neurodevelopmental aberrations in 201 schizophrenia patients and 350 normal control subjects. There was no significant association between either of the two polymorphisms and the risk of schizophrenia (chi-square = 0.001, df = 1, P = 0.971 for C677T; chi-square = 1.319, df = 1, P = 0.251 for A1298C). However, in meta-analysis, the C677T polymorphism showed a significant association in the combined and Asian populations (OR = 1.13, P = 0.005; OR = 1.21, P = 0.011, respectively) but not in the Korean and Caucasian populations alone. Neither polymorphism was associated with MPAs measured by the Waldrop scale (chi-square = 2.513, df = 2, P = 0.285). In conclusion, the present findings suggest that in the Korean population, the MTHFR polymorphisms are unlikely to be associated with the risk for schizophrenia and neurodevelopmental abnormalities related to schizophrenia.

Methylenetetrahydrofolate reductase gene polymorphisms in Turkish children with attention-deficit/hyperactivity disorder

Attention-deficit/hyperactivity disorder (ADHD) is a common, multifactorial genetic disorder. The aim of the present study was to evaluate a possible association between 5,10-methylenetetrahydrofolate reductase (MTHFR) gene polymorphisms and ADHD. There is evidence to suggest that MTHFR C677T and A1298C polymorphisms alter the function of the enzyme, causing reduced folate and increased homocysteine levels in plasma. Two polymorphisms of the MTHFR gene, C677T (rs1801133) and A1298C (rs1801131), were analyzed in a sample of 100 Diagnostic and Statistical Manual of Mental Disorders-IV-diagnosed ADHD and 300 healthy controls using a polymerase chain reaction-restriction fragment length polymorphism method. We did not find any association between MTHFR 677T allele, MTHFR 1298C allele, and ADHD. In addition, there was no genotype association between the MTHFR gene and ADHD (χ(2)=1.711; df=2; p=0.425; χ(2)=2.946; df=2; p=0.229). Our data suggest that neither the MTHFR C677T polymorphism nor the MTHFR A1298C polymorphism was associated with ADHD in Turkish children. Thus, the MTHFR gene does not seem to play a role in the etiopathogenesis of ADHD in the cohort studied.

Methylenetetrahydrofolate reductase (MTHFR) C677T and A1298C polymorphisms and age of onset in schizophrenia: a combined analysis of independent samples

Methylenetetrahydrofolate reductase (MTHFR) is involved in the one-carbon cycle, which is of importance for nucleotide synthesis and methylation of DNA, membranes, proteins and lipids. The MTHFR gene includes two common polymorphisms (rs1801133 or C677T; rs1801131 or A1298C) which both alter enzyme activity. The T-allele of the C677T polymorphism has recently been associated with earlier age at onset of schizophrenia. In the present study we examined the association between the MTHFR C677T and A1298C polymorphisms and age at onset of schizophrenia in twelve samples consisting of 3,213 unrelated schizophrenia patients, including the original Scandinavian sample. There was no consistent relationship between MTHFR C677T, A1298C or combined 677T/1298C carriers and age of onset in schizophrenia when the results of each study were combined using meta-analysis. The present results suggest that the investigated MTHFR polymorphisms do not influence age of onset in schizophrenia.

Dietary protein and protein-rich food in relation to severely depressed mood: A 10 year follow-up of a national cohort

