The COMT L allele modifies the association between MAOB polymorphism and PD in Taiwanese

A preliminary study on the association of single nucleotide polymorphisms and methylation of dopamine system-related genes with psychotic symptoms in patients with methamphetamine use disorder

Methamphetamine use disorder (MAUD) can substantially jeopardize public security due to its high-risk social psychology and behaviour. Given that the dopamine reward system is intimately correlated with MAUD, we investigated the association of single nucleotide polymorphisms (SNPs), as well as methylation status of dopamine receptor type 4 (DRD4), catechol-O-methyltransferase (COMT) genes, and paranoid and motor-impulsive symptoms in MAUD patients. A total of 189 MAUD patients participated in our study. Peripheral blood samples were used to detect 3 SNPs and 35 CpG units of methylation in the DRD4 gene promoter region and 5 SNPs and 39 CpG units in the COMT gene. MAUD patients with the DRD4 rs1800955 C allele have a lower percentage of paranoid symptoms than those with the rs1800955 TT allele. Individuals with paranoid symptoms exhibited a reduced methylation degree at a particular DRD4 CpG2.3 unit. The interaction of the DRD4 rs1800955 C allele and the reduced DRD4CpG2.3 methylation degree were associated with a lower occurrence of paranoid symptoms. Meanwhile, those with the COMT rs4818 CC allele had lower motor-impulsivity scores in MAUD patients but greater COMT methylation levels in the promoter region and methylation degree at the COMT CpG 51.52 unit. Therefore, based only on the COMT rs4818 CC polymorphism, there was a negative correlation between COMT methylation and motor-impulsive scores. Our preliminary results provide a clue that the combination of SNP genotype and methylation status of the DRD4 and COMT genes serve as biological indicators for the prevalence of relatively high-risk psychotic symptoms in MAUD patients.

In-depth analysis of data from the RAS-ALS study reveals new insights in rasagiline treatment for amyotrophic lateral sclerosis

BACKGROUND AND PURPOSE

In 2016, we concluded a randomized controlled trial testing 1 mg rasagiline per day add-on to standard therapy in 252 amyotrophic lateral sclerosis (ALS) patients. This article aims at better characterizing ALS patients who could possibly benefit from rasagiline by reporting new subgroup analysis and genetic data.

METHODS

We performed further exploratory in-depth analyses of the study population and investigated the relevance of single nucleotide polymorphisms (SNPs) related to the dopaminergic system.

RESULTS

Placebo-treated patients with very slow disease progression (loss of Amyotrophic Lateral Sclerosis Functional Rating Scale-Revised [ALSFRS-R] per month before randomization of ≤0.328 points) showed a per se survival probability after 24 months of 0.85 (95% confidence interval = 0.65-0.94). The large group of intermediate to fast progressing ALS patients showed a prolonged survival in the rasagiline group compared to placebo after 6 and 12 months (p = 0.02, p = 0.04), and a reduced decline of ALSFRS-R after 18 months (p = 0.049). SNP genotypes in the MAOB gene and DRD2 gene did not show clear associations with rasagiline treatment effects.

CONCLUSIONS

These results underline the need to consider individual disease progression at baseline in future ALS studies. Very slow disease progressors compromise the statistical power of studies with treatment durations of 12-18 months using clinical endpoints. Analysis of MAOB and DRD2 SNPs revealed no clear relationship to any outcome parameter. More insights are expected from future studies elucidating whether patients with DRD2CC genotype (Rs2283265) show a pronounced benefit from treatment with rasagiline, pointing to the opportunities precision medicine could open up for ALS patients in the future.

The Association between a MAOB Variable Number Tandem Repeat Polymorphism and Cocaine and Opiate Addictions in Polyconsumers

Genetic analysis of the association between alcohol, cocaine, and opiate addiction and variable number tandem repeat (VNTR) polymorphisms in monoamine oxidase B (MAOB) and serotonergic 5-hydroxytryptamine (serotonin) receptor 1B and 2C (HTR1B 21 and HTR2C) pathway genes was performed in a sample of 302 polyconsumers. Our genetic association analysis revealed a significant association between a 184 base pair (bp) VNTR polymorphism in the MAOB gene and addiction to cocaine and opiates. This work highlights new genetic marker associations in cocaine and opiate polyconsumer addictions. These data help to clarify and quantify the complex role of genetics in addictive disorders, as well as their future contribution to the prevention (genetic counselling), diagnosis (genetic diagnosis of vulnerability), and treatment (pharmacogenomics) of these disorders.

Meta-Analysis of the Effects of the Catechol-O-Methyltransferase Val158/108Met Polymorphism on Parkinson's Disease Susceptibility and Cognitive Dysfunction

Background: There is a continued debate and inconsistent findings in previous literature about the relationship of catechol-O-methyltransferase (COMT) and Parkinson’s disease (PD) susceptibility as well as cognitive dysfunction. To substantiate this existing gap, we comprehensively examine COMT genotype effects on the development of PD and test the hypothesis that the Met158 allele of the COMT gene is associated with cognitive dysfunction by conducting a meta-analysis review.

Methods: PubMed/MEDLINE, Embase, Cochrane databases search (18/30/08) yielded 49 included studies. Data were extracted by two reviewers and included COMT genotype, publication year, diagnostic status, ancestry, the proportion of male participants, and whether genotype frequencies were consistent with Hardy–Weinberg equilibrium. Unadjusted odds ratios (ORs) were used to derive pooled estimates of PD risk overall and in subgroups defined by ethnicity, gender, and onset of disease. Moreover, the association of certain cognitive domains in PD and COMT gene type was explored. Meta-analyses were performed using random-effect models and p value–based methods. All statistical tests were two-sided. The present study was registered with PROSPERO (CRD42018087323).

Results: In the current studies, we found no association between COMT Val158/108Met polymorphism and PD susceptibility. However, the gender-stratified analyses revealed marginally significant effects in heterozygote model analyses in women (P = 0.053). In addition, stratification according to onset of PD also shows significant effects of COMT Val158/108Met polymorphism on late-onset population both in recessive (P = 0.017) and allelic (P = 0.017) genetic models. For the intelligence quotient (IQ) score and Unified Parkinson Disease Rating Scale III (UPDRS III), there was no evidence for genetic association, except in subgroup analyses in Asian populations (IQ score, P = 0.016; UPDRS III, P < 0.001).

