THIS ARTICLE HAS BEEN RETRACTED: Pathological biochemistry of α‐synucleinopathy

Lewy bodies (LBs) are hallmark lesions in the brains of patients with Parkinson's disease (PD) and dementia with Lewy bodies (DLB). We raised a monoclonal antibody LB509 against purified LBs from the brains of patients with DLB that strongly immuolabled LBs, and found that α‐synuclein is one of the major components of LBs. Thus, the deposition of α‐synuclein, an abundant presynaptic brain protein, as fibrillary aggregates in affected neurons or glial cells, was highlighted as a hallmark lesion of a subset of neurodegenerative disorders, including PD, DLB and multiple system atrophy collectively referred to as synucleinopathies. Importantly, the identification of missense mutations in and multiplication of α‐synuclein gene in some pedigrees of familial PD has strongly implicated α‐synuclein in the pathogenesis of PD and other synucleinopathies. We then examined the specific post‐translational modifications that characterize and underlie the aggregation of α‐synuclein in synucleinopathy brains by mass spectrometry and using a specific antibody, and found that serine 129 of α‐synuclein deposited in synucleinopathy lesions is selectively and extensively phosphorylated. Furthermore we generated transgenic C. elegans overexpressing α‐synuclein in neurons, and found that overexpression of familial PD‐linked mutant form of α‐synuclein impairs functions of dopamine neurons. These findings collectively underscore the importance of deposition of α‐synuclein as well as its phosphorylation in the pathogenesis of α‐synucleinopathies.     

Engineering synucleinopathy‐resistant human dopaminergic neurons by CRISPR‐mediated deletion of the SNCA gene

An emerging treatment for Parkinson's disease (PD) is cell replacement therapy. Authentic midbrain dopaminergic (mDA) neuronal precursors can be differentiated from human embryonic stem cells (hESCs) and human induced pluripotent stem cells (iPSCs). These laboratory‐generated mDA cells have been demonstrated to mature into functional dopaminergic neurons upon transplantation into preclinical models of PD. However, clinical trials with human fetal mesenchephalic cells have shown that cell replacement grafts in PD are susceptible to Lewy body formation suggesting host‐to‐graft transfer of α‐synuclein pathology. Here, we have used CRISPR/Cas9n technology to delete the endogenous SNCA gene, encoding for α‐synuclein, in a clinical‐grade hESC line to generate SNCA^+/? and SNCA^?/? cell lines. These hESC lines were first differentiated into mDA neurons, and then challenged with recombinant α‐synuclein preformed fibrils (PFFs) to seed the formation for Lewy‐like pathology as measured by phosphorylation of serine‐129 of α‐synuclein (pS129‐αSyn). Wild‐type neurons were fully susceptible to the formation of protein aggregates positive for pS129‐αSyn, while SNCA^+/? and SNCA^?/? neurons exhibited significant resistance to the formation of this pathological mark. This work demonstrates that reducing or completely removing SNCA alleles by CRISPR/Cas9n‐mediated gene editing confers a measure of resistance to Lewy pathology.     

5‐S‐cysteinyldopamine neurotoxicity: Influence on the expression of α‐synuclein and ERp57 in cellular and animal models of Parkinson's disease

Parkinson's disease (PD) is a progressive neurodegenerative disorder whose etiology is still unclear in spite of extensive investigations. It has been hypothesized that 5‐S‐cysteinyldopamine (CysDA), a catechol‐thioether metabolite of dopamine (DA), could be an endogenous parkinsonian neurotoxin. To gain further insight into its role in the neurodegenerative process, both CD1 mice and SH‐SY5Y neuroblastoma cells were treated with CysDA, and the data were compared with those obtained by the use of 6‐hydroxydopamine, a well‐known parkinsonian mimetic. Intrastriatal injection of CysDA in CD1 mice caused a long‐lasting depletion of DA, providing evidence of in vivo neurotoxicity of CysDA. Both in mice and in SH‐SY5Y cells, CysDA treatment induced extensive oxidative stress, as evidenced by protein carbonylation and glutathione depletion, and affected the expression of two proteins, α‐synuclein (α‐Syn) and ERp57, whose levels are modulated by oxidative insult. Real‐time PCR experiments support these findings, indicating an upregulation of both ERp57 and α‐Syn expression. α‐Syn aggregation was also found to be modulated by CysDA treatment. The present work provides a solid background sustaining the hypothesis that CysDA is involved in parkinsonian neurodegeneration by inducing extensive oxidative stress and protein aggregation. © 2013 Wiley Periodicals, Inc.     

