Reprogramming adult hematopoietic progenitors towards fetal-restricted lymphopoiesis via Cbfb2gene dosage

Abstract

Abstract Hematopoietic Stem Cells (HSC) hold the potential to self-renew and differentiate into most immune cell subsets throughout life. However, some specialized immunocytes like microglia, B-1 B cells and γδ T cells emerge only during fetal life, and they cannot be generated by adult HSC. We discovered that CBFβ isoform 2 (CBFβ2), an evolutionarily conserved component of the RUNX transcription factor complex, reprograms adult HSC into acquiring fetal hematopoietic potential. While Cbfb2heterozygous mice generated normal numbers of mature IL-17 producing γδ T (Tγδ17) cells, we found that they lacked DN1d cell containing Tγδ17 precursors. Thus, Cbfb2gene dosage is critical for imprinting Tγδ17 differentiation potential in distinct precursor cells. In line with this reprogramming, Cbfb2haploinsufficient adult bone marrow (BM) progenitors, which are normally inefficient at Tγδ17 cell generation, became permissive for innate T cell development. Analysis of transcriptional profiles of HSCs and lymphoid progenitors (LMPPs and CLPs) from adult BM revealed that, among hemopoietic progenitors, LMPPs from Cbfb2heterozygous mice were the most affected by Cbfb2gene dosage and upregulated genes implicated in embryonic hematopoiesis. Using In Utero Transplantation of adult hematopoietic progenitors into the fetal liver of E14.5 pregnant dams’ fetuses, we were able to successfully reconstitute Tγδ17 cells and confirm an unprecedent bias in Tγδ17 development underpinned by reduced CBFβ2-dependent transcriptional activity. Our findings identify gene network architectures that impose temporal restriction on hematopoietic pluripotency and that could be exploited for the generation of fetal-derived lymphocytes in adult life.