Conclusion: The COMT Val158/108Met polymorphism is associated with the risk for PD in female or late-onset PD. Methionine/methionine carriers of Asian population performed significantly worse than the valine allele carriers in IQ score and UPDRS III.

More than an "inverted-U"? An exploratory study of the association between the catechol-o-methyltransferase gene polymorphism and executive functions in Parkinson's disease

Executive dysfunction is common in Parkinson's disease (PD) patients. The catechol-O-methyltransferase (COMT) Val158Met polymorphism has been proposed to affect executive functions (EFs) in the prefrontal cortex. The present study attempted to explore the influence of the COMT polymorphism on EFs in patients with PD. Fifty-four PD patients were recruited and underwent neuropsychological assessments for three core EFs. The COMT polymorphism was genotyped using the TaqMan SNP Genotyping Assay. Participants were divided into three study groups: Val homozygotes, heterozygotes, and Met homozygotes. The three COMT genotype groups had significantly different performances in set-shifting [χ2 (2, 54) = 9.717, p = 0.008] and working memory tasks [χ2 (2, 54) = 7.806, p = 0.020]. Post-hoc analyses revealed that PD Val homozygotes performed significantly poorer in the set-shifting task than did either the PD Met homozygotes (z = -2.628, p = 0.009) or PD heterozygotes (z = -2.212, p = 0.027). Our explorative results suggest that the putative level of prefrontal dopamine influenced set-shifting through a "cane-shaped" dopamine level-response relationship. Our results have clinical implications, which may influence PD treatment with dopamine in the future because the optimal dopamine level to maximize EFs may vary based on the clinical course and COMT polymorphism status. Further study recruiting a larger number of participants is needed to confirm our preliminary findings.

MAO-B and COMT Genetic Variations Associated With Levodopa Treatment Response in Patients With Parkinson's Disease

The most commonly used Parkinson's disease (PD) treatment is the replacement of dopamine by its levodopa precursor (l-dopa). Monoamine oxidase-B (MAO-B) and catechol-o-methyl transferase (COMT) are enzymes involved in the metabolism and regulation of dopamine availability. In our study we investigated the possible relation among selected single-nucleotide polymorphisms (SNPs) in the MAO-B (rs1799836) and COMT (rs4680) genes and the therapeutic response to levodopa (l-dopa). A total of 162 Brazilian patients from the Pro-Parkinson service of Clinics Hospital of Pernambuco diagnosed with sporadic PD and treated with levodopa were enrolled. PD patients were stratified into 2 groups according to the daily levodopa dose. MAO-B and COMT SNP genotyping was conducted by polymerase chain reaction-restriction fragment length polymorphism. After multivariate analysis, we observed a significant difference between PD groups for the following variables: sex (P = .02), longer duration of disease (P = .02), longer levodopa therapy duration (P = .01), younger onset of PD (P = .01), and use of COMT inhibitor (P = .02). We observed that patients carrying MAO-B (rs1799836) A and AA genotypes and COMT (rs4680) LL genotype suffered more frequently from levodopa-induced-dyskinesia. In addition, we found an increased risk of 2.84-fold for male individuals carrying the MAO-B G allele to be treated with higher doses of levodopa (P = .04). We concluded that before beginning PD pharmacological treatment, it is important to consider the genetic variants of the MAO-B and COMT genes and the sex, reinforcing the evidence that sexual dimorphism in the genes related to dopamine metabolism might affect PD treatment.

The relationship between monoamine oxidase B (MAOB) A644G polymorphism and Parkinson disease risk: a meta-analysis

BACKGROUND AND OBJECTIVES

Many studies were conducted to assess the relationship between Monoamine oxidase B (MAOB) A644G polymorphism and susceptibility to Parkinson disease (PD). However, the results were inconsistent and inconclusive.

DESIGN AND SETTINGS

A meta-analysis was conducted from all published studies on the associations between monoamine oxidase B (MAOB) A644G polymorphism and Parkinson disease.

METHODS

In this present study, the possible relationship between MAOB A644G polymorphism and PD risk was assessed by a meta-analysis. Eligible articles were identified for the period up to March 2013. Pooled odds ratios (OR) with 95% confidence intervals (CI) were appropriately derived from fixed-effects models.

RESULTS

Twenty case-control studies with a total of 2846 cases and 3508 controls were eligible. In a recessive model, MAOB A644G polymorphism was associated with PD risk (OR=1.32, 95% CI 1.18-1.47, P < .001). Subgroup analyses by ethnicity and gender also found significant relationships between this polymorphism and PD risk.

CONCLUSION

This meta-analysis suggested that MAOB A644G polymorphism may be associated with PD development.

Genetic variants of neurotransmitter-related genes and miRNAs in Egyptian autistic patients

Autism is a neurodevelopmental disorder with indisputable evidence for a genetic component. This work studied the association of autism with genetic variations in neurotransmitter-related genes, including MAOA uVNTR, MAOB rs1799836, and DRD2 TaqI A in 53 autistic patients and 30 healthy individuals. The study also analyzed sequence variations of miR-431 and miR-21. MAOA uVNTR was genotyped by PCR, MAOB and DRD2 polymorphisms were analyzed by PCR-based RFLP, and miR-431 and miR-21 were sequenced. Low expressing allele of MAOA uVNTR was frequently higher in female patients compared to that in controls (OR = 2.25). MAOB G allele frequency was more significantly increased in autistic patients than in controls (P < 0.001 for both males and females). DRD2 A1+ genotype increased autism risk (OR = 5.1). Severity of autism tends to be slightly affected by MAOA/B genotype. Plasma MAOB activity was significantly reduced in G than in A allele carrying males. There was no significant difference in patients and maternal plasma MAOA/B activity compared to controls. Neither mutations nor SNPs in miR-431 and miR-21 were found among studied patients. This study threw light on some neurotransmitter-related genes suggesting their potential role in Autism pathogenesis that warrants further studies and much consideration.

