Owen A Ross

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.

Phenotypic variation in a large Swedish pedigree due to SNCA duplication and triplication

Background: The “Lister family complex,” an extensive Swedish family with autosomal dominant Parkinson disease, was first described by Henry Mjönes in 1949. On the basis of clinical, molecular, and genealogic findings on a Swedish and an American family branch, we provide genetic evidence that explains the parkinsonism in this extended pedigree. Methods: Clinical methods included a detailed neurologic exam of the proband of the Swedish family branch, MRI, and ([123]I)–beta–CIT SPECT imaging. Genomic analysis included α-synuclein sequencing, SNCA real-time PCR dosage, chromosome 4q21 microsatellite analysis, and high-resolution microarray genotyping. The geographic origin and ancestral genealogy of each pedigree were researched in the medical literature and Swedish Parish records. Results: The proband of the Swedish family branch presented with early dysautonomia followed by progressive parkinsonism suggestive of multiple system atrophy. Molecular analysis identified a genomic duplication of <0.9 Mb encompassing α-synuclein and multimerin 1 (SNCA-MMRN1), flanked by long interspersed repeat sequences (LINE L1). Microsatellite variability within the genomic interval was identical to that previously described for a Swedish American family with an α-synuclein triplication. Subsequent genealogic investigation suggested that both kindreds are ancestrally related to the Lister family complex. Conclusion: Our findings extend clinical, genetic, and genealogical research on the Lister family complex. The genetic basis for familial parkinsonism is an SNCA-MMRN11 multiplication, but whereas SNCA-MMRN1 duplication in the Swedish proband (Branch J) leads to late-onset autonomic dysfunction and parkinsonism, SNCA-MMRN1 triplication in the Swedish American family (Branch I) leads to early-onset Parkinson disease and dementia.

Parkinsonism, Lrrk2 G2019S, and tau neuropathology.

Lrrk2 G2019S is predominantly associated with α-synuclein–immunopositive Lewy body pathology. We have identified Family SK where Lrrk2 G2019S segregates with slowly progressive parkinsonism and the affected proband has tau-immunopositive neurofibrillary tangle pathology. Thus α-synucleinopathy and tauopathy, the predominant pathologies associated with parkinsonism, may be alternate outcomes of the same underlying genetic cause. Intriguingly, we observe no evidence of a direct interaction between either the tau or α-synuclein protein with Lrrk2.

Glucocerebrosidase gene mutations and Parkinson disease in the Norwegian population

An association between mutations in the glucocerebrosidase (GBA) gene and Parkinson disease (PD) was recently reported in Ashkenazi Jews. The authors screened a series of 311 Norwegian patients with PD and 474 controls for 2 common functional mutations of the GBA protein, N370S and L444P. Seven patients (2.3%) and 8 controls (1.7%) carried a mutant GBA allele (p = 0.58). This study does not indicate increased susceptibility to PD in GBA mutations carriers in Norway.

Characterization of DCTN1 genetic variability in neurodegeneration

Objective: Recently, mutations in DCTN1 were found to cause Perry syndrome, a parkinsonian disorder with TDP-43-positive pathology. Previously, mutations in DCTN1 were identified in a family with lower motor neuron disease, in amyotrophic lateral sclerosis (ALS), and in a family with ALS/frontotemporal dementia (FTD), suggesting a central role for DCTN1 in neurodegeneration. Methods: In this study we sequenced all DCTN1 exons and exon-intron boundaries in 286 samples diagnosed with Parkinson disease (PD), frontotemporal lobar degeneration (FTLD), or ALS. Results: This analysis revealed 36 novel variants (9 missense, 5 silent, and 22 noncoding). Segregation analysis in families and association studies in PD, FTLD, and ALS case–control series did not identify any variants segregating with disease or associated with increased disease risk. Conclusions: This study suggests that pathogenic mutations in DCTN1 are rare and do not play a common role in the development of Parkinson disease, frontotemporal lobar degeneration, or amyotrophic lateral sclerosis.

MAPT H1 haplotype is a risk factor for essential tremor and multiple system atrophy

Mutations in the microtubule-associated protein tau gene ( MAPT ) cause frontotemporal dementia with parkinsonism linked to chromosome 17 (FTDP-17).1 In addition, the major common MAPT- containing H1 haplotype is associated with increased risk for 2 parkinsonian disorders: progressive supranuclear palsy (PSP) characterized by 4-repeat tau pathology and Parkinson disease (PD) with α-synuclein pathology.2,3 However, the role of MAPT variation in other disorders with similar pathology or disease phenotype is unclear. We investigated the frequency of the MAPT H1 haplotype in both essential tremor (ET) and multiple system atrophy (MSA).nnET is the most common movement disorder, and prior evidence has indicated a common link between ET and PD from clinical, epidemiologic, and pathologic studies as well as some reports of brainstem Lewy bodies at autopsy in patients with ET.4 MSA is a neurodegenerative disorder with α-synuclein pathology with a mixed clinical presentation combining autonomic dysfunction, parkinsonism, and cerebellar or pyramidal symptoms. The initial clinical signs of MSA with prominent parkinsonism can make it difficult to differentially diagnose it from early PD. In addition, up to 30% of patients with MSA with prominent parkinsonism may have a transient response to levodopa therapy.5nn### Methods.nnGenotyping of the MAPT H1 discriminating SNP (rs1052553) and H1c subhaplotype SNP (rs242557) was performed on a Sequenom MassArray iPLEX platform (San Diego, CA) (primer sequences are available on request) and analyzed with Typer 4.0 software. The rate of genotype calls was ≥95% in each population. The series contained 356 patients with clinical ET, 61 patients with pathologically confirmed MSA, and 409 US control subjects; all samples are North American Caucasians. Numerical variables were summarized with the sample mean, SD, and range (table e-1 on the …

