Search

Dysregulation of RNA splicing contributes to both rare and complex diseases. RNA-sequencing data from human tissues has shown that this process can be inaccurate, resulting in the presence of novel introns detected at low frequency across samples and within an individual. To enable the full spectrum of intron use to be explored, we have developed IntroVerse, which offers an extensive catalogue on the splicing of 332,571 annotated introns and a linked set of 4,679,474 novel junctions covering 32,669 different genes. This dataset has been generated through the analysis of 17,510 human control RNA samples from 54 tissues provided by the Genotype-Tissue Expression Consortium. IntroVerse has two unique features: (i) it provides a complete catalogue of novel junctions and (ii) each novel junction has been assigned to a specific annotated intron. This unique, hierarchical structure offers multiple uses, including the identification of novel transcripts from known genes and their tissue-specific usage, and the assessment of background splicing noise for introns thought to be mis-spliced in disease states. IntroVerse provides a user-friendly web interface and is freely available at https://rytenlab.com/browser/app/introverse.

To elucidate the molecular basis of multiple system atrophy (MSA), a neurodegenerative disease, we conducted a genome-wide association study (GWAS) in a Japanese MSA case/control series followed by replication studies in Japanese, Korean, Chinese, European and North American samples. In the GWAS stage rs2303744 on chromosome 19 showed a suggestive association (P= 6.5 × 10−7) that was replicated in additional Japanese samples (P= 2.9 × 10−6. OR = 1.58; 95% confidence interval, 1.30 to 1.91), and then confirmed as highly significant in a meta-analysis of East Asian population data (P= 5.0 × 10-15. Odds ratio= 1.49; 95% CI 1.35 to 1.72). The association of rs2303744 with MSA remained significant in combined European/North American samples (P=0.023. Odds ratio=1.14; 95% CI 1.02 to 1.28) despite allele frequencies being quite different between these populations. rs2303744 leads to an amino acid substitution inPLA2G4Cthat encodes the cPLA2γ lysophospholipase/transacylase. The cPLA2γ-Ile143 isoform encoded by the MSA risk allele has significantly decreased transacylase activity compared with the alternate cPLA2γ-Val143 isoform that may perturb membrane phospholipids and α-synuclein biology.

The Faroe Islands are a geographically isolated population in the North Atlantic with a similar prevalence of Alzheimer's disease (AD) and all-cause dementia as other European populations. However, the genetic risk underlying AD and other dementia susceptibility has yet to be elucidated.Forty-nine single-nucleotide polymorphisms (SNPs) were genotyped in 174 patients with AD and other dementias and 159 healthy controls. Single variant and polygenic risk score (PRS) associations, with/without APOE variability, were assessed by logistic regression. Performance was examined using receiver operating characteristic area under the curve (ROC AUC) analysis.APOErs429358 was associated with AD in the Faroese cohort after correction for multiple testing (odds ratio [OR] 6.32, 95% confidence interval [CI] 3.98-10.05, p = 6.31esup-15/sup), with suggestive evidence for three other variants: NECTIN2 rs41289512 (OR 2.05, 95% CI 1.20-3.51, p = 0.01), HLA-DRB1 rs6931277 (OR 0.67, 95% CI 0.48-0.94, p = 0.02) and APOE rs7412 [ε2] (OR 0.28, 95% CI 0.11-0.73, p = 0.01). PRSs were associated with AD with or without the inclusion of APOE (PRSsup+APOE/supOR = 4.5, 95% CI 2.90-5.85, p = 4.56esup-15/sup, and PRSsup-APOE/supOR = 1.53, 95% CI 1.21-1.98, p = 6.82esup-4/sup). AD ROC AUC analyses demonstrated a PRSsup+APOE/supAUC = 80.3% and PRSsup-APOE/supAUC = 63.4%. However, PRSsup+APOE/supwas also significantly associated with all-cause dementia (OR = 3.39, 95% CI 2.51-4.71, p = 2.50esup-14/sup) with an AUC = 76.9%, that is, all-cause dementia showed similar results albeit less significant.In the Faroe Islands, SNP analyses highlighted APOE and immunogenomic variability in AD and dementia risk. PRSsup+APOE/sup, based on 25 SNPs/loci, had excellent sensitivity and specificity for AD with an AUC of 80.3%. High PRSs were also associated with an earlier onset of late-onset AD.

