Liana Fidani

Complete screening for glucocerebrosidase mutations in Parkinson disease patients from Greece

Mutations in beta-glucocerebrosidase gene (GBA) have been implicated in Parkinson disease (PD). A Greek cohort of 172 PD patients and 132 control individuals were screened for GBA mutations by complete sequencing of the genes exons. Four mutations previously associated with Gaucher disease and/or Parkinsons disease (L445P, D409H, E326K, H255Q) were detected, as well as five newly identified variants (R329H, L268L, S271G, T428K, V460L), providing for the first time data regarding the frequency of GBA mutations among PD patients and controls, in the Greek population. H255Q was the most common GBA mutation among Greek PD patients (4/172). V460L was only found in control individuals (2/132). Overall, GBA mutations were significantly overrepresented in a subgroup of early onset PD patients, compared to controls (P = 0.019, OR = 4.2; 95%CI = 1.28 -- 13.82), suggesting that GBA mutations may modify age of onset for PD.

The genetic background of Parkinson's disease: current progress and future prospects.

Almost two decades of genetic research in Parkinsons disease (PD) have remarkably increased our knowledge regarding the genetic basis of PD with numerous genes and genetic loci having been found to cause familial PD or affect the risk for PD. Approximately 5–10% of PD patients have monogenic forms of the disease, exhibiting a classical Mendelian type of inheritance, however, the majority PD cases are sporadic, probably caused by a combination of genetic and environmental risk factors. Nowadays, six genes, alpha synuclein, LRRK2, VPS35, Parkin, PINK1 and DJ‐1, have definitely been associated with an autosomal dominant or recessive PD mode of inheritance. The advent of genome‐wide association studies (GWAS) and the implementation of new technologies, like next generation sequencing (NGS) and exome sequencing has undoubtedly greatly aided the identification on novel risk variants for sporadic PD. In this review, we will summarize the current progress and future prospects in the field of PD genetics.

Pharmacological treatment and the prospect of pharmacogenetics in Parkinson's disease.

Parkinson disease (PD) is a progressive movement disorder marked by tremor, rigidity, bradykinesia and postural instability. Levodopa (l‐dopa), usually combined with a peripheral dopa decarboxylase inhibitor, has been proved to provide the best symptomatic benefit for PD. However, its long‐term efficacy is limited because of motor complications and drug‐induced dyskinesia. Dopamine agonists, catechol‐O‐methyltransferase inhibitors and monoamine oxidase‐B inhibitors are anti‐parkinsonian (anti‐PD) drugs that have been found to further improve the potency of l‐dopa and prevent the onset of motor complications. However, as PD is a progressive disorder, all the drugs used for its therapy, manifest reduced efficacy and adverse effects with time. Research on the field of pharmacogenetics has pointed out that the genetic variability of each individual determines to a large extent the inter‐individual variability in response to anti‐PD drugs. Clinicogenetic trials show that drug efficacy or toxicity or susceptibility to side effects are features governed by genetic principles. This article is a review of the present pharmacological treatment of PD and current pharmacogenetic data for PD.

Methylenetetrahydrofolate reductase C677T polymorphism: Association with risk for childhood acute lymphoblastic leukemia and response during the initial phase of chemotherapy in greek patients

As of late, a number of studies have focused on the association of the gene for methyletetrahydrofolate reductase (MTHFR) with risk for acute lymphoblastic leukemia (ALL) in children and in adults, as well as with response to chemotherapy. The degree of this association may vary according to the ethnic background and geographic localization of the population under study, or the phase of treatment when response to chemotherapy is concerned.

An association study of a functional catalase gene polymorphism, −262C→T, and patients with Alzheimer's disease

According to the oxidative stress hypothesis which has been proposed as one of a number of possible mechanisms underlying pathogenesis of Alzheimers disease (AD), accumulation of hydrogen peroxide in the brain of affected individuals, due to overproduction and/or insufficient detoxification, can trigger a cascade of neurotoxic events, thus contributing to the neuronal damage characteristic of the disease. The upregulation of enzymes that are able to neutralize hydrogen peroxide (catalase, peroxidases) would then be conceivably able to offer at least some protection from the damaging effects of this agent. In this study we examined the distribution of a functional polymorphism in the gene for catalase, -262C-->T, in an independent population of 137 AD patients and 130 control individuals. The presence of the polymorphism, which results in the elimination of a SmaI restriction site, was tested with a PCR amplification/SmaI digestion-based assay. No significant difference has emerged from the comparison of either genotype or allele frequencies (P>0.5). We conclude that the catalase gene -262C-->T polymorphism does not confer a protective effect with respect to AD.

