Probable multiple system atrophy in a German family. J Neurol Neurosurg Psychiatry 75: 924–925

Abstract: Mutations in LRRK2 were first reported as causing Parkinson's disease (PD) in late 2004. Since then, approximately a dozen LRRK2 substitutions have been identified that are believed to be pathogenic mutations. The substitution of adenine for guanine at nucleotide 4541 (4541G>A) in LRRK2 was recently reported. This substitution resulted in the replacement of an arginine at position 1514 with a glutamine (R1514Q). Although this substitution was not found in a large cohort of controls, its pathogenicity could not be verified. We have now genotyped the R1514Q substitution in a sample of 954 PD patients from 429 multiplex PD families. This substitution was identified in 1.8% of the PD patients; however, the majority of the PD sibships segregating this substitution were discordant for this putative mutation. In addition, the R1514Q substitution was detected in 1.4% of neurologically evaluated, control individuals. These data suggest that the R1514Q variant is not a pathogenic LRRK2 mutation. We believe it is imperative that the causative nature of any newly identified genetic variant be determined before it is included in any panel for diagnostic testing. © 2006 Movement Disorder Society Key words: Parkinson's disease; genetics; LRRK2; mutation Parkinson's disease (PD) is the second most common neurodegenerative disorder. Clinical features of PD include resting tremor, rigidity, bradykinesia, and postural instability. Although quite variable, the average age of onset is 60 years. In addition, there is a slight preponderance of affected men. Pathologically, PD is characterized by the presence of Lewy bodies and progressive degeneration of neurons in the substantia nigra, pars compacta, and other brain regions. In our ongoing effort to identify additional PD susceptibility genes, we have recruited a large cohort of PD families. The control sample was collected through three sources and provided appropriate written informed consent. One sample of controls (n ϭ 52) was ascertained in Indiana, and all control subjects were examined by a single Parkinson Study Group movement disorder specialist. These control subjects completed the identical clinical evaluation as the PD sample. Individuals were considered controls if they met the following criteria: did not have a diagnosis or symptoms of PD, Alzheimer's disease (AD), stroke, or other neurological disorder; no tremor; no other first-degree family members reported to be diagnosed with PD; and no history of polio. The average age at examination of these first control subjects was 68.3 years, with a range of 55 to 82 years. All individuals were non-Hispanic Caucasians. A second control sample (n ϭ 40) was obtained from the National Cell Repository for Alzheimer's Disease. The subjects were recruited as part of an ongoing genetic initiative to make available to the research community a sample of rigorously evaluated individuals without any evidence of neurological disease. All control subjects were evaluated, and there was no evidence for either PD or dementia. The average age at examination of the second control cohort was 76.9 years, with a range of 58 to 91 years. As was the case with the first control set, all subjects from the second control set were non-Hispanic Caucasians. DNA was prepared from peripheral blood samples collected from the PD families and control subjects. The third control sample (n ϭ 276) is composed of three neurologically normal Caucasian control panels (NDPT002, NDPT006, NDPT009) obtained from the NINDS Human Genetics Resource Center at the Coriell Institute Coriell Cell Repositories (Camden, NJ). This third control sample contains 132 males and 144 females. The average age at examination of the subjects was 69.7 years, with a range of 55 to 88 years. In total, 368 neurologically normal control samples were evaluated. The guanine to adenine substitution at nucleotide 4541 of the LRRK2 cDNA that results in the R1514Q Lrrk2 (dardarin) protein variant was screened for using a newly developed TaqMan allelic-discrimination assay (Applied Biosystems). The assay was performed with 30 ng of genomic DNA from each PD subject and control individual using conditions recommended by the manufacturer and an Applied Biosystems 7300 Real Time PCR System. Of 954 affected individuals from 12 different families, 16 (1.8%) were shown to be heterozygous carriers of the R1514Q variant. In addition, 5 (1.4%) of 368 control subjects were also found to be heterozygous for the same variant similar to the frequency observed by Zimprich and associates. Discordance for the mutation among affected individuals was observed in 10 of the 13 families in which the variant was segregating. Of the 28 affected individuals in these 12 families for whom DNA was available for study, 12 of them do not carry the R1514Q variant. This finding suggests that the R1514Q variant is not segregating with PD in these families. No statistically significant difference between the R1514Q carrier group (16) and the noncarrier group (938) was detected in our analyses of numerous parameters, including age of disease onset (61.75 years in R1514Q carriers vs. 60.9 years in noncarriers), disease duration (7.18 years carriers vs. 9.53 years noncarriers), Mini-Mental State Examination score (25.62 carriers vs. 26.48 noncarriers), Blessed Functional Activity Scale (3.66 carriers vs. 4.41 noncarriers), Hoehn & Yahr (2.2 carriers vs. 2.48 noncarriers), and ethnicity. Taken together, these data suggest that the R1514Q variant is likely a nonpathogenic variant in Lrrk2 that does not contribute to the development of Parkinson disease, confirming the report of Zimprich and coworkers

