Metabolomics,Unknown,Transcriptomics,Genomics,Proteomics

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MRNA-Seq expression and MS3 proteomics profiling of human post-mortem BA9 brain tissue for Parkinson Disease and neurologically normal individuals

ABSTRACT: Parkinson disease (PD) is a neurodegenerative disease characterized by the accumulation of alpha-synuclein (SNCA) and other proteins in aggregates termed âLewy Bodiesâ within neurons. PD has both genetic and environmental risk factors, and while processes leading to aberrant protein aggregation are unknown, past work points to abnormal levels of SNCA and other proteins. Although several genome-wide studies have been performed for PD, these have focused on DNA sequence variants by genome-wide association studies (GWAS) and on RNA levels (microarray transcriptomics), while genome-wide proteomics analysis has been lacking. After appropriate filters, proteomics identified 3,558 unique proteins and 283 of these (7.9%) were significantly different between PD and controls (q-value<0.05). RNA-sequencing identified 17,580 protein-coding genes and 1,095 of these (6.2%) were significantly different (FDR p-value<0.05), but only 166 of the FDR significant protein-coding genes (0.94%) were present among the 3,558 proteins characterized. Of these 166, eight genes (4.8%) were significant in both studies, with the same direction of effect. Functional enrichment analysis of the proteomics results strongly supports mitochondrial-related pathways, while comparable analysis of the RNA-sequencing results implicates protein folding pathways and metallothioneins. Ten of the implicated genes or proteins co-localized to GWAS loci. Evidence implicating SNCA was stronger in proteomics than in RNA-sequencing analyses. Notably, differentially expressed protein-coding genes were more likely to not be characterized in the proteomics analysis, which lessens the ability to compare across platforms. Combining multiple genome-wide platforms offers novel insights into the pathological processes responsible for this disease by identifying pathways implicated across methodologies. The study consists of mRNA-Seq (29 PD, 44 neurologically normal controls) and three-stage Mass Spectrometry Tandem Mass Tag Proteomics (12 PD, 12 neurologically normal controls) performed in post-mortem BA9 brain tissue. The proteomics samples are a subset of the RNA-Seq samples.

ORGANISM(S): Homo sapiens

SUBMITTER: Alexandra Dumitriu

PROVIDER: E-GEOD-68719 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Importance. Biological markers of Parkinson’s disease are essential for achieving disease modification. Objective. To determine the association of SNCA blood transcript levels with prevalence of Parkinson’s disease. Background. The SNCA locus is preferentially transcribed in neurons and blood cells. Non-coding genetic variants and neuronal aggregates of α-synuclein protein associate this locus with sporadic Parkinson’s disease and suggest a potential role for abnormal SNCA transcription in the disease mechanism. Here we investigated variation in intracellular SNCA gene expression and SNCA transcript isoform abundance in circulating blood cells of cases with PD and controls in a network of biobanks that represent regional, national, and international populations. Design, Setting, Participants. Three cross-sectional, case-control studies nested in observational biomarker studies. 222 cases with early-stage clinical PD and 183 controls were enrolled from 2005 to 2010 in the Harvard Biomarker Study (HBS) at two Harvard-affiliated tertiary care centers. 76 cases with dopamine transporter imaging (DAT)-confirmed PD and 42 controls were enrolled between August 2007 and December 2008 in the Blood α-Synuclein, Gene Expression and Smell Testing as Diagnostic and Prognostic Biomarkers in Parkinson’s Disease Study (PROBE) study from 22 US tertiary care centers. 202 DAT-confirmed cases with de novo PD and 138 controls were enrolled in the Parkinson’s Progression Markers Initiative (PPMI) between July 2010 and November 2012 from 22 US and international tertiary care centers. Main Outcome Measures. Association of intracellular SNCA transcript abundance with PD estimated on analog and digital expression platforms. Results. Reduced levels of SNCA transcripts were associated with early-stage clinical PD, neuroimaging-confirmed PD, and untreated, neuroimaging-confirmed PD in accessible, peripheral blood cells from a total of 863 individuals. SNCA expression was reduced by 17%, 22%, and 16% in cases compared to controls in the HBS, PROBE, and PPMI study with P values of 0.004, 0.025, and 0.018, respectively, after adjusting for clinical, hematological, and processing covariates. Specific SNCA transcripts with long 3’ untranslated regions (UTR) and those skipping exon 5 are implicated in the accumulation and mitochondrial targeting of α-synuclein protein in Parkinson’s pathology. These transcript isoforms were linked to PD through digital expression analysis. Individuals in the lowest quartile of SNCA expression values had covariate-adjusted odds ratios for PD of 2.14 (95% C. I. 1.1-4.1), 4.5 (95% C. I. 1.3-15), and 2.1 (1.1-4.0) compared to individuals in the highest quartile of expression values in the HBS, PROBE, and PPMI study, respectively. Conclusions and Relevance. Reduced levels of SNCA expression, particularly of disease-relevant transcripts with extended 3’ UTR or exon 5 skipping, are associated with early-stage PD. These findings support a potential role for SNCA as a transcriptional marker of PD and may have implications for patient stratification and risk assessment.

