Research Center of the Institute for Brain and Spinal Cord CRICM, National Institute of Health and Medical Research - Inserm UMR_S975, National Center for Scientific Reseach CNRS UMR_7225, Pierre and Marie Curie University UPMC Paris 6, F-75013, Paris, France.
Ann Neurol. 2013 Aug;74(2):180-7. doi: 10.1002/ana.23946.
To define the role that repeat expansions of a GGGGCC hexanucleotide sequence of the C9orf72 gene play in the pathogenesis of amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD). A genetic model for ALS was developed to determine whether loss of function of the zebrafish orthologue of C9orf72 (zC9orf72) leads to abnormalities in neuronal development.
C9orf72 mRNA levels were quantified in brain and lymphoblasts derived from FTLD and ALS/FTLD patients and in zebrafish. Knockdown of the zC9orf72 was performed using 2 specific antisense morpholino oligonucleotides to block transcription. Quantifications of spontaneous swimming and tactile escape response, as well as measurements of axonal projections from the spinal cord, were performed.
Significantly decreased expression of C9orf72 transcripts in brain and lymphoblasts was found in sporadic FTLD and ALS/FTLD patients with normal-size or expanded hexanucleotide repeats. The zC9orf72 is selectively expressed in the developing nervous system at developmental stages. Loss of function of the zC9orf72 transcripts causes both behavioral and cellular deficits related to locomotion without major morphological abnormalities. These deficits were rescued upon overexpression of human C9orf72 mRNA transcripts.
Our results indicate C9orf72 haploinsufficiency could be a contributing factor in the spectrum of ALS/FTLD neurodegenerative disorders. Loss of function of the zebrafish orthologue of zC9orf72 expression in zebrafish is associated with axonal degeneration of motor neurons that can be rescued by expressing human C9orf72 mRNA, highlighting the specificity of the induced phenotype. These results reveal a pathogenic consequence of decreased C9orf72 levels, supporting a loss of function mechanism of disease.
确定 C9orf72 基因中 GGGGCC 六核苷酸序列重复扩展在肌萎缩侧索硬化症（ALS）和额颞叶变性（FTLD）发病机制中的作用。建立了 ALS 的遗传模型，以确定是否丧失斑马鱼 C9orf72 （zC9orf72）的同源物的功能会导致神经元发育异常。
在 FTLD 和 ALS/FTLD 患者的大脑和淋巴母细胞以及斑马鱼中定量测定 C9orf72 mRNA 水平。使用 2 种特异性反义寡核苷酸来阻断转录，以敲低 zC9orf72。进行自发游泳和触觉逃逸反应的定量以及测量脊髓的轴突投射。
在具有正常大小或扩展六核苷酸重复的散发性 FTLD 和 ALS/FTLD 患者的大脑和淋巴母细胞中，发现 C9orf72 转录本的表达明显降低。zC9orf72 在发育阶段特异性表达于发育中的神经系统。zC9orf72 转录本的功能丧失会导致与运动有关的行为和细胞缺陷，而没有主要的形态异常。这些缺陷可以通过过表达人类 C9orf72 mRNA 转录本得到挽救。
我们的结果表明 C9orf72 单倍剂量不足可能是 ALS/FTLD 神经退行性疾病谱中的一个促成因素。在斑马鱼中，zC9orf72 表达的功能丧失与运动神经元的轴突变性有关，而表达人类 C9orf72 mRNA 可以挽救这种变性，这突出了所诱导表型的特异性。这些结果揭示了 C9orf72 水平降低的致病后果，支持疾病的功能丧失机制。
