LIN28A loss-of-function is associated with Parkinson's disease pathogenesis
Ontology highlight
ABSTRACT: Parkinson's disease (PD) is neurodegenerative movement disorder characterized by degeneration of midbrain-type dopamine (mDA) neurons in the substantia nigra (SN). The RNA-binding protein Lin28 plays a role in neuronal stem cell development and neuronal differentiation. In this study we reveal that Lin28 conditional knockout (cKO) mice show degeneration of mDA neurons in the SN, as well as PD-related behavioral deficits. We identify a loss-of-function variant of LIN28A (R192G substitution) in two early-onset PD patients. Using an isogenic human embryonic stem cell (hESC)/human induced pluripotent stem cell (hiPSC)-based disease model, we find that the Lin28 R192G variant leads to developmental defects and PD-related phenotypes in mDA neuronal cells that can be rescued by expression of wildtype Lin28A. Cell transplantation experiments in rats show that correction of the LIN28A variant in the donor patient (pt)-hiPSCs leads to improved behavioral phenotypes. Our data link LIN28A to PD pathogenesis and suggest future personalized medicine targeting this variant in patients.
Project description:Parkinson's disease (PD) is neurodegenerative movement disorder characterized by degeneration of midbrain-type dopamine (mDA) neurons in the substantia nigra (SN). The RNA-binding protein Lin28 plays a role in neuronal stem cell development and neuronal differentiation. In this study, we reveal that Lin28 conditional knockout (cKO) mice show degeneration of mDA neurons in the SN, as well as PD-related behavioral deficits. We identify a loss-of-function variant of LIN28A (R192G substitution) in two early-onset PD patients. Using an isogenic human embryonic stem cell (hESC)/human induced pluripotent stem cell (hiPSC)-based disease model, we find that the Lin28 R192G variant leads to developmental defects and PD-related phenotypes in mDA neuronal cells that can be rescued by expression of wild-type Lin28A. Cell transplantation experiments in PD model rats show that correction of the LIN28A variant in the donor patient (pt)-hiPSCs leads to improved behavioral phenotypes. Our data link LIN28A to PD pathogenesis and suggest future personalized medicine targeting this variant in patients.
Project description:Parkinson's disease (PD) is the second most important age-related neurodegenerative disorder in developed societies, after Alzheimer's disease, with a prevalence ranging from 41 per 100,000 in the fourth decade of life to over 1900 per 100,000 in people over 80 years of age. As a movement disorder, the PD phenotype is characterized by rigidity, resting tremor, and bradykinesia. Parkinson's disease -related neurodegeneration is likely to occur several decades before the onset of the motor symptoms. Potential risk factors include environmental toxins, drugs, pesticides, brain microtrauma, focal cerebrovascular damage, and genomic defects. Parkinson's disease neuropathology is characterized by a selective loss of dopaminergic neurons in the substantia nigra pars compacta, with widespread involvement of other central nervous system (CNS) structures and peripheral tissues. Pathogenic mechanisms associated with genomic, epigenetic and environmental factors lead to conformational changes and deposits of key proteins due to abnormalities in the ubiquitin-proteasome system together with dysregulation of mitochondrial function and oxidative stress. Conventional pharmacological treatments for PD are dopamine precursors (levodopa, l-DOPA, l-3,4 dihidroxifenilalanina), and other symptomatic treatments including dopamine agonists (amantadine, apomorphine, bromocriptine, cabergoline, lisuride, pergolide, pramipexole, ropinirole, rotigotine), monoamine oxidase (MAO) inhibitors (selegiline, rasagiline), and catechol-O-methyltransferase (COMT) inhibitors (entacapone, tolcapone). The chronic administration of antiparkinsonian drugs currently induces the "wearing-off phenomenon", with additional psychomotor and autonomic complications. In order to minimize these clinical complications, novel compounds have been developed. Novel drugs and bioproducts for the treatment of PD should address dopaminergic neuroprotection to reduce premature neurodegeneration in addition to enhancing dopaminergic neurotransmission. Since biochemical changes and therapeutic outcomes are highly dependent upon the genomic profiles of PD patients, personalized treatments should rely on pharmacogenetic procedures to optimize therapeutics.
Project description:Parkinson's disease (PD) is a debilitating neurodegenerative disorder and its rising global incidence highlights the need for the identification of modifiable risk factors. In a gene-based burden test of rare variants (8647 PD cases and 777,693 controls) we discovered a novel association between loss-of-function variants in ITSN1 and PD. This association was further supported with burden data from the Neurodegenerative Disease Knowledge Portal and the Accelerating Medicines Partnership Parkinson's Disease Knowledge Platform. Our findings show that Rho GTPases and disruptions in synaptic vesicle transport may be involved in the pathogenesis of PD, pointing to the possibility of novel therapeutic approaches.
