Alexander Zimprich

Mutations in LRRK2 Cause Autosomal-Dominant Parkinsonism with Pleomorphic Pathology

We have previously linked families with autosomal-dominant, late-onset parkinsonism to chromosome 12p11.2-q13.1 (PARK8). By high-resolution recombination mapping and candidate gene sequencing in 46 families, we have found six disease-segregating mutations (five missense and one putative splice site mutation) in a gene encoding a large, multifunctional protein, LRRK2 (leucine-rich repeat kinase 2). It belongs to the ROCO protein family and includes a protein kinase domain of the MAPKKK class and several other major functional domains. Within affected carriers of families A and D, six post mortem diagnoses reveal brainstem dopaminergic degeneration accompanied by strikingly diverse pathologies. These include abnormalities consistent with Lewy body Parkinsons disease, diffuse Lewy body disease, nigral degeneration without distinctive histopathology, and progressive supranuclear palsy-like pathology. Clinical diagnoses of Parkinsonism with dementia or amyotrophy or both, with their associated pathologies, are also noted. Hence, LRRK2 may be central to the pathogenesis of several major neurodegenerative disorders associated with parkinsonism.

Genome-wide association study of restless legs syndrome identifies common variants in three genomic regions

Restless legs syndrome (RLS) is a frequent neurological disorder characterized by an imperative urge to move the legs during night, unpleasant sensation in the lower limbs, disturbed sleep and increased cardiovascular morbidity. In a genome-wide association study we found highly significant associations between RLS and intronic variants in the homeobox gene MEIS1, the BTBD9 gene encoding a BTB(POZ) domain as well as variants in a third locus containing the genes encoding mitogen-activated protein kinase MAP2K5 and the transcription factor LBXCOR1 on chromosomes 2p, 6p and 15q, respectively. Two independent replications confirmed these association signals. Each genetic variant was associated with a more than 50% increase in risk for RLS, with the combined allelic variants conferring more than half of the risk. MEIS1 has been implicated in limb development, raising the possibility that RLS has components of a developmental disorder.

A mutation in VPS35, encoding a subunit of the retromer complex, causes late-onset Parkinson disease.

To identify rare causal variants in late-onset Parkinson disease (PD), we investigated an Austrian family with 16 affected individuals by exome sequencing. We found a missense mutation, c.1858G>A (p.Asp620Asn), in the VPS35 gene in all seven affected family members who are alive. By screening additional PD cases, we saw the same variant cosegregating with the disease in an autosomal-dominant mode with high but incomplete penetrance in two further families with five and ten affected members, respectively. The mean age of onset in the affected individuals was 53 years. Genotyping showed that the shared haplotype extends across 65 kilobases around VPS35. Screening the entire VPS35 coding sequence in an additional 860 cases and 1014 controls revealed six further nonsynonymous missense variants. Three were only present in cases, two were only present in controls, and one was present in cases and controls. The familial mutation p.Asp620Asn and a further variant, c.1570C>T (p.Arg524Trp), detected in a sporadic PD case were predicted to be damaging by sequence-based and molecular-dynamics analyses. VPS35 is a component of the retromer complex and mediates retrograde transport between endosomes and the trans-Golgi network, and it has recently been found to be involved in Alzheimer disease.

Mutations in the gene encoding ε-sarcoglycan cause myoclonus-dystonia syndrome

The dystonias are a common clinically and genetically heterogeneous group of movement disorders. More than ten loci for inherited forms of dystonia have been mapped, but only three mutated genes have been identified so far. These are DYT1, encoding torsin A and mutant in the early-onset generalized form, GCH1 (formerly known as DYT5), encoding GTP–cyclohydrolase I and mutant in dominant dopa-responsive dystonia, and TH, encoding tyrosine hydroxylase and mutant in the recessive form of the disease. Myoclonus–dystonia syndrome (MDS; DYT11) is an autosomal dominant disorder characterized by bilateral, alcohol-sensitive myoclonic jerks involving mainly the arms and axial muscles. Dystonia, usually torticollis and/or writers cramp, occurs in most but not all affected patients and may occasionally be the only symptom of the disease. In addition, patients often show prominent psychiatric abnormalities, including panic attacks and obsessive–compulsive behavior. In most MDS families, the disease is linked to a locus on chromosome 7q21 (refs. 11–13). Using a positional cloning approach, we have identified five different heterozygous loss-of-function mutations in the gene for ɛ-sarcoglycan (SGCE), which we mapped to a refined critical region of about 3.2 Mb. SGCE is expressed in all brain regions examined. Pedigree analysis shows a marked difference in penetrance depending on the parental origin of the disease allele. This is indicative of a maternal imprinting mechanism, which has been demonstrated in the mouse ɛ-sarcoglycan gene.

Genetic Structure of Europeans: A View from the North–East

Using principal component (PC) analysis, we studied the genetic constitution of 3,112 individuals from Europe as portrayed by more than 270,000 single nucleotide polymorphisms (SNPs) genotyped with the Illumina Infinium platform. In cohorts where the sample size was >100, one hundred randomly chosen samples were used for analysis to minimize the sample size effect, resulting in a total of 1,564 samples. This analysis revealed that the genetic structure of the European population correlates closely with geography. The first two PCs highlight the genetic diversity corresponding to the northwest to southeast gradient and position the populations according to their approximate geographic origin. The resulting genetic map forms a triangular structure with a) Finland, b) the Baltic region, Poland and Western Russia, and c) Italy as its vertexes, and with d) Central- and Western Europe in its centre. Inter- and intra- population genetic differences were quantified by the inflation factor lambda (λ) (ranging from 1.00 to 4.21), fixation index (Fst) (ranging from 0.000 to 0.023), and by the number of markers exhibiting significant allele frequency differences in pair-wise population comparisons. The estimated lambda was used to assess the real diminishing impact to association statistics when two distinct populations are merged directly in an analysis. When the PC analysis was confined to the 1,019 Estonian individuals (0.1% of the Estonian population), a fine structure emerged that correlated with the geography of individual counties. With at least two cohorts available from several countries, genetic substructures were investigated in Czech, Finnish, German, Estonian and Italian populations. Together with previously published data, our results allow the creation of a comprehensive European genetic map that will greatly facilitate inter-population genetic studies including genome wide association studies (GWAS).

