多聚谷氨酰胺延伸蛋白募集细胞内转录因子及对基因转录调控的影响

多聚谷氨酰胺（polyglutamine,PolyQ）疾病是由特定基因序列中CAG三核苷酸的不稳定重复扩增所引发的一类神经退行性疾病。至今已发现9种类型的PolyQ疾病,其中多数疾病的致病蛋白质在转录调控中发挥着重要的病理作用。PolyQ蛋白中谷氨酰胺的异常重复延伸会引发蛋白质错误折叠并在细胞中积聚形成包涵体。积聚的蛋白质可通过自身结构域、泛素修饰和RNA等介导的相互作用,有效地募集细胞内的转录因子、泛素接头或受体蛋白,以及分子伴侣等组分到包涵体中。这些组分在细胞中的可溶性比例减少,使得机体内的转录调控系统功能受损,造成转录失调从而诱发疾病。因此,研究异常延伸的PolyQ蛋白对细胞内转录因子及其他组分的募集作用,可在分子水平上解释神经退行性疾病的发病机制,从而为临床应用提供潜在的预防和治疗方法。     

多聚蛋白聚糖酶与骨关节疾病

多聚蛋白聚糖酶是ADAMTS家族中的一员,受多种细胞因子的调节。它可以降解多聚蛋白聚糖核心蛋白上至少五种不同的位点,使多聚蛋白聚糖降解造成关节软骨变性坏死。关节组织中多聚蛋白聚糖酶及其抑制剂的数量保持着动态平衡,从而维持关节软骨的正常代谢,一旦失衡就会产生病理性损伤。该从多聚蛋白聚糖酶的结构、活化过程、调节因素以及与其他相关生物大分子的关系多个角度阐述了多聚蛋白聚糖酶研究的进展及其与骨关节疾病的关系。     

老年性阿兹海默症发病机制与其果蝇模型

衰老机理的研究是揭示衰老的本质和防治老年性疾病的一个重要环节,同时也为抗衰老提供理论依据.诸多研究表明,阿兹海默症（Alzheimer’s disease,AD）等神经退行性疾病与衰老密切相关.在老年性AD病研究中,果蝇是一种通常被用于研究其发病机理与治疗方法的重要模型.本文就AD病的发病机制、与衰老相关通路的联系、以及果蝇模型在AD病中的研究进展进行了综述.为研究老年性AD病的机理和治疗提供参考.     

多聚ADP-核糖聚合酶与帕金森病

多聚ADP-核糖聚合酶(PARP)可以被DNA损伤断裂激活,使多种核蛋白发生聚ADP核糖化,促DNA的修复。然而,若PARP过度活化则将耗竭细胞内NAD 和能量而导致细胞凋亡和坏死。PARP的过度活化是帕金森病发病的重要危险因素,开发PARP抑制剂,将为临床治疗帕金森病提供新的希望。     

生命科学与人类疾病研究的重要模型——果蝇

黑腹果蝇(Drosophilamelanogaster)是生物学研究中最重要的模式生物之一,它在遗传的染色体理论建立中起到非常重要的作用。由于果蝇自身独特的优势,20世纪70年代以来,它又在发育生物学、神经科学、人类疾病研究等领域得到广泛应用,作出许多新的重要贡献。果蝇在神经退行性疾病研究中是非常有用的模型。可以预期,随着研究手段的丰富及科学的发展,果蝇将作为一种理想的模式生物在生物医学中发挥更大的作用。     

以果蝇模型研究人类神经退行性疾病

人类神经退行性疾病是一类以神经元退行性病变导致个体行为异常乃至死亡为主要特征的疾病.果蝇以其独特的分子遗传学优势成为研究人类神经退行性疾病的理想模型.通过对果蝇模型的研究不仅可以揭示神经退行性疾病发生的细胞分子通路,还可以研究对疾病有调控作用的基因及其表达产物,寻找可能的药物作用靶点并进行药物筛选,为防治人类神经退行性疾病提供新的方法和有效的药物.     

