Autosomal Dominant Parkinson's Disease Research Articles

LRRK2 and α-Synuclein: Distinct or Synergistic Players in Parkinson's Disease?

Parkinson’s disease (PD) is the most common neurodegenerative movement disorder, characterized by prominent degeneration of dopaminergic neurons in the substantia nigra and aggregation of the protein α-synuclein within intraneuronal inclusions known as Lewy bodies. Ninety percent of PD cases are idiopathic while the remaining 10% are associated with gene mutations that affect cellular functions ranging from kinase activity to mitochondrial quality control, hinting at a multifactorial disease process. Mutations in LRRK2 and SNCA (the gene coding for α-synuclein) cause monogenic forms of autosomal dominant PD, and polymorphisms in either gene are also associated with increased risk of idiopathic PD. Although Lewy bodies are a defining neuropathological feature of PD, an appreciable subset of patients with LRRK2 mutations present with a clinical phenotype indistinguishable from idiopathic PD but lack Lewy pathology at autopsy, suggesting that LRRK2-mediated PD may occur independently of α-synuclein aggregation. Here, we examine whether LRRK2 and α-synuclein, as mediators of neurodegeneration in PD, exist in common or distinct pathways. Specifically, we review evidence from preclinical models and human neuropathological studies examining interactions between the two proteins. Elucidating the degree of interplay between LRRK2 and α-synuclein will be necessary for treatment stratification once effective targeted disease-modifying therapies are developed.

LRRK2 Phosphorylation, More Than an Epiphenomenon.

Mutations in the Leucine Rich Repeat Kinase 2 (LRRK2) gene are linked to autosomal dominant Parkinson's disease (PD), and genetic variations at the LRRK2 locus are associated with an increased risk for sporadic PD. This gene encodes a kinase that is physiologically multiphosphorylated, including clusters of both heterologous phosphorylation and autophosphorylation sites. Several pieces of evidence indicate that LRRK2's phosphorylation is important for its pathological and physiological functioning. These include a reduced LRRK2 heterologous phosphorylation in PD brains or after pharmacological inhibition of LRRK2 kinase activity as well as the appearance of subcellular LRRK2 accumulations when this protein is dephosphorylated at heterologous phosphosites. Nevertheless, the regulatory mechanisms governing LRRK2 phosphorylation levels and the cellular consequences of changes in LRRK2 phosphorylation remain incompletely understood. In this review, we present current knowledge on LRRK2 phosphorylation, LRRK2 phosphoregulation, and how LRRK2 phosphorylation changes affect cellular processes that may ultimately be linked to PD mechanisms.

PINK1-dependent phosphorylation of Serine111 within the SF3 motif of Rab GTPases impairs effector interactions and LRRK2-mediated phosphorylation at Threonine72

Loss of function mutations in the PTEN-induced kinase 1 (PINK1) kinase are causal for autosomal recessive Parkinson's disease (PD) whilst gain of function mutations in the LRRK2 kinase cause autosomal dominant PD. PINK1 indirectly regulates the phosphorylation of a subset of Rab GTPases at a conserved Serine111 (Ser111) residue within the SF3 motif. Using genetic code expansion technologies, we have produced stoichiometric Ser111-phosphorylated Rab8A revealing impaired interactions with its cognate guanine nucleotide exchange factor and GTPase activating protein. In a screen for Rab8A kinases we identify TAK1 and MST3 kinases that can efficiently phosphorylate the Switch II residue Threonine72 (Thr72) in a similar manner as LRRK2 in vitro. Strikingly, we demonstrate that Ser111 phosphorylation negatively regulates the ability of LRRK2 but not MST3 or TAK1 to phosphorylate Thr72 of recombinant nucleotide-bound Rab8A in vitro and demonstrate an interplay of PINK1- and LRRK2-mediated phosphorylation of Rab8A in transfected HEK293 cells. Finally, we present the crystal structure of Ser111-phosphorylated Rab8A and nuclear magnetic resonance structure of Ser111-phosphorylated Rab1B. The structures reveal that the phosphorylated SF3 motif does not induce any major changes, but may interfere with effector-Switch II interactions through intramolecular H-bond formation and/or charge effects with Arg79. Overall, we demonstrate antagonistic regulation between PINK1-dependent Ser111 phosphorylation and LRRK2-mediated Thr72 phosphorylation of Rab8A indicating a potential cross-talk between PINK1-regulated mitochondrial homeostasis and LRRK2 signalling that requires further investigation in vivo.