The human genome contains numerous duplicated regions, such as parent-pseudogene pairs, causing sequencing reads to align equally well to either gene. The extent to which this ambiguity complicates transcriptomic analyses is currently unknown. This is concerning as many parent genes have been linked to disease, includingGBA1,causally linked to both Parkinson’s and Gaucher disease. We find that most of the short sequencing reads that map toGBA1, also map to its pseudogene,GBAP1. Using long-read RNA-sequencing in human brain, where all reads mapped uniquely, we demonstrate significant differences in expression compared to short-read data. We identify novel transcripts from bothGBA1andGBAP1, including protein-coding transcripts that are translatedin vitroand detected in proteomic data, but that lack GCase activity. By combining long-read with single-nuclear RNA-sequencing to analyse brain-relevant cell types we demonstrate that transcript expression varies by brain region with cell-type-selectivity. Taken together, these results suggest a non-lysosomal function for both GBA1 and GBAP1 in brain. Finally, we demonstrate that inaccuracies in annotation are widespread among parent genes, with implications for many human diseases.

Introduction Biallelic mutations in PTEN-induced putative kinase 1 (PINK1) is a relatively common cause of autosomal recessive early-onset Parkinson's disease (PD). However, only three PINK1 patients with brain autopsy have been reported in the literature. Methods We describe the clinical and pathological characteristics of a patient with early-onset PD. We screened for copy number variants SNCA, PRKN, PINK1, DJ-1, ATP13A2, LPA and TNFRSF9 by multiplex ligation-dependent probe amplification (MLPA), and subsequently we performed whole-exome sequencing. Results Clinically the patient presented with typical parkinsonism that responded well to levodopa. After 23 years of disease she had a bilateral GPi deep brain stimulation (DBS) surgery. Genetic analyses revealed a heterozygous exon 4–5 deletion and a homozygous exon 1 [c. 230T > C (p.Leu77Pro)] mutation in PINK1. Post-mortem neuropathological examination after more than 30 years of disease revealed gliosis and a large loss of melanin-containing neurons in the substantia nigra. Lewy body pathology was evident in substantia nigra, temporal cortex, locus coeruleus and the parahippocampal region. Conclusion We describe the first clinical and pathological characterization of a PINK1 patient with a typical disease presentation and long disease duration. Previous reports describe two patients with Lewy-related pathologies, albeit with differential distribution, and one patient with no Lewy-related pathology. Hence, it seems that only two patients with parkinsonism due to mutations in PINK1 are consistent with α-synucleinopathy distribution like that seen in the majority of cases with sporadic PD. Our data further extend the clinicopathological characterization of PINK1-associated PD.

Rapid eye movement (REM) sleep behavior disorder (RBD), enactment of dreams during REM sleep, is an early clinical symptom of alpha-synucleinopathies. RBD also defines more severe forms of alpha-synucleinopathies. The genetic background of RBD and its underlying mechanisms are not well understood. Here, we performed the first genome-wide association study of RBD, identifying five RBD risk loci. Expression analyses highlight SNCA-AS1 and SCARB2 differential expression in different brain regions in RBD, with SNCA-AS1 further supported by colocalization analyses. Genetic risk score and other analyses provide further insights into RBD genetics, highlighting RBD as a unique subpopulation that will allow future early intervention.