High-protein diets are advocated to facilitate weight loss, and improve cardiovascular risk factors, but data on psychiatric effects are lacking. We analyzed data from 1947 men and 2909 women aged 25-74 years when examined in 1971-1975 as the baseline of the National Health and Nutrition Examination Follow-Up Study. The amounts of macronutrients were obtained from a 24-hour recall, and frequencies of eating protein-rich foods were estimated using a 3-month food frequency questionnaire. Severely depressed mood (SDM) was defined as Center for Epidemiologic Studies Depression Scale score ≥ 22 or taking anti-depression medication after an average of 10.6 years of follow-up. A significant gender difference was observed in the prevalence of SDM and its association with protein intake. The weighted prevalence of SDM was 11.45 (SE = 0.96) % and 17.45(1.05) % respectively among men and women. Among men, the relative risk (RRs) of SDM were 1.00, 0.46 (95% CI = 0.22-0.99) and 0.38 (0.16-0.92) respectively for the lowest, middle and highest third protein intake (p for trend=0.0347). Among women, the RRs were 1.00, 1.93 (1.23-3.08) and 2.47 (1.24-4.90) respectively with lowest, middle and the highest third intakes (p for trend = 0.0023). These estimates were adjusted for cigarette smoking, alcohol consumption, BMI, socioeconomic status at baseline, and the history of cancer, stroke, heart attack and diabetes assessed at follow-up interview. The authors concluded that increased intake of protein demonstrated a protective effect among men but a deleterious effect among women.

Gene-wide association study between the methylenetetrahydrofolate reductase gene (MTHFR) and schizophrenia in the Japanese population, with an updated meta-analysis on currently available data

Methylenetetrahydrofolate reductase (MTHFR) is a critical molecule for single-carbon transfer reactions. Recent evidence suggests that polymorphisms of MTHFR are related to neural tube deficits and the pathogenesis of schizophrenia. While several studies have demonstrated associations between the gene encoding the MTHFR (MTHFR) polymorphisms and schizophrenia, these studies lack consistency. Therefore, we conducted a gene-wide association study (patients with schizophrenia = 696, control subjects = 747) and performed imputation analysis. Additionally, we performed meta-analysis on currently available data from 18 studies for two common functional polymorphisms (rs1801131 and rs1801133). There were no significant associations with schizophrenia in the single marker analysis for the seven tagging SNPs of MTHFR. In the haplotypic analysis, a nominally significant association was observed between the haplotypes, which included four SNPs (rs1801133, rs17421511, rs17037396, and rs9651118) and the schizophrenic patients. Additionally, the imputation analysis demonstrated there were several associated markers on the MTHFR chromosomal region. However, confirmatory analyses of three tagging SNPs (rs1801133, rs17037396, and rs9651118) and the top SNP (rs17421511) for the imputation results (patients with schizophrenia = 797, control subjects = 1025) failed to replicate the haplotypic analysis and the imputation results. These findings suggest that MTHFR polymorphisms are unlikely to be related to the development of schizophrenia in the Japanese population. However, since our meta-analysis results demonstrated strong support for association of rs1801133 with schizophrenia, further replication studies based on a gene-wide approach need to be considered.

Plasma homocysteine in schizophrenia: determinants and clinical correlations in Tunisian patients free from antipsychotics

The existence of association between hyperhomocysteinaemia (HHC) and schizophrenia has been suggested by several recent studies. This study aimed to determine the prevalence of HHC and its main determinants, and sought a correlation with clinical features in Tunisian patients with schizophrenia. Plasma homocysteine (Hcy), folate, and vitamin B12, as well as the C677T methylene tetrahydrofolate reductase (MTHFR) polymorphism, were studied in 33 patients with schizophrenia, all free from antipsychotic treatment, and 35 age- and smoking-habit-matched healthy subjects as controls. Biochemical determinations and psychometric evaluations were carried out in patients before the administration of antipsychotics. The prevalence of HHC was higher and plasma B12 vitamin was significantly lower in patients. There was no significant difference in genotypic distribution and allelic frequency of the C677T MTHFR polymorphism between groups. Hcy was significantly correlated to the 'anhedonia-asociality' subscales of the Scale for the Assessment of Negative Symptoms (SANS). This study showed an association between HHC and schizophrenia, especially with the negative symptoms of the disease. In the Tunisian population, HHC in schizophrenia seems to be linked to vitamin B12 deficiency, likely caused by a lack of dietary animal proteins.

