Fig. 3. Control experiments: stage 30 embryos were analyzed for CA expression and HA distribution. (A) A representative embryo injected with a control morpholino. (B-D) Embryos injected with 15 ng of XHas2-Mo1 or with 15 ng of XHas2-Mo1 plus 800 pg XHas2 mRNA (rescue experiment). The injected side of the embryo is visualized by Red-gal staining. (B) Uninjected side of a XHas2-Mo1-injected embryo and (C) injected side of the same embryo showing the altered somites structure. (D) A representative case of a rescue experiment in which the canonical somites structure is completely recovered. (E) Ventral view of a wild-type embryo showing normal medial fusion of the two halves of the heart anlage. (F) In XHas2-Mo-injected embryos, heart formation is clearly impaired at the level of the injected side (arrow). (G) Coronal section of stage 26 XHas2-Mo-injected embryos at the trunk level and double stained with neurocan-GFP fusion protein (green) and Hoechst (blue). (H) High magnification of the XHas2-Mo-injected side region indicated by the white square in G; no HA detection is visible in the ECM surrounding the myocytes. (I) High magnification of the control side region indicated by the white square in G showing abundant HA in the ECM filling the myocytes extracellular spaces. n, notochord; nt, neural tube.