Project description:Mitochondria are vitally important organelles involved in an array of functions. The most notable is their prominent role in energy metabolism, where they generate over 90% of our cellular energy in the form of ATP through oxidative phosphorylation. Mitochondria are involved in various other processes including the regulation of calcium homeostasis and stress response. Mitochondrial complex I impairment and subsequent oxidative stress have been identified as modulators of cell death in experimental models of Parkinson's disease (PD). Identification of specific genes which are involved in the rare familial forms of PD has further augmented the understanding and elevated the role mitochondrial dysfunction is thought to have in disease pathogenesis. This paper provides a review of the role mitochondria may play in idiopathic PD through the study of experimental models and how genetic mutations influence mitochondrial activity. Recent attempts at providing neuroprotection by targeting mitochondria are described and their progress assessed.
Project description:Intensive research over the last 15 years has led to the identification of several autosomal recessive and dominant genes that cause familial Parkinson's disease (PD). Importantly, the functional characterization of these genes has shed considerable insights into the molecular mechanisms underlying the etiology and pathogenesis of PD. Collectively; these studies implicate aberrant protein and mitochondrial homeostasis as key contributors to the development of PD, with oxidative stress likely acting as an important nexus between the two pathogenic events. Interestingly, recent genome-wide association studies (GWAS) have revealed variations in at least two of the identified familial PD genes (i.e. α-synuclein and LRRK2) as significant risk factors for the development of sporadic PD. At the same time, the studies also uncovered variability in novel alleles that is associated with increased risk for the disease. Additionally, in-silico meta-analyses of GWAS data have allowed major steps into the investigation of the roles of gene-gene and gene-environment interactions in sporadic PD. The emergent picture from the progress made thus far is that the etiology of sporadic PD is multi-factorial and presumably involves a complex interplay between a multitude of gene networks and the environment. Nonetheless, the biochemical pathways underlying familial and sporadic forms of PD are likely to be shared.
Project description:A full understanding of Parkinson's Disease etiopathogenesis and of the causes of the preferential vulnerability of nigrostriatal dopaminergic neurons is still an unsolved puzzle. A multiple-hit hypothesis has been proposed, which may explain the convergence of familial, environmental and idiopathic forms of the disease. Among the various determinants of the degeneration of the neurons in Substantia Nigra pars compacta, in this review we will focus on the endotoxicity associated to dopamine dyshomeostasis. In particular, we will discuss the relevance of the reactive dopamine metabolite 3,4-dihydroxyphenylacetaldehyde (DOPAL) in the catechol-induced neurotoxicity. Indeed, the synergy between the catechol and the aldehyde moieties of DOPAL exacerbates its reactivity, resulting in modification of functional protein residues, protein aggregation, oxidative stress and cell death. Interestingly, αSynuclein, whose altered proteostasis is a recurrent element in Parkinson's Disease pathology, is considered a preferential target of DOPAL modification. DOPAL triggers αSynuclein oligomerization leading to synapse physiology impairment. Several factors can be responsible for DOPAL accumulation at the pre-synaptic terminals, i.e. dopamine leakage from synaptic vesicles, increased rate of dopamine conversion to DOPAL by upregulated monoamine oxidase and decreased DOPAL degradation by aldehyde dehydrogenases. Various studies report the decreased expression and activity of aldehyde dehydrogenases in parkinsonian brains, as well as genetic variants associated to increased risk in developing the pathology. Thus, we discuss how the deregulation of these enzymes might be considered a contributing element in the pathogenesis of Parkinson's Disease or a down-stream effect. Finally, we propose that a better understanding of the impaired dopamine metabolism in Parkinson's Disease would allow a more refined patients stratification and the design of more targeted and successful therapeutic strategies.
Project description:Mutations in the PARK2 gene are associated with an autosomal recessive form of juvenile parkinsonism (AR-JP). These mutations affect parkin solubility and impair its E3 ligase activity, leading to a toxic accumulation of proteins within susceptible neurons that results in a slow but progressive neuronal degeneration and cell death. Here, we report that RTP801/REDD1, a pro-apoptotic negative regulator of survival kinases mTOR and Akt, is one of such parkin substrates. We observed that parkin knockdown elevated RTP801 in sympathetic neurons and neuronal PC12 cells, whereas ectopic parkin enhanced RTP801 poly-ubiquitination and proteasomal degradation. In parkin knockout mouse brains and in human fibroblasts from AR-JP patients with parkin mutations, RTP801 levels were elevated. Moreover, in human postmortem PD brains with mutated parkin, nigral neurons were highly positive for RTP801. Further consistent with the idea that RTP801 is a substrate for parkin, the two endogenous proteins interacted in reciprocal co-immunoprecipitates of cell lysates. A potential physiological role for parkin-mediated RTP801 degradation is indicated by observations that parkin protects neuronal cells from death caused by RTP801 overexpression by mediating its degradation, whereas parkin knockdown exacerbates such death. Similarly, parkin knockdown enhanced RTP801 induction in neuronal cells exposed to the Parkinson's disease mimetic 6-hydroxydopamine and increased sensitivity to this toxin. This response to parkin loss of function appeared to be mediated by RTP801 as it was abolished by RTP801 knockdown. Taken together these results indicate that RTP801 is a novel parkin substrate that may contribute to neurodegeneration caused by loss of parkin expression or activity.
