Parkinson disease: Insights in clinical, genetic and pathological features of monogenic disease subtypes

Caffeine alleviates anxiety-like behavior and brainstem lesions in a rotenone-induced rat model of Parkinson's disease

BACKGROUND

Parkinson's disease (PD) is a neurodegenerative disorder characterized by motor and non-motor symptoms. In 2016, approximately 6.1 million individuals were affected by PD, with 211,296 deaths attributed to the disease. The understanding of PD initially came from the observation of dopaminergic system alterations in a specific region of the brainstem, indicating that the core motor and non-motor features of PD are closely associated with brainstem dysfunction. The primary treatment approach for PD revolves around dopamine replacement, as many of the symptoms are responsive to this therapeutic intervention. However, long-term administration of this approach is linked to several complications, and a definitive gold-standard therapy for PD is yet to be identified. The pharmacological management of PD has been challenging and inconsistent, mainly due to the unclear underlying cause of the disease. This study aims to evaluate the effects of caffeine on the brainstem of rats with PD induced by rotenone.

METHODOLOGY

Fifty adult male Wistar rats weighing between 150 and 200 g were used in this study. The rats were randomly divided into five groups of ten rats each: Vehicle Group, Rotenone-only treated Group (rotenone only treated with 3 mg/kg, intraperitoneal administration [IP]), Preventive Group (caffeine 30 mg/kg + rotenone 3 mg/kg, IP), Curative Group (rotenone 3 mg/kg + caffeine 30 mg/kg, IP), and Caffeine only treated Group (caffeine only treated with 30 mg/kg, IP). The animals underwent neurobehavioral assessments, followed by sacrifice. The brains were then excised, weighed, and processed histologically. Appropriate brain sections were taken and processed. Photomicrographs were obtained, morphometric and statistical analysis was performed using an Omax LED digital RESULTS: The results demonstrated a significant (p < 0.05) reduction in body weight and relative brain weight, which were increased by caffeine treatments. Rotenone administration led to histological changes similar to those observed in PD, including neuronal structural derangement, degenerated nerve fibers, loss of myelinated neurons, and Nissl substance, as well as downregulation in the expressions of NRF2 and TH in the midbrain. However, these pathological features were counteracted or ameliorated by caffeine treatment.

CONCLUSION

Our study contributes additional evidence to the growing body of research supporting the therapeutic potential of caffeine in Parkinson's disease (PD). The results underscore the neuroprotective properties of caffeine and its capacity to mitigate oxidative stress by modulating TH (tyrosine hydroxylase) and cytoplasmic NRF2 (nuclear factor erythroid 2-related factor 2) in the mesencephalon. These findings suggest that caffeine holds promise as a viable treatment option for PD.

Genetic Testing in Parkinson's Disease

Genetic testing for persons with Parkinson's disease is becoming increasingly common. Significant gains have been made regarding genetic testing methods, and testing is becoming more readily available in clinical, research, and direct-to-consumer settings. Although the potential utility of clinical testing is expanding, there are currently no proven gene-targeted therapies, but clinical trials are underway. Furthermore, genetic testing practices vary widely, as do knowledge and attitudes of relevant stakeholders. The specter of testing mandates financial, ethical, and physician engagement, and there is a need for guidelines to help navigate the myriad of challenges. However, to develop guidelines, gaps and controversies need to be clearly identified and analyzed. To this end, we first reviewed recent literature and subsequently identified gaps and controversies, some of which were partially addressed in the literature, but many of which are not well delineated or researched. Key gaps and controversies include: (1) Is genetic testing appropriate in symptomatic and asymptomatic individuals without medical actionability? (2) How, if at all, should testing vary based on ethnicity? (3) What are the long-term outcomes of consumer- and research-based genetic testing in presymptomatic PD? (4) What resources are needed for clinical genetic testing, and how is this impacted by models of care and cost-benefit considerations? Addressing these issues will help facilitate the development of consensus and guidelines regarding the approach and access to genetic testing and counseling. This is also needed to guide a multidisciplinary approach that accounts for cultural, geographic, and socioeconomic factors in developing testing guidelines. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Development of CRISPR Cas9, spin-off technologies and their application in model construction and potential therapeutic methods of Parkinson's disease

Parkinson's disease (PD) is one of the most common degenerative diseases. It is most typically characterized by neuronal death following the accumulation of Lewis inclusions in dopaminergic neurons in the substantia nigra region, with clinical symptoms such as motor retardation, autonomic dysfunction, and dystonia spasms. The exact molecular mechanism of its pathogenesis has not been revealed up to now. And there is a lack of effective treatments for PD, which places a burden on patients, families, and society. CRISPR Cas9 is a powerful technology to modify target genomic sequence with rapid development. More and more scientists utilized this technique to perform research associated neurodegenerative disease including PD. However, the complexity involved makes it urgent to organize and summarize the existing findings to facilitate a clearer understanding. In this review, we described the development of CRISPR Cas9 technology and the latest spin-off gene editing systems. Then we focused on the application of CRISPR Cas9 technology in PD research, summarizing the construction of the novel PD-related medical models including cellular models, small animal models, large mammal models. We also discussed new directions and target molecules related to the use of CRISPR Cas9 for PD treatment from the above models. Finally, we proposed the view about the directions for the development and optimization of the CRISPR Cas9 technology system, and its application to PD and gene therapy in the future. All these results provided a valuable reference and enhanced in understanding for studying PD.

Alpha-lipoic acid improved motor function in MPTP-induced Parkinsonian mice by reducing neuroinflammation in the nigral and spinal cord

Parkinson's disease (PD) is a chronic neurodegenerative movement disorder, resulting in dopaminergic (DA) neuronal loss in the substantia nigra (SN) and injury of extranigral spinal cord neurons. This study was to investigate the effect of α-lipoic acid (ALA) on 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP) induced neuroinflammation in the substantia nigra and spinal cord as well as motor function of the mice with PD. After MPTP induced mouse model with PD, the effect of ALA on motor defects was evaluated by measurement of fore and hind limb step length and suspension test. The effects of ALA on microglia in the SN and spinal cord of MPTP-induced Parkinsonian mice were detected by immunofluorescence. The effect of ALA on the protein level nuclear factor-κB (NF-κB) in MPTP-induced mice with PD were examined by Western blot. RT-qPCR was used to detect the effect of ALA on gene expression of tumor necrosis factor-α (TNF-α) and inducible nitric oxide synthase (iNOS) in the SN and spinal cord of MPTP-induced mice. The behavioral results showed that ALA treatment significantly increased the step length and suspension time of MPTP-induced mice (P < 0.05). Immunofluorescence results showed that ALA significantly reduced MPTP-induced activation of microglia both in the SN and spinal cord (P < 0.05). Western blot and RT-qPCR showed that ALA significantly reduced the expression of NF-κB, TNF-α and iNOS in the nigra and spinal cord (P < 0.05). ALA can play a neuroprotective role through alleviating the activation of microglia, reducing neuroinflammation in the nigra and extranigra of mice induced by MPTP and therefore improving their motor dysfunction.

