Fig. 2. GAGs are required for GDNF-induced axonogenesis in PC-12 cells. (a) PC-12 cells cultured in the absence of GDNF remain rounded and form no axons, whereas about 12% of cells form axons when treated with GDNF (b). 30 mM sodium chlorate, a competitive inhibitor of GAG sulphation, blocks this response to GDNF (c), unless sulphate is added to antagonise the effects of chlorate (d). PC-12 cells remain able to produce axons in response to another neurogenic factor, NGF, even in the presence of chlorate (e), showing that GAGs are not required for axon morphogenesis but merely for responsiveness to GDNF. The data from a-d are shown quantitatively in f (NGF-treated PC-12 cells form meshworks of neurites too complicated to count). Total numbers of cells, counted whether or not they bear axons, show no significant variation between these conditions (g).

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