Single-cell RNA-seq of mouse dopaminergic neurons informs candidate gene selection for sporadic Parkinson’s disease (original) (raw)
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The American Journal of Human Genetics
Genetic variation modulating risk of sporadic Parkinson's disease (PD) has been primarily explored through genome wide association studies (GWAS). However, like many other common genetic diseases, the impacted genes remain largely unknown. Here, we used single-cell RNAseq to characterize dopaminergic (DA) neuron populations in the mouse brain at embryonic and early postnatal timepoints. These data facilitated unbiased identification of DA neuron subpopulations through their unique transcriptional profiles, including a postnatal neuroblast population and substantia nigra (SN) DA neurons. We use these population-specific data to develop a scoring system to prioritize candidate genes in all 49 GWAS intervals implicated in PD risk, including genes with known PD associations and many with extensive supporting literature. As proof of principle, we confirm that the nigrostriatal pathway is compromised in Cplx1 null mice. Ultimately, this systematic approach establishes biologically pertinent candidates and testable hypotheses for sporadic PD, informing a new era of PD genetic research.
A Cross-Study Transcriptional Analysis of Parkinson's Disease
PLoS ONE, 2009
The study of Parkinson's disease (PD), like other complex neurodegenerative disorders, is limited by access to brain tissue from patients with a confirmed diagnosis. Alternatively the study of peripheral tissues may offer some insight into the molecular basis of disease susceptibility and progression, but this approach still relies on brain tissue to benchmark relevant molecular changes against. Several studies have reported whole-genome expression profiling in post-mortem brain but reported concordance between these analyses is lacking. Here we apply a standardised pathway analysis to seven independent case-control studies, and demonstrate increased concordance between data sets. Moreover data convergence increased when the analysis was limited to the five substantia nigra (SN) data sets; this highlighted the down regulation of dopamine receptor signaling and insulin-like growth factor 1 (IGF1) signaling pathways. We also show that case-control comparisons of affected post mortem brain tissue are more likely to reflect terminal cytoarchitectural differences rather than primary pathogenic mechanisms. The implementation of a correction factor for dopaminergic neuronal loss predictably resulted in the loss of significance of the dopamine signaling pathway while axon guidance pathways increased in significance. Interestingly the IGF1 signaling pathway was also over-represented when data from non-SN areas, unaffected or only terminally affected in PD, were considered. Our findings suggest that there is greater concordance in PD wholegenome expression profiling when standardised pathway membership rather than ranked gene list is used for comparison.
Transcriptomic signatures of brain regional vulnerability to Parkinson’s disease
The molecular mechanisms underlying the caudal-to-rostral progression of Lewy body pathology in Parkinson’s disease (PD) remain poorly understood. Here, we aimed to unravel transcriptomic signatures across brain regions involved in Braak Lewy body stages in non-neurological controls and PD donors. Using human postmortem brain datasets of non-neurological adults from the Allen Human Brain Atlas, we identified expression patterns related to PD progression, including genes found in PD genome-wide associations studies: SNCA, ZNF184, BAP1, SH3GL2, ELOVL7, and SCARB2. We confirmed these patterns in two datasets of non-neurological subjects (Genotype-Tissue Expression project and UK Brain Expression Consortium) and found altered patterns in two datasets of PD patients. Additionally, co-expression analysis across vulnerable regions identified two modules associated with dopamine synthesis, the motor and immune system, blood-oxygen transport, and contained microglial and endothelial cell mar...
Journal of biomedical science, 2010
Background: Parkinson's disease is the second most common neurodegenerative disorder. The pathological hallmark of the disease is degeneration of midbrain dopaminergic neurons. Genetic association studies have linked 13 human chromosomal loci to Parkinson's disease. Identification of gene(s), as part of the etiology of Parkinson's disease, within the large number of genes residing in these loci can be achieved through several approaches, including screening methods, and considering appropriate criteria. Since several of the indentified Parkinson's disease genes are expressed in substantia nigra pars compact of the midbrain, expression within the neurons of this area could be a suitable criterion to limit the number of candidates and identify PD genes.
