Furthermore, those identified KEGG pathways that have been previously described in the literature as being related to ALS include RIG-I-like receptor signaling (2 down and 3 up-regulated genes; Figure 4), tryptophan metabolism (5 down-regulated genes; Figure 4), ErbB signaling (1 down and 5 up-regulated genes; Figure 4) and cell cycle (2 down and 5 up-regulated genes; Figure 4). Here, EGFR is linked to amyotrophic lateral sclerosis.