The Val158Met COMT polymorphism is a modifier of the age at onset in Parkinson's disease with a sexual dimorphism

The catechol-O-methyltranferase (COMT) is one of the main enzymes that metabolise dopamine in the brain. The Val158Met polymorphism in the COMT gene (rs4680) causes a trimodal distribution of high (Val/Val), intermediate (Val/Met) and low (Met/Met) enzyme activity. We tested whether the Val158Met polymorphism is a modifier of the age at onset (AAO) in Parkinson's disease (PD). The rs4680 was genotyped in a total of 16 609 subjects from five independent cohorts of European and North American origin (5886 patients with PD and 10 723 healthy controls). The multivariate analysis for comparing PD and control groups was based on a stepwise logistic regression, with gender, age and cohort origin included in the initial model. The multivariate analysis of the AAO was a mixed linear model, with COMT genotype and gender considered as fixed effects and cohort and cohort-gender interaction as random effects. COMT genotype was coded as a quantitative variable, assuming a codominant genetic effect. The distribution of the COMT polymorphism was not significantly different in patients and controls (p=0.22). The Val allele had a significant effect on the AAO with a younger AAO in patients with the Val/Val (57.1±13.9, p=0.03) than the Val/Met (57.4±13.9) and the Met/Met genotypes (58.3±13.5). The difference was greater in men (1.9 years between Val/Val and Met/Met, p=0.007) than in women (0.2 years, p=0.81). Thus, the Val158Met COMT polymorphism is not associated with PD in the Caucasian population but acts as a modifier of the AAO in PD with a sexual dimorphism: the Val allele is associated with a younger AAO in men with idiopathic PD.

COMT rs4680 Met is not always the 'smart allele': Val allele is associated with better working memory and larger hippocampal volume in healthy Chinese

Catechol-O-methyltransferase (COMT) Val158Met (rs4680) polymorphism plays a crucial role in regulating brain dopamine level. Converging evidence from Caucasian samples showed that, compared with rs4680 Val allele, the Met allele was linked to lower COMT activity, which in turn was linked to better cognitive performance such as working memory (WM) and to a larger hippocampus (a brain region important for WM). However, some behavioral studies have shown that the function of rs4680 appears to vary across different ethnic groups, with Chinese subjects showing an opposite pattern as that for Caucasians (i.e. the Val allele is linked to better cognitive functions related to WM in Chinese). Using a sample of healthy Han Chinese college students (ages from 19 to 21 years), this study investigated the association of COMT Val158Met genotype with behavioral data on a two-back WM task (n = 443, 189M/254F) and T1 MRI data (n = 320, 134M/186F). Results showed that, compared to the Met allele, the Val allele was associated with larger hippocampal volume (the right hippocampus: β = -0.118, t = -2.367, P = 0.019, and the left hippocampus: β = -0.099, t = -1.949, P = 0.052) and better WM performance (β = -0.110, t = -2.315, P = 0.021). These results add to the growing literature on differentiated effects of COMT rs4680 polymorphism on WM across populations and offer a brain structural mechanism for such population-specific genetic effects.

Association of catechol-o-methyltransferase polymorphism (Val108/158Met) with Parkinson's disease: a meta-analysis

Parkinson's disease (PD) is a common neurodegenerative disease, the risk factors of which are gaining more attentions. Among all these risk factors, catechol-o-methyltransferase (COMT) has been widely studied, and believed to be associated with PD. However, the relationship between COMT polymorphism and PD has not been confirmed hitherto. Therefore, a meta-analysis was performed to evaluate the effect of COMT polymorphism on PD patients. A total of 24 study subjects comprising 3,807 patients with PD and 3,942 unrelated healthy controls were recruited in this meta-analysis. Heterogeneity testing and sensitivity analysis were conducted with Review Manager 5.0 software (The Nordic Cochrane Centre, The Cochrane Collaboration, Copenhagen, Denmark) and Stata software (StataCorp, College Station, TX), together with publication bias by funnel plot method and modified Egger's linear regression test. No evidences of publication bias and heterogeneity were detected. In the 24 studies, the estimated odds ratios (OR) in PD patients are 0.98 for the Met allele (95% confidence interval [0.92, 1.05]) under a fixed-effects model. The authors also conducted a stratified analysis according to geographic region among Europe, Asia, and North America, the ORs for the Met allele are 0.92, 1.02, and 1.10, respectively. According to the results of the meta-analysis, a conclusion could be drawn that polymorphism of Val108/158Met are not associated with the risk of PD. However, more convincing studies are warranted to have a solid conclusion supported.

Analysis of Lingo1 variant in sporadic and familial essential tremor among Asians

OBJECTIVE - Genome-wide association study (GWAS) has identified a variant in LINGO1 (rs9652490) that increases the risk of essential tremor (ET) among Caucasians. It has been suggested that among Asians, the risk variant is relevant only for the familial forms of ET. We investigated the association of the rs9652490 variant with sporadic and familial ET in a Chinese population and conducted a pooled analysis to compare the potential differential effect between sporadic and familial ET. METHODS - rs9652490 was genotyped by direct sequencing in 117 ET and 160 controls in a Chinese population. Previous published data from another Asian population were included in the meta-analysis. RESULT - There were no significant differences in the minor allele frequency and genotype frequency between ET and controls in our Chinese population. However, in the pooled analysis involving 1201 subjects, patients with ET had a higher proportion of GG genotype compared to controls. Logistic regression analysis revealed that G allele increased the risk of ET via a recessive model. In both familial ET and sporadic ET, the G allele increased the risk via a recessive model. CONCLUSION -  While we could not demonstrate a significant association of the rs9652490 variant in our own study, pooled analysis of a much larger cohort revealed for the first time that the variant increased the risk in both familial and sporadic forms of ET among Asians, though the effect was stronger in familial ET.

Genetic polymorphisms involved in dopaminergic neurotransmission and risk for Parkinson's disease in a Japanese population

Background

Parkinson's disease (PD) is characterized by alterations in dopaminergic neurotransmission. Genetic polymorphisms involved in dopaminergic neurotransmission may influence susceptibility to PD.

Methods

We investigated the relationship of catechol-O-methyltransferase (COMT), monoamine oxidase B (MAOB), dopamine receptor (DR) D2 and DRD4 polymorphisms and PD risk with special attention to the interaction with cigarette smoking among 238 patients with PD and 369 controls in a Japanese population.

Results

Subjects with the AA genotype of MAOB rs1799836 showed a significantly increased risk of PD (odds ratio (OR) = 1.70, 95% confidence interval (CI) = 1.12 - 2.58) compared with the AG and GG genotypes combined. The AA genotype of COMT rs4680 was marginally associated with an increased risk of PD (OR = 1.86, 95% CI = 0.98 - 3.50) compared with the GG genotype. The DRD2 rs1800497 and DRD4 rs1800955 polymorphisms showed no association with PD. A COMT -smoking interaction was suggested, with the combined GA and AA genotypes of rs4680 and non-smoking conferring significantly higher risk (OR = 3.97, 95% CI = 2.13 - 7.41) than the AA genotype and a history of smoking (P for interaction = 0.061). No interactions of smoking with other polymorphisms were observed.