Folate, homocysteine, interleukin-6, and tumor necrosis factor alfa levels, but not the methylenetetrahydrofolate reductase C677T polymorphism, are risk factors for schizophrenia

The methylenetetrahydrofolate reductase (MTHFR) C677T mutation has been associated to high homocysteine levels and schizophrenia. Since cytokines are altered in schizophrenia and increments of homocysteine could promote an inflammatory response, it was investigated whether interleukin-6 (IL-6) and tumor necrosis factor alfa (TNFalpha) levels are modulated by the MTHFR genotype. Serum levels of TNFalpha, IL-6, B(12), homocysteine, folate and red blood cell (RBC) folate as well as the MTHFR genotype were determined in a group of schizophrenic patients and compared to those of a control group. RBC folate levels were reduced and homocysteine and the two cytokines' concentrations were elevated in all patients as compared to controls. RBC folate in both heterozygous (CT) and homozygous (TT) patients was significantly different to that of their respective control groups. Homocysteine levels found in patients were significantly higher than those found in controls, only in individuals carrying the TT genotype. Cytokine levels were augmented in the group of patients irrespective of the genotype, and significant differences were found in all cases, except for TNFalpha levels in those subjects carrying the CC genotype. After adjusting for sex, low levels of RBC folate, high levels of homocysteine, both medium and high levels of TNFalpha and high IL-6 levels were associated with schizophrenia. MTHFR genotype was not a risk factor for developing the disease, although a larger sample is required to confirm this finding.

Association between methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism and age of onset in schizophrenia

Different lines of evidence indicate that methylenetetrahydrofolate reductase (MTHFR) functional gene polymorphisms, causative in aberrant folate-homocysteine metabolism, are associated with increased vulnerability to several heritable developmental disorders. Opposing views are expressed considering the possible association between MTHFR and susceptibility for schizophrenia. In order to evaluate if age of onset could explain some of this discrepancy we investigated the relationship between two functional MTHFR gene polymorphisms and age at onset in this disorder. Scandinavian patients (n = 820) diagnosed with schizophrenia, schizoaffective disorder, and schizophreniform disorder were investigated. Two functional MTHFR single nucleotide polymorphisms (SNPs; rs1801131 and rs1801133) were genotyped and the effect of MTHFR polymorphisms on the age of onset was examined with survival analysis. In an attempt to replicate the findings from the Scandinavian sample, the association between rs1801133 and age at onset was also analyzed in Chinese high-risk families, with two or more affected siblings (n = 243). Among the Scandinavian patients the functional MTHFR SNP rs1801133 (C677T) significantly affected age at onset of schizophrenia in a dose-dependent manner (P = 0.0015), with lower age of onset with increasing numbers of the mutant T-allele. There was no evidence of rs1801131 (A1298C) affecting age of onset in schizophrenia. Within the Chinese high-risk families carriers of the MTHFR 677T allele showed earlier age at onset than siblings being homozygous for the wild-type allele (P = 0.008). The MTHFR C677T polymorphism may play a role as a modifying factor for age of onset in schizophrenia.

Importance of the COMT gene for sex differences in brain function and predisposition to psychiatric disorders

As outlined elsewhere in this volume, sex differences can affect brain function and its dysfunction in psychiatric disorders. It is known that genetic factors contribute to these sex dimorphisms, but the individual genes have rarely been identified. The catechol-O-methyltransferase (COMT) gene, which encodes an enzyme that metabolises catechol compounds, including dopamine, is a leading candidate in this regard. COMT's enzyme activity, and the neurochemistry and behaviour of COMT knockout mice are both markedly sexually dimorphic. Furthermore, genetic associations between COMT and psychiatric phenotypes frequently show differences between men and women. Although many of these differences are unconfirmed or minor, some appear to be of reasonable robustness and magnitude and are reviewed in this chapter. Sexually dimorphic effects of COMT are usually attributed to transcriptional regulation by oestrogens; however, a careful examination of the literature suggests that additional mechanisms are likely to be at least as important. Here, we review the evidence for a sexually dimorphic influence of COMT upon psychiatric phenotypes and brain function, and discuss potential mechanisms by which this may occur. We conclude that despite the evidence being incomplete, there are accumulating and in places compelling data showing that COMT has markedly sexually dimorphic effects on brain function and its dysfunction in psychiatric disorders. Although oestrogenic regulation of COMT is probably partially responsible for these sex differences, other mechanisms are likely also involved. Since sex differences in the genetic architecture of brain function and psychiatric disorders are the rule not the exception, we anticipate that additional evidence will emerge for sexual dimorphisms, not only in COMT but also in many other autosomal genes.

