Project description:Disruption of local iron homeostasis is a common feature of neurodegenerative diseases. We focused on dopaminergic neurons, asking how iron transport proteins modulate iron homeostasis in vivo. Inactivation of the transmembrane iron exporter ferroportin had no apparent consequences. However, loss of the transferrin receptor 1, involved in iron uptake, caused profound, age-progressive neurodegeneration with features similar to Parkinson’s disease. There was gradual loss of dopaminergic projections in the striatum with subsequent death of dopaminergic neurons in the substantia nigra. After depletion of 30% of the neurons the mice developed neurobehavioral parkinsonism, with evidence of mitochondrial dysfunction and impaired mitochondrial autophagy. Molecular analysis revealed strong signatures indicative of attempted axonal regeneration, a metabolic switch to glycolysis and the unfolded protein response. We speculate that cellular iron deficiency may contribute to neurodegeneration in human patients Using Ribotag technology, from mouse ventral midbrain lysates, we isolated actively translated mRNA species from control and Transferrin receptor 1-null dopaminergic neurons. Two mouse ages were used 3 wks (early neurodegeration) 10 wks (late neurodegeneration)
Project description:Loss-of-function mutations in the parkin gene can cause early onset Parkinson’s disease, a movement disorder resulting from the selective degeneration of dopaminergic neurons in the basal ganglia. Analogously, movement deficits and loss of a subset of dopaminergic neurons are observed in Drosophila melanogaster homozygous for null mutations in parkin. Parkin is an E3 ubiquitin ligase that functions with the mitochondrial localized serine/threonine kinase PINK1 in a pathway required to maintain mitochondrial integrity. We previously established that the PINK1/Parkin pathway functions in Drosophila dopaminergic and cholinergic neurons to maintain mitochondrial membrane potential. However, the mechanisms through which the PINK/Parkin pathway selectively impacts dopaminergic neuron survival remains unclear, as do the mechanisms that lead to the selective vulnerability of dopaminergic neurons in Parkinson’s disease. Because the transcriptome of a cell determines its identity we hypothesized that knowledge of the transcriptional alterations that occur in dopaminergic neurons isolated from parkin null Drosophila would provide insight into the mystery of selective vulnerability in Parkinson's disease. Results: To test our hypothesis we measured the transcriptome of dopaminergic and cholinergic neurons isolated from isogenic heterozygous and homozygous parkin null mutants using a novel flow cytometry-based method we developed. Computational analysis and experimental confirmation demonstrate that our method allows for the successful expression analysis of defined neural subsets from the Drosophila brain. In addition, our dataset implicates iron handling and dopamine signaling as being significantly dysregulated in parkin null dopaminergic neurons. Conclusions: Our flow cytometry-based method allows for the isolation and microarray analysis of neuronal subsets from the adult Drosophila brain. Our microarray analyses implicate iron handling and dopamine metabolism as contributing factors in the etiology of parkin-associated early onset Parkinson’s disease. Here we provide a novel dataset that may serve as a foundation for subsequent functional analyses of the pathways underlying neuronal selective vulnerability in Parkinson's disease.
Project description:Elevated COUP-TFII levels are found in Parkinson’s disease. COUP-TFII overexpression in mouse dopaminergic neurons caused neurodegeneration. The goal of this study is to identify molecular mechanisms of COUP-TFII-mediated cell death through RNAseq.
Project description:Physiological ageing is accompanied by numerous structural and molecular changes in the brain, with varying degrees in different brain areas, and is therefore considered one of the major risk factors for neurodegenerative diseases. As early pathomechanisms of neurodegeneration are often difficult to assess, analysing the ageing brain and its substructures may lead to insights into earliest alterations eventually leading to neurodegeneration. The present study focuses on elucidating age-related changes in the substantia nigra pars compacta, a brain region particularly vulnerable in Parkinson’s disease and its substructures. With a particular emphasis on neuromelanin granules we aimed to gain a spatially resolved view on aging-dependent alterations to draw conclusions on early processes potentially leading to neurodegeneration. Our findings, which included the identification of reduced levels of proteins involved in dopaminergic neurotransmission, suggest either a specific loss of dopaminergic neurons or a reduction in metabolic activity. Furthermore, we observed alterations in the abundances of mitochondrial proteins that are potentially indicative of an age-related shift in their localization within aged tissue donors. Consequently, the present exploratory study suggests that proteomic changes, frequently referred to as potential pathomechanisms of PD, namely dopaminergic dysfunction and aberrations in the mitochondrial population, are already occurring in the physiological aging process of the human SN
Project description:Disruption of local iron homeostasis is a common feature of neurodegenerative diseases. We focused on dopaminergic neurons, asking how iron transport proteins modulate iron homeostasis in vivo. Inactivation of the transmembrane iron exporter ferroportin had no apparent consequences. However, loss of the transferrin receptor 1, involved in iron uptake, caused profound, age-progressive neurodegeneration with features similar to Parkinson’s disease. There was gradual loss of dopaminergic projections in the striatum with subsequent death of dopaminergic neurons in the substantia nigra. After depletion of 30% of the neurons the mice developed neurobehavioral parkinsonism, with evidence of mitochondrial dysfunction and impaired mitochondrial autophagy. Molecular analysis revealed strong signatures indicative of attempted axonal regeneration, a metabolic switch to glycolysis and the unfolded protein response. We speculate that cellular iron deficiency may contribute to neurodegeneration in human patients
Project description:Mitochondrial dysfunction is a hallmark of Parkinson’s disease (PD), but the mechanisms by which it drives autosomal dominant and idiopathic forms of PD remain unclear. To investigate this, we generated and performed a comprehensive phenotypic analysis of a knock-in mouse model carrying the T61I mutation in the mitochondrial protein CHCHD2, which causes late-onset symptoms indistinguishable from idiopathic PD. We observed pronounced mitochondrial disruption in substantia nigra (SN) dopaminergic neurons, including distorted ultrastructure and CHCHD2 aggregation, as well as disrupted mitochondrial protein-protein interactions in brain lysates. These abnormalities were associated with a whole-body metabolic shift towards glycolysis, elevated mitochondrial ROS, and progressive accumulation of aggregated α-synuclein. In idiopathic PD, CHCHD2 gene expression also correlated with α-synuclein levels in vulnerable dopaminergic neurons, and CHCHD2 protein accumulated in early Lewy aggregates. These findings delineate a pathogenic cascade in which CHCHD2 accumulation impairs mitochondrial respiration and increases ROS production, driving α-synuclein aggregation and neurodegeneration.