ACGH study of iPS cells from two normal subjects and two Parkinson's disease patients with parkin mutations
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ABSTRACT: Parkinson's disease (PD) is defined by the degeneration of nigral dopaminergic (DA) neurons and can be caused by monogenic mutations of genes such as parkin. The lack of phenotype in parkin knockout mice suggests that human nigral DA neurons have unique vulnerabilities. Here we generate induced pluripotent stem cells from normal subjects and PD patients with parkin mutations. We demonstrate that loss of parkin in human midbrain DA neurons greatly increases the transcription of monoamine oxidases and oxidative stress, significantly reduces DA uptake and increases spontaneous DA release. Lentiviral expression of parkin, but not its PD-linked mutant, rescues these phenotypes. The results suggest that parkin controls dopamine utilization in human midbrain DA neurons by enhancing the precision of DA neurotransmission and suppressing dopamine oxidation. Thus, the study provides novel targets and a physiologically relevant screening platform for disease-modifying therapies of PD. Genomic DNA was isolated from each of the four lines of iPSCs and labeled with Cy5. Pooled sex mismatched normal human genomic DNA was labeled with Cy3. Both samples are hybridized together on RPCI 21K BAC aCGH array.
Project description:Parkinson's disease (PD) is defined by the degeneration of nigral dopaminergic (DA) neurons and can be caused by monogenic mutations of genes such as parkin. The lack of phenotype in parkin knockout mice suggests that human nigral DA neurons have unique vulnerabilities. Here we generate induced pluripotent stem cells from normal subjects and PD patients with parkin mutations. We demonstrate that loss of parkin in human midbrain DA neurons greatly increases the transcription of monoamine oxidases and oxidative stress, significantly reduces DA uptake and increases spontaneous DA release. Lentiviral expression of parkin, but not its PD-linked mutant, rescues these phenotypes. The results suggest that parkin controls dopamine utilization in human midbrain DA neurons by enhancing the precision of DA neurotransmission and suppressing dopamine oxidation. Thus, the study provides novel targets and a physiologically relevant screening platform for disease-modifying therapies of PD.
Project description:Human pluripotent stem cells (hPSCs) are a promising source of cells for applications in regenerative medicine. Directed differentiation of hPSCs into specialized cells such as spinal motoneurons or midbrain dopamine (DA) neurons has been achieved. However the effective use of hPSCs for cell therapy has lagged far behind. While mouse PSC-derived DA neurons have shown efficacy in models of Parkinson’s disease, DA neurons derived from human PSCs generally display poor in vivo performance. There are also considerable safety concerns for hPSCs related to their potential for teratoma formation or neural overgrowth. Here we present a novel floor plate-based strategy for the derivation of human DA neurons that efficiently engraft, suggesting that past failures were due to incomplete specification rather than a specific vulnerability of the cells. Midbrain floor plate precursors are derived from hPSCs in days following exposure to small molecule activators of sonic hedgehog (SHH) and canonical WNT signaling. Engraftable midbrain DA neurons are obtained by day 25 and can be maintained in vitro for several months. Extensive in vitro molecular profiling, biochemical and electrophysiological data define developmental progression and confirm identity of hPSC-derived midbrain DA neurons. In vivo survival and function is demonstrated in PD animal models in three host species. Long-term engraftment in 6-OHDA-lesioned mouse and rats demonstrates robust survival of midbrain DA neurons, complete restoration of amphetamine-induced rotation behavior and improvements in tests of forelimb use and akinesia. Finally, scalability is demonstrated by transplantation into Parkinsonian monkeys. Excellent DA neuron survival, function and lack of neural overgrowth in the three animal models tested indicate considerable promise for the development of cell based therapies in PD. Differentiated hESC with three conditions (LSB, LSB/S/F8, LSB/S/F8/CHIR) were subjected to RNA extraction in specific timepoint (day 0, 1, 3, 5, 7, 11, 13, 25) and hybridization on Illumina microarrays. Each sample has 3 or 4 biological repeats. Based on previous study* of dual SMAD inhibition neural induction, we developed new midbrain dopamine neuron protocol. It depends on time specific treatment of below factors (LSB/S/F8/CHIR): L (LDN193189 (BMP inhibitor) , day 0-11), SB (SB431542 (TGF-b signal inhibitor), day 0-5), S (SHH + Purmorphamine (Smo agonist), day 1-7), F8 (FGF8, day 1-7) and CHIR (CHIR99021 (GSK3b inhibitor), day 3-13) LSB and LSB/S/F8 are limited control conditions of dual SMAD only (LSB) or traditional patterning with Sonic and FGF (LSB/S/F8) *Chambers,S.M. et al. Highly efficient neural conversion of human ES and iPS cells by dual inhibition of SMAD signaling. Nat. Biotechnol. 27, 275-280 (2009).
