Defining the impact of Frataxin point mutations on Friedreich's ataxia pathogenesis

确定 Frataxin 点突变对 Friedreich 共济失调发病机制的影响

• 批准号: 10591555
• 负责人: Marek Napierala
• 金额: $ 41万
• 依托单位: UT SOUTHWESTERN MEDICAL CENTER
• 依托单位国家: 美国
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-03-01 至 2026-02-28
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10591555
• 关键词: Address; Affect; Afferent Neurons; Alleles; Amino Acids; Anabolism; Ataxia; Axonal Transport; Binding; Biochemical; Biophysics; Cell model; Cell physiology; Cells; Characteristics; Clinical; Compensation; Complex; Data; Disease; Disease Progression; Electron Microscopy; Enzymes; Exhibits; Friedreich Ataxia; Genes; Genotype; Glycine; Hereditary Spastic Paraplegia; Heterozygote; Impairment; In Vitro; Introns; Iron; Knowledge; Link; Lower Extremity; Mediating; Missense Mutation; Mitochondria; Mitochondrial Matrix; Mitochondrial Proteins; Modeling; Molecular; Molecular Chaperones; Molecular Sieve Chromatography; Mutation; NMR Spectroscopy; Neurodegenerative Disorders; Neuronal Differentiation; Neurons; Nonsense Mutation; Pathogenesis; Pathogenicity; Pathologic; Pathway interactions; Patients; Peptide Hydrolases; Phenotype; Point Mutation; Positioning Attribute; Production; Property; Protein Isoforms; Proteins; Reagent; Respiration; Sampling; Sensory; Severities; Speech; Sulfur; Symptoms; Testing; Therapeutic; Translating; Trinucleotide Repeats; Upper Extremity; Valine; Work; autosome; axonal degeneration; design; experience; experimental study; frataxin; induced pluripotent stem cell; lipid metabolism; mouse model; multiple myeloma M Protein; mutant; novel; patient subsets; preservation; response; spasticity; therapy development

Friedreich’s ataxia (FRDA) is an autosomal recessive neurodegenerative disease caused by reduced expression of the mitochondrial protein frataxin (FXN). Frataxin is translated as a 210 amino acid (aa) precursor (FXN-P) that is imported into the mitochondrial matrix where it undergoes sequential cleavage steps, producing a 168 aa intermediate (FXN-I) and the mature isoform of 129 aa (FXN-M). Frataxin participates in iron-sulfur cluster (ISC) biosynthesis in the mitochondria, and many of the overt FRDA phenotypes result from deficient activity of ISC- containing enzymes. Currently, there is no cure for this debilitating disease. Most FRDA patients are homozygous for large expansions of GAA triplet repeat sequences in intron 1 of the FXN gene, while a subset of patients are compound heterozygotes with an expanded GAA repeat tract in one FXN allele and a missense or nonsense mutation in the other. Homozygous and compound heterozygous mutant genotypes both result in reduced levels of FXN-M protein when compared with healthy controls. The most prevalent missense mutation changes a glycine to valine at position 130 (G130V). FRDA G130V patients exhibit different clinical features than patients harboring homozygous GAA expansions, including lower limb spasticity rather than ataxia, preserved sensory responses, spared speech and upper limb functions, and slower disease progression. Paradoxically, substantially less FXN-M protein is detectable in G130V patient samples than in patient samples harboring two expanded alleles. Our preliminary data revealed that normal mitochondrial maturation processing of the FXN protein is perturbed by the G130V mutation, suggesting functional importance of an intermediate isoform (G130V-I). We hypothesize that the G130V mutation impairs FXN mitochondrial maturation processing and/or destabilizes the mature isoform. The unprocessed FXN-G130V-I isoform is functional and partially compensates for the substantial reduction of FXN-M, thus slowing disease progression and contributing to the distinct symptoms of FRDA G130V patients. To address these hypotheses, we will use novel cellular and mouse models of FRDA G130V. First, we will define the structural and functional properties of the FXN-G130V-I isoform to test whether this mutation confers a change of function that contributes to the atypical clinical presentation of FRDA G130V patients. Subsequently, we will determine mechanisms governing steady state levels and maturation processing of FXN-G130V in iPSC-derived cortical and sensory neurons. Finally, using FRDA patient-derived neuronal models as well as our novel Fxn G127V mouse model, we will define molecular mechanisms underlying the unique clinical presentation of FRDA G130V patients. Results of the proposed studies will have a broad impact on therapy development for all FRDA patients.

Friedreich‘s共济失调(FRDA)是一种常染色体隐性遗传性神经退行性疾病，由表达减少引起 线粒体蛋白Frataxin(FXN)。Frataxin被翻译为210个氨基酸(AA)前体(FXN-P) 它被输入到线粒体基质中，在那里经历连续的切割步骤，产生168个氨基酸 中间型(FXN-I)和成熟亚型129 AA(FXN-M)。Frataxin参与铁-硫簇(ISC) 线粒体中的生物合成，许多明显的FRDA表型是由于ISC-1活性不足造成的。 含有酶的。目前，这种令人衰弱的疾病还没有治愈方法。大多数FRDA患者都是 FXN基因内含子1的GAA三联体重复序列的大规模扩张是纯合的，而一个子集 的患者是复合杂合子，在一个FXN等位基因中有一个扩展的GAA重复序列和错义 或者是另一个基因的无谓突变。纯合子和复合杂合子突变基因型都会导致 与健康对照组相比，FXN-M蛋白水平降低。最常见的错义突变 在第130位将甘氨酸改变为缬氨酸(G130V)。FRDA G130V患者表现出不同于 存在GAA纯合子扩张的患者保留下来，包括下肢痉挛而不是共济失调 感官反应，节省言语和上肢功能，并减缓疾病进展。矛盾的是， 在G130V患者样本中检测到的FXN-M蛋白比在携带两种病毒的患者样本中检测到的FXN-M蛋白少得多 扩展的等位基因。我们的初步数据显示，FXN的正常线粒体成熟过程 蛋白质受到G130V突变的干扰，表明中间异构体的功能重要性 (G130V-I)。我们推测G130V突变损害了FXN线粒体成熟过程和/或 破坏成熟的异构体的稳定性。未处理的FXN-G130V-I亚型具有功能并部分补偿 对于FXN-M的大幅减少，从而减缓疾病的进展，并有助于明显的 FRDA G130V患者的症状。为了解决这些假设，我们将使用新的细胞和小鼠模型 FRDA G130V。首先，我们将定义要测试的FXN-G130V-I亚型的结构和功能属性 这种突变是否导致FRDA的非典型临床表现的功能改变 G130V患者。随后，我们将确定控制稳态水平和成熟度的机制 FXN-G130V在IPSC来源的皮质和感觉神经元中的处理。最后，使用FRDA患者派生的 神经元模型以及我们新的FXN G127V小鼠模型，我们将定义 FRDA G130V患者独特的临床表现拟议的研究结果将具有广泛的 对所有FRDA患者的治疗发展的影响。