Fig. 5. Grsf1-silenced embryos mimic mid/hindbrain and posterior truncation phenotypes of Wnt mutants. (A) Posterior truncations are more pronounced at E9.0 (the first forming somite is indicated by an asterisk in A and B). Additionally, Grsf1-silenced embryos show a clear thickening in the midbrain (mb) region (red arrows), a large alantois (al) and abnormal anterior hindbrain development (white arrow; red arrowhead indicates mid/hindbrain boundary). (B) At E8.5, Grsf1-silenced embryos show a reduced tailbud (tb) region (indicated by dotted area). (C,D) Comparison of Hematoxylin and Eosin-stained transverse sections of wild-type and Grsf1-silenced embryos at E9.0. fb, forebrain; hb, hindbrain; nt, neural tube. (E-K) Whole-mount in situ analysis of wild-type and Grsf1-silenced embryos with indicated probes. (E,F) Comparison of Fgf8 expression in 7-8 somite wild-type and Grsf1-silenced embryos. (E) Lateral view, anterior up. (F) Dorsal view on the mid/hindbrain boundary. (G,H) Comparison of hindbrain marker gene expression in wild-type and Grsf1-silenced embryos at 7-somite stage; dorsal view, anterior up. (I-L) Expression analysis of potential (Gbx2) and known Wnt/ß-catenin target genes (Cdx1 and T) in wt and knock-down embryos at gastrulation stage. L, lateral view, anterior to the left; A, anterior view, anterior is up; P, posterior view, posterior is up. (I,J) Gbx2 and Cdx1 are normally expressed in Grsf1-silenced embryos at head-fold stage. Note, that the posterior axis is slightly shortened in knock-down mutants. (K,L) Comparison of T expression in wild-type and Grsf1-silenced embryos at E7.5 (K) and head-fold stage (L). Arrow indicates the anterior expression border. A, anterior view; P, posterior view; L, lateral view.