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: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:Engrailed 1 (EN1) is a conserved transcription factor essential for programming, survival, and maintenance of midbrain dopaminergic neurons. En1-hemizygosity (En1+/-) leads to a spontaneous Parkinson’s disease-like (PD-like) progressive nigrostriatal degeneration as well as motor impairment and depressive-like behavior in SwissOF1 (OF1-En1+/-) mice. This phenotype is absent in C57Bl/6j (C57-En1+/-) mice. Here we studied PD-like phenotypes and early transcriptome profiles in OF1 wild-type (WT) and OF1-En1+/- male mice and compare to that of C57 WT and C57-En1+/- male mice. To detect transcriptional changes prior to dopaminergic cell loss, we performed RNA-seq of 1-week old mice substantia nigra pars compacta (SNpc). Histology and stereology were used to assess dopaminergic nigrostriatal pathology in 4 and 16 weeks old mice. OF1-En1+/- mice showed an increase (79%) in dopaminergic striatal axonal swellings from 4 to 16 weeks and a loss (23%) of dopaminergic neurons in the SNpc at 16 weeks compared to OF1 WT. Axonal swellings were also present in C57-En1+/- mice but did not increase over time. 52 differentially expressed genes (DEGs) were observed between the C57-WT and the C57-En1+/- mice, while 198 DEGs were observed in the OF1 strain. Enrichment analysis revealed that the neuroprotective phenotype of C57-En1+/- mice was associated with an upregulation of oxidative phosphorylation-related genes compared to both C57 WT and to OF1- En1+/- mice. These results highlight the importance of considering genetic background in PD models and provide valuable insight on how expression of mitochondrial proteins before the onset of neurodegeneration is associated to vulnerability of nigrostriatal dopaminergic neurons.