Neuroprotection by the Immunomodulatory Drug Pomalidomide in the Drosophila LRRK2WD40 Genetic Model of Parkinson's Disease.

The search for new disease-modifying drugs for Parkinson’s disease (PD) is a slow and highly expensive process, and the repurposing of drugs already approved for different medical indications is becoming a compelling alternative option for researchers. Genetic variables represent a predisposing factor to the disease and mutations in leucine-rich repeat kinase 2 (LRRK2) locus have been correlated to late-onset autosomal-dominant PD. The common fruit fly Drosophila melanogaster carrying the mutation LRRK2 loss-of-function in the WD40 domain (LRRK2WD40), is a simple in vivo model of PD and is a valid tool to first evaluate novel therapeutic approaches to the disease. Recent studies have suggested a neuroprotective activity of immunomodulatory agents in PD models. Here the immunomodulatory drug Pomalidomide (POM), a Thalidomide derivative, was examined in the Drosophila LRRK2WD40 genetic model of PD. Mutant and wild type flies received increasing POM doses (1, 0.5, 0.25 mM) through their diet from day 1 post eclosion, until postnatal day (PN) 7 or 14, when POM’s actions were evaluated by quantifying changes in climbing behavior as a measure of motor performance, the number of brain dopaminergic neurons and T-bars, mitochondria integrity. LRRK2WD40 flies displayed a spontaneous age-related impairment of climbing activity, and POM significantly and dose-dependently improved climbing performance both at PN 7 and PN 14. LRRK2WD40 fly motor disability was underpinned by a progressive loss of dopaminergic neurons in posterior clusters of the protocerebrum, which are involved in the control of locomotion, by a low number of T-bars density in the presynaptic bouton active zones. POM treatment fully rescued the cell loss in all posterior clusters at PN 7 and PN 14 and significantly increased the T-bars density. Moreover, several damaged mitochondria with dilated cristae were observed in LRRK2WD40 flies treated with vehicle but not following POM. This study demonstrates the neuroprotective activity of the immunomodulatory agent POM in a genetic model of PD. POM is an FDA-approved clinically available and well-tolerated drug used for the treatment of multiple myeloma. If further validated in mammalian models of PD, POM could rapidly be clinically tested in humans.

Low prevalence of known pathogenic mutations in dominant PD genes: A Swedish multicenter study

ObjectiveTo determine the frequency of mutations known to cause autosomal dominant Parkinson disease (PD) in a series with more than 10% of Sweden's estimated number of PD patients. MethodsThe Swedish Parkinson Disease Genetics Network was formed as a national multicenter consortium of clinical researchers who together have access to DNA from a total of 2,206 PD patients; 85.4% were from population-based studies. Samples were analyzed centrally for known pathogenic mutations in SNCA (duplications/triplications, p.Ala30Pro, p.Ala53Thr) and LRRK2 (p.Asn1437His, p.Arg1441His, p.Tyr1699Cys, p.Gly2019Ser, p.Ile2020Thr). We compared the frequency of these mutations in Swedish patients with published PD series and the gnomAD database. ResultsA family history of PD in first- and/or second-degree relatives was reported by 21.6% of participants. Twelve patients (0.54%) carried LRRK2 p.(Gly2019Ser) mutations, one patient (0.045%) an SNCA duplication. The frequency of LRRK2 p.(Gly2019Ser) carriers was 0.11% in a matched Swedish control cohort and a similar 0.098% in total gnomAD, but there was a marked difference between ethnicities in gnomAD, with 42-fold higher frequency among Ashkenazi Jews than all others combined. ConclusionsIn relative terms, the LRRK2 p.(Gly2019Ser) variant is the most frequent mutation among Swedish or international PD patients, and in gnomAD. SNCA duplications were the second most common of the mutations examined. In absolute terms, however, these known pathogenic variants in dominant PD genes are generally very rare and can only explain a minute fraction of familial aggregation of PD. Additional genetic and environmental mechanisms may explain the frequent co-occurrence of PD in close relatives.

