VAV1 and myeloproliferative disorder: These results show that Trp53 inactivation does not modify the amplification of all stages of differentiation observed in endogenous JAK2V617F/Vav-Cre cells, suggesting that JAK2V617F/Vav-Cre immature cell proliferation, just like the MPN phenotype, is not changed by Trp53-inactivation.