Gene therapy for Parkinson's disease

Parkinson's disease (PD) is a debilitating neurodegenerative disorder arising from loss of dopaminergic neurons in the substantia nigra pars compacta and subsequent depletion of striatal dopamine levels, which results in distressing motor symptoms. The current standard pharmacological treatment for PD is direct replacement of dopamine by treatment with its precursor, levodopa (L-dopa). However, this does not significantly alter disease progression and might contribute to the ongoing pathology. Several features of PD make this disease one of the most promising targets for clinical gene therapy of any neurological disease. The confinement of the major pathology to a compact, localised neuronal population and the anatomy of the basal ganglia circuitry mean that global gene transfer is not required and there are well-defined sites for gene transfer. The multifactorial aetiology of idiopathic PD means that it is unlikely any single gene will cure the disease, and as a result at least three separate gene-transfer strategies are currently being pursued: transfer of genes for enzymes involved in dopamine production; transfer of genes for growth factors involved in dopaminergic cell survival and regeneration; and transfer of genes to reset neuronal circuitry by switching cellular phenotype. The merits of these strategies are discussed here, along with remaining hurdles that might impede transfer of gene therapy technology to the clinic as a treatment for PD.     

帕金森病裸DNA法基因治疗的实验研究

采用体内裸DNA基因治疗帕金森病(PD)取得显著疗效.将酪氨酸羟比酶(TH)基冈表达质粒与Lipofectin形成的复合物立体定位注射于PD模型鼠纹状体,显著改善了PD鼠的不对付旋转行为.免疫组化证实神经细胞表达了外源TH.     

Genetic dissection of familial Parkinson's disease

In the past few years, the genetic contribution to Parkinson's disease (PD) has gained major attention and has resulted in the identification of the first mutant gene, called α-synuclein, involved in the pathogenesis of autosomal-dominant PD. α-Synuclein is a major component of Lewy bodies, which are a neuropathological feature of PD. Furthermore, deletions in the parkin gene have been identified as the primary cause in rare forms of autosomal-recessive juvenile PD. The elucidation of polygenic changes in the dopamine pathway, mitochondrial dysfunction, and metabolism of xenobiotics is now technically possible by means of association and genotype studies. The increasing knowledge of the pathogenesis of PD at a molecular level will have important implications for the development of individual therapeutic strategies to prevent disease progression.     

多巴胺代谢系统基因多态性与帕金森病

帕金森病(PD)是人类常见的神经系统退行性疾病之一,其病因和发病机制尚不清楚,可能是遗传和环境等多种因素共同作用的结果。PD以运动减少、肌强直、静止性震颤及姿势障碍为主要症状,其病理特征主要是黑质多巴胺能神经元选择性死亡,多巴胺是纹状体的抑制性神经递质,而乙酰胆碱是兴奋性神经递质,两种神经递质在正常情况下是处于一种动态平衡状态,当多巴胺减少时,乙酰胆碱的作用相对增强,继而进入一种失衡状态,引起临床症状。因此,人们越来越重视多巴胺代谢酶基因研究。多巴胺代谢系统基因包括单胺氧化酶基因、儿茶酚氧位甲基转移酶、多巴胺突触前膜转运体、多巴胺受体基因、多巴胺β羟化酶、酪氨酸羟化酶。近年来,多巴胺代谢系统基因多态性与PD遗传易感性的相关性成为研究的热点,为明确PD的病因带来了希望。     

Analysis of single nucleotide polymorphism rs415430 in the WNT3 gene in the Russian population with the Parkinson disease

The Parkinson disease (PD) is the second most common progressive neurodegenerative disorder that arises due to degeneration of dopaminergic neurons. The causes of this disease are still unknown, but a number of genes involved in pathogenesis of familial and sporadic forms of PD has been identified. According to recent data of genome wide association studies (GWAS), single nucleotide polymorphisms (SNPs) in these genes (including MAPT locus) may play an important role in the development of PD. Therefore, we analyzed distribution of genotype frequencies of SNP rs415430 in the WNT3 gene in the Russian patients with sporadic PD and in the Russian population controls (OR = 0.84, Confidence Interval (95% CI) 0.58-1.23, p = 0.39). It was concluded that SNP rs415430 in the WNT3 gene was not associated with the risk of development of PD.     