Catechol-O-methyltransferase (COMT): a gene contributing to sex differences in brain function, and to sexual dimorphism in the predisposition to psychiatric disorders

Sex differences in the genetic epidemiology and clinical features of psychiatric disorders are well recognized, but the individual genes contributing to these effects have rarely been identified. Catechol-O-methyltransferase (COMT), which metabolizes catechol compounds, notably dopamine, is a leading candidate. COMT enzyme activity, and the neurochemistry and behavior of COMT null mice, are both markedly sexually dimorphic. Genetic associations between COMT and various psychiatric phenotypes frequently show differences between men and women. Many of these differences are unconfirmed or minor, but some appear to be of reasonable robustness and magnitude; eg the functional Val(158)Met polymorphism in COMT is associated with obsessive-compulsive disorder in men, with anxiety phenotypes in women, and has a greater impact on cognitive function in boys than girls. Sex-specific effects of COMT are usually attributed to transcriptional regulation by estrogens; however, additional mechanisms are likely to be at least as important. Here we review the evidence for a sexually dimorphic influence of COMT upon psychiatric phenotypes, and discuss its potential basis. We conclude that despite the evidence being incomplete, and lacking a unifying explanation, there are accumulating and in places compelling data showing that COMT differentially impacts on brain function and dysfunction in men and women. Since sex differences in the genetic architecture of quantitative traits are the rule not the exception, we anticipate that additional evidence will emerge for sexual dimorphisms, not only in COMT but also in many other autosomal genes.

Genomic imprinting in the development and evolution of psychotic spectrum conditions

I review and evaluate genetic and genomic evidence salient to the hypothesis that the development and evolution of psychotic spectrum conditions have been mediated in part by alterations of imprinted genes expressed in the brain. Evidence from the genetics and genomics of schizophrenia, bipolar disorder, major depression, Prader-Willi syndrome, Klinefelter syndrome, and other neurogenetic conditions support the hypothesis that the etiologies of psychotic spectrum conditions commonly involve genetic and epigenetic imbalances in the effects of imprinted genes, with a bias towards increased relative effects from imprinted genes with maternal expression or other genes favouring maternal interests. By contrast, autistic spectrum conditions, including Kanner autism, Asperger syndrome, Rett syndrome, Turner syndrome, Angelman syndrome, and Beckwith-Wiedemann syndrome, commonly engender increased relative effects from paternally expressed imprinted genes, or reduced effects from genes favouring maternal interests. Imprinted-gene effects on the etiologies of autistic and psychotic spectrum conditions parallel the diametric effects of imprinted genes in placental and foetal development, in that psychotic spectrum conditions tend to be associated with undergrowth and relatively-slow brain development, whereas some autistic spectrum conditions involve brain and body overgrowth, especially in foetal development and early childhood. An important role for imprinted genes in the etiologies of psychotic and autistic spectrum conditions is consistent with neurodevelopmental models of these disorders, and with predictions from the conflict theory of genomic imprinting.

