Fig. 3. Expression of Krm genes during Xenopus embryogenesis. (A) Developmental timecourse expression, as analysed by RT-PCR, at the indicated stages. Histone H4 was used for cDNA sample normalisation. (B-F) Spatial expression pattern of krm1 in Xenopus embryos, as analysed by whole-mount in situ hybridisation. (B) Control hybridisation of a stage 14 embryo using krm1 sense riboprobe. (C) Stage 14 embryo showing lateral neural plate expression, strongest in the anterior region. (D) Frontal view of late neurula, dorsal towards the top. (E) Sagittal midline cut of embryo shown in I, revealing expression in prechordal plate (pp). (F) Tailbud embryo showing krm1 expression in fin mesenchyme, hatching gland (hg) and notochord (nc, see also inset of cross-section). (G-M) Spatial expression pattern of krm2. (G) Mid gastrula (stage 11) embryo showing expression in marginal zone but absence from dorsal region. Vegetal view, dorsal towards the top. (H) Early-mid neurula (stage 14) embryo showing lateral neural plate expression. Dorsal view, anterior towards the top. (I,J) krm2 expression in anterior mesoderm. Vibrotome section (50 µm) of horizontally cut stage15 embryos (I) and sagittally cut stage14 embryos (J). The inserts show the plane of the section, indicated by a horizontal line. Arrow in I indicates expression in anterior mesoderm. (K) Frontal view of late neurula embryo (stage 18) showing anterior expression pattern. Dorsal towards the top. (L) Sagittal midline cut of embryo shown in K, revealing expression in prechordal plate (pp) tissue. Anterior is towards the left, dorsal is towards the top. (M) Lateral view of tailbud (stage 28) embryo showing expression in fin mesenchyme, dorsal part of otic vesicle (ov), hatching gland (hg), branchial arches (br) and pronephric duct (pnd, see also inset in cross-section).