Effects of the Edaravone, a Drug Approved for the Treatment of Amyotrophic Lateral Sclerosis, on Mitochondrial Function and Neuroprotection

Edaravone, the first known free radical scavenger, has demonstrated cellular protective properties in animals and humans. Owing to its antioxidant activity, edaravone modulates oxidative damage in various diseases, especially neurodegenerative diseases. In 2015, edaravone was approved in Japan to treat amyotrophic lateral sclerosis. The distinguishing pathogenic features of neurodegenerative diseases include high reactive oxygen species levels and mitochondrial dysfunction. However, the correlation between mitochondria and edaravone has not been elucidated. This review highlights recent studies on novel therapeutic perspectives of edaravone in terms of its effect on oxidative stress and mitochondrial function.

Can a Micronutrient Mixture Delay the Onset and Progression of Symptoms of Single-Point Mutation Diseases?

Single-point mutation diseases in which substitution of one nucleotide with another in a gene occurs include familial Alzheimer's disease (fAD), familial Parkinson's disease (fPD), and familial Creutzfeldt-Jacob disease (fCJD) as well as Huntington's disease (HD), sickle cell anemia, and hemophilia. Inevitability of occurrence of these diseases is certain. However, the time of appearance of symptoms could be influenced by the diet, environment, and possibly other genetic factors. There are no effective approaches to delay the onset or progression of symptoms of these diseases. The fact that increased oxidative stress and inflammation significantly contribute to the initiation and progression of these point mutation diseases shows that antioxidants could be useful. The major objectives are (a) to present evidence that increased oxidative stress and chronic inflammation are associated with selected single-point mutation diseases, such as fAD, fPD, and fCJD, HD, sickle cell anemia, and hemophilia; (b) to describe limited studies on the role of individual antioxidants in experimental models of some of these diseases; and (c) to discuss a rationale for utilizing a comprehensive mixture of micronutrients, which may delay the development and progression of symptoms of above diseases by simultaneously reducing oxidative and inflammatory damages.Key teaching pointsSelected single-point mutation diseases and their pattern of inheritanceCharacteristics of each selected single-point mutation diseaseEvidence for increased oxidative stress and inflammation in each diseasePotential reasons for failure of single antioxidants in human studiesRationale for using a comprehensive mixture of micronutrients in delaying the onset and progression of single-point mutation diseases.

PARKIN, PINK1, and DJ1 analysis in early-onset Parkinson's disease in Ireland

BACKGROUND

Variants in PARKIN, PINK1, and DJ1 are associated with early-onset Parkinson' disease (EOPD, age-at-onset < 45). We previously reported a single PINK1 and a single DJ1 heterozygous variant carrier.

PURPOSE

We aimed to expand upon our previous EOPD studies and investigate for any genotype-phenotype correlations in Irish PD.

METHODS

Three hundred fourteen PD patients were recruited from Dublin Neurological Institute, Ireland. Genetic analysis was performed at the Mayo Clinic, Jacksonville, USA. We screened 81 patients with young-onset PD (age-at-onset < 50), of which 58 had EOPD.

RESULTS

We identified 4 patients with homozygous/compound heterozygous variants and 3 heterozygote carriers (pathogenic PINK1/DJ1 variants were not found). Expansion of one of the pedigrees showed a novel variant in exon 9, in a symptomatic patient. We identified 6.89% PARKIN variant carriers associated with EOPD.

CONCLUSION

These findings suggest that PINK1 and DJ1 are rarely associated with Irish YOPD, while PARKIN variant frequency is similar to that reported worldwide.

Is Attention-Deficit/Hyperactivity Disorder a Risk Syndrome for Parkinson's Disease?

Recent epidemiological evidence indicates that diagnosis of attention-deficit/hyperactivity disorder (ADHD) is associated with increased risk for diseases of the basal ganglia and cerebellum, including Parkinson's disease (PD). The evidence reviewed here indicates that deficits in striatal dopamine are a shared component of the causal chains that produce these disorders. Neuropsychological studies of adult ADHD, prodromal PD, and early-stage PD reveal similar deficits in executive functions, memory, attention, and inhibition that are mediated by similar neural substrates. These and other findings are consistent with the possibility that ADHD may be part of the PD prodrome. The mechanisms that may mediate the association between PD and ADHD include neurotoxic effects of stimulants, other environmental exposures, and Lewy pathology. Understanding the nature of the association between PD and ADHD may provide insight into the etiology and pathogenesis of both disorders. The possible contribution of stimulants to this association may have important clinical and public health implications.

Sporadic Creutzfeldt-Jakob Disease and Other Proteinopathies in Comorbidity

Background: Sporadic Creutzfeldt–Jakob disease (sCJD) is the most common type of a group of transmissible spongiform encephalopathies (prion diseases). The etiology of the sporadic form of CJD is still unclear. sCJD can occur in combination with other neurodegenerative diseases, which further complicates the diagnosis. Alzheimer's disease (AD), e.g., is often seen in conjunction with sCJD.

Method: In this study, we performed a systematic analysis of 15 genes related to the most important neurodegenerative diseases - AD, frontotemporal dementia, amyotrophic lateral sclerosis, prion disease, and Parkinson's disease - in a cohort of sCJD and sCJD in comorbidity with AD and primary age-related proteinopathy (PART). A total of 30 neuropathologically verified cases of sCJD with and without additional proteinopathies were included in the study. In addition, we compared microtubule-associated protein tau (MAPT) haplotypes between sCJD patients and patients with sCJD and PART or sCJD and AD. Then we studied the interaction between the Apolipoprotein E gene (APOE) and PRNP in sCJD patients.

Results: We did not find any causal mutations in the neurodegenerative disease genes. We did detect a p.E318G missense variant of uncertain significance (VUS) in PSEN1 in three patients. In PRNP, we also found a previously described non-pathogenic insertion (p.P84_Q91Q).

Conclusion: Our pilot study failed to find any critical differences between pure sCJD and sCJD in conjunction with other comorbid neurodegenerative diseases. Further investigations are needed to better understand this phenomenon.