Conclusions

The COMT rs4680 and MAOB rs1799836 polymorphisms may increase susceptibility to PD risk among Japanese. Future studies involving larger control and case populations and better pesticide exposure histories will undoubtedly lead to a more thorough understanding of the role of the polymorphisms involved in the dopamine pathway in PD.

Smoking, genes encoding dopamine pathway and risk for Parkinson's disease

Smoking has been reported to be inversely associated with Parkinson's disease (PD) in many studies, but a recent study in China found that smoking increased the risk of PD. Variants in genes associated with dopamine metabolism found to increase the risk for PD have also been associated with smoking behavior. To investigate the association between smoking and PD in a Chinese population and determine whether the genetic variants of genes involved in dopamine metabolism influence the relationship between smoking and risk for PD. Chinese PD patients were recruited from Xuanwu Hospital. Controls were sampled from community. Detailed information on life-long smoking behavior was collected by face-to-face interview. Genotypes were determined for SLC6A3 VNTR, COMT Val108/158Met and MAO-B intron13 A/G polymorphisms by PCR-RFLP, DHPLC and sequencing. Chi-square and logistic regression model were used in the analysis. 176 PD cases and 354 controls were enrolled in this study. 23.9% cases are smokers, compared to 48.0% in controls. Ever smoking is inversely associated with PD (odds ratio=0.14, 95% CI 0.08-0.26, adjusted for age and gender). None of the above-mentioned genetic polymorphisms was associated with PD risk or smoking. When each variant was included in the logistic regression model, the inverse association between smoking and PD remained the same, and the interactions between smoking and variants were not significant in the model. Our data support a reduction of PD risk associated with smoking in a Chinese population. These variants of genes associated with DA uptake and metabolism do not affect the inverse association between smoking and PD.

The LEARn model: an epigenetic explanation for idiopathic neurobiological diseases

Neurobiological disorders have diverse manifestations and symptomology. Neurodegenerative disorders, such as Alzheimer's disease, manifest late in life and are characterized by, among other symptoms, progressive loss of synaptic markers. Developmental disorders, such as autism spectrum, appear in childhood. Neuropsychiatric and affective disorders, such as schizophrenia and major depressive disorder, respectively, have broad ranges of age of onset and symptoms. However, all share uncertain etiologies, with opaque relationships between genes and environment. We propose a 'Latent Early-life Associated Regulation' (LEARn) model, positing latent changes in expression of specific genes initially primed at the developmental stage of life. In this model, environmental agents epigenetically disturb gene regulation in a long-term manner, beginning at early developmental stages, but these perturbations might not have pathological results until significantly later in life. The LEARn model operates through the regulatory region (promoter) of the gene, specifically through changes in methylation and oxidation status within the promoter of specific genes. The LEARn model combines genetic and environmental risk factors in an epigenetic pathway to explain the etiology of the most common, that is, sporadic, forms of neurobiological disorders.

Genome-wide linkage screen in familial Parkinson disease identifies loci on chromosomes 3 and 18

Parkinson disease (PD) is a complex, multifactorial neurodegenerative disease with substantial evidence for genetic risk factors. We conducted a genome-wide linkage screen of 5824 single-nucleotide polymorphisms in 278 families of European, non-Hispanic descent to localize regions that harbor susceptibility loci for PD. By using parametric and nonparametric linkage analyses and allowing for genetic heterogeneity among families, we found two loci for PD. Significant evidence for linkage was detected on chromosome 18q11 (maximum lod score [MLOD] = 4.1) and suggestive evidence for linkage was obtained on chromosome 3q25 (MLOD = 2.5). These results were strongest in families not previously screened for linkage, and simulation studies suggest that these findings are likely due to locus heterogeneity rather than random statistical error. The finding of two loci (one highly statistically significant) suggests that additional PD susceptibility genes might be identified through targeted candidate gene studies in these regions.

The association of functional catechol-O-methyltransferase haplotypes with risk of Parkinson's disease, levodopa treatment response, and complications

INTRODUCTION

Differences in catechol-O-methyltransferase (COMT) activity and genotype may determine individual variations in the therapeutic response to levodopa or Parkinson's disease (PD) susceptibility. The role of functional COMT haplotypes in PD susceptibility and treatment response has not been examined.

OBJECTIVES

In this case-control study, we investigated the association of the most common COMT gene haplotypes (formed by single nucleotide polymorphisms (SNPs): rs6269:A>G; rs4633C>T; rs4818:C>G; and rs4680:A>G) with PD risk and the association of the COMT haplotypes with the dose and complications of levodopa therapy in PD patients.

METHODS

A total of 679 study participants (322 PD and 357 controls) were included. Each participant was genotyped for four SNPs in the COMT gene, located in a common haploblock, that has been shown to influence COMT enzymatic activity. The influence of COMT haplotypes on the dose of levodopa administered during fifth year of treatment, and occurrence of motor complications were examined in PD patients. The EH program (Jurg Ott, Rockefeller University, New York, USA) was used to estimate haplotype frequencies.

RESULTS

The estimated frequencies of low (A_C_C_G) and medium (A_T_C_A) activity haplotypes tended to be slightly lower among PD patients when compared with controls (P=0.09, G_C_G_G-high activity haplotype as reference). The frequency of G_C_G_G (high activity) haplotype carriers was higher in late onset PD patients (P=0.04) compared with controls. The mean levodopa dose increased with the activity of the functional haplotypes (low<medium<high). Doses prescribed for G_C_G_G (high activity) haplotype carriers (mean 604.2+/-261.9 mg) were significantly higher than those for the noncarriers (mean 512.2+/-133.5 mg, P<0.05). The COMT haplotype seemed to have little influence on the development of levodopa-induced dyskinesias.

CONCLUSION

Our study showed a possible association of functional COMT haplotypes with the risk of PD. Both nonsynonymous and synonymous SNPs within functional COMT haplotype blocks may be more relevant than individual SNPs in conferring PD susceptibility. The doses of levodopa treatment can be influenced by specific COMT haplotypes and this may be useful in instituting individualized therapy for PD patients.

Possible relationship between the COMT gene ValMet polymorphism and psychometric IQ in girls of the Qinba region in China

OBJECTIVE

Catechol-O-methyltransferase (COMT) gene was hypothesized to have a relationship with human prefrontal cortex (PFC) function and individual cognitive abilities. The object of this study was to investigate the possible impact of genotypes of COMT Val158Met polymorphism on cognitive ability among children living in the Qinba region in China.