E46K-like α-synuclein mutants increase lipid interactions and disrupt membrane selectivity

Parkinson's disease (PD) is one of the most common neurodegenerative disorders, and both genetic and histopathological evidence have implicated the ubiquitous presynaptic protein α-synuclein (αSyn) in its pathogenesis. Recent work has investigated how disrupting αSyn's interaction with membranes triggers trafficking defects, cellular stress, and apoptosis. Special interest has been devoted to a series of mutants exacerbating the effects of the E46K mutation (associated with autosomal dominant PD) through homologous Glu-to-Lys substitutions in αSyn's N-terminal region (i.e. E35K and E61K). Such E46K-like mutants have been shown to cause dopaminergic neuron loss and severe but L-DOPA–responsive motor defects in mouse overexpression models, presenting enormous translational potential for PD and other “synucleinopathies.” In this work, using a variety of biophysical techniques, we characterize the molecular pathology of E46K-like αSyn mutants by studying their structure and membrane-binding and remodeling abilities. We find that, although a slight increase in the mutants' avidity for synaptic vesicle–like membranes can be detected, most of their deleterious effects are connected to their complete disruption of αSyn's curvature selectivity. Indiscriminate binding can shift αSyn's subcellular localization away from its physiological interactants at the synaptic bouton toward trafficking vesicles and organelles, as observed in E46K-like cellular and murine models, as well as in human pathology. In conclusion, our findings suggest that a loss of curvature selectivity, rather than increased membrane affinity, could be the critical dyshomeostasis in synucleinopathies.

An integrated transcriptomics and proteomics analysis reveals functional endocytic dysregulation caused by mutations in LRRK2

BackgroundMutations in LRRK2 are the most common cause of autosomal dominant Parkinson's disease, and the relevance of LRRK2 to the sporadic form of the disease is becoming ever more apparent. It is therefore essential that studies are conducted to improve our understanding of the cellular role of this protein. Here we use multiple models and techniques to identify the pathways through which LRRK2 mutations may lead to the development of Parkinson's disease. MethodsA novel integrated transcriptomics and proteomics approach was used to identify pathways that were significantly altered in iPSC-derived dopaminergic neurons carrying the LRRK2-G2019S mutation. Western blotting, immunostaining and functional assays including FM1-43 analysis of synaptic vesicle endocytosis were performed to confirm these findings in iPSC-derived dopaminergic neuronal cultures carrying either the LRRK2-G2019S or the LRRK2-R1441C mutation, and LRRK2 BAC transgenic rats, and post-mortem human brain tissue from LRRK2-G2019S patients. ResultsOur integrated -omics analysis revealed highly significant dysregulation of the endocytic pathway in iPSC-derived dopaminergic neurons carrying the LRRK2-G2019S mutation. Western blot analysis confirmed that key endocytic proteins including endophilin I-III, dynamin-1, and various RAB proteins were downregulated in these cultures and in cultures carrying the LRRK2-R1441C mutation, compared with controls. We also found changes in expression of 25 RAB proteins. Changes in endocytic protein expression led to a functional impairment in clathrin-mediated synaptic vesicle endocytosis. Further to this, we found that the endocytic pathway was also perturbed in striatal tissue of aged LRRK2 BAC transgenic rats overexpressing either the LRRK2 wildtype, LRRK2-R1441C or LRRK2-G2019S transgenes. Finally, we found that clathrin heavy chain and endophilin I-III levels are increased in human post-mortem tissue from LRRK2-G2019S patients compared with controls. ConclusionsOur study demonstrates extensive alterations across the endocytic pathway associated with LRRK2 mutations in iPSC-derived dopaminergic neurons and BAC transgenic rats, as well as in post-mortem brain tissue from PD patients carrying a LRRK2 mutation. In particular, we find evidence of disrupted clathrin-mediated endocytosis and suggest that LRRK2-mediated PD pathogenesis may arise through dysregulation of this process.