Project description:Analysis of human dopamine (DA) from postmortem brains of 8 patients with Parkinson’s disease (PD). Results provide insight into the molecular processes perturbed in the PD substantia nigra. Human dopamine (DA) neurons from 8 PD and 9 control subjects were obtained. Double-stranded complementary DNA was made with a biotinylated T7(dT)-24 primer. Biotinylated complementary RNA was fragmented and hybridized to Affymetrix human genome U133_X3P microarrays. The Affymetrix .CEL files were normalized to “all probe sets” in a standardized matter, and scaled to 100 by the MAS5 algorithm implemented in the Bioconductor package.
Project description:Loss-of-function variants in the PRKN gene encoding the ubiquitin E3 ligase PARKIN cause autosomal recessive early-onset Parkinson’s disease (PD). Extensive in vitro and in vivo studies have reported that PARKIN is involved in multiple pathways of mitochondrial quality control, including mitochondrial degradation and biogenesis. However, these findings are surrounded by substantial controversy due to conflicting experimental data. In addition, the existing PARKIN-deficient mouse models have failed to faithfully recapitulate PD phenotypes. Therefore, we have investigated the mitochondrial role of PARKIN during ageing and in response to stress by employing a series of conditional Parkin knockout mice. We report that PARKIN loss does not affect oxidative phosphorylation (OXPHOS) capacity and mitochondrial DNA (mtDNA) levels in the brain, heart, and skeletal muscle of aged mice. We also demonstrate that PARKIN deficiency does not exacerbate the brain defects and the pro-inflammatory phenotype observed in mice carrying high levels of mtDNA mutations. To rule out compensatory mechanisms activated during embryonic development of Parkin-deficient mice, we generated a mouse model where loss of PARKIN was induced in adult dopaminergic (DA) neurons. Surprisingly, also these mice did not show motor impairment or neurodegeneration, and no major transcriptional changes were found in isolated midbrain DA neurons. Finally, we report a patient with compound heterozygous PRKN pathogenic variants that lacks PARKIN and has developed PD. The PARKIN deficiency did not impair OXPHOS activities or induce mitochondrial pathology in skeletal muscle from the patient. Altogether, our results argue that PARKIN is dispensable for OXPHOS function in adult mammalian tissues.
Project description:Aging reduces locomotor capacity. Although a decrease in the activity of the nigrostriatal dopamine (DA) system is one of key mechanisms linked to the drop-in locomotor activity in aging, the specific molecule responsible for controlling this decline remains elusive. Here we report that sirtuin 3 (SIRT3), a mitochondrial deacetylase associated with an anti-aging effect, is downregulated in nigral DA neurons of 20-month-old mice, showing the decline in locomotor activity, and that the declined locomotor activity by aging was deteriorated with more serious alteration in the levels of mitochondria-related proteins in mice with genetic deletion of SIRT3 compared to age-matched control mice. Moreover, SIRT3 upregulation through the administration of adeno-associated virus serotype 1 (AAV1) encoding the SIRT3 gene in the substantia nigra (SN) mitigated the age-dependent loss of locomotor activity by the preservation of the nigrostriatal DA system from aging in vivo. Therefore, we conclude that SIRT3 preservation in the nigrostriatal DA system has resistance to age-related locomotor decline, suggesting that SIRT3 upregulation in nigral DA neurons can be useful to preserve locomotor capacity in aging.
Project description:Dopaminergic (DA) neurons are the predominant cell type in the midbrain that synthesize dopamine, a neurotransmitter implicated in various behavioural processes, including motor function, the reward pathway, and satiety. In diseases affecting these neurons, such as in Parkinson’s disease (PD), there is growing evidence that the gut-brain axis and selective vulnerability of DA neurons plays a crucial role in disease. Most investigations relating to DA neurons in the gut rely on immunoreactivity to tyrosine hydroxylase (TH) - a rate-limiting enzyme in the production of dopamine. However, the reliability of TH staining as a marker of DA neurons has been questioned in recent years. Our aim is to perform a comprehensive characterization of DA neurons in the gut using a well-accepted reporter mouse line, expressing a fluorescent protein under the dopamine transporter promoter (DAT). Our findings confirm a unique localization of DA neurons in the gut, and unveil that there are discrete subtypes of DA neurons in the gut, which we characterized using both immunofluorescence and single-cell transcriptomics. We observed distinct subtypes of DAT neurons expressing co-transmitters and modulators across both plexuses; some of them likely co-releasing acetylcholine, and a smaller population likely releasing nitric oxide; while others were positive for a slew of canonical DA markers (Vmat2, Girk2, Foxa2). Given the clear heterogeneity of DA gut neurons, further investigation is warranted to define their functional signatures and discover their inherent biological differences that predispose these cells to neurodegeneration.
