Characterization of the subtracted cDNA library by Northern blot analysis. In the left panel, 5 μg of total RNA prepared from +/+, mi/mi, or tg/tg CMCs was loaded in each lane and fixed onto nylon membranes by capillary action. In the right panel, sense RNAs were synthesized by the T7 RNA polymerase reaction using the Not I-digested plasmid DNA of the +/+ CMC cDNA library, the (+/+-mi/mi) subtracted cDNA library, or the (+/+-tg/tg) subtracted cDNA library as a template. Two micrograms of synthesized RNA was loaded per lane and fixed onto nylon membranes. Probes were prepared from the cDNAs for β-actin, MC-CPA, MITF, or Gr B using the random hexamer labeling method.