Pathways to Parkinsonism

A novel gene for Parkinson's disease (PD), DJ-1, has been identified that encodes a multifunctional product with several known protein-protein interactions and effects on gene expression. Here, I outline how it is possible to construct hypotheses that place DJ-1 in different relationships to the other known PD genes, alpha-synuclein and parkin. The identification of multiple genetic causes will provide further impetus to describe the pathway leading to PD.     

Significant linkage of Parkinson disease to chromosome 2q36-37

Parkinson disease (PD) is the second most common neurodegenerative disorder, surpassed in frequency only by Alzheimer disease. Elsewhere we have reported linkage to chromosome 2q in a sample of sibling pairs with PD. We have now expanded our sample to include 150 families meeting our strictest diagnostic definition of verified PD. To further delineate the chromosome 2q linkage, we have performed analyses using only those pedigrees with the strongest family history of PD. Linkage analyses in this subset of 65 pedigrees generated a LOD score of 5.1, which was obtained using an autosomal dominant model of disease transmission. This result strongly suggests that variation in a gene on chromosome 2q36-37 contributes to PD susceptibility.     

Early exposure to paraquat sensitizes dopaminergic neurons to subsequent silencing of PINK1 gene expression in mice

Environmental exposure, genetic modification, and aging are considered risky for Parkinson's disease (PD). How these risk factors cooperate to induce progressive neurodegeneration in PD remains largely unknown. Paraquat is an herbicide commonly used for weed and grass control. Exposure to paraquat is associated with the increased incidence of PD. In contrast to familial PD, most sporadic PD cases do not have genetic mutation, but may suffer from partial dysfunction of neuron-protective genes as aging. Using conditional transgenic RNAi, we showed that temporal silencing of PINK1 expression in adult mice increased striatal dopamine, the phenotype that could not be induced by constitutive gene silencing. Moreover, early exposure to paraquat sensitized dopaminergic neurons to subsequent silencing of PINK1 gene expression, leading to a significant loss of dopaminergic neurons. Our findings suggest a novel pathogenesis of PD: exposure to environmental toxicants early in the life reduces the threshold of developing PD and partial dysfunction of neuron-protective genes later in the life initiates a process of progressive neurodegeneration to cross the reduced threshold of disease onset.     

Interaction between genes and environment in neurodegenerative diseases

Alzheimer's disease (AD) and Parkinson's disease (PD) are highly prevalent disorders that account for a large part of the global burden of neurodegenerative diseases. Most AD and PD cases occur sporadically and it is generally agreed that they could arise through interactions among genetic and environmental factors. Candidate genes involved in the metabolism of xenobiotics, neurodegeneration and functioning of dopaminergic neurons were found to be associated with PD. Some of these genes interact with environmental factors that could modify PD risk. Thus, we found that the inverse association between smoking and the risk of PD depended on a polymorphism of the iNOS (inducible NO synthase) gene. We also found that the cytochrome P450 2D6 gene could have a modifying effect on the risk of PD among persons exposed to pesticides. Both interactions have biological plausibility supported by laboratory studies and could contribute to better understand the aetiology of PD. A single susceptibility gene has been identified in sporadic AD. The epsilon4 allele of epsilon polymorphism of the apolipoprotein E gene (APOE) is strongly associated with AD, the risk of AD being multiplied by 5 in persons carrying two epsilon4 alleles. The mechanism of the association between APOE and AD is poorly understood. A few interactions between the epsilon polymorphism and possible risk factors for AD have been described. However, these interactions had no biological plausibility and were likely due to chance.     

Mendelian forms of Parkinson's disease

Over the last few years, genetic findings have changed our views on Parkinson's disease (PD), as mutations in a growing number of genes are found to cause monogenic forms of the disorder. Point mutations in the gene for α-synuclein, as well as duplications and triplications of the wild-type gene cause a dominant form of PD in rare families, pointing towards mishandling of this protein as a crucial step in the molecular pathogenesis of the disorder. Mutations in the gene for leucine-rich repeat kinase 2 (LRRK2) have recently been identified as a much more common cause for dominant PD, while mutations in the parkin gene, in DJ-1, PINK1 and ATP13A2 all cause autosomal-recessive parkinsonism of early onset. Mutations in recessive genes probably are pathogenic through loss-of-function mechanisms, suggesting that their wild-type products protect dopaminergic cells against a variety of insults. Evidence is emerging that at least some of these genes may play a direct role in the etiology of the common sporadic form of PD. Further, it is likely that the cellular pathways identified in rare monogenic variants of the disease also shed light on the molecular pathogenesis in typical sporadic PD.     

