Department of Pharmacology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA.
Mol Genet Metab. 2010 Oct-Nov;101(2-3):238-45. doi: 10.1016/j.ymgme.2010.07.001. Epub 2010 Jul 8.
Friedreich ataxia (FRDA) is an autosomal recessive neurodegenerative disorder caused by reduced amounts of the mitochondrial protein frataxin. Frataxin levels in research studies are typically measured via Western blot analysis from patient fibroblasts, lymphocytes, or muscle biopsies; none of these is ideal for rapid detection in large scale clinical studies. Recently, a rapid, noninvasive lateral flow immunoassay was developed to accurately measure picogram levels of frataxin protein and shown to distinguish lymphoblastoid cells from FRDA carriers, patients and controls. We expanded the immunoassay to measure frataxin directly in buccal cells and whole blood from a large cohort of controls, known carriers and patients typical of a clinical trial population. The assay in buccal cells shared a similar degree of variability with previous studies conducted in lymphoblastoid cells (~10% coefficient of variation in controls). Significant differences in frataxin protein quantity were seen between the mean group values of controls, carriers, and patient buccal cells (100, 50.2, and 20.9% of control, respectively) and in protein extracted from whole blood (100, 75.3, and 32.2%, respectively), although there was some overlap between the groups. In addition, frataxin levels were inversely related to GAA repeat length and correlated directly with age of onset. Subjects with one expanded GAA repeat and an identified frataxin point mutation also carried frataxin levels in the disease range. Some patients displaying an FRDA phenotype but carrying only a single identifiable mutation had frataxin levels in the FRDA patient range. One patient from this group has a novel deletion that included exons 2 and 3 of the FXN gene based on multiplex ligation-dependent probe amplification (MLPA) analysis of the FXN gene. The lateral flow immunoassay may be a useful means to noninvasively assess frataxin levels repetitively with minimal discomfort in FRDA patients in specific situations such as clinical trials, and as a complementary diagnostic tool to aid in identification and characterization of atypical patients.
弗里德赖希共济失调症（FRDA）是一种常染色体隐性神经退行性疾病，由线粒体蛋白 frataxin 的含量减少引起。在研究中，通常通过对患者成纤维细胞、淋巴细胞或肌肉活检进行 Western blot 分析来测量 frataxin 水平；但这些方法都不理想，无法在大规模临床研究中快速检测。最近，开发了一种快速、非侵入性的侧向流动免疫测定法，能够准确测量 picogram 级别的 frataxin 蛋白，并能够区分 FRDA 携带者、患者和对照者的淋巴母细胞。我们将免疫测定法扩展到可以直接测量大量对照者、已知携带者和患者的口腔细胞和全血中的 frataxin 蛋白，这些患者是临床试验人群的典型代表。该测定法在口腔细胞中的变异性与以前在淋巴母细胞中进行的研究相似（对照者的变异系数约为 10%）。在对照组、携带者和患者的口腔细胞（分别为对照组的 100%、50.2%和 20.9%）以及从全血中提取的蛋白中，frataxin 蛋白量的平均值之间存在显著差异（分别为 100%、75.3%和 32.2%），尽管各组之间存在一些重叠。此外，frataxin 水平与 GAA 重复长度呈负相关，与发病年龄呈正相关。携带一个扩展的 GAA 重复和一个已确定的 frataxin 点突变的受试者的 frataxin 水平也处于疾病范围内。一些表现出 FRDA 表型但仅携带一个可识别突变的患者的 frataxin 水平处于 FRDA 患者范围内。在基于 FXN 基因多重连接依赖性探针扩增（MLPA）分析的 FXN 基因分析中，该组中的一名患者携带一个包括 FXN 基因外显子 2 和 3 的新型缺失。侧向流动免疫测定法可能是一种有用的方法，可以在 FRDA 患者特定情况下（如临床试验），以非侵入性方式重复评估 frataxin 水平，且作为一种辅助诊断工具，有助于鉴定和描述非典型患者。