Thyroid hormone levels and structural parameters of thyroid homeostasis are correlated with motor subtype and disease severity in euthyroid patients with Parkinson's disease

Purpose: This study is to investigate the relationship between thyroid function and Parkinson's disease (PD).Materials and Methods: Totally 77 PD patients were included, who were divided into tremor-dominant-type (TDT), akinetic-rigid-type (ART) and mixed-type (MXT) subgroups. Parkinsonism severity and stage was assessed by modified H-Y stage. Thyroid-stimulating hormone (TSH), fT3 and fT4 levels were detected to analyze thyroid function. Parameters of thyroid homeostasis, including thyroid's secretory capacity (SPINA-GT), the total deiodinase activity (SPINA-GD) and Jostel's TSH index and the thyrotroph thyroid hormone sensitivity index (TTSI), were calculated and compared.Results: Thyroid hormone levels in PD patients were lower than normal controls. Patients with TDT/MXT had significantly higher fT4 level than those with ART. TSH levels were 1.73 ± 0.93 and 2.06 ± 1.04 ulU/ml for patients with TDT/MXT and ART, respectively. The patients in the TDT/MXT group had significantly lower SPINA-GD while significantly higher SPINA-GT than ART group. The fT3 level was significantly higher in early group than advanced group. TSH index in the early group was significantly higher than the advanced group. The fT4 level was negatively correlated with UPDRS motor score. Univariate and multivariable logistic regression analysis indicated that fT4 was positively correlated with PD motor subtype, which disappeared after adjusting for confounding factors. The fT3 level was negatively correlated with PD disease severity, even after adjusting for confounding factors. In female PD patients, fT4 level in TDT/MXT group was significantly higher than ART group. Male PD patients had higher fT4 levels in early patients than advanced patients. Percentage of patients exhibiting ART was decreased significantly in higher fT4 level subgroups. With the increase of TSH index and TTSI, the proportion of advanced PD patients gradually decreased. The proportion of PD patients with TDT/MXT motor subtype gradually increased with the quartiles of SPINA-GT.Conclusion: Thyroid hormone levels and structural parameters of thyroid homeostasis are correlated with motor subtype and disease severity in euthyroid patients with PD.

A preliminary study of Parkinson's gene therapy via sono-magnetic sensing gene vector for conquering extra/intracellular barriers in mice

BACKGROUND

Non-virus genetic treatment for Parkinson's disease (PD) via plasmid glial cell-line derived neurotrophic factor (pGDNF) has shown potential for repairing damaged dopaminergic neurons. However, development of this gene therapy is largely hampered by the insufficient transfection efficiency as a result of the cell membrane, lysosome, and cytoskeleton meshwork.

METHODS

In this study, we propose the use of polyethylenimine (PEI)-superparamagnetic iron oxide-plasmid DNA (pDNA)-loaded microbubbles (PSp-MBs) in conjunction with focused ultrasound (FUS) and two-step magnetic navigation to provide cavitation, proton sponge effect and magnetic effects to increase the efficiency of gene delivery.

RESULTS

The gene transfection rate in the proposed system was 2.2-fold higher than that of the commercial agent (TransIT®-LT1). The transfection rate could be boosted ∼11%, ∼10%, and 6% by cavitation-magnetic hybrid enhanced cell membrane permeabilization, proton sponge effect, and magnetic-assisted cytoskeleton-reorganization, respectively. In vivo data suggested that effective gene delivery with this system results in a 3.2-fold increase in recovery of dopaminergic neurons and a 3.9-fold improvement in the motor behavior when compared to untreated genetic PD mice.

CONCLUSIONS

We proposed that this novel FUS-magnetic hybrid gene delivery platform could be integrated with a variety of therapeutic genes for treating neurodegenerative diseases in the future.

Loss of prostatic acid phosphatase and α-synuclein cause motor circuit degeneration without altering cerebellar patterning

Prostatic acid phosphatase (PAP), which is secreted by prostate, increases in some diseases such as prostate cancer. PAP is also present in the central nervous system. In this study we reveal that α-synuclein (Snca) gene is co-deleted/mutated in PAP null mouse. It is indicated that mice deficient in transmembrane PAP display neurological alterations. By using immunohistochemistry, cerebellar cortical neurons and zone and stripes pattern were studied in Pap^{-/- ;}Snca^-/- mouse cerebellum. We show that the Pap^{-/- ;}Snca^-/- cerebellar cortex development appears to be normal. Compartmentation genes expression such as zebrin II, HSP25, and P75NTR show the zone and stripe phenotype characteristic of the normal cerebellum. These data indicate that although aggregation of PAP and SNCA causes severe neurodegenerative diseases, PAP^-/- with absence of the Snca does not appear to interrupt the cerebellar architecture development and zone and stripe pattern formation. These findings question the physiological and pathological role of SNCA and PAP during cerebellar development or suggest existence of the possible compensatory mechanisms in the absence of these genes.

Simvastatin Inhibits Activation of NADPH Oxidase/p38 MAPK Pathway and Enhances Expression of Antioxidant Protein in Parkinson Disease Models

Evidence suggests that oxidative stress is involved in the pathogenesis of Parkinson disease (PD). Simvastatin has been suggested to protect against oxidative stress in several diseases. However, the molecular mechanisms by which simvastatin protects against neuropathology and oxidative damage in PD are poorly elucidated. In this study, we aimed to investigate the potential neuroprotective effects of simvastatin owing to its anti-oxidative properties in 6-hydroxydopamine (6-OHDA)-treated SH-SY5Y cells and mice. The results of 2′,7′-dichlorodihydrofluorescein diacetate (DCFH-DA) fluorescence and CCK-8 assay demonstrated that simvastatin reduced intracellular reactive oxygen species (ROS) levels and reversed apoptosis in 6-OHDA-treated SH-SY5Y cells. Mechanistic studies revealed that 6-OHDA-induced activation of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase/p38 mitogen-activated protein kinase (MAPK) pathway was inhibited and nuclear factor-κB (NF-κB) nuclear transcription decreased in SH-SY5Y cells after simvastatin treatment. Enhanced expression levels of superoxide dismutase (SOD), heme oxygenase-1 (HO-1), peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) and glutamate-cysteine ligase modifier subunit (GCLM) were observed after simvastatin treatment in 6-OHDA-treated SH-SY5Y cells. In vivo studies revealed that administration of simvastatin by gavage decreased limb-use asymmetry and apomorphine-induced rotations in 6-OHDA-lesioned mice. Simvastatin increased dopaminergic neurons and reduced protein tyrosine nitration and gliosis in the midbrain of PD mice. An inhibitory effect on activation of the NADPH oxidase/p38 MAPK was observed, and increased antioxidant protein expression in the midbrain were seen in the simvastatin plus 6-OHDA group compared with the 6-OHDA-lesioned group. Taken together, these results demonstrate that simvastatin might inhibit the activation of NADPH oxidase/p38 MAPK pathway, enhance antioxidant protein expression and protect against oxidative stress, thereby providing a novel antioxidant mechanism that has therapeutic validity.

LRRK2, GBA and SMPD1 Founder Mutations and Parkinson's Disease in Ashkenazi Jews

BACKGROUND/AIM

Parkinson's disease (PD) is associated with mutations in LRRK2, GBA, and SMPD1 genes. We describe the clinical characteristics of PD patients related to their carrier status of the Ashkenazi founder mutations in the aforementioned genes.

