Project description:Mitochondrial DNA (mtDNA) damage is considered as a possible primary cause of Parkinson’s disease (PD). To explore the issue, mtDNA sequences from whole blood were analyzed in PD patients and controls using a resequencing chip and allelic substitutions were estimated for each nucleotide position (np) along the entire mtDNA sequence. Overall, 58 np showed a different allelic distribution in the two groups; of these, 81% showed an increase of non-reference alleles in PD patients, similar to findings reported in patients with Alzheimer’s disease, albeit in reduced proportion. These results suggest that age-related neurodegenerative diseases could share a mechanism involving mtDNA.
Project description:Introduction: Parkinson's disease (PD), typically developing between the ages of 55 and 65 years, is a common neurodegenerative disorder caused by a progressive loss of dopaminergic neurons due to the accumulation of α-synuclein in the substantia nigra. Mitochondria are known to play a key role in cell respiratory function and bioenergetic. Indeed, mitochondrial dysfunction causes an insufficient energy production required to satisfy the needs of several organs, especially the nervous system. Material and methods: The present study explored the mRNA expression of mitochondrial DNA (mtDNA) encoded respiratory chain (RC) subunits in PD patients by using the next generation sequencing analysis (NGS) and the quantitative real-time PCR (qRT-PCR) assay for the confirmation of the NGS results. Results: All tested mitochondrial RC subunits was significantly over-expressed in subjects with PD compared to normal controls . In qRT-PCR the mean expression of all mitochondrial subunits had an expression level of at least 7 times compared to controls. Conclusion: The over-expression of mitochondrial subunits in PD subjects might be secondary to a degeneration-related alteration of the mitochondrial structure or dynamics or to the occurrence of a compensatory mechanism. The study of specific mRNA by peripheral blood mononuclear cells (PBMCs) may provide a better diagnostic frame to early detect PD cases.
Project description:Individual variation in complex traits results from allelic variants of multiple segregating genes, which are expressed as coregulated ensembles that are modulated by the environment. Coregulated transcriptional networks around focal genes, defined as their ‘transcriptional niches’, are sensitive to genetic and environmental perturbations. Understanding how single base pair substitutions affect this complex genotype-phenotype relationship by perturbing transcriptional niches is possible in Drosophila, which allows precise control of both the genetic background and the environment. We used a two-step CRISPR-Cas9 mediated gene deletion and reinsertion strategy to generate in a common genetic background five single nucleotide substitutions in the D. melanogaster Obp56h gene that correspond to naturally occurring allelic variants. Changes in single base pairs give rise to differential, sexually dimorphic effects on a plethora of fitness traits, including viability, sex ratio, feeding behavior, starvation resistance, recovery from a chill-induced coma, response to heat shock, activity, and sleep traits. These pleiotropic effects are accompanied by sexually dimorphic shifts in the transcriptional niche of Obp56h. Pairwise comparisons between the lines show common coregulated genes along with varying numbers of transcripts unique to one or few Obp56h alleles. Gene ontology enrichment analyses indicate that fundamental cellular processes for each sex underlie the phenotypic pleiotropy revealed by the Obp56h allelic series. Furthermore, different Obp56h alleles in a common genetic background give rise to allele-specific, sexually dimorphic microenvironmental variation. The reverse genetic engineering strategy, illustrated here, can be generally applied to other genes to dissect variation in the genotype-phenotype relationship at single base pair resolution.
Project description:Parkinson’s disease (PD) is the most common movement disorder in the aging population, with an estimated prevalence of 1% of people above 60 years old. More recently, PD risk genes, have been found to be regulated by the small non-coding RNAs, (microRNAs or miRNAs), and, as such, may contribute to PD development through a direct regulation on the mitochondrial and immune pathways. Many of these are influenced by epigenetic mechanisms, among which ones mediated by, miRNAs, that regulate gene expression at a post transcriptional level by binding to their 3′ un-translated region (3′ UTR) of target messenger RNAs (mRNAs) inducing mRNA degradation and translational repression. This study aimed to identify and characterize miRNA to evaluate their possible deregulation in PD patients compared to CRTL. In addition, we investigated how specific miRNAs are able to target genes and, thus, to modulate their functions in PD patient. Small RNA expression profiling was performed by next-generation sequencing in PD patients and CTRL after filtered out low-quality reads and trimming the adaptors. The obtained high-quality reads were aligned against the human genome reference.
Project description:Background: Pathological accumulation of aggregated α-synuclein (aSYN) is a common feature of Parkinson’s disease (PD). However, the mechanisms by which intracellular aSYN pathology contributes to dysfunction and degeneration of neurons in the brain are still unclear. A potentially relevant target of aSYN is the mitochondrion. To test this hypothesis, genetic and physiological methods were used to monitor mitochondrial function in substantia nigra pars compacta (SNc) dopaminergic and pedunculopontine nucleus (PPN) cholinergic neurons after stereotaxic injection of aSYN pre-formed fibrils (PFFs) into the mouse brain. Methods: aSYN PPFs were stereotaxically injected into the SNc or PPN of mice. Twelve weeks later, mice were studied using a combination of approaches, including immunocytochemical analysis, cell-type specific transcriptomic profiling, electron microscopy, electrophysiology and two-photon-laser-scanning microscopy of genetically encoded sensors for bioenergetic and redox status. Results: In addition to inducing a significant neuronal loss, SNc injection of PFFs induced the formation of intracellular, phosphorylated aSYN aggregates selectively in dopaminergic neurons. In these neurons, PFF-exposure decreased mitochondrial gene expression, reduced the number of mitochondria, increased oxidant stress, and profoundly disrupted mitochondrial adenosine triphosphate production. Consistent with an aSYN-induced bioenergetic deficit, the autonomous spiking of dopaminergic neurons slowed or stopped. PFFs also up-regulated lysosomal gene expression and increased lysosomal abundance, leading to the formation of Lewy-like inclusions. Similar changes were observed in PPN cholinergic neurons following aSYN PFF exposure. Conclusions: Taken together, our findings suggest that disruption of mitochondrial function is a proximal step in the cascade of events induced by aSYN pathology leading to dysfunction and degeneration of neurons at-risk in PD.
Project description:Emerging evidence suggest that Parkinson's disease (PD), besides being an age-associated disorder, might also have a neurodevelopment component. Disruption of mitochondrial homeostasis has been highlighted as a crucial cofactor in its etiology. Here, we show that PD patient-specific human neuroepithelial stem cells (NESCs) carrying the LRRK2-G2019S mutation recapitulate key mitochondrial defects previously described only in differentiated dopaminergic neurons. By combining high-content imaging approaches, 3D image analysis, and functional mitochondrial readouts we show that LRRK2-G2019S mutation caused aberrations in mitochondrial morphology and functionality compared to isogenic controls. LRRK2-G2019S NESCs displayed an increased number of mitochondria compared to isogenic control lines. However, these mitochondria were more fragmented and exhibited decreased membrane potential. Coherently, the release of total and mitochondrial redox oxidative species increased in LRRK2-G2019S NESC compared to controls. Functional alterations in LRRK2-G2019S cultures were also accompanied by a reduced mitophagic clearance via lysosomes. These findings support the hypothesis that preceding mitochondrial developmental defects contribute to the manifestation of the PD pathology later in life.