Fig. 7. SDN-1 located at the C. elegans nerve ring is specifically phosphorylated at its cytoplasmic domain. (A) Amino acid sequences of the cytoplasmic domain of SDN-1 from C. elegans (C.e) and syndecan-4 from M. musculus (M.m). The synthetic peptide used to generate the specific anti-phosphoserine syndecan-4 antibody (anti-P-syndecan-4) is boxed and the phosphorylated serine indicated. (B) (a) Anti--heparan sulfate immunoreactivity as shown in Fig. 3a. (b) Anti-P-syndecan 4 immunoreactivity in wild-type worms. The inserts show immunostaining with preincubated antibody with phosphorylated (upper insert) and non-phosphorylated peptide (lower insert). (c) Merged image of a and b. The insert shows anti-P-syndecan-4 immunoreactivity in the pan-neural GFP transgenic strain. The anti-P-syndecan-4 antibody stained specific neurons at the nerve ring and some anterior structures, but no immunoreactivity was detected in either the nerve cords or the vulva. (d) An enlarged area of the neurons stained in the nerve ring. In all images, white arrowheads indicate the nerve ring. All images are 3D reconstructions of image stacks. Bar, 20 µm.