Novel extreme homozygote haplotypes at the human caveolin 1 gene upstream purine complex in sporadic Alzheimer's disease

Impact of a variable number tandem repeat in the CYP2C9 promoter on warfarin sensitivity and responsiveness in Jordanians with cardiovascular disease

Purpose

The purpose of this study was to investigate the influence of CYP/CYP450 2C9 (CYP2C9) promoter variable number tandem repeat (p-VNTR) polymorphism on susceptibility to cardiovascular disease and on warfarin sensitivity and responsiveness, in Jordanians with cardiovascular disease during initiation and stabilization phases of therapy.

Patients and methods

A total of 211 cardiovascular patients who were being treated with warfarin anticoagulants and 205 healthy individuals were enrolled in this study. PCR-based methods were performed to analyze the effects of CYP2C9 p-VNTR polymorphism on warfarin metabolism. The p-VNTR polymorphism was composed of tandem repeat motifs sorted into three alleles based on the length and structure: short (p-VNTR-S), middle (p-VNTR-M), and long (p-VNTR-L).

Results

We found that the genotypic and allelic frequencies differ significantly between patients and healthy individuals; therefore, our results suggest that this polymorphism is associated with cardiovascular disease in the Jordanian population. Moreover, during the initiation phase of therapy, 20% of warfarin-sensitive patients were homozygous for a short allele (p-VNTR-S), and 12.2% were heterozygous for this allele (p-VNTR-M/p-VNTR-S). During the stabilization phase, no significant differences were found between these groups and their genotypic frequencies. Additionally, we did not confirm any relationship between the CYP2C9 p-VNTR polymorphism and warfarin response during either the initiation or the stabilization phases of therapy.

Conclusion

Our data show a significant difference between the CYP2C9 p-VNTR polymorphism and risk of cardiovascular disease, in addition to significant association between this polymorphism and sensitivity to warfarin at the initiation phase of therapy in a Jordanian population. However, there is no correlation between this polymorphism and warfarin response, international normalized ratio (INR) values, or required warfarin dose to achieve a target INR either at the initiation or stabilization phases of therapy. To further corroborate our results, additional studies are required with a larger number of samples and different ethnic groups.

Skewing of the genetic architecture at the ZMYM3 human-specific 5' UTR short tandem repeat in schizophrenia

Differential expansion of a number of human short tandem repeats (STRs) at the critical core promoter and 5' untranslated region (UTR) support the hypothesis that at least some of these STRs may provide a selective advantage in human evolution. Following a genome-wide screen of all human protein-coding gene 5' UTRs based on the Ensembl database ( http://www.ensembl.org ), we previously reported that the longest STR in this interval is a (GA)₃₂, which belongs to the X-linked zinc finger MYM-type containing 3 (ZMYM3) gene. In the present study, we analyzed the evolutionary implication of this region across evolution and examined the allele and genotype distribution of the "exceptionally long" STR by direct sequencing of 486 Iranian unrelated male subjects consisting of 196 cases of schizophrenia (SCZ) and 290 controls. We found that the ZMYM3 transcript containing the STR is human-specific (ENST00000373998.5). A significant allele variance difference was observed between the cases and controls (Levene's test for equality of variances F = 4.00, p < 0.03). In addition, six alleles were observed in the SCZ patients that were not detected in the control group ("disease-only" alleles) (mid p exact < 0.0003). Those alleles were at the extreme short and long ends of the allele distribution curve and composed 4% of the genotypes in the SCZ group. In conclusion, we found skewing of the genetic architecture at the ZMYM3 STR in SCZ. Further, we found a bell-shaped distribution of alleles and selection against alleles at the extreme ends of this STR. The ZMYM3 STR sets a prototype, the evolutionary course of which determines the range of alleles in a particular species. Extreme "disease-only" alleles and genotypes may change our perspective of adaptive evolution and complex disorders. The ZMYM3 gene "exceptionally long" STR should be sequenced in SCZ and other human-specific phenotypes/characteristics.

Biased homozygous haplotypes across the human caveolin 1 upstream purine complex in Parkinson's disease

The alpha-synuclein-caveolin 1 axis is suggested to be of role in the pathogenesis of Parkinson's disease in cell line models. The objective of this study was to analyze the homozygous haplotype compartment of the human caveolin 1 gene upstream purine complex in patients afflicted with Parkinson's disease. This complex was screened in patients with Parkinson's disease (n = 141) and compared with a group of controls (n = 760) using polymerase chain reaction and sequencing. The expression activity of the homozygous haplotypes was then examined using luciferase Dual-Glo system in human neuronal cell line, LAN-5. Six haplotypes were found to be homozygous in the patients, and not in the control pool (Fisher exact p < 1 × 10(-6)). Three of those haplotypes were specific to Parkinson's disease (Fisher exact p < 0.002), and the remaining three overlapped with homozygous haplotypes in Alzheimer's disease and multiple sclerosis (Fisher exact p < 0.002). The disease haplotypes contained motif lengths that were nonexistent in the control homozygous haplotype pool and significantly increased gene expression (p < 9 × 10(-6)). We conclude that skew in the caveolin 1 purine complex homozygous haplotype compartment and an additive effect of those haplotypes may be linked with Parkinson's disease.

