JAK2 copy number and correlation of status with PRV1 expression. (A) Representative results of MLPA analysis to measure JAK2 copy number. The relative peak areas for JAK2 are the same for 2 homozygous V617F cases with 9p LOH (M/M) and 2 healthy controls (WT/WT), indicating the presence of 2 copies of JAK2. The second case is male and shows a reduced peak height for the X-linked gene BTK compared with the 3 other cases, all of which were female. (B) PRV1 mRNA levels (log₁₀deltadeltaCtPRV1/ABL) determined by real-time PCR in 30 MPD patients with normal JAK2 (WT) and 23 MPD patients with the V617F mutation. These 23 patients are also shown split into the 12 heterozygous (HET) and 11 homozygous (HOM) cases. Vertical lines indicate the range of results, open boxes indicate the interquartile range, and thick horizontal lines indicate median values.