Analysis of the rs12720208 single-nucleotide polymorphism of the FGF20 gene in Russian patients with sporadic Parkinson’s disease

Parkinson??s disease (PD) is a multifactorial neurodegenerative disease whose pathogenesis involves a number of genes and environmental factors. The FGF20 gene encoding the fibroblast growth factor and paying an important role neuron proliferation and survival is one of candidate genes of PD. There is evidence that this gene is also involved in the control of ??-synuclein (SNCA) gene expression. The rs12720208 single-nucleotide polymorphism (SNP) in the FGF20 gene has been found to be associated with PD; it has been located to the 3??-UTR binding site for microRNA-433, which is involved in the control of FGF20 expression. Therefore, the frequency distribution of rs12720208 genotypes in the FGF20 gene has been analyzed in a sample of patients with sporadic PD and a control sample of the Russian population. The results have not shown any effect of rs12720208 in the FGF20 gene on the risk of PD in patients residing in Russia (OR = 0.95, the 95% confidence interval (CI) is 0.55?C1.63, p = 0.9).     

Neurochemical and Neurogenetic Correlates of Parkinson's Disease

Abstract: We discuss neurochemical and neurogenetic correlates of Parkinson's disease (PD) based on the recent progress in the study of its etiology and pathogenesis. Nigral degeneration with the presence of Lewy bodies in the remaining neurons is the pathologic hallmark of PD, and the resultant loss of striatal dopamine is responsible for most of the clinical manifestations. Although the primary cause is still unknown, mitochondrial respiratory failure and oxidative stress appear to be two major contributors to the nigral cell death. Many endogenous and exogenous compounds with structural similarity to MPTP have been postulated as potential neurotoxins inducing nigral cell death in PD, but there is little evidence of accumulation of such compounds in the nigra. Genetic influence has increasingly been recognized as an important risk factor for PD. In this respect, genetic linkage analysis and molecular cloning of the disease genes in familial parkinsonism are of utmost importance today. Recently, the disease gene for one of the autosomal dominant forms of familial PD was identified, and we cloned the gene for an autosomal recessive type of familial parkinsonism that had been mapped to the long arm of chromosome 6 by our group. Information obtained on familial parkinsonism will contribute to the studies on sporadic PD as well.     

Analysis of new lactotransferrin gene variants in a case–control study related to periodontal disease in dog

The molecular and genetic research has contributed to a better understanding of the periodontal disease (PD) in humans and has shown that many genes play a role in the predisposition and progression of this complex disease. Variations in human lactotransferrin (LTF) gene appear to affect anti-microbial functions of this molecule, influencing the PD susceptibility. PD is also a major health problem in small animal practice, being the most common inflammatory disease found in dogs. Nevertheless, the research in genetic predisposition to PD is an unexplored subject in this species. This work aims to contribute to the characterization of the genetic basis of canine PD. In order to identify genetic variations and verify its association with PD, was performed a molecular analysis of LTF gene in a case–control approach, including 40 dogs in the PD cases group and 50 dogs in the control group. In this study were detected and characterized eight new single nucleotide variations in the dog LTF gene. Genotype and allele frequencies of these variations showed no statistically significant differences between the control and PD cases groups. Our data do not give evidence for the contribution of these LTF variations to the genetic background of canine PD. Nevertheless, the sequence variant L/15_g.411C > T leads to an aminoacid change (Proline to Leucine) and was predicted to be possibly damaging to the LTF protein. Further investigations would be of extreme value to clarify the biological importance of these new findings.     

Analysis of mitochondrial targeting sequence and coding region polymorphisms of the manganese superoxide dismutase gene in German Parkinson disease patients

Two polymorphisms of the MnSOD gene, Ile58Thr and Ala9Val, have been associated with Parkinson disease (PD). The Ile58Thr amino acid exchange affects the stability at the tetrameric interface of the enzyme and reduces the enzymatic activity of MnSOD while the Ala/Val substitution at position -9 of the mitochondrial targeting sequence (MTS) may lead to misdirected intracellular trafficking. We have analyzed 63 German Caucasian PD patients for possible sequence variation in the MTS as well as in exon 3 of the MnSOD gene. All 63 PD patients analyzed exhibited a T at nucleotide position 5777 in exon 3 of the MnSOD gene corresponding to ATA, or Ile at the peptide level, and no other sequence variants were found. In addition, both alleles of the Ala9Val polymorphism in the MTS of MnSOD were equally distributed between German PD patients and controls excluding this gene variant as a risk factor for PD in Caucasian subjects.     

