Sporadic Parkinson's Disease Cases Research Articles

LRRK2 Mutations in Spanish Patients With Parkinson Disease

Several pathogenic mutations in the LRRK2 gene have been implicated in familial and sporadic cases of Parkinson disease (PD). The R1441G mutation is frequent in Spanish patients of Basque ethnicity with PD, and the G2019S mutation is a common mutation found in several populations worldwide. To determine the frequency of the LRRK2 G2019S and R1441G mutations in PD patients from the non-Basque northeast region of Spain (Catalonia), and to characterize their family history and clinical features. We screened patients for the presence of the LRRK2 R1441G and G2019S mutations. These LRRK2 mutations were detected by restriction endonuclease digestion, and samples with an abnormal electrophoresis pattern were sequenced to identify the exact nucleotide change. The clinical features and family history of patients with LRRK2 mutations were studied in detail. The northeast region of Spain. Patients Three hundred two patients with PD. Onset age, clinical features, and family history of PD and LRRK2 mutations. The R1441G mutation was present in 0.7% of total PD cases. The G2019S mutation was found in 6.4% of familial and 3.4% of sporadic cases. Additionally, we found 1 patient with the R1441C mutation. Age at onset ranged from 33 to 78 years. Clinical features were not different from classic PD, except for 1 patient who presented with monosymptomatic leg rest tremor of 8 years' duration. In addition, a 91-year-old unaffected relative of a patient with the G2019S mutation was found to be a mutation carrier. The G2019S mutation frequency in PD patients from northeast Spain is similar to that reported in other European regions. The R1441G mutation is very uncommon in Catalonia. The presence of an aged unaffected G2019S mutation carrier supports the previously described occurrence of incomplete penetrance in PD patients with LRRK2 mutations.

Lack of evidence for a genetic association between FGF20 and Parkinson's disease in Finnish and Greek patients

BackgroundFibroblast growth factor 20 (FGF20) is a neurotrophic factor preferentially expressed in the substantia nigra of rat brain and could be involved in dopaminergic neurons survival. Recently, a strong genetic association has been found between FGF20 gene and the risk of suffering from Parkinson's disease (PD). Our aim was to replicate this association in two independent populations.MethodsAllelic, genotypic, and haplotype frequencies of four biallelic polymorphisms were assessed in 151 sporadic PD cases and 186 controls from Greece, and 144 sporadic PD patients and 135 controls from Finland.ResultsNo association was found in any of the populations studied.ConclusionTaken together, these findings suggest that common genetic variants in FGF20 are not a risk factor for PD in, at least, some European populations.

Ubiquitin–proteasome system and Parkinson's diseases

Parkinson's disease (PD) is a progressive neurodegenerative disorder characterized by nigrostriatal dopaminergic degeneration and development of cytoplasmic inclusions known as Lewy bodies. To date, the mechanisms involved in PD pathogenesis are not clearly understood. Clues from genetic studies including identification of mutations in genes for α-synuclein, parkin, and ubiquitin carboxy hydrolase L1 associated with familial PD and the presence of proteinaceous cytoplasmic inclusions in spared dopaminergic nigral neurons in sporadic cases of PD have suggested an important role for ubiquitin–proteasome system (UPS) and aberrant protein degradation. In vivo and in vitro studies have linked parkin, α-synuclein, and oxidative stress to a compromised UPS and PD pathogenesis suggesting novel therapeutic targets.

Recent advances in research on Parkinson disease: synuclein and parkin.

Until recently, most research effort on Parkinson disease (PD) was focused on possible environmental causes. With the discovery of mutations in two genes, synuclein and parkin, which are responsible for rare familial forms of the disease, there has been a major change in emphasis. The first genetic cause of PD to be identified was in the gene for synuclein, resulting in an alanine to threonine substitution at position 53. The likely pathogenetic significance of this mutation was supported by the discovery of a second mutation, and the presence of synuclein in Lewy bodies in sporadic PD cases. The synuclein protein has a tendency to self aggregate, and this tendency is increased in the mutants, and by oxidative injury to the protein. While there is growing evidence in animal models that overexpression of wildtype or mutant synuclein may lead to intracytoplasmic inclusions, and dysfunction of dopamine neurons, no animal models in rodents have yet replicated all important features of the disease. Deletions or point mutations in the gene for parkin cause an autosomal recessive, early onset form of parkinsonism. The parkin protein functions as an E3 ubiquitin-protein ligase, and it is involved in the degradation of cellular proteins by the proteasomal pathway. It is hypothesized that the loss of this function results in the toxic accumulation of its target proteins. Research on these inherited forms of PD is pointing towards a common theme, that disturbances of cellular protein handling can lead to the death of dopamine neurons in PD.

