Clonal genotypic patterns of erythroid and granulocytic progenitors from ET and PV patients. Bone marrow CD34⁺ cells from PV and ET patients were seeded in methylcellulose in the presence or absence of Epo or G-CSF. Erythroid and granulocytic colonies were picked on day 14 and genotyped by real-time PCR. Mixed profiles of JAK2 617V>F homozygous, heterozygous, and normal colonies were called homozygous profiles. Patterns with heterozygous and normal colonies and without any homozygous colonies were called heterozygous profiles. (A) Detection of the JAK2 1849G>T (617V>F) mutation by real-time PCR. The results of 3 representative erythroid colonies from one PV patient with a homozygous JAK2 617V>F profile (homozygous PV), one PV patient with a heterozygous profile (heterozygous PV), and one ET patient (ET) are shown. The plots represent the fluorescence curves resulting from the amplification of the JAK2 mutated (T) and JAK2 wild-type (G) alleles. The genotype of each colony is indicated to the left of the amplification plots: G/G, wild-type colony; G/T, colony with heterozygous mutation; T/T, colony with homozygous mutation. (B) Histograms showing the mean percentages of JAK2 617V>F homozygous (■), heterozygous (▩), and JAK2 wild-type (□) colonies from 14 PV patients with a homozygous profile (homozygous PV), 6 PV patients with a heterozygous profile (heterozygous PV), and 6 ET patients. Numbers above the bars indicate the total number of colonies that were genotyped. Error bars indicate SEM. Note the high percentage of mutated erythroid and granulocytic colonies in heterozygous PV samples.