METHODS

Ashkenazi PD patients (n = 270) were recruited following informed consent, and tested for the founder Ashkenazi mutations in the above genes. Clinical characteristics were compared between carriers and noncarriers. Homozygotes for mutations in GBA or LRRK2, and those who carried mutations in two causative genes were excluded from the analysis.

RESULTS

Five (1.85%), 54 (20%), and 22 (8.1%) PD patients carried mutations in SMPD1, GBA or LRRK2, respectively. By post hoc Bonferroni analysis, GBA carriers were singled at a significantly earlier age at diagnosis compared to noncarriers (58.06 ± 10.84 and 62.65 ± 10.86 years, respectively; p = 0.036), and due to bilateral manifestation at diagnosis compared to all other PD groups (n = 8, 15.7% compared to n = 2, 1.1%, respectively; p < 0.001). Other clinical manifestations were comparable between groups.

CONCLUSION

Although only GBA mutation carriers, compared to noncarriers, reached statistical significance regarding age at diagnosis, it appears that LRRK2 and SMPD1 mutation carriers may reach significance with larger group numbers.

Targeting Adenosine Signaling in Parkinson's Disease: From Pharmacological to Non-pharmacological Approaches

Parkinson's disease (PD) is one of the most prevalent neurodegenerative disease displaying negative impacts on both the health and social ability of patients and considerable economical costs. The classical anti-parkinsonian drugs based in dopaminergic replacement are the standard treatment, but several motor side effects emerge during long-term use. This mini-review presents the rationale to several efforts from pre-clinical and clinical studies using adenosine receptor antagonists as a non-dopaminergic therapy. As several studies have indicated that the monotherapy with adenosine receptor antagonists reaches limited efficacy, the usage as a co-adjuvant appeared to be a promising strategy. The formulation of multi-targeted drugs, using adenosine receptor antagonists and other neurotransmitter systems than the dopaminergic one as targets, have been receiving attention since Parkinson's disease presents a complex biological impact. While pharmacological approaches to cure or ameliorate the conditions of PD are the leading strategy in this area, emerging positive aspects have arisen from non-pharmacological approaches and adenosine function inhibition appears to improve both strategies.

No genetic association between attention-deficit/hyperactivity disorder (ADHD) and Parkinson's disease in nine ADHD candidate SNPs

Attention-deficit/hyperactivity disorder (ADHD) and Parkinson's disease (PD) involve pathological changes in brain structures such as the basal ganglia, which are essential for the control of motor and cognitive behavior and impulsivity. The cause of ADHD and PD remains unknown, but there is increasing evidence that both seem to result from a complicated interplay of genetic and environmental factors affecting numerous cellular processes and brain regions. To explore the possibility of common genetic pathways within the respective pathophysiologies, nine ADHD candidate single nucleotide polymorphisms (SNPs) in seven genes were tested for association with PD in 5333 cases and 12,019 healthy controls: one variant, respectively, in the genes coding for synaptosomal-associated protein 25 k (SNAP25), the dopamine (DA) transporter (SLC6A3; DAT1), DA receptor D4 (DRD4), serotonin receptor 1B (HTR1B), tryptophan hydroxylase 2 (TPH2), the norepinephrine transporter SLC6A2 and three SNPs in cadherin 13 (CDH13). Information was extracted from a recent meta-analysis of five genome-wide association studies, in which 7,689,524 SNPs in European samples were successfully imputed. No significant association was observed after correction for multiple testing. Therefore, it is reasonable to conclude that candidate variants implicated in the pathogenesis of ADHD do not play a substantial role in PD.

Possible role of Epoxyeicosatrienoic acid in prevention of oxidative stress mediated neuroinflammation in Parkinson disorders

Parkinson's disease (PD) is a multifactorial neurodegenerative disease involving oxidative stress, neuroinflammation and apoptosis. Epoxyeicosatrienoic acids (EETs) are arachidonic acid metabolites and they play a role in cytoprotection by modulating various cell signaling pathways. This cytoprotective role of EETs are well established in cerebral stroke, cardiac failure, and hypertension, and it is due to their ability to attenuate oxidative stress, endoplasmic reticulum stress, inflammation, caspase activation and apoptosis. The actions of EETs in brain closely parallel the effects which is observed in the peripheral tissues. Since many of these effects could potentially contribute to neuroprotection, EETs are, therefore, one of the potential therapeutic candidates in PD. Therefore, by increasing the half life of endogenous EETs in vivo via inhibition of sEH, its metabolizing enzyme can, therefore, constitutes an important therapeutic strategy in PD.

The role of RNA metabolism in neurological diseases

Neurodegenerative disorders are commonly encountered in medical practices. Such diseases can lead to major morbidity and mortality among the affected individuals. The molecular pathogenesis of these disorders is not yet clear. Recent literature has revealed that mutations in RNA-binding proteins are a key cause of several human neuronal-based diseases. This review discusses the role of RNA metabolism in neurological diseases with specific emphasis on roles of RNA translation and microRNAs in neurodegeneration, RNA-mediated toxicity, repeat expansion diseases and RNA metabolism, molecular pathogenesis of amyotrophic lateral sclerosis and frontotemporal dementia, and neurobiology of survival motor neuron (SMN) and spinal muscular atrophy.

Onset and progression factors in Parkinson's disease: A systematic review

Current research has identified several factors thought to be associated with the onset and progression of Parkinson's Disease (PD); however, whether certain factors contribute to or are protective against PD remains unclear. As such, a systematic search of the literature was performed using variations of MeSH and keyword search terms to identify and summarize systematic reviews and primary studies pertaining to factors associated with the onset and progression of PD. Factors referred to both traditional risk factors and prodromal markers. The following databases were searched: MEDLINE, MEDLINE In-Process, EMBASE, PsycINFO, Scopus, Web of Science, Cochrane Database of Systematic Reviews, Cumulative Index to Nursing and Allied Health Literature (CINAHL), ProQuest Dissertations & Theses, AARP AgeLine, and PDGene. A quality assessment of included systematic reviews was completed using the validated Assessment of the Methodological Quality of Systematic Reviews (AMSTAR) tool. Data extraction targeted reported factors, risk estimates, and 95% confidence intervals (CI). Findings identified 11 systematic reviews of sufficient quality reporting factors for PD onset, and no systematic reviews reporting factors for PD progression. In addition, 93 primary articles were identified, of which, 89 articles addressed factors related to PD onset and 4 articles addressed factors related to the PD progression. Pesticide exposure, rural living, well-water drinking, and farming occupation were consistently found to be positively associated with the onset of PD. Moreover, family history and polymorphisms to key genes were also found to be positively associated with the onset of PD. Conversely, coffee consumption, cigarette smoking, and some polymorphisms were consistently found to be negatively associated with the onset of PD. Urate was the only identified factor linked to the progression of PD; it was mostly found to be negatively associated with PD. In sum, the evidence was systematically found and summarized in the literature pertaining to factors related to the onset and progression of PD.