Project description:Parkinsonâs disease (PD), the second most frequent neurodegenerative disorder at old age, can be caused by elevated expression, or the A53T mutation, of the presynaptic protein alpha-synuclein (SNCA). PD is characterized pathologically by the preferential vulnerability of the dopaminergic nigrostriatal projection neurons. Here, we used two mouse lines overexpressing human A53T-SNCA around ages 6 and 18 months and studied striatal dysfunction in the absence of neurodegeneration to understand early disease mechanisms. High pressure liquid chromatography analysis of striatal neurotransmitter content demonstrated that dopamine (DA) levels correlated directly with the level of expression of SNCA, an observation also observed in SNCA deficient mice. In the striatum of aged A53TSNCA overexpressing mice, where DA levels were elevated, a paradoxical upregulation of dopamine receptors DRD1A and DRD2 was detected by immunoblots and autoradiography, findings compatible with the notion of abnormal vesicle release. Extensive transcriptome studies via microarrays and quantitative real-time RT-PCR validation of altered Homer1, Cb1, Atf2 and Pde7b transcript levels indicated a progressive reduction in the postsynaptic DA response. As functional consequences, long term depression was absent in corticostriatal slices from aged transgenic mice and an insidious decrease of spontaneous locomotor activity of these animals was found in open field tests. Taken together, the dysfunctional neurotransmission and decreased synaptic plasticity seen in the A53T-SNCA overexpressing mice reflects early functional changes within the basal ganglia resulting from synucleinopathy prior to frank neurodegeneration. Thus, preclinical stages of PD may be modeled in this mouse. Parkinsonâs disease (PD), the second most frequent neurodegenerative disorder at old age, can be caused by elevated expression, or the A53T mutation, of the presynaptic protein alpha-synuclein (SNCA). PD is characterized pathologically by the preferential vulnerability of the dopaminergic nigrostriatal projection neurons. Here, we used two mouse lines overexpressing human A53T-SNCA around ages 6 and 18 months and studied striatal dysfunction in the absence of neurodegeneration to understand early disease mechanisms. High pressure liquid chromatography analysis of striatal neurotransmitter content demonstrated that dopamine (DA) levels correlated directly with the level of expression of SNCA, an observation also observed in SNCA deficient mice. In the striatum of aged A53TSNCA overexpressing mice, where DA levels were elevated, a paradoxical upregulation of dopamine receptors DRD1A and DRD2 was detected by immunoblots and autoradiography, findings compatible with the notion of abnormal vesicle release. Extensive transcriptome studies via microarrays and quantitative real-time RT-PCR validation of altered Homer1, Cb1, Atf2 and Pde7b transcript levels indicated a progressive reduction in the postsynaptic DA response. As functional consequences, long term depression was absent in corticostriatal slices from aged transgenic mice and an insidious decrease of spontaneous locomotor activity of these animals was found in open field tests. Taken together, the dysfunctional neurotransmission and decreased synaptic plasticity seen in the A53T-SNCA overexpressing mice reflects early functional changes within the basal ganglia resulting from synucleinopathy prior to frank neurodegeneration. Thus, preclinical stages of PD may be modeled in this mouse. Tissue was dissected from the brain of 6 months old (2 WT / 2 TgA / 2 TgB striata, 2 WT / 2 TgA / 2 TgB brainstems/midbrains, 2 WT / 2 TgA / 2 TgB cerebella) and of 18+ months old mice (4 WT / 2 TgA / 2 TgB striata, 6 WT / 4 TgA / 3 TgB brainstems/midbrains, 6 WT / 5 TgA / 4 TgB cerebella). Tissues from individual, particularly old mice up to 28 months age were included here to strengthen the definition of progression markers reflecting old age.

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MRNA-Seq expression and MS3 proteomics profiling of human post-mortem BA9 brain tissue for Parkinson Disease and neurologically normal individuals

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