多聚唾液酸与多聚唾液酸转移酶

多聚唾液酸（PSA）是一种在神经细胞黏附分子（neural cell adhesion molecule,NCAM）上表达的唾液酸聚合物,在神经发育过程中起重要作用.PSA的聚合程度会影响PSA-NCAM的功能.多聚唾液酸酶主要用于合成PSA-NCAM,两种高度同源的多聚唾液酸转移酶ST8SiaⅡ和ST8SiaⅣ都属于唾液酸转移酶家族.多聚唾液酸转移酶中NCAM的识别域和多聚唾液酸化域是截然不同的,且一些异构酶在NCAM多聚唾液酸化中起明显的负作用.多聚唾液酸酶与很多疾病都有关系,以多聚唾液酸转移酶为标靶设计的药物也将成为神经系统及肿瘤治疗的新型药物.     

前体mRNA的选择性多聚腺苷酸化与人类疾病

真核细胞的前体mRNA必须经过复杂的加工过程才能成熟,包括5’端加帽、剪接和3’端加工,其中3’加工包括3’端的切割和多聚腺苷酸化.该过程由前体mRNA上的顺式作用元件以及多个蛋白质因子控制.组成哺乳动物前体mRNA3’端加工机器的核心蛋白质复合体有切割和多聚腺苷酸化特异性因子、切割刺激因子、切割因子Ⅰ和切割因子Ⅱ.其他因子包括poly(A)聚合酶、poly(A)结合蛋白、偶对蛋白(symplekin)等.哺乳动物基因通常含有多个ploy(A)位点,选择性多聚腺苷酸化不仅可产生具有不同长度3’UTR的mRNA异构体,还可能改变基因的CDS区.作为真核生物基因表达调控的关键机制,选择性多聚腺苷酸化在细胞生长、增殖和分化中起着重要作用.本文综述了哺乳动物前体mRNA的3’端加工过程,3’端加工机器的组成及功能,探讨了选择性多聚腺苷酸化在多种人类疾病中的作用机制,以期为读者带来一些新的见解.     

人源Tau蛋白截短片段转基因果蝇模型的建立

人Tau蛋白是一种主要的细胞骨架蛋白,由Tau蛋白组成的神经纤维缠结是阿尔茨海默病的两大病理特征之一,C末端缺失的Tau已经证实是神经纤维缠结的组份之一,体内体外实验已经证实,Tau蛋白可以是多种蛋白酶的水解底物。但是,Tau蛋白水解产生的截短片段在阿尔茨海默病中的作用目前还不清楚。为了能够在在体水平研究Tau蛋白截短片段的毒性机制,将Tau蛋白截短成不同的截短片段:Tau1-44、Tau45-441、Tau45-230、Tau231-441。利用显微注射的方法构建Tau基因截短片段的转基因果蝇,并利用果蝇中的UAS/GAL4系统驱动截短的Tau蛋白片段在果蝇的眼睛中异位表达,该实验结果发现在果蝇眼睛中过表达Tau蛋白截短片段并没有对果蝇眼睛的发育造成明显的毒性,从而推断Tau蛋白水解是机体的一种自我保护机制。     

具有脂肪代谢功能的果蝇细胞

果蝇与人类有很多共同基因,实践证明它们对了解几种人类疾病来说很有用,但它们的脂肪代谢机制一直是个谜,这限制了果蝇（及其很多遗传工具）在肝病和肥胖研究中的应用。所以关于果蝇体内也存在具有脂肪代谢功能的细胞、与人类肝脏中同样功能的细胞类似的发现,可以说是一项重要进展。这些细胞是绛细胞（oenocyte）,首次于140多年前发现于昆虫,但以前未发现其有某种特定功能。     

