Fig. 1. Mutational status in 149 patients with ET. (A) Frequency of JAK2, CALR, and MPL mutations in ET. Eighteen percent of patients were negative for all three kinds of mutations. (B) Analysis of the CALR C-terminal amino acid (AA) sequence. In addition to the common Type 1 and Type 2 mutations, nine types of CALR exon 9 mutations were observed in one case each. All mutation types resulted in +1 bp frameshifts and led to a novel C-terminal peptide sequence, in which the KDEL motif was absent and positively charged AAs (red text) were substituted for negatively charged AAs (blue text).

Abbreviations: ET, essential thrombocythemia; WT, wild type.