Smad6 (SMAD Family Member 6, SMAD-6, hSMAD6, HsT17432, MAD (Mothers Against Decapentaplegic Drosophila) Homolog 6, MAD Mothers Against Decapentaplegic Homolog 6 (Drosophila), Mothers Against Decapentaplegic Drosophila Homolog of 6, Mothers Against Decapen