Association of the MTHFR rs1801131 and rs1801133 variants in sporadic Parkinson's disease patients

Parkinson's disease (PD) is a common age-dependent neurodegenerative movement disorder related to multiple factors, and genetic factors play an important role in the pathogenesis of PD. Variants in the methylenetetrahydrofolate reductase gene (MTHFR), a gene encoding a folate-dependent enzyme that is involved in homocysteine metabolism, have been reported to be associated with PD. To explore the role of the MTHFR gene in the development of PD in Chinese Han population, we analyzed two MTHFR variants (rs1801131 and rs1801133) in a patient cohort consisting of 512 patients with PD from mainland China and a control cohort consisting of 512 age, gender and ethnicity matched normal subjects. Statistically significant differences in genotypic and allelic frequencies were detected in the MTHFR variant rs1801133 (P=0.022 and 0.007, respectively; odds ratio=0.780, 95% confidence interval=0.651-0.934). In addition, the A-T haplotype of rs1801131-rs1801133 showed a protective role against PD development (P=0.007, odds ratio=0.779, 95% confidence interval=0.650-0.933). Our results suggested that the T allele of rs1801133 variant and A-T haplotype of rs1801131-rs1801133 in the MTHFR gene may decrease the risk of developing PD in Chinese Han population from mainland China.

Propofol protects against the neurotoxicity of 1‑methyl‑4‑phenylpyridinium

Parkinson's disease (PD) is a progressive and degenerative disorder of the central nervous system, characterized by the loss of dopaminergic neurons and muscular rigidity. Treatment with propofol (2,6‑diisopropylphenol) has been observed to attenuate oxidative stress injury via inhibition of programmed cell death. Results from the present study indicate that propofol treatment attenuates 1‑methyl‑4‑phenylpyridinium (MPP+)‑induced oxidative stress, which was demonstrated by increased levels of reactive oxygen species, 4‑hydroxy‑2‑nonenal and protein carbonyls. Furthermore, it was demonstrated that propofol may ameliorate MPP+‑induced mitochondrial dysfunction by increasing the level of ATP and the mitochondrial membrane potential. MTT and lactate dehydrogenase assays indicated that propofol treatment reduces cell vulnerability to MPP+‑induced insult. Propofol was also observed to prevent apoptotic signals by reducing the ratio of Bcl‑2‑associated X protein to B‑cell lymphoma 2, reducing the expression level of cleaved caspase‑3 and attenuating cytochrome c release. Thus, propofol may present as a novel therapeutic strategy for the treatment of PD.

The contribution of Niemann-Pick SMPD1 mutations to Parkinson disease in Ashkenazi Jews

INTRODUCTION

Parkinson disease is noted for its association with mutations in GBA and the p.G2019S mutation in LRRK2. This study aimed to evaluate the frequency of Ashkenazi founder mutations in sphingomyelin phosphodiesterase 1 (SMPD1) in Ashkenazi patients diagnosed with Parkinson's disease (PD); and their impact on PD phenotypic expression. SMPD1 underlies the lysosomal storage disease - Niemann-Pick.

METHODS

A case (n = 287) control (n = 400) study was undertaken. All patients underwent a physical, neurobehavioral and neurologic examination that incorporated the Unified Parkinson's Disease Rating Scale. Three founder SMPD1 Ashkenazi mutations (c.996delC (fsP330), p.L302P and p.R496L) were investigated in patients and controls, previously evaluated for carriage of founder mutations in GBA and the p.G2019S mutation in LRRK2.

RESULTS

Nine (3.1%) PD patients compared to two (0.5%) individuals from the control group were found to carry one of the three Ashkenazi SMPD1 founder mutations (p = 0.007). The overall clinical characteristics of PD patients carrying SMPD1 mutations were similar to those of PD patients with no mutations in SMPD1, GBA and LRRK2 (n = 189).

CONCLUSION

We maintain that disruptive mutations in SMPD1 constitute a risk factor for PD.

Inflammatory mediators as biomarkers in brain disorders

Neurodegenerative diseases such as Alzheimer, Parkinson, amyotrophic lateral sclerosis, and Huntington are incurable and debilitating conditions that result in progressive death of the neurons. The definite diagnosis of a neurodegenerative disorder is disadvantaged by the difficulty in obtaining biopsies and thereby to validate the clinical diagnosis with pathological results. Biomarkers are valuable indicators for detecting different phases of a disease such as prevention, early onset, treatment, progression, and monitoring the effect of pharmacological responses to a therapeutic intervention. Inflammation occurs in neurodegenerative diseases, and identification and validation of molecules involved in this process could be a strategy for finding new biomarkers. The ideal inflammatory biomarker needs to be easily measurable, must be reproducible, not subject to wide variation in the population, and unaffected by external factors. Our review summarizes the most important inflammation biomarkers currently available, whose specificity could be utilized for identifying and monitoring distinctive phases of different neurodegenerative diseases.

Splicing variants of porcine synphilin-1

Parkinson's disease (PD), idiopathic and familial, is characterized by degradation of dopaminergic neurons and the presence of Lewy bodies (LB) in the substantia nigra. LBs contain aggregated proteins of which α-synuclein is the major component. The protein synphilin-1 interacts and colocalizes with α-synuclein in LBs. The aim of this study was to isolate and characterize porcine synphilin-1 and isoforms hereof with the future perspective to use the pig as a model for Parkinson's disease. The porcine SNCAIP cDNA was cloned by reverse transcriptase PCR. The spatial expression of SNCAIP mRNA was investigated by RNAseq. The presented work reports the molecular cloning and characterization of the porcine (Sus scrofa) synphilin-1 cDNA (SNCAIP) and three splice variants hereof. The porcine SNCAIP cDNA codes for a protein (synphilin-1) of 919 amino acids which shows a high similarity to human (90%) and to mouse (84%) synphilin-1. Three shorter transcript variants of the synphilin-1 gene were identified, all lacking one or more exons. SNCAIP transcripts were detected in most examined organs and tissues and the highest expression was found in brain tissues and lung. Conserved splicing variants and a novel splice form of synhilin-1 were found in this study. All synphilin-1 isoforms encoded by the identified transcript variants lack functional domains important for protein degradation.

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The full-length porcine SNCAIP cDNA encoding synphilin-1 was cloned and characterized.

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Three splicing variants of synphilin-1 were identified.

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Both conserved and novel splicing variant were found.

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SNCAIP mRNA was differently expressed in analyzed tissues and organs with highest expression in brain tissue and lung.

