TGFB1 and amyotrophic lateral sclerosis: The reduction in TGF-β signaling at an early stage of ALS is thought to block the neuroprotective effects of TGF-β, whereas at later stages of the disease, the over-activation of the TGF-β signaling promotes microglial activation and hence proinflammatory responses which cause further neurotoxicity (Galbiati et al., 2020).