Figure 2.

Stage 12 embryos stained for FasIII (A, B, and E) and Eve (C, D, and F), compare with Fig. 1 B and E for wild-type patterns. (A–D) Induction of full-length MNkx2–5 in homozygous tin mutant background (HsMNkx2–5,tin^EC40). Without heat shock (A and C) no visceral mesoderm (A, asterisks) nor cardiac progenitors (C, asterisks) form, which is typical of tin mutants. In contrast, heat shock at 3.5–4.5 hr of development (stage 9) restores marker gene expression for visceral mesoderm considerably (B, arrowheads), but does not restore heart development markers (D, asterisks, compare with Fig. 1 B and C). (E) Induction of full-length XNkx2–3 in homozygous tin mutant background (HsXNkx2–3,tin^EC40) restores visceral mesoderm (arrowheads) but not heart marker gene expression (data not shown). The same result was obtained with ZNkx2–7 (data not shown). When two consecutive heat shocks were given to each of these three transgenes, they did not result in more rescue. (F) Induction of full-length ZNkx2–3 in homozygous tin mutant background (HsZNkx2–3,tin^EC40) restores not only visceral mesoderm (data not shown) but also cardiac markers (arrowheads).