Autosomal dominant parkinsonism associated with variable synuclein and tau pathology.

Since the original 1995 report of a parkinsonian kindred, four individuals have been affected (mean age at onset, 65 years). All four had cardinal signs of Parkinson disease (PD) and good response to levodopa. Four autopsies showed neuronal loss and gliosis in the substantia nigra. Lewy bodies (LB) limited to brainstem nuclei were detected in one case, diffuse LB in the second, neurofibrillary tangles (NFT) without LB in the third, and neither NFT nor LB in the fourth. Genetic studies suggested linkage to the PARK8 locus on chromosome 12.

Multiple regions of alpha-synuclein are associated with Parkinson's disease.

α‐Synuclein is considered to play an important role in the pathogenesis of both the rare familial and the common sporadic forms of Parkinsons disease. Previous reports primarily have tested the association of α‐synuclein promoter polymorphisms with idiopathic Parkinsons disease, but results are controversial. We first characterized the linkage disequilibrium structure of the α‐synuclein gene region with a dense set of 56 genetic markers and subsequently performed two independent case–control association analyses using tagging markers. We could distinguish two large linkage disequilibrium blocks spanning the α‐synuclein gene. Several markers within the 3′‐block around exons 5 and 6 showed strong association with Parkinsons disease (p = 0.00009). Effects of the associated variants might be mediated by regulatory elements in this highly conserved region or by a frequency shift in a previously described splice variant lacking exon 5. A direct association with promoter polymorphisms could not be replicated in our sample set. A second set of markers in the 5′‐block of the gene were also significantly associated with Parkinsons disease, when young patients and female subjects were analyzed separately. These findings indicate locus heterogeneity for the pathogenesis of Parkinsons disease in different genetic or physiological environments, related to sex and age. Ann Neurol 2005;57:535–541

PTPRD (protein tyrosine phosphatase receptor type delta) is associated with restless legs syndrome

We identified association of restless legs syndrome (RLS) with PTPRD at 9p23–24 in 2,458 affected individuals and 4,749 controls from Germany, Austria, Czechia and Canada. Two independent SNPs in the 5′ UTR of splice variants expressed predominantly in the central nervous system showed highly significant P values (rs4626664, Pnominal/λ corrected = 5.91 × 10−10, odds ratio (OR) = 1.44; rs1975197, Pnominal/λ corrected = 5.81 × 10−9, OR = 1.31). This work identifies PTPRD as the fourth genome-wide significant locus for RLS.

Cloning and expression of an isoform of the rat μ opioid receptor (rMOR1B) which differs in agonist induced desensitization from rMOR1

A novel rat μ opioid receptor (rMOR1B) has been isolated. It shows identity to the recently published sequence of rMOR1 [Chen, et al., Mol. Pharmacol., 44 (1993) 8–12] up to amino acid 386 and differs only in length and amino acid composition at the very carboxy‐terminal tail. Both μ opioid receptor isoforms, when stably expressed in CHO‐K1 cells, show similar affinities to opioid compounds and are equally effective in the inhibition of forskolin‐induced cAMP formation. Reverse transcription polymerase chain reaction (RT‐PCR) revealed that rMOR1B displays a similar distribution as rMOR1 in various rat brain areas. Studies measuring the inhibition of adenylate cyclase in cells that had been pre‐exposed to the μ opioid agonist DAMGO indicated that rMOR1B is much more resistant to agonist‐induced desensitization than rMOR1.

The PARK8 locus in autosomal dominant parkinsonism: confirmation of linkage and further delineation of the disease-containing interval.

Recently, a new locus (PARK8) for autosomal dominant parkinsonism has been identified in one large Japanese family. Linkage has been shown to a 16-cM centromeric region of chromosome 12, between markers D12S1631 and D12S339. We tested 21 white families with Parkinson disease and an inheritance pattern compatible with autosomal dominant transmission for linkage in this region. Criteria for inclusion were at least three affected individuals in more than one generation. A total of 29 markers were used to saturate the candidate region. One hundred sixty-seven family members were tested (84 affected and 83 unaffected). Under the assumption of heterogeneity and through use of an affecteds-only model, a maximum multipoint LOD score of 2.01 was achieved in the total sample, with an estimated proportion of families with linkage of 0.32. This LOD score is significant for linkage in a replication study and corresponds to a P value of.0047. Two families (family A [German Canadian] and family D [from western Nebraska]) reached significant linkage on their own, with a combined maximum multipoint LOD score of 3.33, calculated with an affecteds-only model (family A: LOD score 1.67, P=.0028; family D: LOD score 1.67, P=.0028). When a penetrance-dependent model was calculated, the combined multipoint LOD score achieved was 3.92 (family A: LOD score 1.68, P=.0027; family D: LOD score 2.24, P=.0007). On the basis of the multipoint analysis for the combined families A and D, the 1-LOD support interval suggests that the most likely disease location is between a CA repeat polymorphism on genomic clone AC025253 (44.5 Mb) and marker D12S1701 (47.7 Mb). Our data provide evidence that the PARK8 locus is responsible for the disease in a subset of families of white ancestry with autosomal dominant parkinsonism, suggesting that it could be a more common locus.