Fig. 1. A method for attenuating Bmp signaling in transgenic zebrafish. Diagram of a wild-type cell receiving a Bmp signal (left) and a transgenic cell receiving a Bmp signal after heatshock (right). In a wild-type cell, the Bmp ligand binds to a Type I/Type II receptor complex, which then phosphorylates and activates a receptor SMAD (rSMAD), leading to target gene activation. After heatshock of the transgenic cell, the truncated Type I Bmp receptor containing GFP in place of the kinase domain displaces the endogenous Type I receptor, preventing the receptor complex from activating rSMADs. As a result, downstream target genes are not activated, and the cell is reduced in its capacity to respond to Bmp signals. KD, kinase domain; LB, ligand-binding domain; P, phosphate; TM, transmembrane domain.