Project description:Parkinson’s disease (PD) is characterized by the death of substantia nigra (SNc) dopamine (DA) neurons, but the pathophysiological mechanisms that precede and drive their death remain unknown. The activity of DA neurons is likely altered in PD, but we understand little about if or how chronic changes in activity may contribute to degeneration. To address this question, we developed a chemogenetic (DREADD) mouse model to chronically increase DA neuron activity, and confirmed this increase using ex vivo electrophysiology. Chronic hyperactivation of DA neurons resulted in prolonged increases in locomotor activity during the light cycle and decreases during the dark cycle, consistent with chronic changes in DA release and circadian disturbances. We also observed early, preferential degeneration of SNc projections, recapitulating the PD hallmarks of selective vulnerability of SNc axons and the comparative resilience of ventral tegmental area axons. This was followed by eventual loss of midbrain DA neurons. Continuous DREADD activation resulted in a sustained increase in baseline calcium levels, supporting a role for increased calcium in the neurodegeneration process. Finally, spatial transcriptomics from DREADD mice examining midbrain DA neurons and striatal targets, and cross-validation with human patient samples, provided insights into potential mechanisms of hyperactivity-induced toxicity and PD. Our results thus reveal the preferential vulnerability of SNc DA neurons to increased neural activity, and support a potential role for increased neural activity in driving degeneration in PD.
Project description:Parkinson’s disease (PD) is a prevalent neurodegenerative disorder that is characterized by the selective loss of midbrain dopamine (DA)-producing neurons and the formation of α-synuclein (α-syn)-containing inclusions named Lewy bodies (LBs). Here, we report that the loss of glucocerebrosidase (GCase), coupled with α-syn overexpression, result in substantial accumulation of detergent-resistant α-syn aggregates and Lewy body-like inclusions (LBLIs) in human midbrain-like organoids (hMLOs). These LBLIs exhibit a highly similar structure to PD-associated LBs, by displaying a spherically symmetric morphology with an eosinophilic core, and containing α-syn and ubiquitin. Importantly, hMLOs generated from PD patient-derived inducible pluripotent stem cells (iPSCs) harboring SNCA triplication also exhibit subsequent degeneration of DA neurons and LBLI formation upon chronic GCase inhibitor treatment. Taken together, our hMLOs harbouring two major PD risk factors (GCase deficiency and overproduced α-syn) successfully recapitulate major pathophysiological signatures of the disease, and highlight the broad utility of brain organoid technology in modeling human neurodegenerative diseases.
Project description:PURPOSE: The transcriptional repressor PARIS (ZNF746) was initially identified as a pathogenic co-substrate of PINK1 and parkin that leads to Parkinson’s disease (PD) by disrupting mitochondrial biogenesis through PPARγ coactivator -1α (PGC-1α) suppression. Later, accumulation of PARIS in dopamine (DA) neurons that cause neurotoxicity has been studied widely and growing evidence has linked defective mitochondrial biogenesis to PD pathogenesis. Yet, the mechanistic underpinnings of this link remain elusive. METHODS: We employed translating ribosome affinity purification (TRAP) followed by RNA sequencing (TRAP-seq) for transcriptome profiling of DA neurons in transgenic Drosophila lines we generated expressing human PARIS or human PARIS mutant (C571A). Together with TRAP control and whole brain samples, this data set is composed of a total of 10 (3, 3, 3, and 1 respectively) replicate samples representing 4 different treatment groups for a set of gene-level (a parametric F-test) and transcript-level (a Wald test or a likelihood ratio test) differential expression analysis. RESULTS: Firstly, we identified differentially expressed genes by human PARIS in fly DA neurons successfully. Then, we showed that PPARγ acts as a master regulator of transcriptomic changes induced by PARIS in the clusters of Drosophila dopaminergic neurons. Also, we validated this finding in human neuroblastoma cell line. CONCLUSION: PPARγ plays a crucial regulatory role in PARIS phenotype. Drosophila models of PARIS-induced neurodegeneration used in this work to represent PD phenotype and our TRAP-seq protocol serve as a paradigm for future studies to unravel mechanistic underpinnings of PARIS biology.
Project description:Oxidative stress is a major pathogenic mechanism in Parkinson’s disease (PD). As an important cellular antioxidant, glutathione (GSH) balances the production and incorporation of free radicals to protect neurons from oxidative damage. Unfortunately, the GSH level is greatly decreased in the brains of PD patients. Hence, clarifying the molecular mechanism of GSH deficiency may help deepen our knowledge of PD pathogenesis. Here we report that the astrocytic dopamine D2 receptor (DRD2) regulates GSH synthesis via PKM2-mediated Nrf2 transactivation. Besides, we find that pyridoxine can dimerize PKM2 to promote GSH biosynthesis. Further experiments show that pyridoxine supplementation increases the resistance of nigral dopaminergic neurons to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced neurotoxicity in wild-type mice as well as in astrocytic Drd2 conditional knockout mice. Given that dopamine agonist treatment in PD is limited by their intolerable side effects and diminished effectiveness over time, we anticipate dimerizing PKM2 to be a new strategy for PD treatment.