claimed that THPO was not necessary for expression of the ET phenotype in their mouse model, in agreement with our results, in their JAK2 V617F/THPO knockout transgenic mice, thrombocytosis was eliminated and in vitro HPC proliferation, megakaryocyte number and size, and spleen size were also reduced, indicating THPO dependence in their JAK2 V617F ET transgenic mouse model. The gene discussed is THPO; the disease is essential thrombocythemia.