Mouse Models of Polyglutamine Diseases: Review and Data Table. Part I

Polyglutamine (polyQ) disorders share many similarities, such as a common mutation type in unrelated human causative genes, neurological character, and certain aspects of pathogenesis, including morphological and physiological neuronal alterations. The similarities in pathogenesis have been confirmed by findings that some experimental in vivo therapy approaches are effective in multiple models of polyQ disorders. Additionally, mouse models of polyQ diseases are often highly similar between diseases with respect to behavior and the features of the disease. The common features shared by polyQ mouse models may facilitate the investigation of polyQ disorders and may help researchers explore the mechanisms of these diseases in a broader context. To provide this context and to promote the understanding of polyQ disorders, we have collected and analyzed research data about the characterization and treatment of mouse models of polyQ diseases and organized them into two complementary Excel data tables. The data table that is presented in this review (Part I) covers the behavioral, molecular, cellular, and anatomic characteristics of polyQ mice and contains the most current knowledge about polyQ mouse models. The structure of this data table is designed in such a way that it can be filtered to allow for the immediate retrieval of the data corresponding to a single mouse model or to compare the shared and unique aspects of many polyQ models. The second data table, which is presented in another publication (Part II), covers therapeutic research in mouse models by summarizing all of the therapeutic strategies employed in the treatment of polyQ disorders, phenotypes that are used to examine the effects of the therapy, and therapeutic outcomes.     

Transgenic Rabbit Models for Studying Human Cardiovascular Diseases

Cardiovascular diseases involve the heart or blood vessels and remain a leading cause of morbidity and mortality in developed countries. A variety of animal models have been used to study cardiovascular diseases and have contributed to our understanding of their pathophysiology and treatment. However, mutations or abnormal expression of specific genes play important roles in the pathophysiology of some heart diseases, for which a closely similar animal model often is not naturally available. With the advent of techniques for specific genomic modification, several transgenic and knockout mouse models have been developed for cardiovascular conditions that result from spontaneous mutations. However, mouse and human heart show marked electrophysiologic differences. In addition, cardiac studies in mouse models are extremely difficult because of their small heart size and fast heart rate. Therefore, larger genetically engineered animal models are needed to overcome the limitations of the mouse models. This review summarizes the transgenic rabbit models that have been developed to study cardiovascular diseases.Abbreviations: APD, action potential duration; apo, apolipoprotein; LCAT, lecithin-cholesterol acyltransferase; LPL, lipoprotein lipase; LQT, long QT; MHC, myosin heavy chain; MMP, matrix metalloproteinaseSince the generation of the first transgenic rabbit was reported in 1985,^25,64 transgenic rabbit lines have been established and used as animal models for a variety of human diseases, especially cardiovascular diseases. Although transgenic and knockout mice are predominantly used as models for many human diseases, the causative mutations of some human diseases do not lead to corresponding pathologic changes in mice.⁷ In addition, whereas the major myosin heavy chain (MHC) in rodents is α-MHC, β-MHC is predominantly expressed in larger mammals, including rabbits and humans.^15,43 Moreover, rats and mice are considered inappropriate for modeling cardiac ion channel disorders such as long QT (LQT) syndrome because the ionic mechanisms of repolarization in adult rats and mice differ from those in larger species, including humans.⁵² In addition, various techniques—such as those for studies of the LQT syndrome and hypertrophic cardiomyopathy—are difficult to apply to mice due to their small size and phylogenetic features.^10,40,48,52 Alternatively, because of their intermediate size between rodents and farm animals, rabbits (Oryctolagus cuniculus) are well-suited to various physiologic manipulations; these attributes have made rabbits appealing models of diverse human diseases. Since the generation of transgenic rabbits that overexpressed hepatic lipase,²¹ transgenic rabbits have often been generated for use as models of cardiovascular diseases, including atherosclerosis, hypertrophic cardiomyopathy, and LQT syndrome. The current review focuses on recent publications involving transgenic rabbit models of human cardiovascular diseases.     

Mouse Models of Polyglutamine Diseases in Therapeutic Approaches: Review and Data Table. Part II

Mouse models of human diseases are created both to understand the pathogenesis of the disorders and to find successful therapies for them. This work is the second part in a series of reviews of mouse models of polyglutamine (polyQ) hereditary disorders and focuses on in vivo experimental therapeutic approaches. Like part I of the polyQ mouse model review, this work is supplemented with a table that contains data from experimental studies of therapeutic approaches in polyQ mouse models. The aim of this review was to characterize the benefits and outcomes of various therapeutic strategies in mouse models. We examine whether the therapeutic strategies are specific to a single disease or are applicable to more than one polyQ disorder in mouse models. In addition, we discuss the suitability of mouse models in therapeutic approaches. Although the majority of therapeutic studies were performed in mouse models of Huntington disease, similar strategies were also used in other disease models.     

