SMAD1 and Parkinson disease: Taking into account the fact that amino acid sequences have been highly conserved in the Smad family and their mutation results in aberrant normal pathways [4], targeting specific motifs (SXS in the MH2 domain) in Smad1, 3, and 5 to be phosphorylated using osteogenic small molecules might be the key point in Parkinson's disease therapeutic studies.