TGFB1 and amyotrophic lateral sclerosis: Furthermore, increased expression of Tgfb1 mRNA has been observed in skeletal muscle of ALS mice (Galbiati et al., 2012) and elevated levels of TGF-β cytokine and its canonical downstream mediator, Smad3, have been correlated with muscle fibrosis in these mice (Gonzalez et al., 2017).