Alpha‐synuclein overexpression in mice alters synaptic communication in the corticostriatal pathway

α‐Synuclein (α‐Syn) is a presynaptic protein implicated in Parkinson's disease (PD). Mice overexpressing human wildtype (WT) α‐Syn under the Thy1 promoter show high levels of α‐Syn in cortical and subcortical regions, exhibit progressive sensorimotor anomalies, as well as non‐motor abnormalities and are considered models of pre‐manifest PD as there is little evidence of early loss of dopaminergic (DA) neurons. We used whole‐cell patch clamp recordings from visually identified striatal medium‐sized spiny neurons (MSSNs) in slices from α‐Syn and WT littermate control mice at 35, 90 and 300 days of age to examine corticostriatal synaptic function. MSSNs displayed significant decreases in the frequency of spontaneous excitatory postsynaptic currents (EPSCs) in α‐Syn mice at all ages. This difference persisted in the presence of tetrodotoxin, indicating it was independent of action potentials. Stimulation thresholds for evoking EPSCs were significantly higher and responses were smaller in α‐Syn mice. These data suggest a decrease in neurotransmitter release at the corticostriatal synapse. At 90 days the frequency of spontaneous GABA_A receptor‐mediated synaptic currents was decreased in MSSNs but increased in cortical pyramidal neurons. These observations indicate that high levels of expression of α‐Syn alter corticostriatal synaptic function early and they provide evidence for early synaptic dysfunction in a pre‐manifest model of PD. Of importance, these changes are opposite to those found in DA‐depletion models, suggesting that before degeneration of DA neurons in the substantia nigra synaptic adaptations occur at the corticostriatal synapse that may initiate subtle preclinical manifestations. © 2009 Wiley‐Liss, Inc.     

Mice expressing the A53T mutant form of human alpha‐synuclein exhibit hyperactivity and reduced anxiety‐like behavior

Genetic mutations associated with α‐synuclein (α‐Syn) are implicated in the pathogenesis of Parkinson's disease (PD). PD is primarily a movement disorder, but patients are known to experience anxiety and other mood disorders. In this study, we examined the effect of the hA53T mutation during development by analyzing the protein expression of norepinephrine (NET), serotonin (SERT), and dopamine (DAT) transporters in addition to assessing locomotor and anxiety‐like behavior. We observed significant decreases in DAT expression at 8 months in transgenic animals compared with normal and younger mice. We used the elevated plus maze, open‐field test, and rotarod apparatus to evaluate wild‐type and hA53T hemizygous mice at 2, 8, and 12 months of age. Our results showed that 12‐month‐old transgenic mice spend more time in the open arms and display a greater number of open entries of the elevated plus maze compared with wild‐type controls and younger mice. Open‐field test results showed that 12‐month‐old mice travel a greater distance overall and travel more in the inner zone than either wild‐type or younger mice. Rotarod testing showed that 8‐ and 12‐month‐old transgenic mice perform better than either wild‐type controls or younger mice. Overall, 8–12‐month‐old transgenic mice showed a trend toward reduced anxiety‐like behavior and increased hyperactivity. These results indicate a possible role of the A53T α‐Syn mutation in anxiety‐like and hyperactive behaviors in a PD mouse model, suggesting that these behaviors might be comorbid with this disease. © 2010 Wiley‐Liss, Inc.     

