C9orf72 and amyotrophic lateral sclerosis: We also found that approximately 25–50% of oligodendrocytes and OPCs in the cortex and spinal cord expressed C9orf72. Importantly, we show that a greater fraction of oligodendrocytes in L5 of motor cortex expresses C9orf72, providing further evidence that cell types that degenerate in ALS express C9orf72 more widely than other cell types in the CNS.