FER and acute myeloid leukemia: Although we could not conclude whether it was expanded, the determination versus proliferation of erythrocyte precursors in the absence of Fer, supported a cellular proliferation role, rather than specification, as it has been previously shown in that Fer kinase is required for proper cell cycle control in models ranging from nematode endoderm proliferation and seam cell division [26,27] to acute myeloid leukemia cell lines [53].