AML1 expression in MPN patients. (A) AML1 expression in PV patients and healthy controls. (B) AML1 expression in JAK2^V617F-positive and -negative ET patients and healthy controls. (C) AML1 expression in JAK2^V617F-positive and -negative PMF patients and healthy controls. (D) AML1 expression in erythroid progenitors of MPN patients and healthy controls. Erythroid progenitor cells were cultured from 5 MPN patients and 3 healthy controls as described²⁴  and interrogated for AML-1 and beta-actin expression by Western blot. HC indicates healthy controls. (E) AML1 expression in secondary erythrocytosis and thrombocytosis. (A-C and E) RNA was isolated from purified granulocytes of 31 PV patients, 12 JAK2^V617F-positive and 11 JAK2^V617F-negative ET patients, 17 JAK2^V617F-positive and 8 JAK2^V617F-negative PMF patients, 5 patients with secondary thrombocytosis and 11 patients with secondary erythrocytosis, and 28 healthy controls as indicated and subjected to quantitative RT-PCR analysis for AML1 expression. A standard curve with known copy numbers of AML1 and 18S rRNA was included on each plate. Sample copy numbers of AML1 and 18S rRNA were determined from the standard curve and are expressed as relative ratios (copy number AML1 per 10⁶ 18S molecules). The median is depicted by a horizontal line; *P < .05, **P < .01, ***P < .001 by Kruskal Wallis one-way ANOVA on Ranks and Mann-Whitney Rank sum test.