METHOD

A total of 305 children were included, 163 girls and 142 boys; both complete IQ evaluation and Val158Met genotyping results were obtained. The quantitative traits of psychometric IQ were calculated by using the Chinese Wechsler Intelligence Scale for Children. All subjects' genotypes of COMT gene Val158Met polymorphism were identified with the restriction fragment length polymorphism method.

RESULTS

The F test showed that the average scores (including the Full Scale IQ, Verbal Scale IQ, Performance Scale IQ and three index scores) did not significantly differ among different groups defined by Val158Met genotypes, neither in boys nor in the total group (p > 0.05). There was a significant difference between the average of Freedom from Distractibility score among different genotypes found in girls (p = 0.033).

CONCLUSION

Our results indicate that COMT gene Val158Met polymorphism may be related to the intelligence of Chinese girls, although the results cannot withstand multiple testing. Consequently, further studies with larger samples and perfect design still need place more emphasis on the gender difference and compensation effect of dopamine activity in PFC.

Gene-gene interaction between FGF20 and MAOB in Parkinson disease

The fibroblast growth factor 20 (FGF20) and monoamine oxidase B (MAOB) genes are associated with Parkinson Disease (PD) risk and both are in the dopamine bio-pathway. Therefore, we investigated the joint effect between polymorphisms in the FGF20 and MAOB genes for evidence of interaction contributing to PD risk. Fourteen polymorphisms (eight for FGF20, six for MAOB) were genotyped in 736 families and analyzed using conditional logistic regression (CLR). Significant two-locus interactions were found in females between the polymorphisms rs1721100 of FGF20 and rs1799836 of MAOB, and between the polymorphisms rs1721082 of FGF20 and rs1799836 of MAOB. The risk alleles for each SNP identified from CLR, rs1721100 C, rs1721082 T and rs1799836 A, are consistent with previous reports. Using indicator variables for the SNP genotypes, rs1721100 GC with rs1799836 AA showed significant interaction (P = 0.021), compared with the reference group rs1721100 GG with rs1799836 GG. Using an allele-dose model for the risk alleles, rs1721100 and rs1799836 showed significant interaction (P = 0.019). We found similar interaction results between rs1721082 and rs1799836. In conclusion, variants in FGF20 and MAOB show evidence of statistical interactions, which emphasizes the importance of considering them jointly in genetic analysis of PD and illustrates potential patterns of biological interaction contributing to PD risk.

Which genotype of MAO gene that the patients have are likely to be most susceptible to the symptoms of fibromyalgia?

The objective of this study was to analyze the genotype distributions and allele frequencies for the MAO-A and MAO-B polymorphism of the MAO gene among the patients with fibromyalgia syndrome (FS). One hundred and seven fibromyalgia patients and 90 unrelated healthy subjects were included into the study. Genomic DNA of 107 FS patients and 90 healthy control subjects were analyzed by polymerase chain reaction. Polymorphism of the MAO gene was: 1-1, 1-3, 3-3, 3-4. The "allele 3" had a 2.7 to 4.8-fold increased transcription activity than the "allele 1". The frequencies of the genotypes of the patients with FS and healthy controls were compared. Although no significant difference was found in genotypes of patients and controls (P = 0.0559), it is likely that "allele 3" could be a more riskful factor for FS than "allele 1" (P = 0.033). Fibromyalgia impact questionnaire was administered to FS group as well as control group. One of our findings is that, the patients whose genotype 3-3 may be mostly affected by the symptoms of FS. In conclusion, it seems plausible to say that MAOA-dependent metabolism of the biological amines may be partly related to high-activated MAO-A, allele 3, in the occurrence of FS among Turkish population.

Association study of catechol-O-methyltransferase Val158Met polymorphism with personality traits in japanese healthy volunteers

Catechol-O-methyltransferase (COMT) is one of the major enzymes for the degradation of catecholamines. It has been suggested that catecholaminergic neurotransmission is involved in characterization of personality. Previous studies on the association between the COMT Val158Met polymorphism and personality traits in healthy subjects have produced inconsistent results. Therefore, the relationship between this polymorphism and personality was re-examined in 478 Japanese healthy volunteers. Personality traits were assessed by the Temperament and Character inventory (TCI), and the COMT genotypes were determined by a PCR-RFLP method. in total, there were no significant differences among the Val/Val, Val/Met, and Met/Met genotypes in seven TCI dimension scores. Similarly, no significant relationship was found between the COMT genotypes and the TCI dimensions when males and females were analyzed separately. The present study thus suggests that the COMT Val158Met polymorphism is not associated with personality traits in Japanese healthy subjects.

Polymorphisms of catechol-0-methyltransferase (COMT), monoamine oxidase B (MAOB), N-acetyltransferase 2 (NAT2) and cytochrome P450 2D6 (CYP2D6) gene in patients with early onset of Parkinson’s disease

The aim of the present study was to evaluate the contribution of MAOB, COMT, NAT2 and CYP2D6 gene polymorphisms to early onset Parkinson's disease (PD). The study enrolled 134 patients with Parkinson's disease (early onset-EOPD--67 patients, and late onset--LOPD--patients), and 66 healthy individuals. Polymerane chain reaction restriction fragment length polymorphism (PCR-RFLP) methods were used for genotyping. Univariate analysis revealed a significant two-fold higher EOPD risk among carriers of MAOB allele A or AA genotype. Multivariate analysis revealed that MAOB allele A was an independent factor predisposing to EOPD. It was shown that neither NAT2, CYP2D6 nor COMT genotype was associated with PD.

Pesticide exposure on southwestern Taiwanese with MnSOD and NQO1 polymorphisms is associated with increased risk of Parkinson's disease

BACKGROUND

Hypothetic mechanism of the individual vulnerability to oxidative stress through metabolism of environmental xenobiotics and genotypic polymorphisms has been considered to promote the development of Parkinson's disease (PD). In this case-control study, we determined the role of manganese-containing superoxide dismutase (MnSOD) and NAD(P)H: quinone oxidoreductase 1 (NQO1) genes in PD risk in a population with high prevalence of pesticide exposure.

METHODS

From southwestern region of Taiwan, we enrolled 153 patients with idiopathic PD and 155 healthy control subjects matched for age, sex and origin. Detailed questionnaires of face-to-face interviews among these subjects were collected. PCR-based restriction fragment length polymorphism (RFLP) assays were used to determine the genotypes of MnSOD (-9 T>C) and NQO1 (609 C>T) genes.

