Fig. 2. Xfz3 receptor forms homodimers in Xenopus embryo. (A) Embryos were injected at the two-cell stage with mRNA encoding the Xfz3-myc receptor or the C-terminal truncated form Xfz3C-myc. Protein extracts derived from gastrula were immunoblotted following SDS-PAGE under unreduced conditions, using the 9E10 anti-myc antibody. For both constructs, the blot reveals immunoreactive bands corresponding to the expected monomeric form (arrows) as well as a species of higher molecular mass corresponding to twice that of the monomer (arrowhead) or even higher (star). (B) Embryos were injected at the two-cell stage with mRNA encoding Xfz3-HA. Embryonic extracts were immunoblotted using 12CA5 monoclonal antibody as describe in (A). A band corresponding to the expected monomeric form (arrow) plus a higher form corresponding to the expected size for a dimer (arrowhead) are shown. (C) Xfz3C-myc mRNA (200 pg) was injected alone or co-injected with Xfz3-HA mRNA (800 pg). Protein extracts were analyzed with the anti-myc antibody. Co-expression of a high amount of Xfz3-HA leads to the disappearance of the band corresponding to the dimeric form of Xfz3C-myc. A higher band appears (arrowhead), revealing the presence of Xfz3C-myc/Xfz3-HA heterodimer.