泛酸激酶相关性神经变性疾病遗传学与临床研究进展

泛酸激酶相关性神经变性疾病是脑组织铁沉积性神经变性(NBIA,曾称为Hallervorden-Spatz综合征)疾病的主要发病类型之一,系由泛酸激酶2(PANK2)基因突变所导致的常染色体隐性遗传性疾病。PANK2基因突变可干扰PANK2蛋白表达水平和催化活性,以及线粒体靶蛋白的成熟与稳定性,引起神经元线粒体脂类代谢异常改变,导致脑组织铁沉积性神经变性疾病。本文对该病分子遗传学机制及其与临床表型和影像学特征相关的研究成果和进展进行概述。     

泛酸激酶相关性神经变性病的临床特征和分子机制

泛酸激酶相关性神经变性病( pantothenate kinase associated neurodegeneration,PKAN),又称脑内金属离子沉积性神经变性病1型,即通常所称的Hallervorden-Spatz综合征或苍白球黑质色素变性,是少见的常染色体隐性遗传性神经系统变性病.患病率(1～3)/100万.2001年Zhou等[1]报道了Hallervorden-Spatz综合征患者存在泛酸激酶2基因(pantothenate kinase 2 gene,PANK2)突变,提出了PKAN疾病命名,推动了金属离子沉积性神经变性病的研究进展.我们将PKAN的临床特征和分子机制综述如下.     

脑组织铁沉积性神经变性疾病的临床与基因学特点

脑组织铁沉积性神经变性（NBIA）疾病是一组以铁离子聚集于脑组织为特点的进行性锥体外系疾病,虽然其发病率尚无确切的统计学资料,但已知发病在种族人群、年龄、性别方面并无明显差异。     

P62蛋白在常见神经变性病中的表达观察

目的评价P62蛋白在临床常见神经变性病特征性病理改变中的表达变化,探讨其病理诊断意义。方法收集1994年6月至2017年10月经临床和病理明确诊断的神经变性病脑组织标本共11例,包括阿尔茨海默病5例(其中2例合并嗜银颗粒病)、帕金森病3例、进行性核上性麻痹2例、多系统萎缩1例;另以3例无神经变性病的脑组织标本为对照。分别进行HE、LFB及Gallyas-Braak银染,以及β-淀粉样蛋白、AT8、α-突触核蛋白和P62抗体免疫组织化学染色,显微镜下观察不同神经变性病的特征性病理改变和P62蛋白表达变化。结果阿尔茨海默病神经原纤维缠结、帕金森病路易小体和路易轴索、进行性核上性麻痹丛状星形细胞、嗜银颗粒病的嗜银颗粒,以及多系统萎缩少突胶质细胞内包涵体均表达P62蛋白,且形态特征与其特异性抗体染色结果相一致;另外,阿尔茨海默病神经炎性斑仅少量表达P62蛋白,而弥散斑表达阴性;淀粉样小体P62蛋白表达亦呈阳性;正常对照脑组织不表达P62蛋白。结论 P62蛋白在阿尔茨海默病、帕金森病、进行性核上性麻痹、多系统萎缩等疾病特征性病理改变和淀粉样小体中均表达阳性,且形态与各种神经变性病组织学及相应特异性蛋白表达结果一致,推荐P62抗体作为神经变性病的辅助病理诊断。     

丁酰胆碱酯酶在阿尔茨海默病发病机制中的作用

阿尔茨海默病是一种病因和发病机制尚未明确的神经变性病,其典型病理改变为β-淀粉样蛋白沉积形成的神经炎性斑(亦称老年斑)和tau蛋白异常聚集形成的神经原纤维缠结,常累及胆碱能系统,其中丁酰胆碱酯酶在阿尔茨海默病发病与进展过程中发挥重要作用。本文就丁酰胆碱酯酶在阿尔茨海默病发病机制中的作用进行简要综述。     

Creutzfeldt-Jakob病与睡眠障碍

Creutzfeldt-Jakob病系指朊病毒感染导致的致死性神经变性病,其神经细胞凋亡速度较其他神经变性病更迅速。睡眠障碍常见于慢性神经变性病,且可能早于疾病发生前数年出现。了解睡眠障碍与Creutzfeldt-Jakob病的关系,可以提高临床医师对睡眠障碍与其他常见神经变性病关系的理解。Creutzfeldt-Jakob病合并睡眠障碍较为常见,应定期筛查可能的Creutzfeldt-Jakob病患者睡眠状况,有助于疾病的诊断与治疗。     

