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Fig. S1 Chondroitin sulfate proteoglycans are not involved in the regulation of Engrailed expression. (A-D) Transverse sections of wild-type (A,C) and sly (B,D) embryos at the 20 s stage (A,B, adaxial cell stacking level) and 26 hpf (C,D, anterior tail level). Dorsal is upwards. Anti-CS antibody is in green. In wild type (A,C), CSPGs are found in the basement membrane lining the somite, notochord and ventral neural tube at the 18-20 s stage (n=8/8) and 26 hpf (n=9/9). In sly embryos (B,D), although unaffected at the 18-20 s stage (n=6/6), CSPGs labelling is weak by 26 hpf (n=7/7). (E,I) Lateral views of vehicle solution-injected wild-type (E) and Chondroitinase-injected wild-type (I) embryos at 26 hpf. Anterior is on the left, dorsal is upwards. (F-H,J-L) Magnified views (projection of confocal sections) of the region around somite 10 (F-G,J-K) and somite 18 (H,L) for each type of embryo. (E-L) 4D9 (in green) labels pioneer (arrowheads) and MFF nuclei; Prox1 (in red) labels slow muscle fibre nuclei, including pioneers. Because of the projection, some nuclei artificially overlap. All pioneer nuclei are therefore identified by arrowheads. (E,G,I,K) 4D9 labelling only. After injection at the 10 s stage, Engrailed expression at 26 hpf is normal in the trunk and tail of embryos injected with vehicle solution (n=6/6) (E-H) or Chondroitinase ABC (n=12/12) (I-L). n, notochord; nt, neural tube. Scale bar: 50 μm.