Fig. 3. Somite segmentation abnormality in Sfrp1^-/-;Sfrp2^-/- embryos. (A,B) Gross morphology of control (Sfrp1^-/-;Sfrp2^+/+; A) and Sfrp1^-/-;Sfrp2^-/- (B) embryos at E9.5. Somite size is indicated by a bracket. Inactivation of Sfrp1 and Sfrp2 resulted in reduced length of the posterior region. Scale bar: 500 µm. (C,D) Somite segmentation was aberrant in Sfrp1^-/-;Sfrp2^-/- embryos. Somite segmentation was examined in para-sagittal sections, which were stained with Hematoxylin and Eosin, of control (C) and Sfrp1^-/-;Sfrp2^-/- (D) embryos at E9.5. Regular and similarly sized somites (bracket) were observed in control embryos, whereas incomplete segmentation (arrows in a bracket) was apparent in the region between the forelimb and hindlimb of Sfrp1^-/-;Sfrp2^-/- embryos. Scale bar: 50 µm. (E,F) Immunostaining with 2H3 monoclonal anti-neurofilament antibody (arrowheads) of control (E) and Sfrp1^-/-;Sfrp2^-/- (F) embryos at E10.5. Scale bar: 500 µm. FL, forelimb; HL, hindlimb; Sc, sclerotome.