RESULTS

Exposure to pesticides associated with PD was significant among patients with an increased odds ratio (OR) of 1.69 (95%CI, 1.07-2.65), and this association remained significant after adjustment for age, sex, and cigarette smoking (aOR=1.68, 95%CI, 1.03-2.76, P=0.023). Considering genetic factors, there were no significant differences in frequencies of both genotypes of MnSOD and NQO1 polymorphisms between PD patients and the control subjects (P>0.05). However, this difference in genotype distribution was significant among subjects who had been exposed to pesticide, with aOR of 2.49 (95%CI, 1.18-5.26, P=0.0072) for MnSOD C allele and aOR of 2.42 (95%CI, 1.16-4.76, P=0.0089) for NQO1 T allele, respectively. Moreover, among subjects exposed to pesticide, the combined MnSOD/NQO1 variant genotype was significantly associated with a 4.09-fold increased risk of PD (95%CI, 1.34-10.64, P=0.0052).

CONCLUSION

Susceptible variants of MnSOD and NQO1 genes may interact with occupational pesticide exposure to increase PD risk in southwestern Taiwanese.

Family-based case-control study of MAOA and MAOB polymorphisms in Parkinson disease

Monoamine oxidase (MAO) is an enzyme regulating metabolism of neurotransmitters such as dopamine. Two distinct forms of enzyme, encoded by genes MAOA and MAOB located on the X chromosome, have been considered as possible factors in the pathogenesis of Parkinson disease (PD). Previous association studies of PD and MAO genes reported inconsistent results. In this study, we used a large family-based data set to test associations between MAO genes and a risk of PD. The data set includes 298 female discordant sibpairs and 348 male discordant sibpairs. For this study, all subjects analyzed were white and families with known parkin mutations were removed. We analyzed 15 single nucleotide polymorphisms (SNPs) and a dinucleotide repeat marker in the MAO genes. Association was found with the intron 13 SNP of MAOB in the female subset (P = 0.02). No significant association was found in the male subset. Our results add to the evidence of involvement of MAOB in PD and suggest that the effect may be stronger in women.

X-APL: an improved family-based test of association in the presence of linkage for the X chromosome

Family-based association methods have been developed primarily for autosomal markers. The X-linked sibling transmission/disequilibrium test (XS-TDT) and the reconstruction-combined TDT for X-chromosome markers (XRC-TDT) are the first association-based methods for testing markers on the X chromosome in family data sets. These are valid tests of association in family triads or discordant sib pairs but are not theoretically valid in multiplex families when linkage is present. Recently, XPDT and XMCPDT, modified versions of the pedigree disequilibrium test (PDT), were proposed. Like the PDT, XPDT compares genotype transmissions from parents to affected offspring or genotypes of discordant siblings; however, the XPDT can have low power if there are many missing parental genotypes. XMCPDT uses a Monte Carlo sampling approach to infer missing parental genotypes on the basis of true or estimated population allele frequencies. Although the XMCPDT was shown to be more powerful than the XPDT, variability in the statistic due to the use of an estimate of allele frequency is not properly accounted for. Here, we present a novel family-based test of association, X-APL, a modification of the test for association in the presence of linkage (APL) test. Like the APL, X-APL can use singleton or multiplex families and properly infers missing parental genotypes in linkage regions by considering identity-by-descent parameters for affected siblings. Sampling variability of parameter estimates is accounted for through a bootstrap procedure. X-APL can test individual marker loci or X-chromosome haplotypes. To allow for different penetrances in males and females, separate sex-specific tests are provided. Using simulated data, we demonstrated validity and showed that the X-APL is more powerful than alternative tests. To show its utility and to discuss interpretation in real-data analysis, we also applied the X-APL to candidate-gene data in a sample of families with Parkinson disease.

Gene-environment interactions in sporadic Parkinson's disease

Much has been learned in recent years about the genetics of familial Parkinson's disease. However, far less is known about those malfunctioning genes which contribute to the emergence and/or progression of the vast majority of cases, the 'sporadic Parkinson's disease', which is the focus of our current review. Drastic differences in the reported prevalence of Parkinson's disease in different continents and countries suggest ethnic and/or environmental-associated multigenic contributions to this disease. Numerous association studies showing variable involvement of multiple tested genes in these distinct locations support this notion. Also, variable increases in the risk of Parkinson's disease due to exposure to agricultural insecticides indicate complex gene-environment interactions, especially when genes involved in protection from oxidative stress are explored. Further consideration of the brain regions damaged in Parkinson's disease points at the age-vulnerable cholinergic-dopaminergic balance as being involved in the emergence of sporadic Parkinson's disease in general and in the exposure-induced risks in particular. More specifically, the chromosome 7 ACHE/PON1 locus emerges as a key region controlling this sensitive balance, and animal model experiments are compatible with this concept. Future progress in the understanding of the genetics of sporadic Parkinson's disease depends on globally coordinated, multileveled studies of gene-environment interactions.

Association between a functional COMT polymorphism, mental retardation and cognition in Qinba area children

Catechol-O-methyl transferase (COMT) plays an important role in the metabolism of neurotransmitters. Two alleles of the COMT gene as a result of a G/A transition in the exon 4 can lead to different COMT enzymatic activities. Much genetic research has revealed that this COMT functional polymorphism was related to human psychiatric disorders. Polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) methods were used to discern the relationships among the functional polymorphism of COMT, mental retardation (MR), and general cognitive ability of children. The results of the case-control analysis showed that there was no association between the frequencies of genotypes of COMT and MR (chi2=0.776, P>0.05) or between the frequency of COMT alleles and MR (chi2=0.335, P>0.05). COMT polymorphism was found in children whose intelligence quotient (IQ) was above 55. In normal children (IQ> or =85), the frequencies of high-activity allele COMTH and the homozygote genotype COMTHH were 60.98% and 79.28%, respectively. Both were higher than those of the borderline group (46.67% and 70.67%, 0.10 > P>0.05). Therefore, the result of this study suggests that this functional polymorphism is not an important risk factor for MR, but the COMTHH genotype may have a positive effect on cognitive performance in normal children in the Qinba area.

