Agathon et al. performed transplantation experiments to identify cells capable of inducing the formation of an ectopic tail (Fig 2a, 2d). They then investigated the role of several signaling molecules that were thought to have a role in this process.
1. Identification of the organizer
Spemann and Mangold showed that the dorsal blastopore lip can: 1) induce the cells of a host to change their cell fates; and 2) organize a second axis.
Does the tail organizer identified by Agathon et al meet this standard? Which experiments and Figures are most informative?
2. BMP, Nodal, and Wnt
a. BMP, Nodal, and Wnt are secreted ligands. Your textbook describes each of these gene families. For each of these ligands, describe the cellular or biochemical functions of 2 other proteins that have been shown to regulate ligand function (for example, a receptor or an inhibitorŠ).
b. Describe the experimental methods the authors used to inhibit each pathway (BMP, Nodal, and Wnt). If the ligand itself was not knocked-out, then describe the function of the gene product that was inhibited or mutated.