Two methylenetetrahydrofolate reductase gene (MTHFR) polymorphisms, schizophrenia and bipolar disorder: an association study

Recent meta-analyses of the methylenetetrahydrofolate reductase gene (MTHFR) have suggested association between two of its functional single gene polymorphisms (SNPs; C677T and A1298C) and schizophrenia. Studies have also suggested association between MTHFR C677T and A1298C variation and bipolar disorder. In a replication attempt the MTHFR C677T and A1298C SNPs were analyzed in three Scandinavian schizophrenia case-control samples. In addition, Norwegian patients with bipolar disorder were investigated. There were no statistically significant allele or genotype case-control differences. The present Scandinavian results do not verify previous associations between the putative functional MTHFR gene polymorphisms and schizophrenia or bipolar disorder. However, when combined with previous studies in meta-analyses there is still evidence for association between the MTHFR C677T polymorphism and schizophrenia. Additional studies are warranted to shed further light on these relationships.

Methylenetetrahydrofolate reductase gene polymorphisms in patients with nonalcoholic steatohepatitis (NASH)

Nonalcoholic fatty liver disease (NAFLD) is the most common cause of abnormal hepatic steatosis in the absence of a history of alcohol use. Nonalcoholic steatohepatitis (NASH) is the progressive form of NAFLD. Hyperhomocysteinemia causes steatosis, and the methylenetetrahydrofolate reductase (MTHFR) C677T and A1298C polymorphisms result in hyperhomocysteinemia. To examine whether the C677T and A1298C polymorphisms of the MTHFR gene were associated with NASH, we analysed the allele and genotype distribution of the MTHFR C677T and A1298C polymorphisms in 57 well-diagnosed NASH patients, 324 healthy controls in a case-control study of Turkish subjects of Caucasian origin. The diagnosis of the NASH patients was based on liver biopsy. The method used in the analysis of genotypes was PCR-RFLP. The MTHFR A1298C polymorphism was significantly associated with NASH (chi(2) = 8.439; p = 0.015) in the total NASH patients compared with healthy controls. The MTHFR 1298C allele (odds ratio (OR) = 2.480; 95%CI = 1.286-4.782; chi(2) = 7.703; df = 1; p = 0.006) was significantly associated with NASH in the total NASH patients. The MTHFR C677C/A1298C compound genotype (OR = 2.218; 95%CI = 1.003-4.906; chi(2) = 3.998; df = 1; p = 0.046) in men patients was also significantly associated with NASH. Likewise the MTHFR C1298C genotype was significantly associated with NASH in women patients with NASH (OR = 2.979; 95%CI = 1.027-8.641; chi(2) = 4.343; df = 1; p = 0.037). In conclusion, the MTHFR 1298C allele in all NASH patients, C1298C genotype, C677C/C1298C compound genotype in women NASH patients and C677C/A1298C compound genotype in men NASH patients were genetic risk factors for NASH.

Contribution of methylenetetrahydrofolate reductase (MTHFR) polymorphisms to negative symptoms in schizophrenia

BACKGROUND

Folate deficiency may contribute to negative symptoms in schizophrenia, but the underlying mechanism remains uncertain. We examined whether the methylenetetrahydrofolate reductase (MTHFR) C677T and A1298C functional polymorphisms contribute to negative symptoms.

METHODS

Outpatients with schizophrenia (n = 200) were evaluated with the Positive and Negative Syndrome Scale (PANSS). Subjects also provided a blood sample for MTHFR genotype and serum chemistries. Comparisons of PANSS symptoms, folate, and homocysteine status were conducted based on genotype.

RESULTS

The 677T allele load was associated with negative symptom severity. Contrary to our expectations, the T allele was also found to be protective against positive symptoms. The A1298C polymorphism did not contribute to negative symptoms, and only weakly to positive symptoms. The specific effects of the C677T polymorphism were confirmed with haplotype analysis. Among patients homozygous for the 667T allele, serum folate levels correlated with negative symptom severity.

CONCLUSIONS

Increased MTHFR 677T allele load confers risk for negative symptoms in schizophrenia, while reducing severity of positive symptoms. Further, the biochemical interaction of low serum folate with 677T-variant MTHFR may induce downstream effects salient to the expression of negative symptoms.