Objective The aim of this study was to search for genes/variants that modify the effect of LRRK2 mutations in terms of penetrance and age-at-onset of Parkinson's disease. Methods We performed the first genome-wide association study of penetrance and age-at-onset of Parkinson's disease in LRRK2 mutation carriers (776 cases and 1,103 non-cases at their last evaluation). Cox proportional hazard models and linear mixed models were used to identify modifiers of penetrance and age-at-onset of LRRK2 mutations, respectively. We also investigated whether a polygenic risk score derived from a published genome-wide association study of Parkinson's disease was able to explain variability in penetrance and age-at-onset in LRRK2 mutation carriers. Results A variant located in the intronic region of CORO1C on chromosome 12 (rs77395454; P-value = 2.5E-08, beta = 1.27, SE = 0.23, risk allele: C) met genome-wide significance for the penetrance model. Co-immunoprecipitation analyses of LRRK2 and CORO1C supported an interaction between these two proteins. A region on chromosome 3, within a previously reported linkage peak for Parkinson's disease susceptibility, showed suggestive associations in both models (penetrance top variant: P-value = 1.1E-07; age-at-onset top variant: P-value = 9.3E-07). A polygenic risk score derived from publicly available Parkinson's disease summary statistics was a significant predictor of penetrance, but not of age-at-onset. Interpretation This study suggests that variants within or near CORO1C may modify the penetrance of LRRK2 mutations. In addition, common Parkinson's disease associated variants collectively increase the penetrance of LRRK2 mutations. This article is protected by copyright. All rights reserved.

Although next-generation sequencing technologies have accelerated the discovery of novel gene-to-disease associations, many patients with suspected Mendelian diseases still leave the clinic without a genetic diagnosis. An estimated one third of these patients will have disorders caused by mutations impacting splicing. RNA-sequencing has been shown to be a promising diagnostic tool, however few methods have been developed to integrate RNA-sequencing data into the diagnostic pipeline. Here, we introduce dasper, an R/Bioconductor package that improves upon existing tools for detecting aberrant splicing by using machine learning to incorporate disruptions in exon-exon junction counts as well as coverage. dasper is designed for diagnostics, providing a rank-based report of how aberrant each splicing event looks, as well as including visualization functionality to facilitate interpretation. We validate dasper using 16 patient-derived fibroblast cell lines harbouring pathogenic variants known to impact splicing. We find that dasper is able to detect pathogenic splicing events with greater accuracy than existing LeafCutterMD or z-score approaches. Furthermore, by only applying a broad OMIM gene filter (without any variant-level filters), dasper is able to detect pathogenic splicing events within the top 10 most aberrant identified for each patient. Since using publicly available control data minimises costs associated with incorporating RNA-sequencing into diagnostic pipelines, we also investigate the use of 504 GTEx fibroblast samples as controls. We find that dasper leverages publicly available data effectively, ranking pathogenic splicing events in the top 25. Thus, we believe dasper can increase diagnostic yield for a pathogenic splicing variants and enable the efficient implementation of RNA-sequencing for diagnostics in clinical laboratories.

BACKGROUND AND PURPOSE Pathogenic variants in PLEKHG5 have been reported to date to be causative in three unrelated families with autosomal recessive intermediate Charcot-Marie-Tooth disease (CMT) and in one consanguineous family with spinal muscular atrophy (SMA). PLEKHG5 is known to be expressed in the human peripheral nervous system, and previous studies have shown its function in axon terminal autophagy of synaptic vesicles, lending support to its underlying pathogenetic mechanism. Despite this, there is limited knowledge of the clinical and genetic spectrum of disease. METHODS We leverage the diagnostic utility of exome and genome sequencing and describe novel biallelic variants in PLEKHG5 in 13 individuals from nine unrelated families originating from four different countries. We compare our phenotypic and genotypic findings with a comprehensive review of cases previously described in the literature. RESULTS We found that patients presented with variable disease severity at different ages of onset (8-25 years). In our cases, weakness usually started proximally, progressing distally, and can be associated with intermediate slow conduction velocities and minor clinical sensory involvement. We report three novel nonsense and four novel missense pathogenic variants associated with these PLEKHG5-associated neuropathies, which are phenotypically spinal muscular atrophy (SMA) or intermediate Charcot-Marie-Tooth disease. CONCLUSIONS PLEKHG5-associated neuropathies should be considered as an important differential in non-5q SMAs even in the presence of mild sensory impairment and a candidate causative gene for a wide range of hereditary neuropathies. We present this series of cases to further the understanding of the phenotypic and molecular spectrum of PLEKHG5-associated diseases.

