Frequency of V617F homozygosity in patients with PV. (A) JAK2 sequence analysis of granulocyte DNA samples from a patient with PV. Note the V617F-heterozygous sequence pattern in a sample from 1992, and a V617F-homozygous pattern in a sample from 1998. (B) BsaXI digestion of JAK2 exon 14 and SCL intron 1 was used to genotype DNA from BFU-Es, EECs and CFU-GMs cultured from PV patient 13. Lanes 1-4 indicate BFU-Es; lanes 5-8, EECs; lanes 9-12, CFU-GMs; lane 13, undigested granulocyte DNA from a V617F-negative control; lane 14, BsaXI-digested granulocyte DNA from a V617F-negative control; and lane 15, water. V617F-homozygous colonies are seen in lanes 1, 6, 7, and 11; heterozygous colonies are seen in lanes 3, 5, 8, 9, and 12. (C) Frequencies of wild-type, V617F-heterozygous, and V617F-homozygous peripheral blood BFU-Es in 17 PV patients with a heterozygous JAK2 granulocyte sequence trace were determined using PCR and BsaXI digestion. The absolute number of colonies genotyped from each patient is at the top of each column. Column 18 shows a V617F-positive PV patient with a wild-type sequence trace; column 19, a PV patient with a V617F-homozygous sequence trace.