Parkinson’s disease-linked D620N VPS35 knockin mice manifest tau neuropathology and dopaminergic neurodegeneration

Mutations in the vacuolar protein sorting 35 ortholog (VPS35) gene represent a cause of late-onset, autosomal dominant familial Parkinson's disease (PD). A single missense mutation, D620N, is considered pathogenic based upon its segregation with disease in multiple families with PD. At present, the mechanism(s) by which familial VPS35 mutations precipitate neurodegeneration in PD are poorly understood. Here, we employ a germline D620N VPS35 knockin (KI) mouse model of PD to formally establish the age-related pathogenic effects of the D620N mutation at physiological expression levels. Our data demonstrate that a heterozygous or homozygous D620N mutation is sufficient to reproduce key neuropathological hallmarks of PD as indicated by the progressive degeneration of nigrostriatal pathway dopaminergic neurons and widespread axonal pathology. Unexpectedly, endogenous D620N VPS35 expression induces robust tau-positive somatodendritic pathology throughout the brain as indicated by abnormal hyperphosphorylated and conformation-specific tau, which may represent an important and early feature of mutant VPS35-induced neurodegeneration in PD. In contrast, we find no evidence for α-synuclein-positive neuropathology in aged VPS35 KI mice, a hallmark of Lewy body pathology in PD. D620N VPS35 expression also fails to modify the lethal neurodegenerative phenotype of human A53T-α-synuclein transgenic mice. Finally, by crossing VPS35 KI and null mice, our data demonstrate that a single D620N VPS35 allele is sufficient for survival and early maintenance of dopaminergic neurons, indicating that the D620N VPS35 protein is fully functional. Our data raise the tantalizing possibility of a pathogenic interplay between mutant VPS35 and tau for inducing neurodegeneration in PD.

LRRK2 impairs PINK1/Parkin-dependent mitophagy via its kinase activity: pathologic insights into Parkinson's disease.

Mutations of LRRK2, encoding leucine-rich repeat kinase 2 (LRRK2), are the leading cause of autosomal dominant Parkinson's disease (PD). The most frequent of these mutations, G2019S substitution, increases kinase activity, but it remains unclear how it causes PD. Recent studies suggest that LRRK2 modulates mitochondrial homeostasis. Mitochondrial dysfunction plays a key role in the pathogenesis of autosomal recessive PD forms linked to PARK2 and PINK1, encoding the cytosolic E3 ubiquitin-protein ligase Parkin and the mitochondrial kinase PINK1, which jointly regulate mitophagy. We explored the role of LRRK2 and its kinase activity in PINK1/Parkin-dependent mitophagy. LRRK2 increased mitochondrial aggregation and attenuated mitochondrial clearance in cells coexpressing Parkin and exposed to the protonophore carbonylcyanide m-chlorophenylhydrazone. Förster resonance energy transfer imaging microscopy showed that LRRK2 impaired the interactions between Parkin and Drp1 and their mitochondrial targets early in mitophagy. The inhibition of LRRK2 kinase activity by a 'kinase-dead' LRRK2 mutation or with a pharmacological inhibitor (LRRK2-IN-1) restored these interactions. The monitoring of mitophagy in human primary fibroblasts with the novel dual-fluorescence mtRosella reporter and a new hypothermic shock paradigm revealed similar defects in PD patients with the G2019S LRRK2 substitution or PARK2 mutations relative to healthy subjects. This defect was restored by LRRK2-IN-1 treatment in LRRK2 patients only. Our results suggest that PD forms due to LRRK2 and PARK2 mutations involve pathogenic mechanisms converging on PINK1/Parkin-dependent mitophagy.