Lysosomal‐associated membrane protein 2 isoforms are differentially affected in early Parkinson's disease

Lysosomes are the primary catabolic compartment for the degradation of intracellular proteins through autophagy. The presence of abnormal intracellular α‐synuclein‐positive aggregates in Parkinson's disease (PD) indicates that the degradative capacity of lysosomes is impaired in PD. Specific dysfunction of chaperone‐mediated autophagy (CMA) in PD is suggested by reductions in the CMA membrane receptor, lysosomal‐associated membrane protein (LAMP) 2A, although whether LAMP2A is the only LAMP2 isoform affected by PD is unknown. Messenger RNA (mRNA) and protein expression of all three LAMP2 isoforms was assessed in brain extracts from regions with and without PD‐related increases in α‐synuclein in autopsy samples from subjects in the early pathological stage of PD (n = 9), compared to age‐ and postmortem delay‐matched controls (n = 10). In the early stages of PD, mRNA expression of all LAMP2 isoforms was not different from controls, with LAMP2B and LAMP2C protein levels also unchanged in PD. The selective loss of LAMP2A protein directly correlated with the increased levels of α‐synuclein and decreased levels of the CMA chaperone heat shock cognate protein 70 in the same PD samples, as well as with the accumulation of cytosolic CMA substrate proteins. Our data show that LAMP2 protein isoforms are differentially affected in the early stages of PD, with LAMP2A selectively reduced in association with increased α‐synuclein, and suggests that dysregulation of CMA‐mediated protein degradation occurs before substantial α‐synuclein aggregation in PD. © 2015 International Parkinson and Movement Disorder Society.     

Immunization with α‐synuclein/Grp94 reshapes peripheral immunity and suppresses microgliosis in a chronic Parkinsonism model

Neuroinflammation mediated by chronically activated microglia, largely caused by abnormal accumulation of misfolded α‐synuclein (αSyn) protein, is known to contribute to the pathophysiology of Parkinson's disease (PD). In this work, based on the immunomodulatory activities displayed by particular heat‐shock proteins (HSPs), we tested a novel vaccination strategy that used a combination of αSyn and Grp94 (HSPC4 or Gp96) chaperone and a murine PD model. We used two different procedures, first, the adoptive transfer of splenocytes from αSyn/Grp94‐immunized mice to recipient animals, and second, direct immunization with αSyn/Grp94, to study the effects in a chronic mouse MPTP‐model of parkinsonism. We found that both approaches promoted a distinct profile in the peripheral system—supported by humoral and cellular immunity—consisting of a Th1‐shifted αSyn‐specific response accompanied by an immune‐regulatory/Th2‐skewed general phenotype. Remarkably, this mixed profile sustained by αSyn/Grp94 immunization led to strong suppression of microglial activation in the substantia nigra and striatum, pointing to a newly described positive effect of anti‐αSyn Th1‐responses in the context of PD. This strategy is the first to target αSyn and report the suppression of PD‐associated microgliosis. Overall, we show that the αSyn/Grp94 combination supports a distinct and long‐lasting immune profile in the peripheral system, which has an impact at the CNS level by suppressing chronic microglial activation in an MPTP model of PD. Furthermore, our study demonstrates that reshaping peripheral immunity by vaccination with appropriate misfolding protein/HSP combinations could be highly beneficial as a treatment for neurodegenerative misfolding diseases.     

The usual suspects,dopamine and alpha‐synuclein,conspire to cause neurodegeneration

Parkinson's disease (PD) is primarily a movement disorder driven by the loss of dopamine‐producing neurons in the substantia nigra (SN). Early identification of the oxidative properties of dopamine implicated it as a potential source of oxidative stress in PD, yet few studies have investigated dopamine neurotoxicity in vivo. The discovery of PD‐causing mutations in α‐synuclein and the presence of aggregated α‐synuclein in the hallmark Lewy body pathology of PD revealed another important player. Despite extensive efforts, the precise role of α‐synuclein aggregation in neurodegeneration remains unclear. We recently manipulated both dopamine levels and α‐synuclein expression in aged mice and found that only the combination of these 2 factors caused progressive neurodegeneration of the SN and an associated motor deficit. Dopamine modified α‐synuclein aggregation in the SN, resulting in greater abundance of α‐synuclein oligomers and unique dopamine‐induced oligomeric conformations. Furthermore, disruption of the dopamine‐α‐synuclein interaction rescued dopaminergic neurons from degeneration in transgenic Caenorhabditis elegans models. In this Perspective, we discuss these findings in the context of known α‐synuclein and dopamine biology, review the evidence for α‐synuclein oligomer toxicity and potential mechanisms, and discuss therapeutic implications. © 2019 International Parkinson and Movement Disorder Society     

Plasma α‐synuclein in patients with Parkinson's disease with and without treatment