Objective: The aim of this study was to search for genes/variants that modify the effect of LRRK2 mutations in terms of penetrance and age-at-onset of Parkinson's disease. Methods: We performed the first genome-wide association study of penetrance and age-at-onset of Parkinson's disease in LRRK2 mutation carriers (776 cases and 1,103 non-cases at their last evaluation). Cox proportional hazard models and linear mixed models were used to identify modifiers of penetrance and age-at-onset of LRRK2 mutations, respectively. We also investigated whether a polygenic risk score derived from a published genome-wide association study of Parkinson's disease was able to explain variability in penetrance and age-at-onset in LRRK2 mutation carriers. Results: A variant located in the intronic region of CORO1C on chromosome 12 (rs77395454; P-value=2.5E-08, beta=1.27, SE=0.23, risk allele: C) met genome-wide significance for the penetrance model. A region on chromosome 3, within a previously reported linkage peak for Parkinson's disease susceptibility, showed suggestive associations in both models (penetrance top variant: P-value=1.1E-07; age-at-onset top variant: P-value=9.3E-07). A polygenic risk score derived from publicly available Parkinson's disease summary statistics was a significant predictor of penetrance, but not of age-at-onset. Interpretation: This study suggests that variants within or near CORO1C may modify the penetrance of LRRK2 mutations. In addition, common Parkinson's disease associated variants collectively increase the penetrance of LRRK2 mutations.

The genetic basis of Lewy body dementia (LBD) is not well understood. Here, we performed whole-genome sequencing in large cohorts of LBD cases and neurologically healthy controls to study the genetic architecture of this understudied form of dementia and to generate a resource for the scientific community. Genome-wide association analysis identified five independent risk loci, whereas genome-wide gene-aggregation tests implicated mutations in the gene GBA. Genetic risk scores demonstrate that LBD shares risk profiles and pathways with Alzheimer’s and Parkinson’s disease, providing a deeper molecular understanding of the complex genetic architecture of this age-related neurodegenerative condition.

Knowledge of genomic features specific to the human lineage may provide insights into brain-related diseases. We leverage high-depth whole genome sequencing data to generate a combined annotation identifying regions simultaneously depleted for genetic variation (constrained regions) and poorly conserved across primates. We propose that these constrained, non-conserved regions (CNCRs) have been subject to human-specific purifying selection and are enriched for brain-specific elements. We find that CNCRs are depleted from protein-coding genes but enriched within lncRNAs. We demonstrate that per-SNP heritability of a range of brain-relevant phenotypes are enriched within CNCRs. We find that genes implicated in neurological diseases have high CNCR density, including APOE, highlighting an unannotated intron-3 retention event. Using human brain RNA-sequencing data, we show the intron-3-retaining transcript/s to be more abundant in Alzheimer’s disease with more severe tau and amyloid pathological burden. Thus, we demonstrate the importance of human-lineage-specific sequences in brain development and neurological disease. We release our annotation through vizER (https://snca.atica.um.es/browser/app/vizER).

DNAJC13 (RME-8) is a core co-chaperone that facilitates membrane recycling and cargo sorting of endocytosed proteins. DNAJ/Hsp40 (heat shock protein 40) proteins are highly conserved throughout evolution and mediate the folding of nascent proteins, and the unfolding, refolding or degradation of misfolded proteins while assisting in associated-membrane translocation. DNAJC13 is one of five DNAJ 'C' class chaperone variants implicated in monogenic parkinsonism. Here we examine the effect of the DNAJC13 disease-linked mutation (p.Asn855Ser) on its interacting partners, focusing on sorting nexin 1 (SNX1) membrane dynamics in primary cortical neurons derived from a novel Dnajc13 p.Asn855Ser knock-in (DKI) mouse model. Dnajc13 p.Asn855Ser mutant and wild type protein expression were equivalent in mature heterozygous cultures (DIV21). While SNX1-positive puncta density, area, and WASH-retromer assembly were comparable between cultures derived from DKI and wild type littermates, the formation of SNX1-enriched tubules in DKI neuronal cultures was significantly increased. Thus, Dnajc13 p.Asn855Ser disrupts SNX1 membrane-tubulation and trafficking, analogous to results from RME-8 depletion studies. The data suggest the mutation confers a dominant-negative gain-of-function in RME-8. Implications for the pathogenesis of Parkinson's disease are discussed.

