Critical modulation of hematopoietic lineage fate by Hepatic Leukemia Factor

A gradual restriction in lineage potential of multipotent stem/progenitor cells is a hallmark of adult hematopoiesis, but the underlying molecular events governing these processes remain incompletely understood. Here, we identified robust expression of the leukemia-associated transcription factor Hepatic Leukemia Factor (Hlf) in normal multipotent hematopoietic progenitors, which was rapidly downregulated upon differentiation. Interference with its' normal downregulation revealed Hlf as a strong negative regulator of lymphoid development, while remaining compatible with myeloid fates. Reciprocally, we observed rapid lymphoid commitment upon reduced Hlf activity. The arising phenotypes resulted from Hlf-binding to active enhancers of myeloid-competent cells, transcriptional induction of myeloid and ablation of lymphoid gene programs, with Hlf induction of Nuclear Factor I C (Nfic) as a functionally relevant target gene. Thereby, our studies establish Hlf as a key regulator of the earliest lineage-commitment events at the transition from multipotency to lineage-restricted progeny, with implications for both normal and malignant hematopoiesis. Overall design: Gene expression profiling of control or Hlf/Hlf lentivirus infected GMLPs (2 replicates per group) and Hlf inducible GMLPs maintained for 4 days on OP9 stroma in the presence or absence of doxycycline (2 replicates per group)