The cathepsin G mutation eliminates cathepsin G mRNA and protein expression in the bone marrow of cathepsin G−/− mice. (A) Lanes 1 through 3 show an S1 nuclease protection analysis of cathepsin G and β2 microglobulin mRNAs in bone marrow samples derived from +/+, +/−, and −/− mice. In lanes 4 through 6, a Western blot was performed with a rabbit antimurine cathepsin G antibody prepared against a peptide from a unique region of the cathepsin G protein (see Materials and Methods). After hybridization and chemiluminescence, the blot was stripped and reprobed for the presence of β-actin to control for protein loading. (B) Analysis of mMCP-2 mRNA in cultured mast cells derived from the bone marrow of cathepsin G+/+ and −/− mice. An S1 nuclease protection assay was performed with probes for mouse β₂ microglobulin and either mouse cathepsin G or mMCP-2, as indicated. The positions of probe fragments protected from S1 nuclease digestion by correctly spliced mcathepsin G and mMCP-2 are shown. Mast cell mRNA from cathepsin G+/+ animals contains easily detectable mcathepsin G mRNA. RNA derived from cathepsin G−/− mast cells shows no cathepsin G mRNA, as expected, and a 10-fold reduction in mMCP-2 mRNA levels.