SMAD9 and amyotrophic lateral sclerosis: In a cohort study using human ALS (amyotrophic lateral sclerosis) muscle samples (27 patients, 33 controls), qRT-PCR showed that the expression of SMAD8 mRNA increased approximately 19-fold compared to that in the control group (p < 0.0001), whereas SMAD5 (~3-fold) and SMAD1 mRNA showed lesser increases (p < 0.05).