Association of methylenetetrahydrofolate reductase gene polymorphisms and sex-specific survival in patients with metastatic colon cancer

PURPOSE

Methylenetetrahydrofolate reductase (MTHFR) is a key enzyme regulating intracellular folate levels, which affects DNA synthesis and methylation. Two MTHFR gene polymorphisms, C677T and A1298C, are linked to altered enzyme activity. Several studies have shown these two polymorphisms to be associated with response to fluorouracil (FU) -based treatment in advanced colon cancer patients, but data are inconsistent and contradictory. Meanwhile, epidemiologic studies demonstrated that these MTHFR polymorphisms were associated with cancer risk in a sex-specific manner. We tested the hypothesis of whether these two polymorphisms are associated with sex-specific clinical outcome in metastatic colon cancer patients treated with FU-based chemotherapy.

PATIENTS AND METHODS

This study included 318 patients (177 men and 141 women) with metastatic colon cancer treated between 1992 and 2003 at the University of Southern California/Norris Comprehensive Cancer Center or Los Angeles County/University of Southern California Medical Center. Peripheral blood samples were collected from each patient, and genomic DNA was extracted from WBCs. Two MTHFR gene polymorphisms (C677T and A1298C) were tested by fluorogenic 5'-nuclease assay.

RESULTS

The A1298C polymorphism showed statistically significant differences in overall survival (OS) in female, but not male, patients with metastatic colon cancer (log-rank test, P = .038). Among females, OS was greater for patients with the A/A genotype (n = 67; median OS, 18.4 months) compared with patients with the A/C genotype (n = 50; median OS, 13.9 months) or C/C genotype (n = 10; median OS, 15.6 months).

CONCLUSION

Although preliminary, these data support the role of the A1298C polymorphism in MTHFR as prognostic marker in female patients with metastatic colon cancer. Further studies are needed to confirm these findings.

The role of one-carbon metabolism in schizophrenia and depression

OBJECTIVE

Physicians often check folate and cobalamin levels in patients with schizophrenia and depression. The reasons for this practice are reviewed, as well as implications for treatment.

METHOD

The physiology of the one-carbon cycle, involving folate, cobalamin, homocysteine, S-adenosyl-methionine, and methylene tetrahydrofolate reductase (MTHFR) is first reviewed, and then the particular contributions of folate and B12 are reviewed. PubMed was searched for studies of the association between folate, cobalamin, homocysteine, and MTHFR polymorphisms and schizophrenia and depression.

RESULTS

The recent key studies from the large literature addressing these topics are summarized. Treatment implications are discussed.

CONCLUSION

It is important to check folate and B12 levels in certain situations, such as alcoholism, malnutrition, malabsorption, and the concurrent use of some medications. Checking homocysteine and methylmalonic levels might be useful. With respect to treatment, folate and cobalamin deficiencies should be corrected. Cobalamin supplementation is probably not helpful. Folate supplementation is indicated in pregnancy but may exacerbate the effects of cobalamin deficiency. SAMe may prove to be a useful antidepressant. In the future, screening for MTHFR polymorphisms might be useful.

No association of the C677T methylenetetrahydrofolate reductase polymorphism with schizophrenia

Some serological and genetic studies have suggested that alterations in folate metabolism are associated with increased vulnerability to schizophrenia. In particular, these findings are most striking for the role of a putatively functional variant (C677T) in the methylenetetrahydrofolate reductase (MTHFR) gene. To test the hypothesis that the T allele and the TT genotype are risk factors for psychosis, we genotyped the C677T polymorphism in 206 participants with schizophrenia or schizoaffective disorder and 359 participants from a population control sample. Neither the T allele nor the TT genotype was associated with increased risk for schizophrenia. These results do not support a role for the C677T MTHFR variant in schizophrenia.

