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Study Description

We performed a two-tiered, whole-genome association study of Parkinson disease (PD). For tier 1, we individually genotyped 198,345 uniformly spaced and informative single-nucleotide polymorphisms (SNPs) in 443 sibling pairs discordant for PD. For tier 2a, we individually genotyped 1,793 PD-associated SNPs (P<.01 in tier 1) and 300 genomic control SNPs in 332 matched case-unrelated control pairs. We identified 11 SNPs that were associated with PD (P<.01) in both tier 1 and tier 2 samples and had the same direction of effect. For these SNPs, we combined data from the case-unaffected sibling pair (tier 1) and case-unrelated control pair (tier 2) samples and employed a liberalization of the sibling transmission/disequilibrium test to calculate odds ratios, 95% confidence intervals, and P values. A SNP within the semaphorin 5A gene (SEMA5A) had the lowest combined P value (P=7.62E-6). The protein encoded by this gene plays an important role in neurogenesis and in neuronal apoptosis, which is consistent with existing hypotheses regarding PD pathogenesis. A second SNP tagged the PARK11 late-onset PD susceptibility locus (P=1.70E-5). In tier 2b, we also selected for genotyping additional SNPs that were borderline significant (P<.05) in tier 1 but that tested a priori biological and genetic hypotheses regarding susceptibility to PD (n=941 SNPs). In analysis of the combined tier 1 and tier 2b data, the two SNPs with the lowest P values (P=9.07E-6; P=2.96E-5) tagged the PARK10 late-onset PD susceptibility locus. Independent replication across populations will clarify the role of the genomic loci tagged by these SNPs in conferring PD susceptibility.

Note: The following instruments were used: 1)clinical assessments form and manual; 2) sibling screening form and manual; 3) unrelated control screening and manual; and 4) risk factors questionnaire and manual. All cases underwent #1, as did sibling controls screening positive (see below). Unrelated controls were not examined. All siblings underwent #2. All unrelated controls underwent #3. All subjects (cases, sibling controls, and unrelated controls) underwent #4.

Any publications using the data are to cite the original American Journal of Human Genetics article (Maraganore et al., 2005).

Investigators using the data collection instruments are to acknowledge Drs. Maraganore and Rocca, and cite grants ES-10751 and NS-33978.

  • Study Type: Case-Control
  • Number of study subjects that have individual level data available through Authorized Access: 1550

Authorized Access
Publicly Available Data (Public ftp)

Connect to the public download site. The site contains release notes and manifests. If available, the site also contains data dictionaries, variable summaries, documents, and truncated analyses.

Study Inclusion/Exclusion Criteria

Criteria for Cases: Cases were enrolled prospectively from the clinical practice of the Department of Neurology of the Mayo Clinic in Rochester, MN, from June 1996 through May 2004. They all resided within Minnesota or one of the surrounding four states (Wisconsin, Iowa, South Dakota, or North Dakota). All cases underwent a standardized clinical assessment performed by a neurologist sub-specialized in movement disorders. Cases had at least two of four cardinal signs of parkinsonism (rest tremor, rigidity, bradykinesia, and/or postural instability) and no features atypical for PD (such as unexplained upper motor neuron signs or cerebellar signs). When non-motor manifestations such as dysautonomia or dementia were present, they were mild and occurred late in the disease course. Subjects with secondary causes of parkinsonism (e.g., history of neuroleptic exposure, encephalitis, or multiple strokes) were excluded. All patients treated with a daily dosage total of 1 g of levodopa (in combination with carbidopa) had a more than minimal improvement in parkinsonism symptoms and signs.

Criteria for Controls: Unaffected siblings of cases, matched on gender when able then on closest age at study (tier 1); or unrelated population controls, matched on gender and age at study (tier 2). All controls screened negative for parkinsonism via telephone interview, or were confirmed to not have parkinsonism via clinical assessment.

Molecular Data
TypeSourcePlatformNumber of Oligos/SNPsSNP Batch IdComment
Whole Genome Genotyping Perlegen PERLEGEN-85K 85000 N/A
Selected publications
Diseases/Traits Related to Study (MESH terms)
Links to Other NCBI Resources
Authorized Data Access Requests
Study Attribution
  • Lead Principal Investigator
    • Demetrius M. Maraganore. Mayo Clinic, Rochester, MN, USA