Progranulin Gene Delivery Protects Dopaminergic Neurons in a Mouse Model of Parkinson’s Disease

Parkinson’s disease (PD) is a progressive neurodegenerative disorder characterized by tremor, rigidity and akinesia/bradykinesia resulting from the progressive loss of nigrostriatal dopaminergic neurons. To date, only symptomatic treatment is available for PD patients, with no effective means of slowing or stopping the progression of the disease. Progranulin (PGRN) is a 593 amino acid multifunction protein that is widely distributed throughout the CNS, localized primarily in neurons and microglia. PGRN has been demonstrated to be a potent regulator of neuroinflammation and also acts as an autocrine neurotrophic factor, important for long-term neuronal survival. Thus, enhancing PGRN expression may strengthen the cells resistance to disease. In the present study, we have used the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) model of PD to investigate the possible use of PGRN gene delivery as a therapy for the prevention or treatment of PD. Viral vector delivery of the PGRN gene was an effective means of elevating PGRN expression in nigrostriatal neurons. When PGRN expression was elevated in the SN_C, nigrostriatal neurons were protected from MPTP toxicity in mice, along with a preservation of striatal dopamine content and turnover. Further, protection of nigrostriatal neurons by PGRN gene therapy was accompanied by reductions in markers of MPTP-induced inflammation and apoptosis as well as a complete preservation of locomotor function. We conclude that PGRN gene therapy may have beneficial effects in the treatment of PD.     

诱导多能干细胞在帕金森病治疗中的应用进展

帕金森病（Parkinson's disease, PD）是由于黑质中多巴胺能神经元（dopaminergic neurons, DAns）的病变导致多巴胺含量降低而引起的一种神经退行性疾病,其发病机制尚不明确,而且临床缺乏有效的早期诊断和治疗手段。诱导多能干细胞（induced pluripotent stem cells, iPSCs）的出现为神经系统疾病特别是神经退行性疾病的治疗带来了希望。基于iPSCs的细胞模型可以广泛开展PD发病机制的研究,同时以iPSCs来源的DAns、神经干细胞（neural stem cells, NSCs）等的细胞移植治疗,更是未来PD治疗最有希望的手段。从基于iPSCs的不同基因突变类型的细胞模型与不同分化程度的细胞移植治疗两个方面介绍诱导多能干细胞在PD研究中的进展,旨在分析诱导多能干细胞在帕金森病方面的应用及不足。     

The identification of dysfunctional crosstalk of pathways in Parkinson disease

Parkinson disease (PD) is the second most common neurodegenerative disorder after Alzheimer's disease, affecting 1–2% of the population over the age of 65. Both genetic and environmental factors trigger risks of and protection from PD. However, the molecular mechanism of PD is far from being clear. In this study, we downloaded the gene expression profile of PD from Gene Expression Omnibus and identified differentially expressed genes (DEGs) and dysfunctional pathways in PD patients compared with controls. To further understand how these pathways act together to account for the initiation of PD, we constructed a pathway crosstalk network by calculating the Jaccard index among pathways. A total of 873 DEGs and 16 dysfunctional pathways between PD patients and controls were identified. Through constructing a network of pathways, the relationships among PD pathways were visually presented by their interactions. Our results demonstrate the existence of crosstalk between different pathways in PD pathogenesis. These results not only may explain the causes of PD, but could also open the door to new therapeutic approaches for this disease.     

In search of genes involved in neurodegenerative disorders

Dissecting the genetics of Alzheimer's disease (AD) and Parkinson's disease (PD) has contributed significantly to our understanding of the pathogenesis of neurodegeneration in these two complex disorders. For AD, three highly penetrant genes (amyloid precursor protein (APP, PSEN1 and PSEN2) and one susceptibility gene (APOE) have been identified. For PD, seven genes (SNCA, Parkin, UCHL1, NR4A2, DJ1, PINK1 and LRRK2) have been found. These genes explain only a small proportion of AD and PD patients and are mostly associated with an early onset presentation of the disease. APOE remains the only common gene, which increases the risk of both rare early and late onset AD. The ongoing challenge is to unravel the genetics of the most frequent forms of these complex disorders. In the present paper, we briefly review the state of the art in the genetics of AD and PD. We also discuss the prospects of finding new genes associated with common forms of these diseases in light of two hypotheses concerning the genetic variation of complex diseases: common disease/common variants and common disease/rare variants.