VAV1 and essential thrombocythemia: To study MPN neutrophil efferocytosis, we used mice carrying JAK2V617F mutation driven by Mx1-Cre or Vav1-Cre, which respectively develop MPN resembling polycythemia vera (PV) or essential thrombocythemia (ET)28, and ET-like mice carrying the second most common mutation (CALRdel52)29.