ENU mutagenesis induced a T to C mutation at position c170 in the first exon, resulting in a phenylalanine to serine mutation at amino acid 57. RT-PCR shows no difference in mRNA expression levels compared to wild-type, however, Western blot analysis indicates a significant reduction of protein in the bone marrow of homozygotes. TPI1 enzyme activity is 10%, 12%, 13% and 16% of wild-type levels in red blood cells, in the brain, in bone marrow-derived macrophages, and in unsorted bone marrow, respectively. (J:263104)