PD-linked CHCHD2 mutations impair CHCHD10 and MICOS complex leading to mitochondria dysfunction.

Coiled-coil-helix-coiled-coil-helix domain containing protein 2 (CHCHD2) mutations were linked with autosomal dominant Parkinson’s disease (PD) and recently, Alzheimer’s disease/frontotemporal dementia. In the current study, we generated isogenic human embryonic stem cell (hESC) lines harboring PD-associated CHCHD2 mutation R145Q or Q126X via clustered regularly interspaced short palindromic repeats (CRISPR)-CRISPR-associated protein 9 (Cas9) method, aiming to unravel pathophysiologic mechanism and seek potential intervention strategy against CHCHD2 mutant-caused defects. By engaging super-resolution microscopy, we identified a physical proximity and similar distribution pattern of CHCHD2 along mitochondria with mitochondrial contact site and cristae organizing system (MICOS), a large protein complex maintaining mitochondria cristae. Isogenic hESCs and differentiated neural progenitor cells (NPCs) harboring CHCHD2 R145Q or Q126X mutation showed impaired mitochondria function, reduced CHCHD2 and MICOS components and exhibited nearly hollow mitochondria with reduced cristae. Furthermore, PD-linked CHCHD2 mutations lost their interaction with coiled-coil-helix-coiled-coil-helix domain containing protein 10 (CHCHD10), while transient knockdown of either CHCHD2 or CHCHD10 reduced MICOS and mitochondria cristae. Importantly, a specific mitochondria-targeted peptide, Elamipretide/MTP-131, now tested in phase 3 clinical trials for mitochondrial diseases, was found to enhance CHCHD2 with MICOS and mitochondria oxidative phosphorylation enzymes in isogenic NPCs harboring heterozygous R145Q, suggesting that Elamipretide is able to attenuate CHCHD2 R145Q-induced mitochondria dysfunction. Taken together, our results suggested CHCHD2–CHCHD10 complex may be a novel therapeutic target for PD and related neurodegenerative disorders, and Elamipretide may benefit CHCHD2 mutation-linked PD.

Systematically analyzing rare variants of autosomal-dominant genes for sporadic Parkinson's disease in a Chinese cohort

Studies have shown that rare variants of Mendelian genes for Parkinson's disease (PD) contribute to sporadic PD in the Caucasian population, which lacked confirmation in the Chinese population. Because the autosomal-dominant PD (AD-PD) had a phenotype closely resembling sporadic PD, we performed a systematic analysis of 7 AD-PD genes (SNCA, LRRK2, GIGYF2, VPS35, EIF4G1, DNAJC13, and CHCHD2) in 1456 Chinese sporadic PD patients and 1568 controls. Overall, 72 rare variants were identified, 7 of which were classified as likely pathogenic, 63 of which were categorized as of uncertain significance, and 2 of them were predicted to be likely benign. These AD-PD genes represented a clear enrichment of rare variants in PD patients from a burden analysis (p = 0.003), and significant differences could still be observed when likely pathogenic variants were removed (p = 0.027). The gene-based association testing also reached significance for LRRK2 (p = 0.004) and remained statistically significant after the Bonferroni correction. This report suggested that rare variants of AD-PD genes had a role in the Chinese sporadic PD cohort, especially for those rare variants of LRRK2.

Parkinsonism due to A53E α-synuclein gene mutation: Clinical, genetic, epigenetic, and biochemical features.

