Effect of depletion of the transcriptional factor FoxP1 on gene expression in mouse normal adult hematopoietic stem and progenitor cells.

Transcription factor Forkhead box P1 (FOXP1) is a key regulator of various immune cell functions, including monocyte differentiation, B cell terminal differentiation and CD4+ or CD8+ T cell quiescence. In previous studies, we have shown that FOXP1 contributes to human hematopoietic stem progenitor cell (HSPC) and acute myeloid leukemia (AML) cell growth. Here we investigated the in vivo role of Foxp1 in early adult murine hematopoiesis. We showed that hematopoietic-specific loss of Foxp1 expression leads to attrition of the medullar HSC/Multipotent progenitor (MPP)-1 compartment in parallel with an enhancement of the myeloid-biased MPP3 compartment, without impact on MPP2 or MPP4 compartments. Foxp1-deficient HSCs exhibited a reduced self-renewal capacity in competitive hematopoietic reconstitution assays, and HSC and all MPP compartments showed enhanced proliferation with a G0 phase reduction. To further investigate the role of Foxp1 in the regulation of HSC and MPP compartments, we performed gene expression profiling analysis of HSC/MPP1 and MPP3 compartments from WT and Foxp1-deficient mice using data obtained from RNASeq of 3 different cell populations.