Critical modulation of hematopoietic lineage fate by Hepatic Leukemia Factor

Hematopoiesis commences with a gradual restriction in lineage potential of multipotent stem/progenitor cells, but the underlying molecular events of this remain incompletely understood. We here identify robust expression of the transcription factor Hepatic Leukemia Factor (Hlf) in multipotent hematopoietic progenitors, which is rapidly lost with differentiation. Prolonged Hlf expression reveals it as a strong negative regulator of lymphoid development and results in a pronounced and reversible differentiation block in the B-cell lineage, while remaining compatible with myeloid fates. Reciprocally, we observe rapid lymphoid commitment upon eduction of Hlf activity. These phenotypes result from Hlf-binding to active enhancers of myeloid-competent cells, induction of myeloid-affiliated transcription and ablation of lymphoid gene programs, with Hlf induction of Nuclear Factor I C (Nfic) as a functionally relevant target gene. Collectively, we establish Hlf as a key regulator of the earliest lineage-commitment events at the transition from multipotency to lineage restricted progeny. Analysis of the genome wide binding profiles of Hlf in mulitpotent hematopoietic progenitors.