Krzysztof Czyzewski

Identification of a Novel LRRK2 Mutation Linked to Autosomal Dominant Parkinsonism: Evidence of a Common Founder across European Populations

Autosomal dominant parkinsonism has been attributed to pathogenic amino acid substitutions in leucine-rich repeat kinase 2 (LRRK2). By sequencing multiplex families consistent with a PARK8 assignment, we identified a novel heterozygous LRRK2 mutation. A referral sample of 248 affected probands from families with autosomal dominant parkinsonism was subsequently assessed; 7 (2.8%) were found to carry a heterozygous LRRK2 6055G-->A transition (G2019S). These seven patients originate from the United States, Norway, Ireland, and Poland. In samples of patients with idiopathic Parkinson disease (PD) from the same populations, further screening identified six more patients with LRRK2 G2019S; no mutations were found in matched control individuals. Subsequently, 42 family members of the 13 probands were examined; 22 have an LRRK2 G2019S substitution, 7 with a diagnosis of PD. Of note, all patients share an ancestral haplotype indicative of a common founder, and, within families, LRRK2 G2019S segregates with disease (multipoint LOD score 2.41). Penetrance is age dependent, increasing from 17% at age 50 years to 85% at age 70 years. In summary, our study demonstrates that LRRK2 G2019S accounts for parkinsonism in several families within Europe and North America. Our work highlights the fact that a proportion of clinically typical, late-onset PD cases have a genetic basis.

Genetic variation of Omi/HtrA2 and Parkinson's disease

Variants in the Omi/HtrA2 gene have been nominated as a cause of Parkinsons disease. This sequencing study of Omi/HtrA2 in 95 probands with apparent autosomal dominant inheritance of Parkinsons disease did not identify any pathogenic mutations. In addition, there was no association between common variations in the Omi/HtrA2 gene and susceptibility to Parkinsons disease in any of our four patient-control series (n=2373). Taken together our results do not support a role for Omi/HtrA2 variants in the pathogenesis of Parkinsons disease.

Hyperhomocysteinemia and methylenetetrahydrofolate reductase polymorphism in patients with Parkinson's disease

Elevated levels of homocysteine have been observed in Parkinsons disease (PD) patients treated with levodopa. However, it is not studied if duration of PD or PD per se is associated with hyperhomocysteinemia. In the present study, the levels of homocysteine in 99 levodopa-treated PD patients, 15 untreated PD patients and 100 controls were examined. We focused on the influence of levodopa dose, duration of therapy and disease as well as genetic (C677T methylenetetrahydrofolate reductase (MTHFR) polymorphism) and environmental factors. We found that levodopa-treated PD patients had elevated homocysteine plasma levels as compared to controls (p < 0.05), but the levels did not depend on levodopa doses. Another factor influencing homocysteine level was the duration of PD (p < 0.001). The frequency of allele C677T of MTHFR gene did not differ between PD and controls. In conclusion, hyperhomocysteinemia is associated with the duration of PD and levodopa treatment and possibly also with PD per se.

Behavioural Pathology in Alzheimer’s Disease with Special Reference to Apolipoprotein E Genotype

The aim of this study was to define the co-occurrence of behavioural symptoms and Alzheimer’s disease (AD) in relation to apolipoprotein E (APOE) genotype. Probable AD patients from the Alzheimer’s Day Clinic (n = 139) were assessed with the ‘Behavioural Pathology in Alzheimer’s Disease’ rating scale, and their APOE genotype was determined. This study demonstrated no relationship between presence of the APOE Ε4 allele and any of the behavioural symptoms assessed, including delusions, hallucinations, depression, activity disturbances, aggressiveness and anxiety. Activity disturbances, delusions, hallucinations and aggressiveness paralleled the severity of AD, increasing in frequency with the severity of the dementia. The prevalence of delusions, hallucinations, aggressiveness and depression were found to be associated with lower levels of education.

Mitochondrial transcription factor A variants and the risk of Parkinson's disease.

The mitochondrial transcription factor A (TFAM) has been recently shown to decrease reactive oxygen species (ROS) generation. It is also known that mitochondrial DNA (mtDNA) haplogroups might confer different coupling properties, resulting in different ROS levels. We hypothesized that potentially functional TFAM variants could influence PD risk depending on haplogroup background. To test this we assessed the role of six TFAM variants on PD risk in 326 PD patients and 316 controls, and correlated it with mtDNA haplogroup clusters (HV, JTKU and a putative functionally different group U4U5a1KJ1cJ2, connected previously with partial uncoupling of oxidative phosphorylation). Both genotype and haplotype analysis showed that intronic variant rs2306604 modifies PD risk. Multivariate logistic regression analysis confirmed that rs2306604 G/G genotype is an independent risk factor for PD (OR 1.789, 95% CI 1.162-2.755, p=0.008). There was a borderline interaction between G/G genotype and HV haplogroup (p=0.075). Haplotype analysis showed that all three haplotypes containing rs2306604 allele A occurred at higher frequencies in controls, but only one of them reached statistical significance (chi(2) 4.523, p=0.0334). Conversely, four of five haplotypes containing allele G had higher frequencies in PD group, with no statistical significance.

