Hematopoiesis serves as a useful model system for studies of cell fate determination and lineage plasticity. Lineage-specific transcription factors play essential roles in these processes by activating terminal maturation genes, while simultaneously repressing alternate lineage and stem cell genes. Yet, how these factors selectively activate some genes while repressing others remains unclear. Importantly, normal hematopoietic transcription factors are also frequently mutated in human leukemias and pre-leukemic conditions. Therefore, further understanding their regulatory mechanisms should provide novel insights into the molecular pathogenesis of these cancers and potentially lead to new therapeutic strategies.

Current emphasis in my lab is on GATA, RUNX and ETS family transcription factors and their association with epigenetic regulators and cell-signaling molecules. We are currently taking a number of approaches to these studies, including: (1) a proteomic strategy involving the isolation and characterization of their associated multiprotein complexes. This utilizes metabolic biotin tagging and streptavidin affinity purification followed by whole lane mass spectrometry. The functional significance of validated proteins is then assessed by lentiviral shRNA gene silencing in primary cells, zebrafish morpholino experiments, and/or conventional mouse knockout and knockin techniques; (2) ChIP-seq to identify genome-wide chromatin occupancy sites of these factors and their associated proteins; (3) RNA-seq analysis to examine gene expression changes associated with chromatin occupancy events; (4) gel filtration chromatography and mass spectrometry to identify key post-translational modifications involved in assembly of the transcription factor multiprotein complexes; (5) manipulation of induced pluripotent (iPS) cells from patients with hematopoietic disorders to test mechanistic hypotheses ; (6) linkage analysis and whole exome sequencing to identify novel genes involved in families with leukemia predisposition; (7) CRISPR/Cas9 gene editing to test functional significance of genetic elements; and (8) ChIA-PET to examine chromatin architecture.

Key recent findings include identification of physical and functional interactions between GATA and RUNX factors with Polycomb Repressive Complexes; elucidation of a novel regulatory axis for RUNX1 involving src-mediated tyrosine phosphorylation and Shp2 mediated tyrosine dephosphorylation; identification of the Kruppel-type zinc finger transcription factor ZBP-89 as a novel GATA associated protein that plays a role in erythroid development and human globin gene regulation; and identification of key developmental differences between fetal and adult megakaryocytes that contribute to a unique form of leukemia found in newborns with Down syndrome.