Identification of specifically expressed genes in RANKL-stimulated RAW 264.7 cells. Northern blot analysis of genes expressed during osteoclast differentiation. Total RNA was extracted from RAW264.7 and RAW-RacN17 cells stimulated with RANKL for the indicated periods. Total RNA (20 μg) was applied to each lane. cDNAs for cathepsin K, carbonic anhydrase II, osteopontin, Ifi202, IRG1, and COX-2 were used to prepare probes and hybridized to total RNA. GAPDH (glyceraldehyde-3-phosphate dehydrogenase) was used as a control for total RNA loading.