C9ORF72 repeat expansions in cases with previously identified pathogenic mutations
C9ORF72 repeat expansions in cases with previously identified pathogenic mutations
复制标题
DOI：
10.1212/wnl.0b013e3182a8250c
复制
发表时间：
2013-10-08
期刊：
影响因子：
9.9
通讯作者：
Rademakers, Rosa
中科院分区：
文献类型：
--
作者：
van Blitterswijk, Marka;Baker, Matthew C.;Rademakers, Rosa
目的：为了鉴定潜在的遗传修饰剂，其有助于在9号染色体开放阅读框72（C9 ORF 72）中重复扩增的患者中检测到的表型变异性，我们在先前发现携带已知与神经退行性疾病谱相关的基因突变的334名受试者的队列中调查了这些扩增的频率。使用荧光PCR和重复引物PCR的2步方案来确定C9 ORF 72中六核苷酸扩增的存在。对于一个双突变体，我们进行Southern印迹，以评估扩展的大小，和免疫组化表征neuropathics.Results：我们检测到C9 ORF 72重复扩增4 334例（1.2% [或1.8%的217个家庭]）。所有这些受试者都具有行为表型，并且在颗粒蛋白前体（GRN：p.C466LfsX46，p.R493X，p.C31LfsX35）或微管相关蛋白tau（MAPT：p.P301L）中也具有众所周知的致病性突变。Southern印迹显示，一个具有p.C466LfsX46 GRN突变的双突变体在脑中长重复扩增（> 3，000个重复），免疫组化显示混合的神经病理学特征，包括C9 ORF 72扩增和GRN突变。我们的研究结果表明，共同-2个明显致病性突变的出现可能有助于在具有C9 ORF 72重复扩增的患者中检测到的多效性。这些发现表明，不应该将已知突变的患者排除在进一步的研究之外，遗传咨询师在为患者及其家人提供建议时应该意识到这种现象。
Objective: To identify potential genetic modifiers contributing to the phenotypic variability that is detected in patients with repeat expansions in chromosome 9 open reading frame 72 (C9ORF72), we investigated the frequency of these expansions in a cohort of 334 subjects previously found to carry mutations in genes known to be associated with a spectrum of neurodegenerative diseases.Methods: A 2-step protocol, with a fluorescent PCR and a repeat-primed PCR, was used to determine the presence of hexanucleotide expansions in C9ORF72. For one double mutant, we performed Southern blots to assess expansion sizes, and immunohistochemistry to characterize neuropathology.Results: We detected C9ORF72 repeat expansions in 4 of 334 subjects (1.2% [or 1.8% of 217 families]). All these subjects had behavioral phenotypes and also harbored well-known pathogenic mutations in either progranulin (GRN: p.C466LfsX46, p.R493X, p.C31LfsX35) or microtubule-associated protein tau (MAPT: p.P301L). Southern blotting of one double mutant with a p.C466LfsX46 GRN mutation demonstrated a long repeat expansion in brain (> 3,000 repeats), and immunohistochemistry showed mixed neuropathology with characteristics of both C9ORF72 expansions and GRN mutations.Conclusions: Our findings indicate that co-occurrence of 2 evidently pathogenic mutations could contribute to the pleiotropy that is detected in patients with C9ORF72 repeat expansions. These findings suggest that patients with known mutations should not be excluded from further studies, and that genetic counselors should be aware of this phenomenon when advising patients and their family members.