GDNF and amyotrophic lateral sclerosis: Stimulation of astrocytes with TNFα dramatically induces the expression of GDNF, and Gdnf, Tnfα and Tnfr1 are all upregulated in the spinal cords of ALS patients, suggesting that GDNF induction by TNFR1 activation is an adaptive response during the progression of ALS (Brambilla et al., 2016).