The dardarin G 2019 S mutation is a common cause of Parkinson's disease but not other neurodegenerative diseases.
ABSTRACT Mutations in the leucine-rich kinase 2 gene (LRRK 2) encoding dardarin, on chromosome 12, are a common cause of familial and sporadic Parkinson's disease. The most common mutation, a heterozygous 6055 G>A transition (G 2019 S) accounts for approximately 3--10% of familial Parkinson's disease and 1--8% sporadic Parkinson's disease in several European-derived populations. Some families with disease caused by LRRK 2 mutations have been reported to include patients with highly variable clinical and pathological features. We screened for the most common LRRK 2 mutation in a series of patients with Parkinson's Disease, Alzheimer's disease, Progressive Supranuclear Palsy, Multiple System Atrophy and frontotemporal dementia, as well as in neurologically normal controls. The mutation was found only in Parkinson's disease patients or their relatives and not in those with other neurodegenerative disease.
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ABSTRACT: Parkinson’s disease (PD) is characterised by a progressive loss of dopaminergic neurones from the SNpc, leading to numerous downstream changes in the basal ganglia circuitry. Overactivity of the glutamatergic subthalamonigral pathway may underlie this continual degeneration of the nigrostriatal system. With this in mind, this thesis examined whether selective activation of group III metabotropic glutamate receptor subtypes may offer a novel strategy to halt persistent degeneration in PD. Initial distribution studies revealed mGlu4 and 7 group III mGlu receptor subtypes, demonstrated particularly intense immunoreactivity in the SNpc, suggesting these receptors may be ideally positioned to provide neuroprotective effects. Therefore, the first objective was to confirm this neuroprotective possibility using a broad spectrum agonist, L-AP4. Sub-chronic supranigral L-AP4 treatment mediated functional neuroprotection against a unilateral 6-OHDA lesion of the SN, confirmed by behavioural assessment and post-mortem analyses. Secondly, the pharmacological identity of the group III mGlu receptor mediating this protective effect was examined. To investigate mGlu4 receptors, the novel mGlu4 selective PAM VU0155041, was also shown to provide functional neuroprotection in the 6-OHDA rat model to an almost comparable level reached with L-AP4. Whilst these neuroprotective effects are likely mediated by an inhibition of glutamate to protect from glutamate-mediated excitotoxicity, VU015504 also led to a significant reduction in levels of GFAP and IBA-1 suggesting an additional anti-inflammatory action. Further studies revealed little evidence for co-localisation of mGlu4 receptors with GFAP in the SN suggesting this anti-inflammatory component likely reflects an indirect effect via stimulation of neuronal mGlu4 receptors. Finally, to investigate mGlu7 receptors, the selective allosteric agonist AMN082, was also shown to protect the nigrostriatal tract and demonstrate a degree of preservation of motor function. In contrast, mGlu8 receptor activation using the selective agonist DCPG, failed to protect the nigrostriatal tract or preserve motor behaviour. Collectively, these findings demonstrate that, of the group III mGlu receptors investigated, mGlu4 offers the most potential as a promising target for establishing disease modification in PD.
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ABSTRACT: Parkinson's disease (PD), the second most common neurodegenerative disorder, is characterized by a loss of dopaminergic neurons in the substantia nigra, as well as in other brain areas. The currently available dopamine replacement therapy provides merely symptomatic benefit and is ineffective because habituation and side effects arise relatively quickly. Studying the genetic forms of PD in animal models provides novel insight that allows targeting of specific aspects of this heterogenic disease more specifically. Among others, two important cellular deficits are associated with PD; these deficits relate to (1) synaptic transmission and vesicle trafficking, and (2) mitochondrial function, relating respectively to the dominant and recessive mutations in PD-causing genes. With increased knowledge of PD, the possibility of identifying an efficient, long-lasting treatment is becoming more conceivable, but this can only be done with an increased knowledge of the specific affected cellular mechanisms. This review discusses how discoveries in animal models of PD have clarified the therapeutic potential of pathways disrupted in PD, with a specific focus on synaptic transmission, vesicle trafficking, and mitochondrial function.Annals of the New York Academy of Sciences 12/2014; 1338(1). DOI:10.1111/nyas.12577 · 4.31 Impact Factor
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ABSTRACT: The pathogenic mechanism(s) contributing to loss of dopamine neurons in Parkinson's disease (PD) remain obscure. Leucine-rich repeat kinase 2 (LRRK2) mutations are linked, as a causative gene, to PD. LRRK2 mutations are estimated to account for 10 % of familial and between 1 % and 3 % of sporadic PD. LRRK2 proximate single nucleotide polymorphisms have also been significantly associated with idiopathic/sporadic PD by genome-wide association studies. LRRK2 is a multidomain-containing protein and belongs to the protein kinase super-family. We constructed two inducible dopaminergic cell lines expressing either human-LRRK2-wild-type or human-LRRK2-mutant (G2019S). Phenotypes of these LRRK2 cell lines were examined with respect to cell viability, morphology, and protein function with or without induction of LRRK2 gene expression. The overexpression of G2019S gene promoted 1) low cellular metabolic activity without affecting cell viability, 2) blunted neurite extension, and 3) increased phosphorylation at S910 and S935. Our observations are consistent with reported general phenotypes in LRRK2 cell lines by other investigators. We used these cell lines to interrogate the biological function of LRRK2, to evaluate their potential as a drug-screening tool, and to investigate screening for small hairpin RNA-mediated LRRK2 G2019S gene knockdown as a potential therapeutic strategy. A proposed LRRK2 kinase inhibitor (i.e., IN-1) decreased LRRK2 S910 and S935 phosphorylation in our MN9DLRRK2 cell lines in a dose-dependent manner. Lentivirus-mediated transfer of LRRK2 G2019S allele-specific small hairpin RNA reversed the blunting of neurite extension caused by LRRK2 G2019S overexpression. Taken together, these inducible LRRK2 cell lines are suitable reagents for LRRK2 functional studies, and the screening of potential LRRK2 therapeutics.Journal of the American Society for Experimental NeuroTherapeutics 08/2013; 10(4). DOI:10.1007/s13311-013-0208-3 · 3.88 Impact Factor