Survival in patients with spinocerebellar ataxia types 1, 2, 3, and 6 (EUROSCA): a longitudinal cohort study

BACKGROUND: Spinocerebellar ataxias are dominantly inherited progressive ataxia disorders that can lead to premature death. We aimed to study the overall survival of patients with the most common spinocerebellar ataxias (SCA1, SCA2, SCA3, and SCA6) and to identify the strongest contributing predictors that affect survival. METHODS: In this longitudinal cohort study (EUROSCA), we enrolled men and women, aged 18 years or older, from 17 ataxia referral centres in ten European countries; participants had positive genetic test results for SCA1, SCA2, SCA3, or SCA6 and progressive, otherwise unexplained, ataxias. Survival was defined as the time from enrolment to death for any reason. We used the Cox regression model adjusted for age at baseline to analyse survival. We used prognostic factors with a p value less than 0·05 from a multivariate model to build nomograms and assessed their performance based on discrimination and calibration. The EUROSCA study is registered with ClinicalTrials.gov, number NCT02440763. FINDINGS: Between July 1, 2005, and Aug 31, 2006, 525 patients with SCA1 (n=117), SCA2 (n=162), SCA3 (n=139), or SCA6 (n=107) were enrolled and followed up. The 10-year survival rate was 57% (95% CI 47–69) for SCA1, 74% (67–81) for SCA2, 73% (65–82) for SCA3, and 87% (80–94) for SCA6. Factors associated with shorter survival were: dysphagia (hazard ratio 4·52, 95% CI 1·83–11·15) and a higher value for the Scale for the Assessment and Rating of Ataxia (SARA) score (1·26, 1·19–1·33) for patients with SCA1; older age at inclusion (1·04, 1·01–1·08), longer CAG repeat length (1·16, 1·03–1·31), and higher SARA score (1·15, 1·10–1·20) for patients with SCA2; older age at inclusion (1·44, 1·20–1·74), dystonia (2·65, 1·21–5·53), higher SARA score (1·26, 1·17–1·35), and negative interaction between CAG and age at inclusion (0·994, 0·991–0·997) for patients with SCA3; and higher SARA score (1·17, 1·08–1·27) for patients with SCA6. The nomogram-predicted probability of 10-year survival showed good discrimination (c index 0·905 [SD 0·027] for SCA1, 0·822 [0·032] for SCA2, 0·891 [0·021] for SCA3, and 0·825 [0·054] for SCA6). INTERPRETATION: Our study provides quantitative data on the survival of patients with the most common spinocerebellar ataxias, based on a long follow-up period. These results have implications for the design of future interventional studies of spinocerebellar ataxias; for example, the prognostic survival nomogram could be useful for selection and stratification of patients. Our findings need validation in an external population before they can be used to counsel patients and their families. FUNDING: European Union 6th Framework programme, German Ministry of Education and Research, Polish Ministry of Scientific Research and Information Technology, European Union 7th Framework programme, and Fondation pour la Recherche Médicale