微循环与神经变性病

神经变性病是神经系统的退行性疾病,病因不明,病程持续进展,且无特效的药物治疗。因此对其病因和机制的研究业已成为国际神经科学领域的研究热点。现有研究认为,缺血缺氧、炎性反应、免疫、血管病理等多种因素可引起微循环障碍,而微循环障碍参与神经元变性过程,甚至先于神经元的变性发生,本文就微循环障碍与神经变性病,特别是阿尔茨海默病和肌萎缩侧索硬化的相关机制进行综述,以期为治疗性研究提供线索。     

原发性家族性脑钙化研究进展

原发性家族性脑钙化是一组以双侧对称性基底节区及其他脑区钙化为影像学特点的神经变性病,可伴多种神经精神症状,具有高度临床和遗传异质性。目前已知的4种致病基因(SLC20A2、PDGFRB、PDGFB、XPR1)及其相关功能研究提示原发性家族性脑钙化可能与细胞内外无机磷转运障碍和血-脑屏障损害相关。本文拟对近年原发性家族性脑钙化诊断标准、分子遗传学机制、基因型与临床表型相关性、治疗等方面研究进展进行概述。     

蛋白质氧化与阿尔茨海默病

阿尔茨海默病（AD）是与老年相关的进展性神经变性疾病,主要分子病理学特征为脑内淀粉样蛋白（Aβ）沉积形成的老年斑和过度磷酸化tau蛋白所形成的神经纤维缠结.氧化应激是包括AD在内的神经变性病的一个重要发病机制.本文介绍了氧化应激后蛋白质发生改变的类型、AD进展期间脑内蛋白质的氧化、Aβ沉积和tau蛋白过度磷酸化的原因以及今后对AD进行预防与治疗的一些策略.     

α-synuclein基因突变在英国散发性帕金森病病人中的作用

特发性帕金森病是一种常见的神经系统变性病,具有特征性的神经病理改变,终身发病率达2％。与残存神经元中的Lewy体有关的神经变性改变集中在黑质、基底核、脑神经运动核、下丘脑、大脑皮层和自主神经系统。导致这一神经变性的发病机制尚不明了,但越来越多的证据表明遗传易感性起着一定作用。     

Update on neurodegeneration with brain iron accumulation

Neurodegeneration with brain iron accumulation (NBIA) defines a heterogeneous group of progressive neurodegenerative disorders characterized by excessive iron accumulation in the brain, particularly affecting the basal ganglia. In the recent years considerable development in the field of neurodegenerative disorders has been observed. Novel genetic methods such as autozygosity mapping have recently identified several genetic causes of NBIA. Our knowledge about clinical spectrum has broadened and we are now more aware of an overlap between the different NBIA disorders as well as with other diseases. Neuropathologic point of view has also been changed. It has been postulated that pantothenate kinase-associated neurodegeneration (PKAN) is not synucleinopathy. However, exact pathologic mechanism of NBIA remains unknown. The situation implicates a development of new therapies, which still are symptomatic and often unsatisfactory. In the present review, some of the main clinical presentations, investigational findings and therapeutic results of the different NBIA disorders will be presented.     

Syndromes of neurodegeneration with brain iron accumulation (NBIA): an update on clinical presentations, histological and genetic underpinnings, and treatment considerations

In recent years, understanding of the syndromes of neurodegeneration with brain iron accumulation (NBIA) has grown considerably. In addition to the core syndromes of pantothenate kinsase-associated neurodegeneration (PKAN, NBIA1) and PLA2G6-associated neurodegeneration (PLAN, NBIA2), several other genetic causes have been identified. The acknowledged clinical spectrum has broadened, age-dependent presentations have been recognized, and we are becoming aware of overlap between the different NBIA disorders as well as with other diseases. Autopsy examination of genetically confirmed cases has demonstrated Lewy bodies and/or tangles in some subforms, bridging the gap to more common neurodegenerative disorders such as Parkinson's disease. NBIA genes map into related pathways, the understanding of which is important as we move toward mechanistic therapies. Our aim in this review is to provide an overview of not only the historical developments, clinical features, investigational findings, and therapeutic results but also the genetic and molecular underpinnings of the NBIA syndromes.     

Clinical heterogeneity of neurodegeneration with brain iron accumulation (Hallervorden-Spatz syndrome) and pantothenate kinase-associated neurodegeneration.