SNCA mutations cause autosomal dominant parkinsonism and inform our understanding of the molecular underpinnings of synucleinopathies. The most recently identified mutation, p.Ala53Glu (A53E), has only been observed in Finland. The objectives of this study were to examine clinical, genetic, epigenetic, and biochemical features of the first family outside Finland with A53E. We examined a Canadian family with parkinsonism because of A53E using haplotype and DNA methylation analyses. We assessed aggregation properties of A53E α-synuclein in vitro. Family members with parkinsonism shared a common haplotype distinct from Finnish patients with A53E. Increased acceleration of DNA methylation age was accompanied by earlier age at onset in the family members. We demonstrate that A53E α-synuclein has a propensity to form oligomers and phosphorylation promotes fibrillation. A53E as a cause of parkinsonism is not restricted to Finnish individuals. DNA methylation may contribute to disease age at onset. A53E enriches α-synuclein oligomers and fibrils dependent on the phosphorylation state. © 2018 International Parkinson and Movement Disorder Society.

RAB7L1-Mediated Relocalization of LRRK2 to the Golgi Complex Causes Centrosomal Deficits via RAB8A.

Mutations in the LRRK2 gene cause autosomal-dominant Parkinson’s disease (PD), and both LRRK2 as well as RAB7L1 have been implicated in increased susceptibility to idiopathic PD. RAB7L1 has been shown to increase membrane-association and kinase activity of LRRK2, and both seem to be mechanistically implicated in the same pathway. Another RAB protein, RAB8A, has been identified as a prominent LRRK2 kinase substrate, and our recent work demonstrates that aberrant LRRK2-mediated phosphorylation of RAB8A leads to centrosomal alterations. Here, we show that RAB7L1 recruits LRRK2 to the Golgi complex, which causes accumulation of phosphorylated RAB8A in a pericentrosomal/centrosomal location as well as centrosomal deficits identical to those observed with pathogenic LRRK2. The centrosomal alterations induced by wildtype LRRK2 in the presence of RAB7L1 depend on Golgi integrity. This is in contrast to pathogenic LRRK2 mutants, which cause centrosomal deficits independent of Golgi integrity or largely independent on RAB7L1 expression. Furthermore, centrosomal alterations in the presence of wildtype LRRK2 and RAB7L1 are at least in part mediated by aberrant LRRK2-mediated RAB8A phosphorylation, as abolished by kinase inhibitors and reduced upon knockdown of RAB8A. These results indicate that pathogenic LRRK2, as well as increased levels of RAB7L1, cause centrosomal deficits in a manner dependent on aberrant RAB8A phosphorylation and centrosomal/pericentrosomal accumulation, suggesting that centrosomal cohesion deficits may comprise a useful cellular readout for a broader spectrum of the disease.

Genotype-phenotype relations for the Parkinson's disease genes SNCA, LRRK2, VPS35: MDSGene systematic review.

This comprehensive MDSGene review is devoted to the three autosomal-dominant PD forms: PARK-SNCA, PARK-LRRK2, and PARK-VPS35. It follows MDSGene's standardized data extraction protocol, screened a total of 2,972 citations, and is based on fully curated phenotypic and genotypic data on 937 patients with dominantly inherited PD attributed to 44 different mutations in SNCA, LRRK2, or VPS35. All of these data are also available in an easily searchable online database (www.mdsgene.org), which additionally provides descriptive summary statistics on phenotypic and genetic data. Despite the high degree of missingness of phenotypic features and unsystematic reporting of genotype data in the original literature, the present review recapitulates many of the previously described findings including later onset of disease (median age at onset: ∼49 years) compared to recessive forms of PD of an overall excellent treatment response. Our systematic review validates previous reports showing that SNCA mutation carriers have a younger age at onset compared to LRRK2 and VPS35 (P < 0.001). SNCA mutation carriers often have additional psychiatric symptoms, and although not exclusive to only LRRK2 or VPS35 mutation carriers, LRRK2 mutation carriers have a typical form of PD, and, lastly, VPS35 mutation carriers have good response to l-dopa. © 2018 International Parkinson and Movement Disorder Society.

CHCHD10 is involved in the development of Parkinson's disease caused by CHCHD2 loss-of-function mutation p.T61I.

