NPM1 and acute myeloid leukemia: As shown in Fig. 1B, the antibody FC82291 recognized NPM1 but did not recognize NPM 1.3, a splice variant of NPM1 which lacks the 37 C-terminal amino acids of NPM1, nor did it recognize NPM1c, an AML patient-related NPM1 mutant in which the 7 C-terminal amino acids of NPM1 are substituted to 11 unrelated amino acids by a frameshift mutation (Fig. 1B, lanes 2–4).