Association of the Tau haplotype with Parkinson's disease in the Greek population.

We compared the distribution of the Tau H1 haplotype and related subhaplotypes in a group of clinically diagnosed Parkinsons disease patients (n = 133) and in control individuals (n = 113) from northern Greece. We were able to detect a statistically significant overrepresentation of the H1H1 genotype in our patient group (OR for H1H1 vs. H1H2 and H2H2: 1.73; 95% CI: 1.03–2.90; P = 0.037). The H1 subhaplotype significantly associated with the disease in our population was different from the one previously reported for a Norwegian population, suggesting that the nature of the association of Tau with Parkinsons disease is influenced by ethnic variation.

An association study of the cholesteryl ester transfer protein TaqI B polymorphism with late onset Alzheimer's disease

Cholesteryl ester transfer protein (CETP) is reportedly able to affect the amount of cholesterol available for deposition and/or removal from peripheral tissues, in its capacity to mediate the transfer of cholesterol from high density lipoprotein (HDL) to very low density lipoprotein, in exchange for triacylglycerols from the latter. The TaqI B polymorphism of the human CETP gene has been associated with decreased CETP mass and an increase in HDL-cholesterol. While many studies have addressed the atherogenic or anti-atherogenic potential of this polymorphism, little is known about its effect on neurodegeneration, despite the fact that CETP is expressed in the brain and the disturbance of cholesterol homeostasis appears to be an important factor in the pathogenesis of Alzheimers disease (AD). In this report, we have compared the distribution of the TaqI B polymorphism in an independent population of 102 clinically diagnosed late onset AD patients and a spousal control group of 97 individuals. We have also examined the possible interaction between this polymorphism and two other polymorphisms suspected of affecting cholesterol flux, namely apolipoprotein E APOE epsilon4, and lipoprotein lipase LPLS447X. No statistically significant differences have emerged with respect to either genotype or allele frequencies between the AD and control populations. CETP TaqI B did not interact significantly with either APOE epsilon4 or LPLS447X, in this study.

No association between the lipoprotein lipase S447X polymorphism and Alzheimer's disease

Results from various genetic association studies of the lipoprotein lipase (LPL) S447X polymorphism and Alzheimers disease (AD), range from a statistically significant negative association of clinically examined patients to a non-significant but consistent trend for under-representation of the X447 allele in neuropathologically confirmed subjects. In this report we have compared the distribution of the above polymorphism in an independent group of clinically diagnosed AD patients, including a subgroup where the disease was pathologically confirmed, and a spousal control group. No statistically significant differences emerged from this comparison. We conclude that LPL cannot be a major factor in pathogenesis of AD.

Interleukin-1A polymorphism is not associated with late onset Alzheimer's disease

Over the past few years, association studies have proposed a number of potential genetic risk factors for Alzheimers disease (AD). With the exception of the varepsilon4 allele of the apolipoprotein E gene, whose association with the late onset type of AD (LOAD) has been confirmed, the relative significance of most of these associations is still in question. A polymorphism in the interleukin-1A gene (IL-1A2) has been suggested as a risk factor for the early onset as well as for LOAD. In this study, the distribution of IL-1A alleles was examined in a cohort of predominantly LOAD patients and in control individuals. No significant difference was detected in genotype or allele frequencies (odds ratios of 0.929 and 0.743, respectively; P>0.5). We conclude that IL-1A genotype is not a major risk factor for LOAD.

GSK3β polymorphisms, MAPT H1 haplotype and Parkinson's disease in a Greek cohort

To determine whether polymorphisms in the microtubule-associated protein tau (MAPT) and/or glycogen synthase kinase-3β (GSK3β) genes underpin susceptibility to Parkinsons disease (PD), we conducted a case-control association study in a Greek cohort of 196 PD cases and 163 healthy controls. In our study, the MAPT H1 haplotype was found to be significantly associated with PD, no association was detected between the intronic rs6438552 (-157 T/C) GSK3β polymorphism and PD, whereas the C/C genotype of the promoter rs334558 (-50 T/C) GSK3β polymorphism was found to exert a protective role. The C/C genotype of the rs334558 GSK3β polymorphism was also found to have an additional protective role in our MAPT H1/H1 PD subgroup. Haplotype analysis revealed that, the T-T haplotype of both GSK3β polymorphisms was over-represented in PD patients compared to controls, and this association was independent of MAPT H1 haplotype.