Project description:The lack of disease-modifying treatments for Parkinson's disease (PD) is in part due to an incomplete understanding of the disease's etiology. Alpha-synuclein (α-syn) has become a point of focus in PD due to its connection to both familial and idiopathic cases-specifically its localization to Lewy bodies (LBs), a pathological hallmark of PD. Within this review, we will present a comprehensive overview of the data linking synuclein-associated Lewy pathology with intracellular dysfunction. We first present the alterations in neuronal proteins and transcriptome associated with LBs in postmortem human PD tissue. We next compare these findings to those associated with LB-like inclusions initiated by in vitro exposure to α-syn preformed fibrils (PFFs) and highlight the profound and relatively unique reduction of brain-derived neurotrophic factor (BDNF) in this model. Finally, we discuss the multitude of ways in which BDNF offers the potential to exert disease-modifying effects on the basal ganglia. What remains unknown is the potential for BDNF to mitigate inclusion-associated dysfunction within the context of synucleinopathy. Collectively, this review reiterates the merit of using the PFF model as a tool to understand the physiological changes associated with LBs, while highlighting the neuroprotective potential of harnessing endogenous BDNF.
Project description:BackgroundThe diagnosis of Parkinson's disease (PD) is complex and there are no biomarkers for early identification. Many studies have reported altered gut microbiota in patients with PD compared with healthy individuals. However, results from previous studies vary across countries.AimsThe aim of this study was to identify gut microbiota biomarkers that could be used as a marker for the diagnosis of PD.MethodsFirstly, the differential gut microbiota was obtained by meta-analysis, and then the results of meta-analysis were validated through metagenomic cohort. Finally, the ROC curve was drawn based on the metagenomic validation results.ResultsThe meta-analysis showed a lower relative abundance of Prevotellaceae (p < 0.00001) and Lachnospiraceae (p = 0.002), and a higher of Ruminococcaceae (p < 0.00001), Christensenellaceae (p = 0.03), Bifidobacteriaceae (p < 0.00001), and Verrucomicrobiaceae (p = 0.02) in patients with PD. Only Bifidobacteriaceae was also at high levels in the validation cohort of the metagenome. Meanwhile, three species from the Bifidobacteriaceae, including Scardovia_inopinata (p = 0.022), Bifidobacterium_dentium (p = 0.005), and Scardovia_wiggsiae (p = 0.024) were also high. The ROC curve showed that the three species (71.2%) from Bifidobacteriaceae had good predictive efficiency for PD.ConclusionElevated Bifidobacteriaceae may be associated with PD. Elevated three species from the Bifidobacteriaceae, including Scardovia_inopinata, Bifidobacterium_dentium and Scardovia_wiggsiae may provide new potential biomarkers for the diagnosis of PD.
Project description:Dizziness is common in Parkinson's disease (PD) patients. It is known that orthostatic hypotension (OH) is the main cause of such dizziness, but even without OH, quite a few PD patients complain of dizziness in the clinic. It can be regarded as non-specific because most of these patients have no neurological abnormalities. We hypothesized that this type of dizziness would be associated with vestibular function, although included patients did not have clinically confirmed vestibulopathy. We studied 84 patients without OH among 121 PD patients. Their clinical features and function were compared between patients with and without dizziness. Hoehn and Yahr stage (H&Y stage), the Unified Parkinson's Disease Rating Scale (UPDRS) part III, the Korean version of the Mini-Mental State Examination (K-MMSE), education years, disease duration, total levodopa equivalent daily dose (LEDD), the presence of dizziness, the dizziness severity, and orthostatic hypotension were tested. Vestibular evoked myogenic potentials (VEMPs) were used to characterize vestibular function. Ocular (oVEMPs) and cervical (cVEMPs) were recorded. oVEMPs in the right side showed significantly reduced potentials (p = 0.016) in PD patients with dizziness, but cVEMPs did not (all ps > 0.2). Bilateral absent oVEMP responses were more common in PD patients with dizziness (p = 0.022), but the frequencies of bilateral absent cVEMP responses were not different between the dizzy and non-dizzy groups (p = 0.898). Dizziness in PD patients without orthostatic hypotension may be associated with vestibular hypofunction. Our results provide evidence that can aid clinicians when making a treatment plan for patients with dizziness. i.e., strategies to enhance reduced vestibular function may be helpful, but this suggestion remains to be evaluated.