C/EBPα primes HSPCs for neutrophilic differentiation. We hypothesize that downregulation of C/EBPα in the bone marrow in mice results in the following phases. The early phase: a block of neutrophilic differentiation causes a feedback mechanism on HSCs and progenitors to stimulate more differentiation. This results in an increase in cycling of HSCs and expansion of downstream progenitors. Advanced phase: HSCs are consumed, while progenitors still show expansion. Late phase: HSC and progenitor exhaustion leading to bone marrow failure. GMP, granulocytic/monocytic progenitor; MPP, multipotent progenitor; N, neutrophils.