Functional COMT variant predicts response to high dose pyridoxine in Parkinson's disease

Pyridoxal-5-phosphate, the biological active form of pyridoxine, is a cofactor for dopa-decarboxylase (DDC) enzyme. Pyridoxine may augment the conversion of levodopa to dopamine in the periphery and therefore decrease availability of levodopa to the brain. However, this effect can be negated in the presence of a DDC inhibitor, which potentiates plasma levodopa level. A single nucleotide polymorphism at the nucleotide 1947 in the catechol-O-methyltransferase (COMT) gene encodes the high (COMT(H)) and low activity (COMT(L)) forms of the enzyme. In this study, we examined the effect of the COMT(L) allele on the clinical response to pyridoxine in Parkinson's disease (PD) patients. PD patients who were on stable and optimized dose of levodopa were included in this study. Their mean motor and activities of living score improved after high dose pyridoxine (P = 0.09, P = 0.04), and worsened after a washout period (P = 0.005, P = 0.001). Using a multivariate model, the presence of the COMT(L) allele predicted response to pyridoxine, with the best outcome observed in COMT(L/L) homozygotes. Our observational study suggests that the status the functional COMT(L) variant may be potentially useful to select PD patients for high dose pyridoxine therapy.

Genetic contributions to Parkinson's disease

Sporadic Parkinson's disease (PD) is a common neurodegenerative disorder, characterized by the loss of midbrain dopamine neurons and Lewy body inclusions. It is thought to result from a complex interaction between multiple predisposing genes and environmental influences, although these interactions are still poorly understood. Several causative genes have been identified in different families. Mutations in two genes [alpha-synuclein and nuclear receptor-related 1 (Nurr1)] cause the same pathology, and a third locus on chromosome 2 also causes this pathology. Other familial PD mutations have identified genes involved in the ubiquitin-proteasome system [parkin and ubiquitin C-terminal hydroxylase L1 (UCHL1)], although such cases do not produce Lewy bodies. These studies highlight critical cellular proteins and mechanisms for dopamine neuron survival as disrupted in Parkinson's disease. Understanding the genetic variations impacting on dopamine neurons may illuminate other molecular mechanisms involved. Additional candidate genes involved in dopamine cell survival, dopamine synthesis, metabolism and function, energy supply, oxidative stress, and cellular detoxification have been indicated by transgenic animal models and/or screened in human populations with differing results. Genetic variation in genes known to produce different patterns and types of neurodegeneration that may impact on the function of dopamine neurons are also reviewed. These studies suggest that environment and genetic background are likely to have a significant influence on susceptibility to Parkinson's disease. The identification of multiple genes predisposing to Parkinson's disease will assist in determining the cellular pathway/s leading to the neurodegeneration observed in this disease.

Polymorphism in candidate genes: implications for the risk and treatment of idiopathic Parkinson's disease

Idiopathic Parkinson's disease (IPD) is a progressive neurodegenerative disorder for which no restorative or neuroprotective therapy is available. Interest has recently been directed to association studies on polymorphisms of various genes, mainly those related to dopamine metabolism and transport, and their effect on response to PD, which includes primarily levodopa and dopaminomimetics. Approximately 15-20% of patients with PD do not respond to levodopa, and the majority of those who do respond develop adverse fluctuations in motor response, primarily levodopa-induced dyskinesias. This review summarizes the influence of polymorphisms in various genes on the relative risk of IPD and on levodopa efficacy. It focuses on the importance of well-designed polymorphism studies that include large samples of patients with IPD and tightly matched controls and use identical methodologies. Valid data on such polymorphisms might increase the efficacy of levodopa, decrease its side effects, and reduce the occurrence of levodopa-induced dyskinesias. They might also provide a novel diagnostic tool for PD.

Neurodegenerative disorders associated with diabetes mellitus

More than 20 syndromes among the significant and increasing number of degenerative diseases of neuronal tissues are known to be associated with diabetes mellitus, increased insulin resistance and obesity, disturbed insulin sensitivity, and excessive or impaired insulin secretion. This review briefly presents such syndromes, including Alzheimer disease, ataxia-telangiectasia, Down syndrome/trisomy 21, Friedreich ataxia, Huntington disease, several disorders of mitochondria, myotonic dystrophy, Parkinson disease, Prader-Willi syndrome, Werner syndrome, Wolfram syndrome, mitochondrial disorders affecting oxidative phosphorylation, and vitamin B(1) deficiency/inherited thiamine-responsive megaloblastic anemia syndrome as well as their respective relationship to malignancies, cancer, and aging and the nature of their inheritance (including triplet repeat expansions), genetic loci, and corresponding functional biochemistry. Discussed in further detail are disturbances of glucose metabolism including impaired glucose tolerance and both insulin-dependent and non-insulin-dependent diabetes caused by neurodegeneration in humans and mice, sometimes accompanied by degeneration of pancreatic beta-cells. Concordant mouse models obtained by targeted disruption (knock-out), knock-in, or transgenic overexpression of the respective transgene are also described. Preliminary conclusions suggest that many of the diabetogenic neurodegenerative disorders are related to alterations in oxidative phosphorylation (OXPHOS) and mitochondrial nutrient metabolism, which coincide with aberrant protein precipitation in the majority of affected individuals.

Lack of effect of polymorphisms in dopamine metabolism related genes on imaging of TRODAT-1 in striatum of asymptomatic volunteers and patients with Parkinson's disease

SPECT scanning using (99)Tc-TRODAT-1, a ligand that binds to dopamine transporters, may be useful for detection of early Parkinson's disease (PD), diagnosis of presymptomatic individuals, and monitoring disease progression. Understanding whether genetic factors contribute to inter-individual variability is crucial for interpreting imaging results in the context of disease pathophysiology. We tested whether polymorphisms in the genes for catechol-O-methyltransferase (COMT), monoamine-oxidase B (MAO-B), and the dopamine transporter (DAT) influence dopamine uptake parameters in the striatum in vivo in asymptomatic volunteers and patients with PD as measured with (99)Tc-TRODAT-1. (99)Tc-TRODAT-1 binding declined with age in both asymptomatic volunteers and PD patients, and depended on disease duration in PD patients. We found no significant association between COMT, MAO-B, and DAT polymorphisms and results of (99)Tc-TRODAT-1 testing in asymptomatic volunteers or patients with PD. In PD patients, the age of disease onset and speed of progression did not differ based on these polymorphisms. These results demonstrate that these specific genetic variations do not alter the fidelity of (99)Tc-TRODAT-1 as a measure of dopaminergic function in asymptomatic volunteer individuals or patients with PD.

