Fig. 4

Knockdown of def6 does not alter mesodermal cell fate specification and anterior-posterior patterning.

Uninjected and def6 MO-injected embryos were fixed at 6 hpf or 10 hpf and in situ hybridisation was carried out with the indicated probes. Chordin (chd; A and B; 21/21 embryos) and goosecoid (gsc; E and F; 15/15 embryos) are expressed in the dorsal mesoderm and specify dorsal cell fates. Bone morphogenetic proteins (bmp2b; C and D; 18/18 embryos; bmp4; I and J; 15/15 embryos) are involved in ventral cell fate specification. The non-axial marker caudal homeobox transcription factor 4 (cdx4; I and J; 19/19 embryos) and the mesendodermal marker no-tail (ntl; K and L; 31/31 embryos) are also shown. The expression pattern of all these genes in wt and def6 morphants was indistinguishable at 6 hpf, indicating normal cell fate specification in def6 MO-injected embryos. At 10 hpf, expression of the anterior specific genes krox20 (M and N; 37/41 embryos) and pax2 (O and P; 16/19 embryos,) persisted in def6 MO-injected embryos indicating that no anterior structures were deleted. The expression domain of these markers was posteriorly shifted and expanded in def6 MO-injected embryos in comparison to wt siblings (M′–P′) when viewed from the dorsal side. Lateral views (A–F, I, J, M–P), animal pole views (G, H, K, L) and dorsal views (M′–P′) with anterior to the top are shown.