Alpha‐synuclein (α‐syn) is an intracellular protein with a high tendency to aggregation. It is the major component of Lewy bodies and may play a key role in the pathogenesis of Parkinson's disease (PD). α‐Syn is also released by neurons and can be detected in biological fluids, such as plasma. The purpose of this study was to determine whether plasma α‐syn concentrations are elevated in newly diagnosed PD patients before treatment (nontreated PD group, ntPD; n = 53) and to compare them with concentrations in PD patients with at least 1 year of specific treatment (tPD; n = 42) and in healthy controls (n = 60). Plasma α‐syn concentrations in the ntPD and tPD groups were similar and significantly higher than in healthy controls. In conclusion, α‐syn was elevated early in the development of PD and specific PD treatment did not change plasma α‐syn levels. © 2010 Movement Disorder Society     

Hyperphosphorylated Tau in an α-synuclein-overexpressing transgenic model of Parkinson's disease

Although clinically distinct diseases, tauopathies and synucleinopathies share a common genesis and mechanisms, leading to overlapping degenerative changes within neurons. In human postmortem striatum of Parkinson’s disease (PD) and PD with dementia, we have recently described elevated levels of tauopathy, indexed as increased hyperphosphorylated Tau (p‐Tau). Here we assessed tauopathy in striatum of a transgenic animal model of PD, overexpressing human α‐synuclein under the platelet‐derived growth factor promoter. At 11 months of age, large and progressive increases in p‐Tau in transgenic mice, hyperphosphorylated at sites reminiscent of Alzheimer’s disease, were noted, along with elevated levels of α‐synuclein and glycogen synthase kinase 3β phosphorylated at Tyr216 (p‐GSK‐3β), a major kinase involved in the hyperphosphorylation of Tau. Differential Triton X‐100 extraction of striata showed the presence of aggregated α‐synuclein in the transgenic mice, along with p‐Tau and p‐GSK‐3β, which was also confirmed through immunohistochemistry. After p‐Tau formation, both Tau and microtubule‐associated protein 1 (MAP1) dissociated from the cytoskeleton, consistent with the diminished ability of these cytoskeleton‐binding proteins to bind microtubules. Increases in free tubulin and actin were also noted, indicative of cytoskeleton remodeling and destabilization. In vivo magnetic resonance imaging of the transgenic animals showed a reduction in brain volume of transgenic mice, indicating substantial atrophy. From immunohistochemical studies, α‐synuclein, p‐Tau and p‐GSK‐3β were found to be overexpressed and co‐localized in large inclusion bodies, reminiscent of Lewy bodies. The elevated state of tauopathy seen in these platelet‐derived growth factor–α‐synuclein mice provides further confirmation that PD may be a tauopathic disease.     

Brain region‐dependent differential expression of alpha‐synuclein

α‐Synuclein, the major constituent of Lewy bodies (LBs), is normally expressed in presynapses and is involved in synaptic function. Abnormal intracellular aggregation of α‐synuclein is observed as LBs and Lewy neurites in neurodegenerative disorders, such as Parkinson's disease (PD) or dementia with Lewy bodies. Accumulated evidence suggests that abundant intracellular expression of α‐synuclein is one of the risk factors for pathological aggregation. Recently, we reported differential expression patterns of α‐synuclein between excitatory and inhibitory hippocampal neurons. Here we further investigated the precise expression profile in the adult mouse brain with special reference to vulnerable regions along the progression of idiopathic PD. The results show that α‐synuclein was highly expressed in the neuronal cell bodies of some early PD‐affected brain regions, such as the olfactory bulb, dorsal motor nucleus of the vagus, and substantia nigra pars compacta. Synaptic expression of α‐synuclein was mostly accompanied by expression of vesicular glutamate transporter‐1, an excitatory presynaptic marker. In contrast, expression of α‐synuclein in the GABAergic inhibitory synapses was different among brain regions. α‐Synuclein was clearly expressed in inhibitory synapses in the external plexiform layer of the olfactory bulb, globus pallidus, and substantia nigra pars reticulata, but not in the cerebral cortex, subthalamic nucleus, or thalamus. These results suggest that some neurons in early PD‐affected human brain regions express high levels of perikaryal α‐synuclein, as happens in the mouse brain. Additionally, synaptic profiles expressing α‐synuclein are different in various brain regions. J. Comp. Neurol. 524:1236–1258, 2016. © 2015 Wiley Periodicals, Inc.     

