To determine the effect of Plek2 inhibitors in cells from MPN patients, we purified CD34-positive hematopoietic progenitor cells from 3 normal individuals and 3 patients with PV (a subtype of MPNs; patients’ clinical information is presented in Supplemental Table 3) and cultured them separately in medium promoting erythroid differentiation and proliferation. The gene discussed is PLEK2; the disease is acquired polycythemia vera.