Figure 2D. Copyright: Reprinted with permission from Elsevier from [doi:10.1016/j.ydbio.2006.04.442] Dev Biol 296: 104-18, Arnold SJ; Maretto S; Islam A; Bikoff EK; Robertson EJ, "Dose-dependent Smad1, Smad5 and Smad8 signaling in the early mouse embryo." Copyright 2006 [PMID:16765933]