Summary Background Leucine-rich repeat kinase 2 ( LRRK2 ) mutation 6055G→A (Gly2019Ser) accounts for roughly 1% of patients with Parkinson's disease in white populations, 13–30% in Ashkenazi Jewish populations, and 30–40% in North African Arab-Berber populations, although age of onset is variable. Some carriers have early-onset parkinsonism, whereas others remain asymptomatic despite advanced age. We aimed to use a genome-wide approach to identify genetic variability that directly affects LRRK2 Gly2019Ser penetrance. Methods Between 2006 and 2012, we recruited Arab-Berber patients with Parkinson's disease and their family members (aged 18 years or older) at the Mongi Ben Hamida National Institute of Neurology (Tunis, Tunisia). Patients with Parkinson's disease were diagnosed by movement disorder specialists in accordance with the UK Parkinson's Disease Society Brain Bank criteria, without exclusion of familial parkinsonism. LRRK2 carrier status was confirmed by Sanger sequencing or TaqMan SNP assays-on-demand. We did genome-wide linkage analysis using data from multi-incident Arab-Berber families with Parkinson's disease and LRRK2 Gly2019Ser (with both affected and unaffected family members). We assessed Parkinson's disease age of onset both as a categorical variable (dichotomised by median onset) and as a quantitative trait. We used data from another cohort of unrelated Tunisian LRRK2 Gly2019Ser carriers for subsequent locus-specific genotyping and association analyses. Whole-genome sequencing in a subset of 14 unrelated Arab-Berber individuals who were LRRK2 Gly2019Ser carriers (seven with early-onset disease and seven elderly unaffected individuals) subsequently informed imputation and haplotype analyses. We replicated the findings in separate series of LRRK2 Gly2019Ser carriers originating from Algeria, France, Norway, and North America. We also investigated associations between genotype, gene, and protein expression in human striatal tissues and murine LRRK2 Gly2019Ser cortical neurons. Findings Using data from 41 multi-incident Arab-Berber families with Parkinson's disease and LRRK2 Gly2019Ser (150 patients and 103 unaffected family members), we identified significant linkage on chromosome 1q23.3 to 1q24.3 (non-parametric logarithm of odds score 2·9, model-based logarithm of odds score 4·99, θ=0 at D1S2768). In a cohort of unrelated Arab-Berber LRRK2 Gly2019Ser carriers, subsequent association mapping within the linkage region suggested genetic variability within DNM3 as an age-of-onset modifier of disease (n=232; rs2421947; haplotype p=1·07 × 10 −7 ). We found that DNM3 rs2421947 was a haplotype tag for which the median onset of LRRK2 parkinsonism in GG carriers was 12·5 years younger than that of CC carriers (Arab-Berber cohort, hazard ratio [HR] 1·89, 95% CI 1·20–2·98). Replication analyses in separate series from Algeria, France, Norway, and North America (n=263) supported this finding (meta-analysis HR 1·61, 95% CI 1·15–2·27, p=0·02). In human striatum, DNM3 expression varied as a function of rs2421947 genotype, and dynamin-3 localisation was perturbed in murine LRRK2 Gly2019Ser cortical neurons. Interpretation Genetic variability in DNM3 modifies age of onset for LRRK2 Gly2019Ser parkinsonism and informs disease-relevant translational neuroscience. Our results could be useful in genetic counselling for carriers of this mutation and in clinical trial design. Funding The Canada Excellence Research Chairs (CERC), Leading Edge Endowment Fund (LEEF), Don Rix BC Leadership Chair in Genetic Medicine, National Institute on Aging, National Institute of Neurological Disorders and Stroke, the Michael J Fox Foundation, Mayo Foundation, the Roger de Spoelberch Foundation, and GlaxoSmithKline.

