Regarding GDNF, most studies that examined expression in muscle observed an increase in Gdnf mRNA and protein in muscle biopsies from ALS patients as compared to controls, or in the Sod1G93A mouse model, although one study observed a decline (Yamamoto et al., 1996; Grundstrom et al., 1999; Yamamoto et al., 1999; Stanga et al., 2018). The gene discussed is GDNF; the disease is amyotrophic lateral sclerosis.