FMNL1 and acute lymphoblastic leukemia: Given the importance of cell migration for leukemia dissemination, and the reported role of mDia1 in T cell migration (20, 21, 24) and of the related Formin FMNL1 in leukemia migration (27), we investigated if mDia1 depletion affected the ability of B-ALL cells to complete the various steps of transendothelial migration.