Mutations in dynactin DCTN1 (p150(glued)) have previously been linked to familial motor neuron disease or Perry syndrome (PS) consisting of depression, parkinsonism and hypoventilation.We sequenced DCTN1 in 636 Caucasian patients with parkinsonism (Parkinson's disease and Parkinson-plus syndromes) and 508 healthy controls. Variants (MAF 0.01) were subsequently genotyped in Caucasian (1360 cases and 1009 controls) and Asian cohorts (1046 cases and 830 controls), and the functional implications of pathogenic variants were assessed.We identified 17 rare variants leading to non-synonymous amino-acid substitutions. Four of the variants were only observed in control subjects, four in both cases and controls and the remaining nine in cases only. One of the variants, DCTN1 p.K56R, was present in two patients with progressive supranuclear palsy (PSP) with a shared minimal 2.2 Mb haplotype. Both subjects have parkinsonism as the most prominent symptom with abnormal ocular movements, moderate cognitive impairment and little to no l-dopa response. Neither subject presents with depression, central hypoventilation or weight loss. For one of the subjects MRI shows symmetrical atrophy of temporal and frontoparietal lobes. In HEK293 cells mutant p150(glued) (p.K56R) shows less affinity for microtubules than wild-type, with a more diffuse cytoplasmic distribution.We have identified DCTN1 p.K56R in patients with PSP. This variant is immediately adjacent to the N-terminal p150(glued) 'CAP-Gly' domain, affects a highly conserved amino acid and alters the protein's affinity to microtubules and its cytoplasmic distribution.

Introduction Primary periodic paralyses (PPs) are rare genetic neuromuscular disorders commonly caused by mutations in genes related to ion channel function. However, 10%-20% of cases remain as genetically unexplained. Herein we present a family with PP with paralytic episodes generally lasting for 1-7 days at a time, associated with a drop in K+ levels. Methods Screening for mutations in known disease-causing genes was negative, hence we performed whole-exome sequencing of 5 family members. Results Minichromosome maintenance 3-associated protein (MCM3AP) c.2615G>A (p.C872Y) was found to cosegregate with disease in the family and was not present in control subjects. The mutation is novel, highly conserved across multiple species, and predicted to be damaging. Discussion MCM3AP encodes germinal center-associated nuclear protein (GANP), a protein involved in the export of certain messenger RNAs from the nucleus to the cytoplasm. Our findings suggest that a novel mutation in MCM3AP is associated with hypokalemic PP. Muscle Nerve, 2019.

Introduction The Faroe Islands is a geographically isolated population in the North Atlantic with a high prevalence of Parkinson disease (PD). The disease etiology is still unknown, although dietary pollutants are considered a risk factor. The genetic risk underlying disease susceptibility has yet to be elucidated. Methods Sequence analysis was performed in genes previously linked with PD in 91 patients and 96 healthy control subjects. Results Fourteen missense mutations, of which one was novel, were identified in six genes. One patient (1%) did carry the known pathogenic mutation LRRK2 p.G2019S mutation, 19 patients (22%) did carry mutations of unknown significance while 70 patients (78.0%) did not have any identifiable genetic risk. A total of 14 controls (14.6%) carried mutations of unknown significance. Conclusion This study suggests that rare variants in genes previously linked to PD are not major contributors to PD in the Faroe Islands. Further exome sequencing and comparative analyses within and among well-described pedigrees with multi-incident PD are now warranted.