Previously we identified the p.Thr61Ile mutation in coiled-coil-helix-coiled-coil-helix domain containing 2 (CHCHD2) in a Chinese family with autosomal dominant Parkinson's disease. But the mechanism is still unclear. In this study, we explored the effects of CHCHD2 p.Thr61Ile mutation in cells and its association with coiled-coil-helix-coiled-coil-helix domain containing 10 (CHCHD10). We found that overexpression of Parkinson's disease-associated T61I mutant CHCHD2 did not produce mitochondrial dysfunction. Rather, its protective effect from stress was abrogated. And, the level of the CHCHD2 protein and mRNA in patient fibroblasts was not significantly different from control. In addition, CHCHD2 T61I mutation caused increased interaction with CHCHD10 and reduced CHCHD10 level. The mitochondrial ultrastructural alterations in CHCHD2 T61I mutant patient fibroblasts are similar to that of CHCHD10 mutations. We therefore propose that CHCHD10 is involved in the development of Parkinson's disease caused by CHCHD2 loss-of-function mutation p.T61I.

123I-FP-CIT SPECT [(123) I-2β-carbomethoxy-3β-(4-iodophenyl)-N-(3-fluoropropyl) nortropane single photon emission computed tomography] Imaging in a p.A53T α-synuclein Parkinson's disease cohort versus Parkinson's disease.

The p.A53T point mutation in the α-synuclein gene (SNCA) is a rare but highly relevant cause of autosomal dominant Parkinson's disease (PD). The objective of this study was to assess striatal dopaminergic denervation in a cohort of symptomatic carriers of the p.A53T SNCA mutation as compared to PD patients. Data from the Parkinson's Progression Markers Initiative database of 11 symptomatic p.A53T SNCA mutation carriers who underwent 123I-FP-CIT SPECT [(123) I-2β-carbomethoxy-3β-(4-iodophenyl)-N-(3-fluoropropyl) nortropane single photon emission computed tomography] imaging at our site were compared with those of 33 age-, sex-, and disease duration-matched PD patients. The p.A53T mutation carriers had significantly lower caudate nucleus binding ratio both contralaterally and ipsilaterally to the most affected side (P = .002 and P = .006) and a decreased contralateral caudate/putamen signal ratio (P = .007) as compared to PD. A similar degree of striatal asymmetry was observed in both subgroups. No correlation between scores in neuropsychological tests and caudate nucleus dopaminergic denervation could be demonstrated. PD patients harboring the p.A53T SNCA mutation show evidence of a more severe nigrostriatal denervation, especially evident in the caudate nucleus. The lack of significant differences in the putaminal binding ratios may reflect a floor effect or a true preferential targeting of the caudate terminals in p.A53T SNCA-associated PD. © 2018 International Parkinson and Movement Disorder Society.

CHCHD2 accumulates in distressed mitochondria and facilitates oligomerization of CHCHD10.

Mutations in paralogous mitochondrial proteins CHCHD2 and CHCHD10 cause autosomal dominant Parkinson Disease (PD) and Amyotrophic Lateral Sclerosis/Frontotemporal Dementia (ALS/FTD), respectively. Using newly generated CHCHD2, CHCHD10 and CHCHD2/10 double knockout cell lines, we find that the proteins are partially functionally redundant, similarly distributed throughout the mitochondrial cristae, and form heterodimers. Unexpectedly, we also find that CHCHD2/CHCHD10 heterodimerization increases in response to mitochondrial stress. This increase is driven by differences in the proteins' stability and mutual affinity: CHCHD2 is preferentially stabilized by loss of mitochondrial membrane potential, and CHCHD10 oligomerization depends on CHCHD2 expression. Exploiting the dependence of CHCHD10 oligomerization on CHCHD2, we developed a heterodimer incorporation assay and demonstrate that CHCHD2 and CHCHD10 with disease-causing mutations readily form heterodimers. As we also find that both proteins are highly expressed in human Substantia nigra and cortical pyramidal neurons, mutant CHCHD2 and CHCHD10 may directly interact with their wild-type paralogs in the context of PD and ALS/FTD pathogenesis. Together, these findings demonstrate that differences in the stability and mutual affinity of CHCHD2 and CHCHD10 regulate their heterodimerization in response to mitochondrial distress, revealing an unanticipated link between PD and ALS/FTD pathogenesis.

