C9orf72 and amyotrophic lateral sclerosis: Genes upregulated in C9-ALS excitatory neurons were linked to processes that are essential for all cell types (e.g., mitochondria function, proteostasis, protein synthesis), whereas genes downregulated in motor cortex were enriched for categories that are specific to neuronal cells (e.g., neuronal cell body category that includes C9orf72, and genes that encode several potassium channels) (Fig. 4a; Supplementary Fig. 8; Supplementary Dataset 3, 4).