Background A pathogenic mutation (VPS35 p.D620N) within the retromer complex has been shown to segregate with late-onset Parkinson's disease (PD). Several studies have subsequently detected the mutation in patients with PD and not in controls. Methods Mutation screening of the coding regions of the retromer cargo recognition complex genes (VPS26A/B, VPS29, and VPS35) was carried out in patients with PD (n = 396), atypical parkinsonism (n = 229), and in 368 controls. Results Overall, we identified five rare nonsynonymous mutations in VPS26A and one in VPS35; none were observed in VPS26B or VPS29. Three VPS26A variants (p.K93E, p.M112V, and p.K297X), identified in patients with atypical parkinsonism, were not observed in controls from this study (n = 368) or from publically available data sets (n = 4,426). Conclusion Our results support the hypothesis that rare variants in the retromer complex genes may be involved in the development of parkinsonism, although further studies are warranted before any solid conclusions can be drawn.

Vacuolar protein sorting 35 (VPS35) is a core component of the retromer trimer required for endosomal membrane-associated protein trafficking. The discovery of a missense mutation, Vps35 p.D620N implicates retromer dysfunction in the pathogenesis of Parkinson’s disease (PD). We have characterized a knock-in mouse with a Vps35 p.D620N substitution (hereafter referred to as VKI) at 3 months of age. Standardized behavioral testing did not observe overt movement disorder. Tyrosine hydroxylase (TH)-positive nigral neuron counts and terminal expression in striata were comparable across genotypes. Fast scan cyclic voltammetry revealed increased dopamine release in VKI striatal slices. While extracellular dopamine collected via striatal microdialysis of freely moving animals was comparable across genotypes, the ratio of dopamine metabolites to dopamine suggests increased dopamine turnover in VKI homozygous mice. Western blot of striatal proteins revealed a genotype-dependent decrease in dopamine transporter (DAT) along with an increase in vesicular monoamine transporter 2 (VMAT2), albeit independent of changes in other synaptic markers. The reduction in DAT was further supported by immunohistochemical analysis. The data show that the dopaminergic system of VKI mice is profoundly altered relative to wild-type littermates. We conclude early synaptic dysfunction contributes to age-related pathophysiology in the nigrostriatal system that may lead to parkinsonism in man., Neurogenetics: Impaired recycling impacts neurotransmission A mutation linked to late-onset Parkinson’s disease (PD) disrupts dopaminergic neurotransmission in mice. A study led by Matthew J. Farrer at the Centre for Applied Neurogenetics, University of British Columbia, Canada, examined the effects of a missense mutation in the gene encoding a core subunit of a complex required for recycling membrane-associated proteins, Vacuolar Protein Sorting 35 (VPS35; Vps35), in young adult mice. Although no significant effects on motor function or neurodegeneration were found, an increase in dopamine release and turnover in the dorsolateral striatum were observed in the mutant mice. Deficits in the transport and recycling of transporters required for dopamine re-uptake and storage may underlie these effects. Further analyses of Vps35 mutant mice could improve our understanding of the synaptic dysfunction that precedes neurodegeneration in PD.

Background An initial diagnosis of Parkinson's disease (PD) is challenging, especially in patients who have early onset and atypical disease. A genetic etiology for parkinsonism, when established, ends that diagnostic odyssey and may inform prognosis and therapy. The objective of this study was to elucidate the genetic etiology of parkinsonism in patients with early onset disease (age at onset

A novel mutation (p.N855S) in DNAJC13 has been linked to familial, late-onset Lewy body parkinsonism in a Dutch-German-Russian Mennonite multi-incident kindred.DNAJC13 was sequenced in 201 patients with parkinsonism and 194 controls from Canada. Rare (minor allele frequency0.01) missense variants identified in patients were genotyped in two Parkinson's disease case-controls cohorts.Eighteen rare missense mutations were identified; four were observed in controls, three were observed in both patients and controls, and eleven were identified only in patients. Subsequent genotyping showed p.E1740Q and p.L2170W to be more frequent in patients, and p.R1516H being more frequent in controls. Additionally, p.P336A, p.V722L, p.N855S, p.R1266Q were seen in one patient each, and p.T1895M was found in two patients.Although the contribution of rare genetic variation in DNAJC13 to parkinsonisms remains to be further elucidated, this study suggests that, in addition to p.N855S, other rare variants might affect disease susceptibility.

