Development of a Cellular Model for C9ORF72-related Amyotrophic Lateral Sclerosis

Background: ALS is an incurable late onset neurodegenerative disease that is characterised by progressive loss of motor neurons. A (G4C2)n repeat expansion in C9ORF72 is the most common genetic cause of ALS, but it is unknown how the repeat causes pathogenesis, although a gain of toxic function is likely.
Aims and Objectives: 1) Generate stable, isogenic motor neuron-like NSC34 cellular models that have tetracycline-inducible (G4C2)n repeat expression. 2) Characterise the cell models for C9ORF72-ALS pathology and biochemical alterations. 3) Identify biological functions and pathways that may be transcriptionally dysregulated by (G4C2)n repeat expression early in C9ORF72-ALS pathogenesis.
Results: Stable, isogenic NSC34 cell models with tetracycline-inducible (G4C2)n expression were successfully generated. Sense RNA foci and RAN translation products were detected in the cell models. No antisense derived RNA foci or RAN translation products were detected. Expression of the (G4C2)102 caused subtle toxicity and recapitulated some aspects of C9ORF72-ALS pathology in the NSC34 (G4C2)102. The (G4C2)102 expression caused transcriptomic dysregulation in RNA metabolism, protein transport, and also caused splicing alterations.
Conclusions: Stable, isogenic motor neuron-like cellular models that had tetracycline-inducible (G4C2)n expression were successfully generated, and allowed interrogation of the early biochemical effects associated with sense only (G4C2)n expression in a reductionist manner. Transcriptomic analysis of the NSC34 (G4C2)102 identified dysregulation in RNA splicing, which was corroborated by transcriptomic data from C9ORF72-ALS patient CNS tissue.