Parkinson's disease-associated PINK1 G309D mutation increases abnormal phosphorylation of Tau

Mutations in PINK1 gene have been considered the second most common cause of Autosomal Recessive Parkinsonism (ARP). So far, different homozygous PINK1 mutations have been identified in different ARP patients. Abnormal hyperphosphorylation of tau leads to the loss of its biological activity. Multiple lines of evidence have demonstrated that hyperphosphorylated tau is associated with Alzheimer's disease and Parkinson's disease (PD). However, the effects of PD associated PINK1 mutations in tau phosphorylation are unknown. In this study, we investigated the effect of G309D PINK1 mutation in tau phosphorylation. Cells transfected with mutant G309D PINK1 exhibited a significant increase in the phosphorylation of tau protein at the PHF-1 (ser396/404) site. The levels of CDK5, an important activator of tau phosphorylation, did not change in mutant G309D PINK1 transfected cells, suggesting that CDK5 is not involved in tau phosphorylation induced by mutant G309D PINK1. Notably, we found that mutant G309D PINK1 significantly reduced phosphorylation of GSK3β at serine 9, suggesting that alterations in GSK3β activity play an essential role in mutant G309D PINK1-induced tau phosphorylation at the PHF-1 site. PP2A activity maintained consistent in mutant G309D PINK1 transfected cells, suggesting that the increased tau hyperphosphorylation is not ascribed to reduction in PP2A activity.

Modeling LRRK2 Pathobiology in Parkinson's Disease: From Yeast to Rodents

Mutations in the leucine-rich repeat kinase 2 (LRRK2, PARK8) gene represent the most common cause of familial Parkinson's disease (PD) with autosomal dominant inheritance, whereas common variation at the LRRK2 genomic locus influences the risk of developing idiopathic PD. LRRK2 is a member of the ROCO protein family and contains multiple domains, including Ras-of-Complex (ROC) GTPase, kinase, and protein-protein interaction domains. In the last decade, the biochemical characterization of LRRK2 and the development of animal model s have provided important insight into the pathobiology of LRRK2. In this review, we comprehensively describe the different models employed to understand LRRK2-associated PD, including yeast, invertebrates, transgenic and viral-based rodents, and patient-derived induced pluripotent stem cells. We discuss how these models have contributed to understanding LRRK2 pathobiology and the advantages and limitations of each model for exploring aspects of LRRK2-associated PD.

MTHFR C677T variant reduces risk of sporadic Parkinson's disease in ethnic Chinese

BACKGROUND

Genetic variability of methylenetetrahydrofolate reductase (MTHFR) may be associated with Parkinson's disease (PD). Its role in ethnic Chinese population is still unclear. Our study aimed to investigate whether MTHFR C677T variation was linked to PD risk in a Han Chinese population from mainland China.

METHODS

To investigate the association with the risk of PD, we analyzed the single-nucleotide polymorphism C677T in MTHFR gene using a case-control methodology. A total of 1482 subjects included 765 patients with idiopathic PD, and 717 age- and sex-matched controls were recruited in this study.

RESULTS

The T allele of MTHFR C677T was associated with a decreased risk of PD (OR = 0.80, 95% CI: 0.688-0.926, P = 0.003). Patients with CT + TT genotypes have a decreased risk of PD compared with those with CC genotypes (OR = 0.66, 95%CI: 0.532-0.813, P = 0.000). CT + TT subjects cannot be differentiated from CC subjects based on their clinical features.

CONCLUSION

We showed that the C677T polymorphism in MTHFR gene was associated with decreased PD susceptibility in a Han Chinese population from mainland China. Efforts to fully elucidate the pathophysiologic role of the variant in PD should be necessary.

Missense dopamine transporter mutations associate with adult parkinsonism and ADHD

Parkinsonism and attention deficit hyperactivity disorder (ADHD) are widespread brain disorders that involve disturbances of dopaminergic signaling. The sodium-coupled dopamine transporter (DAT) controls dopamine homeostasis, but its contribution to disease remains poorly understood. Here, we analyzed a cohort of patients with atypical movement disorder and identified 2 DAT coding variants, DAT-Ile312Phe and a presumed de novo mutant DAT-Asp421Asn, in an adult male with early-onset parkinsonism and ADHD. According to DAT single-photon emission computed tomography (DAT-SPECT) scans and a fluoro-deoxy-glucose-PET/MRI (FDG-PET/MRI) scan, the patient suffered from progressive dopaminergic neurodegeneration. In heterologous cells, both DAT variants exhibited markedly reduced dopamine uptake capacity but preserved membrane targeting, consistent with impaired catalytic activity. Computational simulations and uptake experiments suggested that the disrupted function of the DAT-Asp421Asn mutant is the result of compromised sodium binding, in agreement with Asp421 coordinating sodium at the second sodium site. For DAT-Asp421Asn, substrate efflux experiments revealed a constitutive, anomalous efflux of dopamine, and electrophysiological analyses identified a large cation leak that might further perturb dopaminergic neurotransmission. Our results link specific DAT missense mutations to neurodegenerative early-onset parkinsonism. Moreover, the neuropsychiatric comorbidity provides additional support for the idea that DAT missense mutations are an ADHD risk factor and suggests that complex DAT genotype and phenotype correlations contribute to different dopaminergic pathologies.

Genetic variants and animal models in SNCA and Parkinson disease

Parkinson disease (PD; MIM 168600) is the second most common progressive neurodegenerative disorder characterized by a variety of motor and non-motor features. To date, at least 20 loci and 15 disease-causing genes for parkinsonism have been identified. Among them, the α-synuclein (SNCA) gene was associated with PARK1/PARK4. Point mutations, duplications and triplications in the SNCA gene cause a rare dominant form of PD in familial and sporadic PD cases. The α-synuclein protein, a member of the synuclein family, is abundantly expressed in the brain. The protein is the major component of Lewy bodies and Lewy neurites in dopaminergic neurons in PD. Further understanding of its role in the pathogenesis of PD through various genetic techniques and animal models will likely provide new insights into our understanding, therapy and prevention of PD.

Genome-wide analysis of CNV (copy number variation) and their associations with narcolepsy in a Japanese population

In humans, narcolepsy with cataplexy (narcolepsy) is a sleep disorder that is characterized by sleepiness, cataplexy and rapid eye movement (REM) sleep abnormalities. Narcolepsy is caused by a reduction in the number of neurons that produce hypocretin (orexin) neuropeptide. Both genetic and environmental factors contribute to the development of narcolepsy.Rare and large copy number variations (CNVs) reportedly play a role in the etiology of a number of neuropsychiatric disorders. Narcolepsy is considered a neurological disorder; therefore, we sought to investigate any possible association between rare and large CNVs and human narcolepsy. We used DNA microarray data and a CNV detection software application, PennCNV-Affy, to detect CNVs in 426 Japanese narcoleptic patients and 562 healthy individuals. Overall, we found a significant enrichment of rare and large CNVs (frequency ≤1%, size ≥100 kb) in the patients (case-control ratio of CNV count=1.54, P=5.00 × 10(-4)). Next, we extended a region-based association analysis by including CNVs with its size ≥30 kb. Rare and large CNVs in PARK2 region showed a significant association with narcolepsy. Four patients were assessed to carry duplications of the gene region, whereas no controls carried the duplication, which was further confirmed by quantitative PCR assay. This duplication was also found in 2 essential hypersomnia (EHS) patients out of 171 patients. Furthermore, a pathway analysis revealed enrichments of gene disruptions by rare and large CNVs in immune response, acetyltransferase activity, cell cycle regulation and regulation of cell development. This study constitutes the first report on the risk association between multiple rare and large CNVs and the pathogenesis of narcolepsy. In the future, replication studies are needed to confirm the associations.

