Gene expression profiling distinguishes patients with MPN from normal controls and homozygous JAK2V617F-mutant MPN patients from others. (A) Hierarchical clustering was performed on gene expression microarray data from the granulocytes of 55 MPN patients and 11 normal subjects. MPN patients were characterized by a distinct gene expression profile compared with normal subjects. Correlation of patient samples with clinical MPN subtype and JAK2 genotype showed that MPN patients with homozygous JAK2V617F mutations were characterized by a unique cluster of differentially expressed genes among MPN patients. (B) Heatmap representation of significant differentially expressed genes between normal subjects and MPN patients with homozygous JAK2V617F (265 genes FC >3 and FDR <0.01), heterozygous JAK2V617F (222 genes FC >2 and FDR <0.05), and JAK2 WT genotypes (209 genes FC >2 and FDR <0.05). A red-blue color scale depicts normalized gene expression levels (red: high; blue: low).