There is a growing awareness of the influence of mitochondrial genetic variation on life-history phenotypes, particularly via epistatic interactions with nuclear genes. Owing to their direct effect on traits such as metabolic and growth rates, mitonuclear interactions may also affect variation in behavioural types or personalities (i.e. behavioural variation that is consistent within individuals, but differs among individuals). However, this possibility is largely unexplored. We used mitonuclear introgression lines, where three mitochondrial genomes were introgressed into three nuclear genetic backgrounds, to disentangle genetic effects on behavioural variation in a seed beetle. We found within-individual consistency in a suite of activity-related behaviours, providing evidence for variation in personality. Composite measures of overall activity of individuals in behavioural assays were influenced by both nuclear genetic variation and by the interaction between nuclear and mitochondrial genomes. More importantly, the degree of expression of behavioural and life-history phenotypes was correlated and mitonuclear genetic variation affected expression of these concerted phenotypes. These results show that mitonuclear genetic variation affects both behavioural and life-history traits, and they provide novel insights into the maintenance of genetic variation in behaviour and personality.

A Saskatchewan multi-incident family was clinically characterized with Parkinson disease (PD) and Lewy body pathology. PD segregates as an autosomal-dominant trait, which could not be ascribed to any known mutation. DNA from three affected members was subjected to exome sequencing. Genome alignment, variant annotation and comparative analyses were used to identify shared coding mutations. Sanger sequencing was performed within the extended family and ethnically matched controls. Subsequent genotyping was performed in a multi-ethnic case–control series consisting of 2928 patients and 2676 control subjects from Canada, Norway, Taiwan, Tunisia, and the USA. A novel mutation in receptor-mediated endocytosis 8/RME-8 (DNAJC13 p.Asn855Ser) was found to segregate with disease. Screening of cases and controls identified four additional patients with the mutation, of which two had familial parkinsonism. All carriers shared an ancestral DNAJC13 p.Asn855Ser haplotype and claimed Dutch–German–Russian Mennonite heritage. DNAJC13 regulates the dynamics of clathrin coats on early endosomes. Cellular analysis shows that the mutation confers a toxic gain-of-function and impairs endosomal transport. DNAJC13 immunoreactivity was also noted within Lewy body inclusions. In late-onset disease which is most reminiscent of idiopathic PD subtle deficits in endosomal receptor-sorting/recycling are highlighted by the discovery of pathogenic mutations VPS35, LRRK2 and now DNAJC13. With this latest discovery, and from a neuronal perspective, a temporal and functional ecology is emerging that connects synaptic exo- and endocytosis, vesicular trafficking, endosomal recycling and the endo-lysosomal degradative pathway. Molecular deficits in these processes are genetically linked to the phenotypic spectrum of parkinsonism associated with Lewy body pathology.

Parkinson disease is a progressive neurodegenerative disease for which leucine-rich repeat kinase 2 (LRRK2 carriers) p.G2019S confers substantial genotypic and population attributable risk. With informed consent, we have recruited clinical data from 778 patients from Tunisia (of which 266 have LRRK2 parkinsonism) and 580 unaffected subjects. Motor, autonomic, and cognitive assessments in idiopathic Parkinson disease and LRRK2 patients were compared with regression models. The age-associated cumulative incidence of LRRK2 parkinsonism was also estimated using case-control and family-based designs. LRRK2 parkinsonism patients had slightly less gastrointestinal dysfunction and rapid eye movement sleep disorder. Overall, disease penetrance in LRRK2 carriers was 80% by 70 years but women become affected a median 5 years younger than men. Idiopathic Parkinson disease patients with younger age at diagnosis have slower disease progression. However, age at diagnoses does not predict progression in LRRK2 parkinsonism. LRRK2 p.G2019S mutation is a useful aid to diagnosis and modifiers of disease in LRRK2 parkinsonism may aid in developing therapeutic targets.