GDNF and amyotrophic lateral sclerosis: A few receptor tyrosine kinase (RTK) signaling pathways, which promote cell survival and act protectively on motor neurons both in in vivo and in vitro ALS models, have been uncovered and include glial-derived neurotrophic factor (GDNF), ciliary neurotrophic factor (CNTF), and insulin-like growth factor 1 (IGF-1) (Tovar et al., 2014; Kasai et al., 2011; Riboldi et al., 2011).