Clinical pharmacology and neuroprotection in Parkinson's disease

There has been significant progress in the study of the causes, the pathogenesis, and the mechanism of cell death in Parkinson's disease (PD). Mutations in single genes have been shown to cause PD, and accumulation of α-synuclein seems to be a clue to the pathogenesis of neurodegeneration. However, mutations of single genes account for only a small number of cases. Environmental factors seem to play a large role in the majority of cases of sporadic PD. Genetic factors may predispose patients to develop PD if combined with other gene mutations or environmental toxins. In an attempt to design a neuroprotective therapy, the pathogenesis of neurodegeneration, and the mechanism of cell death have been studied. Aggregation of insoluble α-synuclein, oxidant stress, mitochondrial dysfunction, excitotoxicity, and glia and inflammatory processes are all thought to contribute to the cell death process and agents that interfere with these events may be neuroprotective. The final culmination of these events is supposed to be the induction of apoptosis in nigral dopaminergic neurons and this too offers opportunities for providing neuroprotection. A large number of different approaches are under discussion in the hope of developing a neuroprotective therapy, using clinical indices and neuroimaging markers of nigral dopaminergic neurons. Conventional approaches to studies that use large numbers of patients in search of small effects are costly and time consuming, and it would be impossible to test all the potentially valuable neuroprotective agents because of a lack of time, money, or subjects. As a translational research, it is more profitable to test agents in a small number of selected patients in search of a more neuroprotective effect. Well designed translational research might allow us to reduce the risk of missing a powerful neuroprotective treatment.

Familial and sporadic Parkinson's disease usually display the same clinical features

We examined the clinical features of familial ( n=26) and sporadic ( n=52) Parkinson's disease (PD) in patients presenting over the age of 40 years. Familial PD cases were tested for alpha-synuclein or parkin mutations as appropriate. No mutations were found in any of the families investigated. We found no between-group differences in the age at onset of PD, the pattern or severity of parkinsonian features, the dose of antiparkinsonian medications or treatment related complications. Cases of familial and sporadic PD in our cohort of patients display similar clinical features. This may suggest similar etiologies for both familial and sporadic PD.

Alpha -Synucleinopathy and selective dopaminergic neuron loss in a rat lentiviral-based model of Parkinson's disease.

Parkinson's disease (PD) is characterized by the progressive loss of substantia nigra dopaminergic neurons and the presence of cytoplasmic inclusions named Lewy bodies. Two missense mutations of the alpha-synuclein (alpha-syn; A30P and A53T) have been described in several families with an autosomal dominant form of PD. alpha-Syn also constitutes one of the main components of Lewy bodies in sporadic cases of PD. To develop an animal model of PD, lentiviral vectors expressing different human or rat forms of alpha-syn were injected into the substantia nigra of rats. In contrast to transgenic mice models, a selective loss of nigral dopaminergic neurons associated with a dopaminergic denervation of the striatum was observed in animals expressing either wild-type or mutant forms of human alpha-syn. This neuronal degeneration correlates with the appearance of abundant alpha-syn-positive inclusions and extensive neuritic pathology detected with both alpha-syn and silver staining. Lentiviral-mediated expression of wild-type or mutated forms of human alpha-syn recapitulates the essential neuropathological features of PD. Rat alpha-syn similarly leads to protein aggregation but without cell loss, suggesting that inclusions are not the primary cause of cell degeneration in PD. Viral-mediated genetic models may contribute to elucidate the mechanism of alpha-syn-induced cell death and allow the screening of candidate therapeutic molecules.

Polymorphisms in iron-responsive binding protein 2 and lack of association with sporadic Parkinson's disease.

