LAUSR

Hematopoiesis orchestrates the daily requirement of producing and maintaining the various blood cell lineages in the right quantities. It must also respond rapidly to injury and infection to expand specific lineages on demand then return them to steady state levels. Understanding the sophisticated mechanisms regulating this balancing act can uncover therapeutic targets for manipulating blood cell production in disease treatment. In a forward genetic screen for zebrafish myeloid mutants, we identified a requirement for ZBTB11, a ZBTB (BTB/POZ) transcriptional repressor, in definitive hematopoiesis. To understand its relevance to mammalian systems, we extended these studies to mouse. When Zbtb11 is deleted in the hematopoietic compartment embryos do not survive past E18.5 likely due to insufficient hematopoiesis. Phenotypic HSCs (SLAM) are specified in over-abundance at E14.5 through E17.5 compared to controls. Functional analysis, however, shows they are unable to effectively differentiate into committed progenitors and mature lineages in fetal liver. Hematopoietic content in fetal bone marrow is mostly absent at E16.5 – E17.5 pointing to bone marrow failure. Further analysis showed Zbtb11-/- HSCs fail to proliferate in an in vitro proliferation assay and are constrained in their progression through the cell cycle demonstrating a role for Zbtb11 in proliferation and cell cycle regulation in mammalian hematopoiesis. We have undertaken scRNAseq in Zbtb11 /- and control HSC populations to understand heterogeneity within and between these populations, and what genetic programs have been altered. Mechanistic evaluation is under way. In summary, our findings establish a conserved cell autonomous role for Zbtb11 in mammalian definitive hematopoiesis, specifically in HSC function, opening up new avenues for understanding and manipulating HSCs.