 (Reviewer \#0).  The reviewers have discussed the reviews with one another and the Reviewing Editor has drafted this decision to help you prepare a revised submission.  0\) In revising the manuscript, further experiments are necessary to clarify some basic issues about the model. For example, why Vg0 remains as monomers and thus available to dimerize with Nodal. The suggested experiment is to perform additional WB under-non reducing conditions to test this. It would also be advisable to experimentally clarify where exactly in the cell heterodimerization is occurring. Additionally two of the reviewers raise the issue as to why heterodimers are required to mediate nodal signaling versus homodimers? It would be important to show a direct interaction between these heterodimers and the nodal receptor complexes. An alternative approach would be to over-express different relative amounts of Vg0 and Nodal in Vg0 mutants and use Phospho-Smad0 activity as a read-out (as suggested by reviewer 0).  0\) Two of the reviewers raise concerns with the Vg0 mutant rescue by YSL injection of Vg0. In particular reviewer 0 requests that the experiment be repeated using lineage tracing to show that the injection is confined to the YSL, ideally with the inclusion of Smad0 staining as further verification.  