Smad5 Background Information Smad proteins, the mammalian homologs of the Drosophila Mothers against dpp (Mad) have been implicated as downstream effectors of TGF∫/BMP signaling (1). Smad1 (also designated Madr1 or JV4-1), Smad5 and mammalian Smad8 (also designated Smad9 or MADH6) are effectors of BMP2 and BMP4
function while Smad2 (also designated Madr2 or JV18-1) and Smad3 are involved in TGF∫ and activin-mediated growth modulation (2-5,8). Smad4 (also designated DPC4) has been shown to mediate all of the above activities through interaction with various Smad family members (6). Smad6 and Smad7 regulate the response to activin/TGF∫ signaling by interfering with TGF∫-mediated phosphorylation of other Smad family
members (7,8).