Hallervorden Spatz syndrome (HSS), also referred to as neurodegeneration with brain iron accumulation (NBIA), is a rare inherited neurodegenerative disorder with childhood, adolescent, or adult onset. Patients with HSS/NBIA have a combination of motor symptoms in the form of dystonia, parkinsonism, choreoathetosis, corticospinal tract involvement, optic atrophy, pigmentary retinopathy, and cognitive impairment. After the recent identification of mutations in the PANK2 gene on chromosome 20p12.3-p13 in some patients with the HSS/NBIA phenotype, the term pantothenate kinase-associated neurodegeneration (PKAN) has been proposed for this group of disorders. To characterize clinically and genetically HSS/NBIA, we reviewed 34 affected individuals from 10 different families, who satisfied the inclusion criteria for NBIA. Relatives of patients who had clinical, magnetic resonance imaging (MRI), or pathological findings of NBIA were included in the study. Four patients were found to have mutations in the pantothenate kinase 2 (PANK2) gene. We compared the clinical features and MRI findings of those with and without PANK2 mutations. The presence of mutation in the PANK2 gene is associated with younger age at onset and a higher frequency of dystonia, dysarthria, intellectual impairment, and gait disturbance. Parkinsonism is seen predominantly in adult-onset patients whereas dystonia seems more frequent in the earlier-onset cases. The phenotypic heterogeneity observed in our patients supports the notion of genetic heterogeneity in the HSS/NBIA syndrome.     

Mitochondrial protein associated neurodegeneration – Case report

Neurodegeneration with brain iron accumulation (NBIA) is a group of genetic disorders with a progressive extrapyramidal syndrome and excessive iron deposition in the brain, particularly in the globus pallidus and substantia nigra. We present the case of a 31-year-old woman with mitochondrial protein associated neurodegeneration (MPAN). MPAN is a new identified subtype of NBIA, caused by mutations in C19orf12 gene. The typical features are speech and gait disturbances, dystonia, parkinsonism and pyramidal signs. Common are psychiatric symptoms such as impulsive or compulsive behavior, depression and emotional lability. In almost all cases, the optic atrophy has been noted and about 50% of cases have had a motor axonal neuropathy. In the MRI on T2- and T2*-weighted images, there are hypointense lesions in the globus palidus and substantia nigra corresponding to iron accumulation.     

Review: Insights into molecular mechanisms of disease in neurodegeneration with brain iron accumulation: unifying theories

Neurodegeneration with brain iron accumulation (NBIA) is a group of disorders characterized by dystonia, parkinsonism and spasticity. Iron accumulates in the basal ganglia and may be accompanied by Lewy bodies, axonal swellings and hyperphosphorylated tau depending on NBIA subtype. Mutations in 10 genes have been associated with NBIA that include Ceruloplasmin (Cp) and ferritin light chain (FTL), both directly involved in iron homeostasis, as well as Pantothenate Kinase 2 (PANK2), Phospholipase A2 group 6 (PLA2G6), Fatty acid hydroxylase 2 (FA2H), Coenzyme A synthase (COASY), C19orf12, WDR45 and DCAF17 (C2orf37). These genes are involved in seemingly unrelated cellular pathways, such as lipid metabolism, Coenzyme A synthesis and autophagy. A greater understanding of the cellular pathways that link these genes and the disease mechanisms leading to iron dyshomeostasis is needed. Additionally, the major overlap seen between NBIA and more common neurodegenerative diseases may highlight conserved disease processes. In this review, we will discuss clinical and pathological findings for each NBIA‐related gene, discuss proposed disease mechanisms such as mitochondrial health, oxidative damage, autophagy/mitophagy and iron homeostasis, and speculate the potential overlap between NBIA subtypes.     

C19orf12 mutations in neurodegeneration with brain iron accumulation mimicking juvenile amyotrophic lateral sclerosis

Mutations in C19orf12 have been recently identified as the molecular genetic cause of a subtype of neurodegeneration with brain iron accumulation (NBIA). Given the mitochondrial localization of the gene product the new NBIA subtype was designated mitochondrial membrane protein-associated neurodegeneration. Frequent features in the patients described so far included extrapyramidal signs and pyramidal tract involvement. Here, we report three C19orf12-mutant patients from two families presenting with predominant upper and lower motor neuron dysfunction mimicking amyotrophic lateral sclerosis with juvenile onset. While extrapyramidal signs were absent, all patients showed neuropsychological abnormalities with disinhibited or impulsive behavior. Optic atrophy was present in the simplex case. T2-weighted cranial MRI showed hypointensities suggestive of iron accumulation in the globi pallidi and the midbrain in all patients. Sequence analysis of C19orf12 revealed a novel mutation, p.Gly66del, compound heterozygous with known mutations in all patients. These patients highlight that C19orf12 defects should be considered as a differential diagnosis in patients with juvenile onset motor neuron diseases. Patients have to be examined carefully for neuropsychological abnormalities, optic neuropathy, and signs of brain iron accumulation in MRI.     