Novel p.Ile151Val mutation in VCP in a patient of African American descent with sporadic ALS.

The valosin containing protein (VCP) is a member of the AAA-ATPase family, a group of enzymatic molecular chaperones that have been associated with a range of cellular processes including ubiquitin-proteasome mediated degradation, membrane fusion, apoptosis, cell-cycle control, and autophagy.1 Mutations in VCP were first identified to cause familial inclusion body myopathy with early-onset Paget disease and frontotemporal dementia2 (IBMPFD) and more recently were found to be implicated in familial amyotrophic lateral sclerosis (ALS).3 It was suggested that VCP mutations may account for 1%–2% of familial ALS cases.3 Whether VCP mutations also contribute to sporadic ALS (SALS), however, has not yet been studied. Here, we report the identification of a novel p.Ile151Val mutation in VCP in a patient of African American descent with SALS.nn### Case report.nnIn the course of screening patients with ALS ascertained by the ALS Center at Mayo Clinic Florida (MCF) for mutations in the known ALS genes ( SOD1 , TARDBP , FUS , OPTN , and VCP ), we identified an African American patient with the c.451A>G mutation in exon 5 of VCP predicted to result in the p.Ile151Val substitution. Mutations were excluded in all other exons and genes analyzed in this patient. The VCP p.Ile151Val mutation was not previously reported in dbSNP or the 1000 Genomes databases and genotyping using a custom-designed ABI Taqman assay excluded this mutation from 407 healthy African American controls obtained from MCF (n = 317) and the Coriell Institute for Medical Research (n …

Investigation of KIR diversity in immunosenecence and longevity within the Irish population

Natural killer (NK) cells play a pivotal role in the innate immune response. During the ageing process, variations occur in NK cell number and function. The cytolytic activity of NK cells is controlled by an array of activating and inhibitory cell surface receptors, including the killer cell immunoglobulin-like receptors (KIRs). In the present study, genetic diversity of the KIR loci was analysed with respect to successful ageing in the Irish population. A PCR-SSOP KIR gene identification system was employed to determine the frequency of the named KIR genes/pseudogenes and KIR genotypes within a healthy aged cohort and young control group. Although, two KIR genes (2DS3, 2DL5) displayed an initial increased frequency in the aged group, the significance of this association was lost when repeated in a second cohort. In view of the lack of studies to date, investigating the role of the KIR gene system in healthy ageing, further analysis of KIR diversity is required to fully elucidate its role in respect to age-related disease and longevity.

An independent replication of park16 in asian samples

Parkinson disease (PD) is the most common neurodegenerative movement disorder with age-related prevalence. Approximately 1% of the population is affected at 65 years, which increases to 4%–5% in 85-year-olds.1 To date, several loci containing pathogenic or risk variants have been identified; the most recent, PARK16 , was nominated through 2 genome-wide association studies (GWAS) using samples of Japanese and European ancestry.2,3 This new locus, located in 1q32, was originally identified in the Asian study with p values ranging from 10 −7 to 10 −12 . PARK16 did not reach significance level in the European GWAS or its replication ( p value >10 −4 ); however, combining samples from stage I and II indicated an association. The most significant SNP in the European study (rs823128) showed a 1% difference in minor allele frequency (MAF) between patients with PD (4%) and control subjects (3%), resulting in an odds ratio (OR) of 0.66 ( p value = 7.3 × 10 −8 ) (of note, the allele frequencies seem to have been mistakenly switched in the combined analysis).3 In contrast, the MAF of rs823128 appears to be more common in the Japanese population, with a lower frequency in patients with PD (10%) …

Hypothetical soluble KIR2DS4 natural killer cell receptor molecule does not associate with successful ageing in the Irish

The identification of immunogenetic longevity markers is a major area of molecular gerontological research. A number of genetic loci have been examined, e.g. the HLA and cytokine networks. This study investigated a genetic marker within the highly polymorphic KIR gene system with successful ageing in the Irish population. A 22 bp deletion was identified in the KIR2DS4 gene that predicts a truncated soluble KIR molecule with one intact Ig-like domain. The frequency of this variant was determined using a specific-primer PCR methodology. There was no observed association between this common polymorphic variation within this activatory KIR gene and the aged Irish population. This is the first study of KIR polymorphism in ageing and although no association was identified, the importance of the KIR network in the immune response and its polymorphic nature warrants more detailed analysis to ascertain its role in immunosenescence.