Xenbase Image ID: 78951

Fig. 4. Cer-S inhibition of Nodal contributes to heart induction. (A–E) Embryos were injected into two dorsal/vegetal blastomeres at the 8 cell stage with either 2 pmol control MO (A), 1 pmol Hex MO (B), 2 pmol Cer MO (C) or combination of 2 pmol Cer MO and 1 pmol Hex MO (D). DMZ explants isolated at early gastrula stages (10–10.25) and grown until age-matched siblings had reached stage 23–25 when they were processed by in situ hybridization for expression of Nkx2.5 (arrowhead in panel A). Incidence of Nkx2.5 expression is shown in in panel E. Asterisks indicate statistical significance (p < 0.01, Student's T-test) between indicated conditions for greater than 3 independent experiments. (F–I) Embryos were injected into one ventral blastomere at the 4–8 cell stage with either the truncated form of Cerberus, Cer-S (F), the truncated version of the BMP receptor, tBR (G), or the two constructs together (H). VMZ explants were isolated at early gastrula stages 10.25 to 10.5 and grown until age-matched siblings had reached stage 23–25 and processed by in situ hybridization for expression of either Nkx2.5 (arrowhead in in panel H) or Tbx5. Neither Cer-S nor tBR alone induced expression of Nkx2,5 or Tbx5 whereas co-injection of Cer-S and tBR induced robust expression of both markers. The incidence of expression is plotted in the histogram (I). (J) The data indicate that two pathways for specification of the heart field in mesoderm are independent at the level of Hex and Cerberus. Dkk1 (and other canonical Wnt antagonists) act through the homeodomain transcriptional repressor Hex to induce an as yet unidentified diffusible intermediate whereas activation of the Nodal pathway results in production of the secreted factor Cerberus. Image published in: Foley AC et al. (2007) Copyright © 2007. Image reproduced with permission of the Publisher, Elsevier B. V. Larger Image Printer Friendly View

Return to previous page