Fig. 9. CS is required for Nodal signal transmission from the node to LPM. (A,H) Schematic representation of proteoglycans from normal (A) or xyloside-treated (H) mouse embryos. Xyloside (purple) acts as primer for GAG elongation, resulting in the syntheses of unlinked GAGs and naked proteoglycans. (B-D,I-K) Transverse frozen sections of embryos cultured with 0.1% dimethyl sulfoxide vehicle (B-D) or 1 mM xyloside (I-K) to the six-somite stage were subjected either to immunofluorescence analysis with antibodies to HS (B,I) or to CS (C,J) or to staining with Alcian Blue (D,K). (E-G,L-N) In situ hybridization for Nodal (E,L), GDF1 (F,M) or Cryptic (G,N) mRNAs in embryos cultured in the absence (E-G) or presence (L-N) of xyloside. (O,P) Expression vectors for Nodal and GFP were co-injected into the right LPM of embryos before culture with xyloside. The resulting embryos were examined for GFP fluorescence (O) and then subjected to in situ hybridization for Nodal mRNA (P). (Q) The number and percentage of embryos with (blue) or without (white) Nodal expression in LPM after culture in the absence or presence of xyloside. Scale bars: 100 µm in B-D,I-K; 200 µm in E-G,L-P.