Fig. 1. Growth factor-induced differentiation of SH-SY5Y/wt cells. A, phase-contrast micrographs of SH-SY5Y/wt cells grown in the presence of bFGF + IGF-I and/or NT-3 + NGF. Cells were grown for 4 days in serum-free medium alone (a), in serum-free medium supplemented with 100 ng/ml NT-3 + 100 ng/ml NGF (b), 3 nM bFGF + 5 nM IGF-I (c), or 3 nM bFGF + 5 nM IGF-I + 100 ng/ml NT-3 + 100 ng/ml NGF (d). Bar in a, 25 µm. B, Northern blot analysis of the expression of the neuronal differentiation marker genes, NPY (0.8 kb) and GAP-43 (1.4 kb) in SH-SY5Y/wt cells. Cells were grown for 4 days in serum-containing medium alone or in serum-containing medium supplemented with 100 ng/ml NT-3, 100 ng/ml NGF, 100 ng/ml NT-3 + 100 ng/ml NGF, or the differentiation inducer TPA (16 nM). Fifteen µg of total RNA of each sample were electrophoretically separated and blotted onto the same filter. GAPDH (1.5 kb) mRNA levels were used as a reference for the amount of loaded RNA.