Distribution of JAK2 mutations in peripheral blood lineages. (A) The location of exon 12 mutations and JAK2-V617F in the Jak2 protein is shown (top). The amino acid changes caused by the individual exon 12 mutations are shown below using the single letter code. Previously described mutations (asterisk) and newly found mutations (no asterisk) are shown with the unique patient numbers (UPN) of the patients included in this study. (B) Lineage distribution of JAK2 exon 12 mutations (top) and JAK2-V617F (bottom part). Numbers in boxes indicate the percentages of chromosomes 9 with exon 12 mutations, and the shading of boxes corresponds to the ranges shown at the bottom. UPN indicates unique patient number; F, female; M, male; GRA, granulocytes; NK cells, natural killer cells; nd, not determined. Numbers in column for T-cell cloning indicate JAK2-V617F positive clones/total clones analyzed. The phenotypes of JAK2-V617F positive clones were determined by flow cytometry. NK cell phenotype: CD3⁻CD56⁺; T-cell phenotype: CD3⁺CD56⁻. * Note that patient p021 was positive for exon 12 mutation N542-E543del and for JAK2-V617F. (C) Phenotypic analysis of JAK2-V617F positive clones. Flow cytometic analyses. One JAK2-V617F positive clone from patient p035 consisted of CD3⁺CD56⁻ T cells. All other positive clones from patients p136 and p116 were CD3⁻CD56⁺ NK cells (top panel). Allele-specific PCR for JAK2-V617F showing T-cell clone from p035 was homozygous for JAK2-V617F, whereas the clones from patients p136 and p116 were heterozygous for JAK2-V617F (bottom panel).