Relative abundance of the alternatively transcribed NF-E2 mRNA isoforms 1A and 1F in PV patients and healthy controls. (A) Schematic diagram of the human NF-E2 genomic locus. Two alterative promoters, 1A and 1F, are present, transcribing noncoding exons 1A or 1F, respectively. Both NF-E2 mRNA isoforms share exons 2 and 3, which contain the ORF (indicated in black). (B) Northern blot analysis of exon 1A– or exon 1F–containing NF-E2 mRNA expression in PV patients and healthy controls. Total RNA from purified peripheral blood granulocytes was probed with cDNA fragments specific for Exon 1A (top) or 1F (middle), respectively. A cDNA fragment of the GAPDH gene was used a RNA loading control (bottom). (C) Quantitation of NF-E2 Exon 1A (left) and Exon 1F (right) expression in PV patients and healthy controls. RNA was isolated from purified granulocytes of 10 PV patients as well 9 healthy controls (HC) and subjected to quantitative RT-PCR analysis for NF-E2 exon 1A and exon 1F expression. A standard curve with known copy numbers of the 2 NF-E2 exons and β-2-microglobulin (B2M) was included on each plate. Sample copy numbers of each NF-E2 exon and β-2-microglobulin were determined from the standard curve and are expressed as relative ratios (copy number NF-E2 exon per 10³ B2M molecules). The median is depicted by a horizontal line; **P < .01, ***P < .001 by t test.