New Developments in Genetic rat models of Parkinson's Disease

Preclinical research on Parkinson's disease has relied heavily on mouse and rat animal models. Initially, PD animal models were generated primarily by chemical neurotoxins that induce acute loss of dopaminergic neurons in the substantia nigra. On the discovery of genetic mutations causally linked to PD, mice were used more than rats to generate laboratory animals bearing PD‐linked mutations because mutagenesis was more difficult in rats. Recent advances in technology for mammalian genome engineering and optimization of viral expression vectors have increased the use of genetic rat models of PD. Emerging research tools include “knockout” rats with disruption of genes in which mutations have been causally linked to PD, including LRRK2, α‐synuclein, Parkin, PINK1, and DJ‐1. Rats have also been increasingly used for transgenic and viral‐mediated overexpression of genes relevant to PD, particularly α‐synuclein. It may not be realistic to obtain a single animal model that completely reproduces every feature of a human disease as complex as PD. Nevertheless, compared with mice with the same mutations, many genetic rat animal models of PD better reproduce key aspects of PD including progressive loss of dopaminergic neurons in the substantia nigra, locomotor behavior deficits, and age‐dependent formation of abnormal α‐synuclein protein aggregates. Here we briefly review new developments in genetic rat models of PD that may have greater potential for identifying underlying mechanisms, for discovering novel therapeutic targets, and for developing greatly needed treatments to slow or halt disease progression. © 2018 International Parkinson and Movement Disorder Society     

α‐Synuclein staging in the amygdala of a Parkinson's disease model: cell types involved

Lewy bodies (ubiquitin and α‐synuclein aggregates) can be detected in brain areas in a predictable sequence of six neuropathological stages in Parkinson's disease. Brainstem and olfactory structures are involved in stage 1, whereas the substantia nigra and amygdala are involved in stage 3, prior to cortical spreading. Amygdaloid pathology has been suggested to contribute to non‐motor symptoms such as olfactory dysfunction and emotional impairment. This work analysed the distribution of α‐synuclein at 16, 30, 43 and 56 weeks in the basolateral, central and cortical amygdaloid complexes of A53T transgenic mice. The expression of calbindin, calretinin and somatostatin was compared in control and transgenic animals. Co‐localisation of these markers with α‐synuclein was performed. Triple labeling of calbindin, somatostatin and α‐synuclein was also investigated. Quantification was carried out using an optical dissector, ImageJ software and confocal microscopy. α‐Synuclein‐positive cells were mainly concentrated in the basolateral and cortical amygdaloid complexes with a non‐significant increase over time from 16 to 30–43 weeks and a significant decrease thereafter. The expression of interneuron markers showed a significant decrease with aging in control animals. When comparing these markers between control and transgenic mice, calretinin was moderately decreased, but calbindin and somatostatin were highly reduced, particularly in the cortical amygdaloid complex. α‐Synuclein mostly co‐localised with calbindin and a number of these cells also co‐expressed somatostatin. These data on α‐synucleinopathy staging in the amygdala could help to explain non‐motor symptoms as well as to understand the progression of Parkinson's disease in the brain.     

GFP-tagged mutant prion protein forms intra-axonal aggregates in transgenic mice

A nine-octapeptide insertional mutation in the prion protein (PrP) causes a fatal neurodegenerative disorder in both humans and transgenic mice. To determine the precise cellular localization of this mutant PrP (designated PG14), we have generated transgenic mice expressing PG14-EGFP, a fluorescent fusion protein that can be directly visualized in vivo. Tg(PG14-EGFP) mice develop an ataxic neurological illness characterized by astrogliosis, PrP aggregation, and accumulation of a partially protease-resistant form of the mutant PrP. Strikingly, PG14-EGFP forms numerous fluorescent aggregates in the neuropil and white matter of multiple brain regions. These aggregates are particularly prominent along axonal tracts in both brain and peripheral nerve, and similar intracellular deposits are visible along the processes of cultured neurons. Our results reveal intra-axonal aggregates of a mutant PrP, which could contribute to the pathogenesis of familial prion disease by disrupting axonal transport.     

