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. Author manuscript; available in PMC: 2021 Feb 1.
Published in final edited form as: Trends Genet. 2019 Dec 11;36(2):81–92. doi: 10.1016/j.tig.2019.11.003

Figure 1: A G4C2 hexanucleotide repeat expansion is found within C9orf72 in ALS/FTD.

Figure 1:

A. A hexanucleotide expansion of >30 (G4C2)n repeats is found within the C9orf72 gene in ~40% of familial ALS/FTD cases and ~7% of sporadic ALS/FTD cases. Three mRNA variants are produced from C9orf72, with the repeat expansion occurring within intron 1 of mRNA Variants 1 and 3. For mRNA Variant 2, it is in the promoter. B. Bidirectional transcription of mutant C9orf72 produces two RNA species containing the hexanucleotide repeat expansion: a sense- and an antisense-strand. These RNAs can undergo repeat-associated non-AUG translation to produce five aggregate-prone dipeptides: GA, GR, GP, PA, PR. (GP is produced by both RNA strands.) As peptides are detected in disease tissue, the RNAs for both strands containing the repeats must be made and accumulate.