Fig. 4 Mesodermal defects in hoxa13;ntlcs embryos maintained at 18.5°C. In situ hybridization of 15-somite wild-type and hoxa13;ntlcs embryos. (A). In mutant embryos, expression of tbxta at the posterior end (NMp domain) of the embryo is absent, whereas expression in the notochord progenitors (gray arrowhead) is retained. Note that in mutant embryos tbxta expression in the notochord is normal (black arrowheads). (B-D) Expression of wnt3a (B), wnt8a (C) and cyp26a1 (D) are strongly downregulated in the posterior of mutant embryos. (E,F) Expression of cdx4 (E) and fgf8a (F) are largely normal or only partially reduced in the posterior of mutant embryos. (G) sox2 expression expands into the mesodermal progenitor region in the mutants, whereas in wild-type embryos sox2 is absent from this region (black arrowheads). (H-J) tbx16 (H), msgn1 (I) and pcdh8 (J) are strongly downregulated in mutant embryos. A-G show side views and H-J show dorsal views.