In contrast to previous gene expression profiling that found both mRNA and protein levels of transcription factor NF-E2 to be overexpressed in granulocytes from PV patients11, the quantitative data from MS and western blot in the present study demonstrated no change in NF-E2 levels in cultured erythroblasts from the three groups (Fig. S1 and Table 3). The gene discussed is NFE2; the disease is acquired polycythemia vera.