Ricerc@Sapienza

During embryogenesis and postnatal life, self-renewal, lineage commitment, and maturation of human hematopoietic stem/progenitor cells (HSCs/HPCs) are regulated by extrinsic signals from the bone marrow microenvironment and by the dynamic and cooperative interplay between lineage-affiliated transcription factors and posttranscriptional regulators1. However, the molecular mechanisms controlling HSCs/HPCs identity and lineage specification remain poorly understood. In HSCs/HPCs, lineage commitment is accompanied by chromatin modifications occurring at lineage-affiliated gene promoter ¿bivalent domains¿ presenting overlapping repressive H3K27me3 and activating H3K4me3 marks2-5. This bivalency allows cell commitment to be postponed and progenitor cells to be kept primed for an alternative lineage fate8. Polycomb (PcGs) and Trithorax (TrxGs) proteins are responsible for the trimethylation of H3K27 and H3K4, respectively. Genes presenting bivalent domains show low or intermediate expression levels in HSCs/HPCs. When HSCs/HPCs are induced to differentiate, bivalent domains are resolved into either repressive H3K27me3 or activating H3K4me3 marks paralleling changes in gene expression and transcriptional competence2-4. However, which molecular mechanisms drive the resolution of the bivalent domains and their inheritance through cell divisions is still an open question. The recent discovery of histone demethylases, LSD and the Jumonji C proteins family, adds new insights7. Histone demethylases integrate the activity of PcGs/TrxGs complexes in order to modulate the expression of genes required for lineage-specific determination. Their altered activity may support the activation of specific leukemic programs. The aim of this proposal is to identify genes targeted by histone demethylases activities during normal hematopoiesis and dysregulated in acute myeloid leukemia by theirs altered functions.