Mechanisms of toxicity in C9FTLD/ALS

作者：Gendron Tania F; Belzil Veronique V; Zhang Yong Jie; Petrucelli Leonard^*

来源：Acta Neuropathologica, 2014, 127(3): 359-376.

DOI：10.1007/s00401-013-1237-z

• Amyotrophic lateral sclerosis
• Bidirectional transcription
• C9ORF72
• Epigenetics
• Expanded repeat
• Frontotemporal lobar degeneration
• Repeat-associated non-ATG translation
• RNA foci

A hexanucleotide repeat expansion within a non-coding region of the C9ORF72 gene is the most common mutation causative of frontotemporal lobar degeneration (FTLD) and amyotrophic lateral sclerosis (ALS). Elucidating how this bidirectionally transcribed G(4)C(2)center dot C(4)G(2) expanded repeat causes "C9FTLD/ALS" has since become an important goal of the field. Likely pathogenic mechanisms include toxicity induced by repeat-containing RNAs, and loss of C9orf72 function due to epigenetic changes resulting in decreased C9ORF72 mRNA expression. With regards to the former, sense and antisense transcripts of the expanded repeat aberrantly interact with various RNA-binding proteins and form discrete nuclear structures, termed RNA foci. These foci have the capacity to sequester select RNA-binding proteins, thereby impairing their function. (G(4)C(2))(exp) and (C(4)G(2))(exp) transcripts also succumb to an alternative fate: repeat-associated non-ATG (RAN) translation. This unconventional mode of translation, which occurs in the absence of an initiating codon, results in the abnormal production of poly(GA), poly(GP), poly(GR), poly(PR) and poly(PA) peptides, collectively referred to as C9RAN proteins. C9RAN proteins form neuronal inclusions throughout the central nervous system of C9FTLD/ALS patients and may contribute to disease pathogenesis. This review aims to summarize the important findings from studies examining mechanisms of disease in C9FTLD/ALS, and will also highlight some of the many questions in need of further investigation.

• 出版日期2014-3