Dyslipidemia and dementia: current epidemiology, genetic evidence, and mechanisms behind the associations

The role of cholesterol in the etiology of Alzheimer's disease (AD) is still controversial. Some studies exploring the association between lipids and/or lipid lowering treatment and AD indicate a harmful effect of dyslipidemia and a beneficial effect of statin therapy on AD risk. The findings are supported by genetic linkage and association studies that have clearly identified several genes involved in cholesterol metabolism or transport as AD susceptibility genes, including apolipoprotein E, apolipoprotein J, and the sortilin-related receptor. Functional cell biology studies support a critical involvement of lipid raft cholesterol in the modulation of amyloid-β protein precursor (AβPP) processing by β- and γ-secretase resulting in altered amyloid-β production. Contradictory evidence comes from epidemiological studies showing no or controversial association between dyslipidemia and AD risk. Additionally, cell biology studies suggest that there is little exchange between circulating and brain cholesterol, that increased membrane cholesterol is protective by inhibiting loss of membrane integrity through amyloid cytotoxicity, and that cellular cholesterol inhibits co-localization of BACE1 and AβPP in non-raft membrane domains, thereby increasing generation of plasmin, an amyloid-β-degrading enzyme. The aim of this review is to summarize the findings of epidemiological and cell biological studies to elucidate the role of cholesterol in AD etiology.

The genetics and neuropathology of Alzheimer's disease

Here we review the genetic causes and risks for Alzheimer's disease (AD). Early work identified mutations in three genes that cause AD: APP, PSEN1 and PSEN2. Although mutations in these genes are rare causes of AD, their discovery had a major impact on our understanding of molecular mechanisms of AD. Early work also revealed the ε4 allele of the APOE as a strong risk factor for AD. Subsequently, SORL1 also was identified as an AD risk gene. More recently, advances in our knowledge of the human genome, made possible by technological advances and methods to analyze genomic data, permit systematic identification of genes that contribute to AD risk. This work, so far accomplished through single nucleotide polymorphism arrays, has revealed nine new genes implicated in AD risk (ABCA7, BIN1, CD33, CD2AP, CLU, CR1, EPHA1, MS4A4E/MS4A6A, and PICALM). We review the relationship between these mutations and genetic variants and the neuropathologic features of AD and related disorders. Together, these discoveries point toward a new era in neurodegenerative disease research that impacts not only AD but also related illnesses that produce cognitive and behavioral deficits.

CYP2C9 promoter variable number tandem repeat polymorphism regulates mRNA expression in human livers

CYP2C9 is involved in metabolism of nearly 25% of clinically used drugs. Coding region polymorphisms CYP2C9*2 and *3 contribute to interperson variability in drug dosage and clinical outcomes, whereas the role of a regulatory polymorphism remains uncertain. Measuring allelic RNA expression in 87 human liver samples, combined with genotyping, sequencing, and reporter gene assays, we identified a promoter variable number tandem repeat polymorphism (pVNTR) that fully accounted for allelic CYP2C9 mRNA expression differences. Present in three different variant forms [short (pVNTR-S), medium (pVNTR-M), and long (pVNTR-L)], only the pVNTR-S allele reduced the CYP2C9 mRNA level compared with the pVNTR-M (reference) allele. pVNTR-S is in linkage disequilibrium with *3, with linkage disequilibrium r(2) of 0.53 to 0.75 in different populations. In patients who were taking a maintenance dose of warfarin, the mean warfarin dose was associated with the copies of pVNTR-S (p = 0.0001). However, in multivariate regression models that included the CYP2C9*3, pVNTR-S was no longer a significant predictor of the warfarin dose (p = 0.60). These results indicate that although pVNTR-S reduced CYP2C9 mRNA expression, the in vivo effects of pVNTR-S on warfarin metabolism cannot be separated from the effects of *3. Therefore, it is not necessary to consider pVNTR-S as an additional biomarker for warfarin dosing. Larger clinical studies are needed to define whether the pVNTR-S has a minimal effect in vivo, or whether the effect attributed to *3 is really a combination of effects on expression by the pVNTR-S along with effects on catalytic activity from the nonsynonymous *3 variant.