Genome-wide analysis of rare copy number variations reveals PARK2 as a candidate gene for attention-deficit/hyperactivity disorder

Attention-deficit/hyperactivity disorder (ADHD) is a common, highly heritable neurodevelopmental disorder. Genetic loci have not yet been identified by genome-wide association studies. Rare copy number variations (CNVs), such as chromosomal deletions or duplications, have been implicated in ADHD and other neurodevelopmental disorders. To identify rare (frequency ≤1%) CNVs that increase the risk of ADHD, we performed a whole-genome CNV analysis based on 489 young ADHD patients and 1285 adult population-based controls and identified one significantly associated CNV region. In tests for a global burden of large (>500 kb) rare CNVs, we observed a nonsignificant (P=0.271) 1.126-fold enriched rate of subjects carrying at least one such CNV in the group of ADHD cases. Locus-specific tests of association were used to assess if there were more rare CNVs in cases compared with controls. Detected CNVs, which were significantly enriched in the ADHD group, were validated by quantitative (q)PCR. Findings were replicated in an independent sample of 386 young patients with ADHD and 781 young population-based healthy controls. We identified rare CNVs within the parkinson protein 2 gene (PARK2) with a significantly higher prevalence in ADHD patients than in controls (P=2.8 × 10(-4) after empirical correction for genome-wide testing). In total, the PARK2 locus (chr 6: 162 659 756-162 767 019) harboured three deletions and nine duplications in the ADHD patients and two deletions and two duplications in the controls. By qPCR analysis, we validated 11 of the 12 CNVs in ADHD patients (P=1.2 × 10(-3) after empirical correction for genome-wide testing). In the replication sample, CNVs at the PARK2 locus were found in four additional ADHD patients and one additional control (P=4.3 × 10(-2)). Our results suggest that copy number variants at the PARK2 locus contribute to the genetic susceptibility of ADHD. Mutations and CNVs in PARK2 are known to be associated with Parkinson disease.

Recognizing genetic forms of parkinsonism

SUMMARY It has been generally recognized that, in most cases of Parkinson’s disease (PD), the causes are a result of the complex interaction of genetic and environmental factors. Only approximately 10–15% of PD cases appear to be rare forms with a Mendelian genetic cause. There has been an increasing need and demand in daily clinical work to look for a molecular diagnosis, although a number of neurologists feel uneasy when dealing with the growing number of possible genes and risk factors related to PD that are accessible for diagnosis. Research has highlighted the consequences not only for hereditary but also sporadic forms of PD. This review will provide an overview of the principal aspects of the genetics of PD. It will focus on their differences and similarities, and discuss several useful tools for clinicians, and the role and importance of a neurogeneticist.

The hallmarks of Parkinson's disease

Since the discovery of dopamine as a neurotransmitter in the 1950s, Parkinson's disease (PD) research has generated a rich and complex body of knowledge, revealing PD to be an age-related multifactorial disease, influenced by both genetic and environmental factors. The tremendous complexity of the disease is increased by a nonlinear progression of the pathogenesis between molecular, cellular and organic systems. In this minireview, we explore the complexity of PD and propose a systems-based approach, organizing the available information around cellular disease hallmarks. We encourage our peers to adopt this cell-based view with the aim of improving communication in interdisciplinary research endeavors targeting the molecular events, modulatory cell-to-cell signaling pathways and emerging clinical phenotypes related to PD.

Edaravone prevents neurotoxicity of mutant L166P DJ-1 in Parkinson's disease

Parkinson's disease (PD), which is estimated to affect approximately 1 % of the population over the age of 65, is the second most common neurodegenerative disorder after Alzheimer's disease. It was reported that pathogenic mutations in DJ-1 lead to autosomal recessive early-onset familial Parkinsonism. The L166P mutant of DJ-1 is the most commonly studied loss-of-function mutation in early onset familial PD, but the underlying mechanisms are still unknown. Edaravone is a powerful free radical scavenger used in clinical treatment for cerebral ischemic stroke. In the present study, we investigated the effects of edaravone on the neurotoxicity in PD-induced isoforms of DJ-1 containing the mutation L166P. Our results indicated that edaravone was able to significantly attenuate oxidative stress and improve mitochondrial function. Furthermore, edaravone was found to reduce apoptosis in Neuro2a cells through modulation of mitochondria-dependent apoptosis pathways. Interestingly, our result also demonstrated that edaravone was able to up-regulate VMAT2 expression in N2a cells in a dose-dependent manner. Our findings enhance the understanding of the neuro-protective effects of edaravone in cell models and suggest that edaravone offers significant protection in a PD-related in vitro model.

Dopamine-mediated oxidation of methionine 127 in α-synuclein causes cytotoxicity and oligomerization of α-synuclein

Parkinson's disease (PD) is a neurodegenerative disorder characterized by the selective loss of dopaminergic neurons and the presence of Lewy bodies. Many recent studies focused on the interaction between α-synuclein (α-syn) and dopamine in the pathogenesis of PD, and fluorescent anisotropy suggested that the C-terminal region of α-syn may be a target for modification by dopamine. However, it is not well understood why PD-related pathogenesis occurs selectively in dopaminergic neurons. We investigated the interaction between dopamine and α-syn with regard to cytotoxicity. A soluble oligomer was formed by co-incubating α-syn and dopamine in vitro. To clarify the effect of dopamine on α-syn in cells, we generated PC12 cells expressing human α-syn, as well as the α-syn mutants, M116A, Y125D, M127A, S129A, and M116A/M127A, in a tetracycline-inducible manner (PC12-TetOFF-α-syn). Overexpression of wildtype α-syn in catecholaminergic PC12 cells decreased cell viability in long-term cultures, while a competitive inhibitor of tyrosine hydroxylase blocked this vulnerability, suggesting that α-syn-related cytotoxicity is associated with dopamine metabolism. The vulnerabilities of all mutant cell lines were lower than that of wildtype α-syn-expressing cells. Moreover, α-syn containing dopamine-mediated oxidized methionine (Met(O)) was detected in PC12-TetOFF-α-syn. Met(O) was lower in methionine mutant cells, especially in the M127A or M116A/M127A mutants, but also in the Y125D and S129A mutants. Co-incubation of dopamine and the ₁₂₅YEMPS₁₂₉ peptide enhanced the production of H₂O₂, which may oxidize methionine residues and convert them to Met(O). Y125- or S129-lacking peptides did not enhance the dopamine-related production of H₂O₂. Our results suggest that M127 is the major target for oxidative modification by dopamine, and that Y125 and S129 may act as enhancers of this modification. These results may describe a mechanism of dopaminergic neuron-specific toxicity of α-syn in the pathogenesis of PD.

