Fig. 3

Heterodimers signal more potently than BMP2 and BMP4 homodimers in a Xenopus development assay. A Dose-response experiment determined the minimal effective dose of homodimers/heterodimers for developmental assays. Based on embryo viability, 0.5 pmol was the highest dose used for subsequent assays. B, C Xenopus axial development assay scored using Dorso-Anterior Index [45]. Stage 9 Xenopus laevis blastula were injected with 0.15 pmol in 13 nL (B) or 0.5 pmol in 40 nL doses (C) of BMP homodimeric or heterodimeric proteins in 10 mM HCl, or a vehicle control. Embryos developed until stage NF37 (tadpole stage) and were then scored using the (D) Dorso-Anterior Index for signs of aberrant ventralization, on a scale of 5 (normal development) to 0 (fully ventralized, no visible somites) [49]. *p<0.05, **p<0.01 by 1W-ANOVA, n=10–15 embryos, N=3–4 independent experiments. E N=20 stage NF9 Xenopus laveis blastula microinjected 0.05 pmol in 4.3 nL or 0.15 pmol in 13 nL of BMP homodimeric or heterodimeric proteins or vehicle control were assayed at early gastrula stage NF10, by in situ hybridization for expression of direct BMP/SMAD1 response genes ventx1 and ventx2 (dark staining). Ventral side to the right. Representative images shown. F Gastrula embryos were scored for degree of ventx1 and ventx2 staining expression and categorized as normal, partially expanded, or completely expanded expression domains. ****p<0.0001 by chi-square test n=20 embryos, N=1 experiment