In Vivo NMR Studies of Neurodegenerative Diseases in Transgenic and Rodent Models

In vivo magnetic resonance spectroscopy (MRS) and magnetic resonance imaging (MRI) provide unique quality to attain neurochemical, physiological, anatomical, and functional information noninvasively. These techniques have been increasingly applied to biomedical research and clinical usage in diagnosis and prognosis of diseases. The ability of MRS to detect early yet subtle changes of neurochemicals in vivo permits the use of this technology for the study of cerebral metabolism in physiological and pathological conditions. Recent advances in MR technology have further extended its use to assess the etiology and progression of neurodegeneration. This review focuses on the current technical advances and the applications of MRS and MRI in the study of neurodegenerative disease animal models including amyotrophic lateral sclerosis, Alzheimer's, Huntington's, and Parkinson's diseases. Enhanced MR measurable neurochemical parameters in vivo are described in regard to their importance in neurodegenerative disorders and their investigation into the metabolic alterations accompanying the pathogenesis of neurodegeneration.     

Role of Ubiquitin Protein Ligases in the Pathogenesis of Polyglutamine Diseases

The accumulation of intracellular protein deposits as inclusion bodies is the common pathological hallmark of most age related neurodegenerative disorders including polyglutamine diseases. Appearances of aggregates of the misfolded mutant disease proteins suggest that the cells are unable to efficiently degrade them, and failure of clearance leads to the severe disturbances of the cellular quality control system. The quality control ubiquitin ligases are now increasingly implicated in the biology of polyglutamine diseases, Parkinson’s diseases, Amyotrophic lateral sclerosis and Alzheimer’s disease. Here we review the recent studies that have revealed a critical role of E3 ubiquitin ligases in understanding the pathogenesis of polyglutamine diseases.     

Polyglutamine genes interact to modulate the severity and progression of neurodegeneration in Drosophila

The expansion of polyglutamine tracts in a variety of proteins causes devastating, dominantly inherited neurodegenerative diseases, including six forms of spinal cerebellar ataxia (SCA). Although a polyglutamine expansion encoded in a single allele of each of the responsible genes is sufficient for the onset of each disease, clinical observations suggest that interactions between these genes may affect disease progression. In a screen for modifiers of neurodegeneration due to SCA3 in Drosophila, we isolated atx2, the fly ortholog of the human gene that causes a related ataxia, SCA2. We show that the normal activity of Ataxin-2 (Atx2) is critical for SCA3 degeneration and that Atx2 activity hastens the onset of nuclear inclusions associated with SCA3. These activities depend on a conserved protein interaction domain of Atx2, the PAM2 motif, which mediates binding of cytoplasmic poly(A)-binding protein (PABP). We show here that PABP also influences SCA3-associated neurodegeneration. These studies indicate that the toxicity of one polyglutamine disease protein can be dramatically modulated by the normal activity of another. We propose that functional links between these genes are critical to disease severity and progression, such that therapeutics for one disease may be applicable to others.     

Expression of Expanded Polyglutamine Protein Induces Behavioral Changes in Drosophila (Polyglutamine-Induced Changes in Drosophila)

Spinocerebellar ataxia type-3 or Machado-Joseph disease (SCA3/MJD) is an autosomal dominant neurodegenerative disease caused by triplet nucleotide expansion. The expansion of the polyglutamine tract near the C terminus of the MJD1 gene product, ataxin-3, above a threshold of 40 glutamine repeats causes neuronal loss and degeneration. The expanded ataxin-3 forms aggregates, and nuclear inclusions, within neurons, possibly due to the misfolding of mutant proteins. Here we report upon the behavioral test changes related to truncated and expanded forms of MJD protein (MJDtr) in Drosophila, and show that expanded MJDtr, when expressed in the nervous system, causes characteristic locomotor dysfunction and anosmia. This phenomenon has not been previously reported in humans or in transgenic Drosophila models. In addition, the in vivo expression of the antiapoptotic gene bcl-2 showed no evidence of ameliorating the deleterious effect of MJDtr-Q78s, either in the eye or in the nervous system. The study shows that such Drosophila transgenic models express olfactory dysfunction and ataxic behavior as observed in human patients.