Neurodegeneration as an RNA disorder

Neurodegenerative diseases constitute one of the single most important public health challenges of the coming decades, and yet we presently have only a limited understanding of the underlying genetic, cellular and molecular causes. As a result, no effective disease-modifying therapies are currently available, and no method exists to allow detection at early disease stages, and as a result diagnoses are only made decades after disease pathogenesis, by which time the majority of physical damage has already occurred. Since the sequencing of the human genome, we have come to appreciate that the transcriptional output of the human genome is extremely rich in non-protein coding RNAs (ncRNAs). This heterogeneous class of transcripts is widely expressed in the nervous system, and is likely to play many crucial roles in the development and functioning of this organ. Most exciting, evidence has recently been presented that ncRNAs play central, but hitherto unappreciated roles in neurodegenerative processes. Here, we review the diverse available evidence demonstrating involvement of ncRNAs in neurodegenerative diseases, and discuss their possible implications in the development of therapies and biomarkers for these conditions.

Oxidative stress in genetic mouse models of Parkinson's disease

There is extensive evidence in Parkinson's disease of a link between oxidative stress and some of the monogenically inherited Parkinson's disease-associated genes. This paper focuses on the importance of this link and potential impact on neuronal function. Basic mechanisms of oxidative stress, the cellular antioxidant machinery, and the main sources of cellular oxidative stress are reviewed. Moreover, attention is given to the complex interaction between oxidative stress and other prominent pathogenic pathways in Parkinson's disease, such as mitochondrial dysfunction and neuroinflammation. Furthermore, an overview of the existing genetic mouse models of Parkinson's disease is given and the evidence of oxidative stress in these models highlighted. Taken into consideration the importance of ageing and environmental factors as a risk for developing Parkinson's disease, gene-environment interactions in genetically engineered mouse models of Parkinson's disease are also discussed, highlighting the role of oxidative damage in the interplay between genetic makeup, environmental stress, and ageing in Parkinson's disease.

QTLs for murine red blood cell parameters in LG/J and SM/J F(2) and advanced intercross lines

Red blood cells are essential for oxygen transport and other physiologic processes. Red cell characteristics are typically determined by complete blood counts which measure parameters such as hemoglobin levels and mean corpuscular volumes; these parameters reflect the quality and quantity of red cells in the circulation at any particular moment. To identify the genetic determinants of red cell parameters, we performed genome-wide association analysis on LG/J×SM/J F2 and F34 advanced intercross lines using single nucleotide polymorphism genotyping and a novel algorithm for mapping in the combined populations. We identified significant quantitative trait loci for red cell parameters on chromosomes 6, 7, 8, 10, 12, and 17; our use of advanced intercross lines reduced the quantitative trait loci interval width from 1.6- to 9.4-fold. Using the genomic sequences of LG/J and SM/J mice, we identified nonsynonymous coding single nucleotide polymorphisms in candidate genes residing within quantitative trait loci and performed sequence alignments and molecular modeling to gauge the potential impact of amino acid substitutions. These results should aid in the identification of genes critical for red cell physiology and metabolism and demonstrate the utility of advanced intercross lines in uncovering genetic determinants of inherited traits.

The role of α-synuclein in neurodegeneration — An update

Genetic, neuropathological and biochemical evidence implicates α-synuclein, a 140 amino acid presynaptic neuronal protein, in the pathogenesis of Parkinson’s disease and other neurodegenerative disorders. The aggregated protein inclusions mainly containing aberrant α-synuclein are widely accepted as morphological hallmarks of α-synucleinopathies, but their composition and location vary between disorders along with neuronal networks affected. α-Synuclein exists physiologically in both soluble and membran-bound states, in unstructured and α-helical conformations, respectively, while posttranslational modifications due to proteostatic deficits are involved in β-pleated aggregation resulting in formation of typical inclusions. The physiological function of α-synuclein and its role linked to neurodegeneration, however, are incompletely understood. Soluble oligomeric, not fully fibrillar α-synuclein is thought to be neurotoxic, main targets might be the synapse, axons and glia. The effects of aberrant α-synuclein include alterations of calcium homeostasis, mitochondrial dysfunction, oxidative and nitric injuries, cytoskeletal effects, and neuroinflammation. Proteasomal dysfunction might be a common mechanism in the pathogenesis of neuronal degeneration in α-synucleinopathies. However, how α-synuclein induces neurodegeneration remains elusive as its physiological function. Genome wide association studies demonstrated the important role for genetic variants of the SNCA gene encoding α-synuclein in the etiology of Parkinson’s disease, possibly through effects on oxidation, mitochondria, autophagy, and lysosomal function. The neuropathology of synucleinopathies and the role of α-synuclein as a potential biomarker are briefly summarized. Although animal models provided new insights into the pathogenesis of Parkinson disease and multiple system atrophy, most of them do not adequately reproduce the cardinal features of these disorders. Emerging evidence, in addition to synergistic interactions of α-synuclein with various pathogenic proteins, suggests that prionlike induction and seeding of α-synuclein could lead to the spread of the pathology and disease progression. Intervention in the early aggregation pathway, aberrant cellular effects, or secretion of α-synuclein might be targets for neuroprotection and disease-modifying therapy.

Restriction of trophic factors and nutrients induces PARKIN expression

Parkinson’s disease (PD) is the most frequent neurodegenerative movement disorder and manifests at old age. While many details of its pathogenesis remain to be elucidated, in particular the protein and mitochondrial quality control during stress responses have been implicated in monogenic PD variants. Especially the mitochondrial kinase PINK1 and the ubiquitin ligase PARKIN are known to cooperate in autophagy after mitochondrial damage. As autophagy is also induced by loss of trophic signaling and PINK1 gene expression is modulated after deprivation of cytokines, we analyzed to what extent trophic signals and starvation stress regulate PINK1 and PARKIN expression. Time course experiments with serum deprivation and nutrient starvation of human SH-SY5Y neuroblastoma cells and primary mouse neurons demonstrated phasic induction of PINK1 transcript up to twofold and PARKIN transcript levels up to sixfold. The corresponding threefold starvation induction of PARKIN protein was limited by its translocation to lysosomes. Analysis of primary mouse cells from PINK1-knockout mice indicated that PARKIN induction and lysosomal translocation occurred independent of PINK1. Suppression of the PI3K-Akt-mTOR signaling by pharmacological agents modulated PARKIN expression accordingly. In conclusion, this expression survey demonstrates that PARKIN and PINK1 are coregulated during starvation and suggest a role of both PD genes in response to trophic signals and starvation stress.