Childhood disorders of neurodegeneration with brain iron accumulation (NBIA)

Neurodegeneration with brain iron accumulation (NBIA) comprises a heterogeneous group of progressive complex motor disorders characterized by the presence of high brain iron, particularly within the basal ganglia. A number of autosomal recessive NBIA syndromes can present in childhood, most commonly pantothenate kinase-associated neurodegeneration (PKAN; due to mutations in the PANK2 gene) and phospholipase A2 group 6-associated neurodegeneration (PLAN; associated with genetic defects in PLA2G6). Mutations in the genes that cause these two neuroaxonal dystrophies are thought to disrupt the normal cellular functions of phospholipid remodelling and fatty acid metabolism. A significant proportion of children with an NBIA phenotype have no genetic diagnosis and there are, no doubt, additional as yet undiscovered genes that account for a number of these cases. NBIA disorders can be diagnostically challenging as there is often phenotypic overlap between the different disease entities. This review aims to define the clinical, radiological, and genetic features of such disorders, providing the clinician with a stepwise approach to appropriate neurological and genetic investigation, as well as a clinical management strategy for these neurodegenerative syndromes.     

Syndromes of neurodegeneration with brain iron accumulation

In parallel to recent developments of genetic techniques, understanding of the syndromes of neurodegeneration with brain iron accumulation has grown considerably. The acknowledged clinical spectrum continues to broaden, with age-dependent presentations being recognized. Postmortem brain examination of genetically confirmed cases has demonstrated Lewy bodies and/or tangles in some forms, bridging the gap to more common neurodegenerative disorders, including Parkinson disease. In this review, the major forms of neurodegeneration with brain iron accumulation (NBIA) are summarized, concentrating on clinical findings and molecular insights. In addition to pantothenate kinase-associated neurodegeneration (PKAN) and phospholipase A2-associated neurodegeneration (PLAN), fatty acid hydroxylase-associated neurodegeneration (FAHN) NBIA, mitochondrial protein-associated neurodegeneration, Kufor-Rakeb disease, aceruloplasminemia, neuroferritinopathy, and SENDA syndrome (static encephalopathy of childhood with neurodegeneration in adulthood) are discussed.     

R632W mutation in PLA2G6 segregates with dystonia-parkinsonism in a consanguineous Iranian family

Background:  PLA2G6 mutations are known to be responsible for infantile neuroaxonal dystrophy (INAD) and neurodegeneration with brain iron accumulation (NBIA). In addition, novel mutations in PLA2G6 have recently been associated with dystonia-parkinsonism in two unrelated consanguineous families.
Methods:  Direct sequencing analysis of the PLA2G6 gene.
Results:  Here, we report the segregation of R632W with disease in an Iranian consanguineous dystonia-parkinsonism pedigree. The identical mutation was previously observed in a patient affected with NBIA.
Conclusion:  We conclude that different and even identical PLA2G6 mutations may cause neurodegenerative diseases with heterogeneous clinical manifestations, including INAD, NBIA and dystonia-parkinsonism.     

Therapeutic advances in neurodegeneration with brain iron accumulation

Neurodegeneration with brain iron accumulation (NBIA) includes a heterogeneous group of genetically defined disorders characterized by progressive extrapyramidal deterioration and iron accumulation in the basal ganglia. Current medical options for these disorders remain largely unsatisfactory and do not prevent the disease from progressing to a severe and disabling state. In select cases, surgical techniques, such as deep brain stimulation, may be effective in ameliorating some of the symptoms of the disease. The availability of chelating agents with specific properties that have been demonstrated to be effective in other disorders with regional iron accumulation as well as magnetic resonance imaging techniques that allow for quantitative assessment of iron have stimulated interest in the use of chelating agents in NBIA. This review aims to describe the role of surgical therapies in NBIA, discuss the use of chelating agents in NBIA, and presents new therapeutic approaches under consideration.