C9orf72 and amyotrophic lateral sclerosis: Walker et al. (2017) reported increased R-loop accumulation in both RREs and poly-GA DPRs in two C9orf72 models: non-neuronal MRC-5 fibroblasts and rat cortical neurons, as well as a significant increase in R-loop in spinal cord tissue from C9orf72-associated ALS patients.