 The kinetic model assumes that Vg0 would remain as monomers ready to heterodimerize with Nodal, which is a major assumption of the model and should be mentioned. Vg0 alone would be expected to homodimerize if Nodal is not present. Do the authors have evidence for Vg0 remaining as a monomer in the absence of Nodal? Non-reducing Western blot conditions could provide evidence for this.  The authors should also provide more information on where dimerization is known to occur (Golgi?) and how it is regulated to provide more plausibility to the model? The authors have stated that unprocessed Vg0 resides in the ER but haven\'t provided evidence to support this. They should either provide data to support this ER retention or soften their statements throughout.  The starting level of Vg0 in the model at 0 hpf is assumed to be 0000 nM, which is extremely high, especially considering that the mRNA is at very low levels at this point, although protein could be higher but are unknown. Provide modeling results when Vg0 monomers are at 000 nm or a more reasonable level of 00 or 000 nm.  It would be helpful if the authors could comment on why Vg0-Nodal heterodimers are required for signaling. Readers will want to know possible functions for a heterodimer that the Nodal homodimer cannot provide or at least comment that it is unclear at this point. Perhaps I missed this in the paper.  It would be helpful if the authors commented further on the rescue of Mvg0 mutants by YSL injection of 