Monoamine oxidase B polymorphism, cigarette smoking and risk of Parkinson's disease: a study in an Asian population

Cigarette smoking is associated with reduced monoamine oxidase B (MAO B) activity. Polymorphisms of the MAO B gene may modify the relationship between smoking and Parkinson's Disease (PD). We examined the association of MAO B intron 13 G/A polymorphism and risk of PD, and the modulation of the polymorphism on smoking and PD in an Asian study population in Singapore. Two hundred and thirty PD patients (mean age 66.0 +/- 9.4 years, 63% men) and 241 age, gender, and race matched controls (mean age 64 +/- 9.2 years, 58.9% males) were studied. The frequency of G and A alleles in PD and controls was; 66/315 (21.0%) vs. 73/340 (21.5%) and 249/315 (79.0%) vs. 267/340 (78.5%). For women, the genotype frequency in PD and controls was; GG: 7/85 (8.2%) vs. 8/99 (8.1%); GA: 25/85 (29.4%) vs. 27/99 (27.3%); AA: 53/85 (62.4%) vs. 64/99 (64.6%). For men, allele frequency in PD and controls was; A: 118/145 (81.4%) vs. 112/142 (78.9%) and G: 27/145 (18.6%) vs. 30/142 (21.1%). The allele and genotype frequencies were not significantly different between young and late onset PD. The frequency of "ever" smokers in PD and controls was 31/230 (13.5%) vs. 52/241 (21.6%), P = 0.02. A stepwise logistic regression analysis did not reveal any interaction of smoking and the G allele and risk of PD. The MAO B G/A genotype frequency in our Asian population was quite different from Caucasians suggesting that ethnicity specific effects need to be considered in evaluating gene-environmental interaction.

Case-control study of dopamine transporter-1, monoamine oxidase-B, and catechol-O-methyl transferase polymorphisms in Parkinson's disease

We investigated the association of Parkinson's disease (PD) with dopamine transporter-1 (DAT1), monoamine oxidase-B (MAO-B), and catechol-O-methyltransferase (COMT) gene polymorphisms. Overall, we observed no significant association of PD with the DAT1-3'-variable numbers of tandem repeats, the MAO-B-(GT)(n), and the COMT-Val108Met gene polymorphisms in a sample of 319 unrelated PD cases and 196 control subjects. Analyses stratified by sex, age at examination, family history of PD, and ethnic origin also yielded negative findings, with three exceptions. We found statistically significant associations of PD with MAO-B polymorphisms in older patients and with a COMT polymorphism in younger subjects and in women. These significant differences at the two-tailed alpha level of 0.05 and restricted to subgroup analyses may have a biological basis or may be chance findings.

Association between dopamine transporter gene polymorphism and susceptibility to Parkinson's disease in Japan

We studied a polymorphism in the dopamine transporter (DAT) gene in 236 Japanese patients with Parkinson's disease (PD) and compared the results with 220 controls. The 1215A/G genotype of the DAT gene was significantly different between PD patients and controls, suggesting a possible involvement of DAT in genetic susceptibility to PD.

Genetic modelling of the estrogen metabolism as a risk factor of hormone-dependent disorders

Estradiol is a pleiotropic hormone, involved in the etiology of a wide variety of diseases. Over the last decade individual genetic variability of the estradiol metabolism has been described as a significant contributor to disease susceptibility with variations depending on ethnic background. Among others, genetic variations of genes encoding cytochrome P450 (CYP) enzymes play an important role in this regard. Mutant alleles of the CYP 1A1 gene are major modulators of lung cancer risk among smokers, mediate gender differences in lung cancer susceptibility, and have been associated with an elevated risk for developing breast, prostate, colorectal, and oral squamous cell cancer. Variants of the CYP 1B1 gene modulate the risk for developing prostate, ovarian, lung, and breast cancer. Also, mutations in the CYP 1B1 gene are the major genetic determinant of congenital glaucoma. Mutant CYP 17 alleles are associated with serum and plasma levels of steroid hormones, use of hormone replacement therapy, and the development of endometrial, prostate, and breast cancer. Available data indicate that the protective effect against breast cancer of a later age at menarche is limited to wild-type CYP 17 allele carriers. Among women with the polycystic ovary syndrome, carriage of mutant CYP 17 alleles is sufficient to aggravate the clinical presentation of the disease. Molecular variants of the CYP 19 gene are associated with an increased risk for developing breast cancer, advanced breast cancer stages, and tumor aromatase production. Carriage of a mutant catechol-O-methyltransferase allele is associated with breast cancer, neurologic disorders such as Parkinson's disease, and modulates behavior among patients with schizophrenia, alcoholics and the general population. In summary, the available evidence points to genes that encode estrogen-metabolizing enzymes as strong hereditary determinants of the susceptibility to benign as well as malignant conditions.

Genetic modeling of estrogen metabolism as a risk factor of hormone-dependent disorders

Estradiol is a pleiotropic hormone, involved in the etiology of a wide variety of diseases. Over the last decade individual genetic variability of the estradiol metabolism has been described as a significant contributor to disease susceptibility with variations depending on ethnic background. Among others, genetic variations of genes encoding cytochrome P450 (CYP) enzymes play an important role in this regard. Mutant alleles of the CYP 1A1 gene are major modulators of lung cancer risk among smokers, mediate gender differences in lung cancer susceptibility, and have been associated with an elevated risk for breast, prostate, colorectal, and oral squamous cell cancer. Variants of the CYP 1B1 gene modulate the risk for prostate, ovarian, lung, and breast cancer. Also, mutations in the CYP 1B1 gene are the major genetic determinant of congenital glaucoma. Mutant CYP 17 alleles are associated with serum and plasma levels of steroid hormones, use of hormone replacement therapy, and endometrial, prostate, and breast cancer. Available data indicate that the protective effect of a later age at menarche is limited to mutant CYP 17 allele carriers. Among women with the Polycystic Ovary (PCO) syndrome, mutant CYP 17 alleles are sufficient to aggravate the clinical presentation of the disease. Molecular variants of the CYP 19 gene are associated with an increased risk for breast cancer, advanced disease stage, and tumor aromatase production. Carriage of a mutant catechol-O-methyltransferase (COMT) allele is associated with breast cancer, neurologic disorders such as Parkinson's disease, and modulates behavior among patients with schizophrenia, alcoholics and the general population. In summary, the available evidence points to estrogen metabolising genes as strong hereditary determinants of the susceptibility to benign and malignant conditions.