Mice with targeted disruptions in the iron-responsive binding protein 2 (IRP2) gene accumulate iron in distinct regions of the brain and develop neurodegenerative characteristics resembling Parkinson's disease after 6 months of age. To determine whether polymorphisms in IRP2 predispose humans to Parkinson's disease (PD), we sequenced the IRP2 gene of subjects with sporadic PD and normal controls. Three polymorphisms which result in an amino acid change were identified: L159V, F272L, and T560I. The L159V and T560I polymorphisms, identified in an African-American PD subject, were found in the African-American population at an allele frequency of 0.102 (n = 1,236) and 0.111 (n = 1,228), respectively, and were not associated with an increased prevalence of PD. The F272L polymorphism was found in a normal 58-year-old, Caucasian subject whose father had PD, but it was not observed in 38 additional patients with sporadic PD. The F272L polymorphism occurred at an allele frequency of 0.0014 (n = 1,384) in the normal Caucasian population. Additional F272L heterozygous subjects identified in the normal population did not have a family or personal history of PD. We conclude that these IRP2 polymorphisms do not play an important role in the development of sporadic cases of PD. It remains to be determined whether other polymorphisms in IRP2 play a role in familial PD.

Motor unit changes in sporadic idiopathic Parkinson's disease.

We studied motor unit changes in 20 patients with Parkinson's disease (PD) and 20 age-matched control subjects to look for evidence of motorneuron degeneration in sporadic idiopathic PD. Patients and control subjects were screened by clinical criteria and nerve conduction studies to exclude those with peripheral neuropathic processes. Changes in motor unit morphology were investigated with subjective and computerized quantitative electromyography (QEMG) of the anterior tibialis (AT) and first dorsal interosseous. Multivariate comparisons showed a significant difference in the QEMG analysis for motor unit enlargement in patients with PD versus control subjects. Some of the univariate comparisons for both the subjective and QEMG analyses of the AT were also significant. These results demonstrate that motorneuron drop-out with reinnervation occurs in sporadic idiopathic PD. In summary, our findings provide evidence that clinically silent motorneuron disease occurs in typical cases of sporadic idiopathic PD, suggesting that it may be a normal part of the pathologic picture of PD. Any hypothesis concerning the pathogenic mechanism of PD would need to take into account such a finding.

The causes of Parkinson's disease are being unraveled and rational neuroprotective therapy is close to reality.

There has been significant progress in our knowledge of the cause, the pathogenesis, and the nature of the mechanism of cell death in Parkinson's disease (PD). Mutations in single genes have now been shown to be able to cause PD but likely only account for a small number of cases. Alternatively, there is evidence that environmental factors play a large role in the majority of cases of sporadic PD. Most likely, genetic factors predispose patients to develop PD if combined with other gene mutations or environmental toxins. Interest has thus focused on factors that contribute to the pathogenesis of neurodegeneration and the mechanism of cell death in an attempt to design a neuroprotective therapy. Oxidant stress, mitochondrial dysfunction, excitotoxicity with excess nitric oxide formation, and glia and inflammatory processes are all thought to contribute to the cell death process and agents that interfere with these events may be neuroprotective. It is now generally held that the final culmination of these events is the induction of apoptosis in nigral dopaminergic neurons and this too offers opportunities for providing neuroprotection. A rational argument can be made for investigating a large number of different approaches or combination of approaches in the hope of developing a meaningful neuroprotective therapy, using clinically relevant indices and neuroimaging markers of nigral dopaminergic neurons. It is evident that conventional approaches to trials that utilize large numbers of patients in search of small incremental effects are costly and time consuming. As such, it will be virtually impossible to test all of the potentially valuable neuroprotective agents that are now at hand, let alone those that will likely soon emerge. We suggest that it may be more profitable to test a large number of agents in a small number of selected patients in search of a more robust neuroprotective effect. In this way, we will reduce the risk of missing a powerful neuroprotective treatment with a treatment that might not otherwise have been studied because of a lack of time, money, or patients.

A clinical and genetic study of familial Parkinson's disease

The clinical features of familial Parkinson's disease (PD) were investigated by examining the families of 20 British probands who were selected on the basis of having clinically typical PD and at least one affected relative. Forty-nine secondary cases were identified. These subjects were clinically indistinguishable from sporadic cases of idiopathic PD. If it is assumed that familial PD has a genetic basis, pedigree and segregation analysis suggested autosomal dominant inheritance of a gene or genes with reduced penetrance as the most likely explanation. The data did not support the possibilities of either mitochondrial or polygenic inheritance, although the latter cannot be excluded. The role of genetic factors in sporadic cases of PD remains unclear.