Methylenetetrahydrofolate reductase gene polymorphisms are associated with ischemic and hemorrhagic stroke: Dual effect of MTHFR polymorphisms C677T and A1298C

Hyperhomocysteinemia is an independent risk factor for ischemic stroke. The enzyme methylenetetrahydrofolate reductase (MTHFR) plays a critical role in modulating the levels of plasma homocysteine. Two polymorphisms in the MTHFR gene, C677T, A1298C result in reduced enzyme activity. The mechanisms of ischemic and hemorrhagic stroke are not well understood. Although controversial, previous studies have shown evidence of causality of both stroke subtypes in patients with methylenetetrahydrofolate reductase gene polymorphisms. Therefore, we examined whether the C677T and A1298C polymorphisms of MTHFR gene are genetic risk factors for both ischemic and hemorrhagic stroke in a Turkish Caucasian population. In a case-control study, 120 total unrelated stroke patients (92 ischemic stroke, 28 hemorrhagic stroke), and 259 healthy controls were genotyped for C677T and A1298C polymorphisms of the MTHFR gene using a PCR-RFLP based-method. The MTHFR 1298C allele (chi(2)=8.589; P=0.014), C1298C genotype (OR=2.544; P=0.004), and C677C/C1298C compound genotype (OR=3.020; P=0.001) were associated with overall stroke. The MTHFR 1298C allele (chi(2)=11.166; P=0.004), C1298C genotype (OR=2.950; P=0.001), and C677C/C1298C compound genotype (OR=3.463, P=0.0001) were strongly associated with ischemic stroke. Interestingly however, the MTHFR 677T allele (chi(2)=6.033; P=0.049), T677T genotype (OR=3.120; P=0.014), and T677T/A1298A compound genotype (OR=4.211; P=0.002) were associated with hemorrhagic stroke. In conclusion, the C677T and A1298C polymorphisms of the MTHFR gene are genetic risk factors for hamorrhagic and ischemic stroke respectively, independent of other atherothrombotic risk factors.

Molecular phylogenetic analysis of methylenetetrahydrofolate reductase family of proteins

Methylenetetrahydrofolate reductase (MTHFR) family of proteins catalyze the conversion of 5,10-methylenetetrahydrofolate to 5-methyltetrahydrofolate. They contain a flavin adenine dinucleotide (FAD) as the cofactor and the enzyme in eukaryotes, except in yeast, is known to be allosterically regulated by S-adenosylmethionine. Some cardiovascular diseases, neural tube defects, neuropsychiatric diseases and certain type of cancers in humans are associated with certain polymorphisms of MTHFR. Here, we analyzed 57 of MTHFR polypeptide sequences by multiple sequence alignment and determined previously unrecognized conserved residues that may have a functional or structural importance. A previously unrecognized ATP synthase motif was found in all of the examined plant MTHFRs, suggesting a different functional capability to the plant MTHFRs in addition to the known function. On a phylogenetic tree built, eukaryotic MTHFR proteins formed a clear cluster separated from prokaryotic and archeal relatives. The sequence identities among the eukaryotic MTHFRs were less divergent than the bacterial MTHFRs.

Association of 677C>T polymorphism of methylenetetrahydrofolate reductase (MTHFR) gene with bipolar disorder and schizophrenia

Methylenetetrahydrofolate reductase (MTHFR) gene polymorphism 677C>T has been shown to be a risk factor for psychiatric disorders. We investigated the genotype and allelic frequencies of MTHFR 677C>T polymorphism in the group of patients with bipolar disorder type I (BDI) (n=200) and schizophrenia (n=200), and in the control group (n=300). Odds ratio (OR) for patients with BD and schizophrenia with 677T allele was 1.988 ((95% CI=1.370-2.883); P=0.0003 (P=0.0006 after Bonferroni correction)) and 1.796 ((95% CI=1.237-2.609); P=0.0020 (P=0.0040 after Bonferroni correction)), respectively. The stratification of patients based on gender revealed significant association of 677T allele with male patients with BDI and schizophrenia (OR=2.393; 95% CI=1.429-4.006; P=0.0008 and OR=2.036; 95% CI=1.207-3.433; P=0.0073, respectively). This finding indicates possible association of BD and schizophrenia with the 1p36.3 MTHFR locus.