The Parkinson's disease VPS35[D620N] mutation enhances LRRK2-mediated Rab protein phosphorylation in mouse and human.

Missense mutations in the LRRK2 (Leucine-rich repeat protein kinase-2) and VPS35 genes result in autosomal dominant Parkinson's disease. The VPS35 gene encodes for the cargo-binding component of the retromer complex, while LRRK2 modulates vesicular trafficking by phosphorylating a subgroup of Rab proteins. Pathogenic mutations in LRRK2 increase its kinase activity. It is not known how the only thus far described pathogenic VPS35 mutation, [p.D620N] exerts its effects. We reveal that the VPS35[D620N] knock-in mutation strikingly elevates LRRK2-mediated phosphorylation of Rab8A, Rab10, and Rab12 in mouse embryonic fibroblasts. The VPS35[D620N] mutation also increases Rab10 phosphorylation in mouse tissues (the lung, kidney, spleen, and brain). Furthermore, LRRK2-mediated Rab10 phosphorylation is increased in neutrophils as well as monocytes isolated from three Parkinson's patients with a heterozygous VPS35[D620N] mutation compared with healthy donors and idiopathic Parkinson's patients. LRRK2-mediated Rab10 phosphorylation is significantly suppressed by knock-out or knock-down of VPS35 in wild-type, LRRK2[R1441C], or VPS35[D620N] cells. Finally, VPS35[D620N] mutation promotes Rab10 phosphorylation more potently than LRRK2 pathogenic mutations. Available data suggest that Parkinson's patients with VPS35[D620N] develop the disease at a younger age than those with LRRK2 mutations. Our observations indicate that VPS35 controls LRRK2 activity and that the VPS35[D620N] mutation results in a gain of function, potentially causing PD through hyperactivation of the LRRK2 kinase. Our findings suggest that it may be possible to elaborate compounds that target the retromer complex to suppress LRRK2 activity. Moreover, patients with VPS35[D620N] associated Parkinson's might benefit from LRRK2 inhibitor treatment that have entered clinical trials in humans.

DNAJC13 mutation screening in patients with Parkinson's disease from South Italy

BackgroundParkinson's disease (PD) is the second most common neurodegenerative disorder, and the most common neurodegenerative form of parkinsonism. Recently, a pathogenic mutation (p.N855S) in DNAJC13 was linked to autosomal dominant Lewy body PD in a Dutch–German–Russian Mennonite multi-incident kindred, and was found in five additional patients. In this study, we performed a comprehensive screening of the DNAJC13 gene in familial PD and sporadic PD to assess the frequency of known and novel rare nonsynonymous variants. MethodsWe screened 563 sporadic and 168 familial PD patients and a control series (n = 1000) for the coding region of DNAJC13. ResultsOur sequencing analysis identified two carriers of the c.2708G > A (p.R903K) variant in exon 24 of DNAJC13. One of these carriers is a familial PD. ConclusionThe p. R903K variant was not found in 1000 healthy controls and it is localized in a functional domain of the DNAJC13 protein. Further studies are necessary to evaluate the role of DNAJC13 variants in PD.

TMEM230 in Parkinson's disease in a southern Spanish population.

TMEM230 has been associated with autosomal dominant Parkinson’s disease (PD). Subsequent studies have remained negative, and none of previous described mutation has been reported anymore. We investigated the implication of this gene in the PD in a population of 703 PD patients and 695 unrelated healthy controls from southern Spain. Thirteen variants were found, twelve of them observed only in controls or in patients and controls, and one (c.190A>G) observed only in one patient. Subsequent analysis of this variant indicates that probably it is not pathogenic. In addition, we found a variation in the 3’-UTR (rs183551373) and related with the miRNA hsa-miR-4299 but it was observed only in healthy controls. Our results suggest that variants in TMEM230 gene are not associated with the development of PD.