Bladder dysfunction in a transgenic mouse model of multiple system atrophy

Multiple system atrophy (MSA) is an adult‐onset neurodegenerative disorder presenting with motor impairment and autonomic dysfunction. Urological function is altered in the majority of MSA patients, and urological symptoms often precede the motor syndrome. To date, bladder function and structure have never been investigated in MSA models. We aimed to test bladder function in a transgenic MSA mouse featuring oligodendroglial α‐synucleinopathy and define its applicability as a preclinical model to study urological failure in MSA. Experiments were performed in proteolipid protein (PLP)–human α‐synuclein (hαSyn) transgenic and control wild‐type mice. Diuresis, urodynamics, and detrusor strip contractility were assessed to characterize the urological phenotype. Bladder morphology and neuropathology of the lumbosacral intermediolateral column and the pontine micturition center (PMC) were analyzed in young and aged mice. Urodynamic analysis revealed a less efficient and unstable bladder in MSA mice with increased voiding contraction amplitude, higher frequency of nonvoiding contractions, and increased postvoid residual volume. MSA mice bladder walls showed early detrusor hypertrophy and age‐related urothelium hypertrophy. Transgenic hαSyn expression was detected in Schwann cells ensheathing the local nerve fibers in the lamina propria and muscularis of MSA bladders. Early loss of parasympathetic outflow neurons and delayed degeneration of the PMC accompanied the urological deficits in MSA mice. PLP‐hαSyn mice recapitulate major urological symptoms of human MSA that may be linked to αSyn‐related central and peripheral neuropathology and can be further used as a preclinical model to decipher pathomechanisms of MSA. © 2013 Movement Disorder Society     

Neuropathology of multiple system atrophy: New thoughts about pathogenesis

Multiple system atrophy (MSA) is a fatal adult‐onset neurodegenerative disorder of uncertain etiology, clinically manifesting with autonomic failure associated with parkinsonism, cerebellar dysfunction, and pyramidal signs in variable combination. The pathological process affects central autonomic, striatonigral, and olivopontocerebellar systems. These show varying degrees of neurodegeneration and underlie the stratification of the heterogenous disorder into MSA‐P and MSA‐C clinical variants, which correlate to the morphologic phenotypes of striatonigral degeneration and olivopontocerebellar atrophy (MSA‐C). The lesions are not limited to these most consistently and severely affected systems but may involve many other parts of the central, peripheral, and autonomic nervous systems, underpinning the multisystem character of MSA. The histological core feature are glial cytoplasmic inclusions (GCIs, Papp‐Lantos bodies) in all types of oligodendroglia that contain aggregates of misfolded α‐Synuclein (α‐Syn). In addition to the ectopic appearance of α‐Syn in oligodendrocytes and other cells, oxidative stress, proteasomal and mitochondrial dysfunction, excitotoxiciy, neuroinflammation, metabolic changes, and energy failure are important contributors to the pathogenesis of MSA, as shown by various neurotoxic and transgenic animal models. Although the basic mechanisms of α‐Syn–triggered neurodegeneration are not completely understood, neuron‐to‐oligodendrocyte transfer of α‐Syn by prion‐like spreading, inducing oligodendroglial and myelin dysfunction associated with chronic neuroinflammation, are suggested finally to lead to a system‐specific pattern of neurodegeneration. © 2014 International Parkinson and Movement Disorder Society     

Deficiency of ganglioside GM1 correlates with Parkinson's disease in mice and humans

Several studies have successfully employed GM1 ganglioside to treat animal models of Parkinson's disease (PD), suggesting involvement of this ganglioside in PD etiology. We recently demonstrated that genetically engineered mice (B4galnt1^?/?) devoid of GM1 acquire characteristic symptoms of this disorder, including motor impairment, depletion of striatal dopamine, selective loss of tyrosine hydroxylase‐expressing neurons, and aggregation of α‐synuclein. The present study demonstrates similar symptoms in heterozygous mice (HTs) that express only partial GM1 deficiency. Symptoms were alleviated by administration of L‐dopa or LIGA‐20, a membrane‐permeable analog of GM1 that penetrates the blood–brain barrier and accesses intracellular compartments. Immunohistochemical analysis of paraffin sections from PD patients revealed significant GM1 deficiency in nigral dopaminergic neurons compared with age‐matched controls. This was comparable to the GM1 deficiency of HT mice and suggests that GM1 deficiency may be a contributing factor to idiopathic PD. We propose that HT mice with partial GM1 deficiency constitute an especially useful model for PD, reflecting the actual pathophysiology of this disorder. The results point to membrane‐permeable analogs of GM1 as holding promise as a form of GM1 replacement therapy. © 2012 Wiley Periodicals, Inc.     