JAMA Neurology
; for the United Kingdom Brain Expression Consortium (UKBEC) and the International Parkinson's Disease Genomics Consortium (IPDGC) IMPORTANCE Substantial genome-wide association study (GWAS) work in Parkinson disease (PD) has led to the discovery of an increasing number of loci shown reliably to be associated with increased risk of disease. Improved understanding of the underlying genes and mechanisms at these loci will be key to understanding the pathogenesis of PD. OBJECTIVE To investigate what genes and genomic processes underlie the risk of sporadic PD. DESIGN AND SETTING This genetic association study used the bioinformatic tools Coloc and transcriptome-wide association study (TWAS) to integrate PD case-control GWAS data published in 2017 with expression data (from Braineac, the Genotype-Tissue Expression [GTEx], and CommonMind) and methylation data (derived from UK Parkinson brain samples) to uncover putative gene expression and splicing mechanisms associated with PD GWAS signals. Candidate genes were further characterized using cell-type specificity, weighted gene coexpression networks, and weighted protein-protein interaction networks. MAIN OUTCOMES AND MEASURES It was hypothesized a priori that some genes underlying PD loci would alter PD risk through changes to expression, splicing, or methylation. Candidate genes are presented whose change in expression, splicing, or methylation are associated with risk of PD as well as the functional pathways and cell types in which these genes have an important role. RESULTS Gene-level analysis of expression revealed 5 genes (WDR6 [OMIM 606031], CD38 [OMIM 107270], GPNMB [OMIM 604368], RAB29 [OMIM 603949], and TMEM163 [OMIM 618978]) that replicated using both Coloc and TWAS analyses in both the GTEx and Braineac expression data sets. A further 6 genes (ZRANB3 [OMIM 615655], PCGF3 [OMIM 617543], NEK1 [OMIM 604588], NUPL2 [NCBI 11097], GALC [OMIM 606890], and CTSB [OMIM 116810]) showed evidence of disease-associated splicing effects. Cell-type specificity analysis revealed that gene expression was overall more prevalent in glial cell types compared with neurons. The weighted gene coexpression performed on the GTEx data set showed that NUPL2 is a key gene in 3 modules implicated in catabolic processes associated with protein ubiquitination and in the ubiquitin-dependent protein catabolic process in the nucleus accumbens, caudate, and putamen. TMEM163 and ZRANB3 were both important in modules in the frontal cortex and caudate, respectively, indicating regulation of signaling and cell communication. Protein interactor analysis and simulations using random networks demonstrated that the candidate genes interact significantly more with known mendelian PD and parkinsonism proteins than would be expected by chance. CONCLUSIONS AND RELEVANCE Together, these results suggest that several candidate genes and pathways are associated with the findings observed in PD GWAS studies.
Brain, 2021
Idiopathic Parkinson’s disease is characterized by a progressive loss of dopaminergic neurons, but the exact disease aetiology remains largely unknown. To date, Parkinson’s disease research has mainly focused on nigral dopaminergic neurons, although recent studies suggest disease-related changes also in non-neuronal cells and in midbrain regions beyond the substantia nigra. While there is some evidence for glial involvement in Parkinson’s disease, the molecular mechanisms remain poorly understood. The aim of this study was to characterize the contribution of all cell types of the midbrain to Parkinson’s disease pathology by single-nuclei RNA sequencing and to assess the cell type-specific risk for Parkinson’s disease using the latest genome-wide association study. We profiled >41 000 single-nuclei transcriptomes of post-mortem midbrain from six idiopathic Parkinson’s disease patients and five age-/sex-matched controls. To validate our findings in a spatial context, we utilized im...
Nature Genetics, 2020
Genome-wide association studies have discovered hundreds of loci associated with complex brain disorders, but it remains unclear in which cell types these loci are active. Here we integrate genome-wide association study results with single-cell transcriptomic data from the entire mouse nervous system to systematically identify cell types underlying brain complex traits. We show that psychiatric disorders are predominantly associated with projecting excitatory and inhibitory neurons. Neurological diseases were associated with different cell types, which is consistent with other lines of evidence. Notably, Parkinson's disease was genetically associated not only with cholinergic and monoaminergic neurons (which include dopaminergic neurons) but also with enteric neurons and oligodendrocytes. Using post-mortem brain transcriptomic data, we confirmed alterations in these cells, even at the earliest stages of disease progression. Our study provides an important framework for understanding the cellular basis of complex brain maladies, and reveals an unexpected role of oligodendrocytes in Parkinson's disease.
2021
Background Dopaminergic (DA) neurons of the substantia nigra pars compacta (SNpc) selectively and progressively degenerate in Parkinson’s disease (PD). Until now, molecular analyses of DA neurons in PD have been limited to genomic and transcriptomic approaches, whereas, to the best of our knowledge, no proteomic or combined polyomic study examining the protein profile of these neurons, is currently available. Methods In this exploratory study, we used laser microdissection to extract DA neurons from 10 human SNpc samples obtained at autopsy in PD patients and control subjects. Extracted RNA and proteins were identified by RNA sequencing and nano-LC-MS/MS, respectively, and the differential expression between the PD and control group was assessed. Results Qualitative analyses confirmed that the microdissection protocol preserves the integrity of our samples and offers access to specific molecular pathways. This polyomic analysis highlighted differential expression of 52 genes and 33 ...
A review of genome-wide transcriptomics studies in Parkinson's disease
The European journal of neuroscience, 2018
Parkinson's disease (PD) is a progressive and incurable neurodegenerative disorder. Although numerous genetic and environmental factors have been linked to the aetiology of PD the underlying pathobiology remains poorly understood, hampering the development of improved therapies. Transcriptomics has the potential to reveal significant insights into disease processes. In this review, we focused on published transcriptomics studies on PD with the aim of summarizing studies and identifying common biological pathways. A total of 96 articles were identified as follows: 12 meta-analyses, 21 re-analyses of existing data and 63 original studies. Of the 63 original studies, 33 were performed on brain tissue, 26 on blood, three on cerebrospinal fluid and one on skin. In the brain studies, altered pathways identified included those involved in dopamine metabolism, mitochondrial function, oxidative stress, protein degradation, neuroinflammation, vesicular transport and synaptic transmission....
PLoS ONE, 2010
Background: Epidemiological data suggest that the male gender is one of the risks factors for the development of Parkinson Disease (PD). Also, differences in the clinical manifestation and the course of PD have been observed between males and females. However, little is known about the molecular aspects underlying gender-specificity in PD. To address this issue, we determined the gene expression profiles of male and female dopamine (DA) neurons in sporadic PD.