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

基本信息

批准号：
10563061
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
项目类别：
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/10563061
关键词：
Address Affect Afferent Neurons Alleles Amino Acids Anabolism Ataxia Axonal Transport Binding Biochemical Biophysics Cell model Cell physiology Cells Characteristics Clinical 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 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 axonal degeneration base 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

项目摘要

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.

弗里德赖希共济失调 (FRDA) 是一种由表达减少引起的常染色体隐性神经退行性疾病线粒体蛋白 Frataxin (FXN) 被翻译为 210 个氨基酸 (aa) 前体 (FXN-P)。被导入线粒体基质中，在那里经历连续的裂解步骤，产生 168 个氨基酸中间体 (FXN-I) 和 129 个氨基酸的成熟亚型 (FXN-M) 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- 活性缺陷造成的目前，大多数 FRDA 患者都无法治愈这种衰弱性疾病。 FXN 基因内含子 1 中 GAA 三联体重复序列的大量扩展是纯合的，而一个子集的患者是复合杂合子，在一个 FXN 等位基因中具有扩展的 GAA 重复序列和错义或其他的无义突变都会导致纯合和复合杂合突变基因型。与健康对照相比，FXN-M 蛋白水平降低最常见的错义突变。将 130 位甘氨酸更改为缬氨酸 (G130V) 患者表现出与其他患者不同的临床特征。携带纯合 GAA 扩展的患者，包括下肢痉挛而不是共济失调，保留矛盾的是，感觉反应，言语和上肢功能不受损害，并且疾病进展较慢。在 G130V 患者样本中检测到的 FXN-M 蛋白比在含有两种蛋白的患者样本中检测到的 FXN-M 蛋白要少得多我们的初步数据显示 FXN 的线粒体成熟过程正常。蛋白质受到 G130V 突变的干扰，表明中间亚型的功能重要性 (G130V-I) 我们发现 G130V 突变会损害 FXN 线粒体成熟加工和/或未加工的 FXN-G130V-I 亚型具有功能性并部分补偿。 FXN-M 的大幅减少，从而减缓疾病进展并有助于明显的为了解决这些假设，我们将使用新型细胞和小鼠模型。首先，我们将定义要测试的 FXN-G130V-I 同工型的结构和功能特性。这种突变是否会导致功能改变，从而导致 FRDA 的非典型临床表现随后，我们将确定控制稳态水平和成熟的机制。最后，使用源自患者的 FRDA 在 iPSC 衍生的皮质和感觉神经元中处理 FXN-G130V。神经模型以及我们的新型 Fxn G127V 小鼠模型，我们将定义潜在的分子机制 FRDA G130V 患者的独特临床表现将产生广泛的研究结果。对所有 FRDA 患者的治疗开发的影响。