Intra‐axonal protein aggregation in the peripheral nervous system

Intracellular protein aggregates are common pathological hallmarks of many neurodegenerative disorders, and a defect in axonal transport is also incriminated. Here, we studied intra‐axonal abnormal protein aggregation and axonopathy by using immunohistochemistry and electron microscopy on peripheral nerve biopsies from 12 patients with chronic axonal peripheral neuropathy (PN) of unknown etiology. Among these patients, three had idiopathic Parkinson's disease (PD). Intra‐axonal ubiquitin aggregates were more numerous in the patients with PD. Intra‐axonal aggregates of tau AT8 were found in five patients without PD. Phosphorylated α‐synuclein aggregation was absent in all cases, while intra‐axonal colocalization of 14‐3‐3 β and ubiquitin was observed in two PD cases. Electron microscopy revealed enlarged axons crowded with organelles in six cases, including the three patients with PD, thus attesting a slowing of the axoplasmic flux. The number of ubiquitin aggregates was correlated with features of reduced axonal flux, while no such correlation was found for tau and 14‐3‐3 β. Age did not correlate with the number of tau, ubiquitin, and 14‐3‐3 aggregates. Thus, both ubiquitin and/or abnormal tau intra‐axonal aggregates may be found in chronic axonal PN. Ubiquitin aggregates might reduce the axonal flux or result from a disease producing slowing of axonal transport.     

Idiopathic Parkinson's disease patient‐derived induced pluripotent stem cells function as midbrain dopaminergic neurons in rodent brains

Patient‐specific induced pluripotent stem cells (iPSCs) are a promising source for cell transplantation therapy. In Parkinson's disease (PD) patients, however, their vulnerability and the transmission of pathological α‐Synuclein are possible drawbacks that may prevent PD‐specific iPSCs (PDiPSCs) from being used in clinical settings. In this study, we generated iPSCs from idiopathic PD patients and found that there was no significant vulnerability between dopaminergic (DA) neurons generated from healthy individuals and idiopathic PD patients. PDiPSC‐derived DA neurons survived and functioned in the brains of PD model rats. In addition, in the brains of α‐Synuclein transgenic mice, PDiPSC‐derived DA neurons did not cause pathological α‐Synuclein accumulation in the host brain or in the grafts. These results suggested that iPSCs derived from idiopathic PD patients are feasible as donor cells for autologous transplantation to treat PD. © 2017 Wiley Periodicals, Inc.     

Review: Spreading the word: precise animal models and validated methods are vital when evaluating prion‐like behaviour of alpha‐synuclein

Synucleinopathies are characterized by abnormal proteinaceous aggregates, mainly composed of fibrillar α‐synuclein (α‐syn). It is now believed that α‐syn can form small aggregates in a restricted number of cells, that propagate to neighbouring cells and seed aggregation of endogenous α‐syn, in a ‘prion‐like manner’. This process could underlie the stereotypical progression of Lewy bodies described by Braak and colleagues across different stages of Parkinson's disease (PD). This prion‐like behaviour of α‐syn has been recently investigated in animal models of PD or multiple system atrophy (MSA). These models investigate the cell‐to‐cell transfer of α‐syn seeds, or the induction and spreading of α‐syn pathology in transgenic or wild‐type rodent brain. In this review, we first outline the involvement of α‐syn in Lewy body diseases and MSA, and discuss how ‘prion‐like’ mechanisms can contribute to disease. Thereon, we debate the relevance of animal models used to study prion‐like propagation. Finally, we review current main histological methods used to assess α‐syn pathology both in animal models and in human samples and their relevance to the disease. Specifically, we discuss using α‐syn phosphorylated at serine 129 as a marker of pathology, and the novel methods available that allow for more sensitive detection of early pathology, which has relevance for modelling synucleinopathies.