C677T and A1298C methylenetetrahydrofolate reductase gene polymorphisms in schizophrenia, bipolar disorder and depression: a meta-analysis of genetic association studies

A meta-analysis of the previous studies of allelic association between schizophrenia, bipolar disorder and depression with the C677T and A1298C polymorphisms of the methylenetetrahydrofolate reductase (MTHFR) gene was carried out. Attention was paid to genetic differences in ancestral groups. Ten studies of the C677T MTHFR polymorphism and schizophrenia were included, along with four studies with the A1298C MTHFR polymorphism and schizophrenia. Four association studies of the C677T MTHFR polymorphism with bipolar disorder, and five studies of the C677T base pair change with depression were included. The studies contained Caucasian and east Asian samples. For schizophrenia, the main analysis for investigating the association of the C677T allele T and the risk of developing schizophrenia relative to the allele C showed lack of heterogeneity (P = 0.22, I(2) = 24%) between samples. In these samples, the fixed effects odds ratio was marginally significant [odds ratio 1.13 (95% confidence interval, 1.04-1.23)]. In an analysis of subgroups, the odds ratio were not significant for the Caucasian sample [random effects odds ratio 1.14 (0.95-1.36) and fixed effects odds ratio 1.13 (1.00-1.27)](P = 0.14, I(2) = 43%) and in Asians [random effects odds ratio 1.15 (0.98-1.35) and fixed effects odds ratio 1.15 (1.01-1.31)] (P = 0.19, I(2) = 37). The recessive model for allele T produced significant results in the main analysis [fixed effects odds ratio 1.32 (1.12-1.56)] in east Asians [fixed effects odds ratio 1.45 (1.13-1.85)] and female participants [fixed effects odds ratio 1.70 (1.07-2.71)], whereas for Caucasians the results were nonsignificant. For the A1298C polymorphism, in the main analysis the allele frequency difference between C and A, and the dominant model for allele C produced marginally significant associations [fixed effects odds ratio 1.16 (1.03-1.31) and fixed effects odds ratio 1.19 (1.02-1.40), respectively]. In bipolar disorder, overall, there was no significant association between either allele of the C677T polymorphism and the risk of developing bipolar disorder. Only in the east Asian population was the C677T association of marginal significance, with fixed effects odds ratio 1.23 (1.00-1.52). No sources of potential bias were found in the selected studies. The meta-analysis results suggested that east Asians have a greater genetic risk from the MTHFR gene in developing schizophrenia and depression, and that the genetic effects in bipolar disorder and depression are different. A further exploration of the involvement of the MTHFR gene in the susceptibility to schizophrenia and affective disorders, with a greater number of studies with larger sample sizes, however, are needed to fully establish the role of the MTHFR gene.

Delayed neurotoxicity associated with therapy for children with acute lymphoblastic leukemia

Most children diagnosed today with acute lymphoblastic leukemia (ALL) will be cured. However, treatment entails risk of neurotoxicity, causing deficits in neurocognitive function that can persist in the years after treatment is completed. Many of the components of leukemia therapy can contribute to adverse neurologic sequelae, including craniospinal irradiation, nucleoside analogs, corticosteroids, and antifolates. In this review, we describe the characteristic radiographic findings and neurocognitive deficits seen among survivors of childhood ALL. We summarize what is known about the pathophysiology of delayed treatment-related neurotoxicity, with a focus on the toxicity resulting from pharmacologic disruption of folate physiology within the central nervous system. Finally, we suggest testable strategies to ameliorate the symptoms of treatment-related neurotoxicity or decrease its incidence.