Mitochondrial targeting sequence variants of the CHCHD2 gene are a risk for Lewy body disorders

Objective: To assess the role of CHCHD2 variants in patients with Parkinson disease (PD) and Lewy body disease (LBD) in Caucasian populations. Methods: All exons of the CHCHD2 gene were sequenced in a US Caucasian patient-control series (878 PD, 610 LBD, and 717 controls). Subsequently, exons 1 and 2 were sequenced in an Irish series (355 PD and 365 controls) and a Polish series (394 PD and 350 controls). Immunohistochemistry and immunofluorescence studies were performed on pathologic LBD cases with rare CHCHD2 variants. Results: We identified 9 rare exonic variants of unknown significance. These variants were more frequent in the combined group of PD and LBD patients compared to controls (0.6% vs 0.1%, p = 0.013). In addition, the presence of any rare variant was more common in patients with LBD (2.5% vs 1.0%, p = 0.050) compared to controls. Eight of these 9 variants were located within the genes mitochondrial targeting sequence. Conclusions: Although the role of variants of the CHCHD2 gene in PD and LBD remains to be further elucidated, the rare variants in the mitochondrial targeting sequence may be a risk factor for Lewy body disorders, which may link CHCHD2 to other genetic forms of parkinsonism with mitochondrial dysfunction.

Novel A18T and pA29S substitutions in α-synuclein may be associated with sporadic Parkinson's disease.

OBJECTIVE Mutations in the α-synuclein-encoding gene SNCA are considered as a rare cause of Parkinsons disease (PD). Our objective was to examine the frequency of the SNCA point mutations among PD patients of Polish origin. METHODS Detection of the known SNCA point mutations A30P (c.88G>C), E46K (c.136G>A) and A53T (c.157A>T) was performed either using the Sequenom MassArray iPLEX platform or by direct sequencing of the SNCA exons 2 and 3. As the two novel substitutions A18T (c.52G>A) and A29S (c.85G>T) were identified, their frequency in a control population of Polish origin was assessed and in silico analysis performed to investigate the potential impact on protein structure and function. RESULTS We did not observe the previously reported point mutations in the SNCA gene in our 629 PD patients; however, two novel potentially pathogenic substitutions A18T and A29S were identified. Each variant was observed in a single patient presenting with a typical late-onset sporadic PD phenotype. Although neither variant was observed in control subjects and in silico protein analysis predicts a damaging effect for A18T and pA29S substitutions, the lack of family history brings into question the true pathogenicity of these rare variants. CONCLUSIONS Larger population based studies are needed to determine the pathogenicity of the A18T and A29S substitutions. Our findings highlight the possible role of rare variants contributing to disease risk and may support further screening of the SNCA gene in sporadic PD patients from different populations.

Strong association between Saitohin gene polymorphism and tau haplotype in the Polish population

The saitohin (STH) gene is located in intron 9 of the tau protein gene. It has been postulated that the R allele of Q7R polymorphism at the Saitohin gene is over-represented in the homozygous state in sporadic Alzheimers disease (AD). Tau protein was implicated in AD pathophysiology and the tau gene haplotype is probably connected with sporadic late-onset Parkinsons disease (PD). We analyzed the STH polymorphism and tau gene haplotype in 100 clinically diagnosed AD cases, 100 PD cases and 100 age-matched healthy controls. We found that the R allele of the STH gene is associated with the H2 haplotype of tau in all cases. Additionally we observed no correlation between R allele frequency and AD or PD.

TOMM40 and APOE common genetic variants are not Parkinson's disease risk factors

Polymorphic, deoxythymidine-tract in intron 6 of the TOMM40 gene has been associated with Alzheimers disease. We have investigated the impact of this polymorphism on Parkinsons disease risk and age of onset, independently and in combination with apolipoprotein E alleles, in a group of 407 PD patients and 305 control subjects. No significant association was observed at the single allele, genotype, or haplotype levels. Our data suggest that the polymorphism is not a risk factor for Parkinsons disease in the Polish population.

DNAJC13 p.Asn855Ser mutation screening in Parkinson's disease and pathologically confirmed Lewy body disease patients

Recently, a novel mutation in exon 24 of DNAJC13 gene (p.Asn855Ser, rs387907571) has been reported to cause autosomal dominant Parkinsons disease (PD) in a multi‐incident Mennonite family.