Hierarchical organization of haematopoietic stem- and progenitor cell populations during steady state and stress haematopoiesis

Normal blood cell production occurs in the bone marrow and deteriorates during ageing and is impaired by blood
cancer development. In this program we will study how normal blood cell production is regulated, and in particular
how regulatory genes form interlinked networks that allow the many different blood cell cell types to be generated
from a single stem cell. We will use this knowledge to investigate how blood cell production is perturbed in clonal
hematopoiesis (CH – a preleukemic syndrome) and myelofibrosis (MF – a hyperproliferative disorder that leads to
bone marrow failure). For this purpose, we will design and develop new genetic mouse models that accurately
replicate the genetic events that cause CH and MF in humans. As both CH and MF occurs more frequently in the
elderly, we will use these models to to identify the physiological changes that occur during ageing that contribute
to perturbation of the normal regulatory networks within hematopoietic stem cells and lead to disease
development. The identified molecules or cell types will then be targeted with appropriate drugs (which will be
developed in necessary) for their ability to counteract disease development. In this manner we hope to develop
new therapeutic strategies for these blood disorders.

Recent work from our group and others have provided an improved understanding of the hematopoietic stem- and
progenitor compartment, including the identification of novel hematopoietic stem cell (HSC) subtypes and
progenitor populations. The challenge we face now is to translate this knowledge into a better understanding of the
molecular mechanisms that control the specification of HSC subtypes and the downstream progenitor hierarchy,
and to subsequently identify and target the molecular perturbations that cause hematopoietic decline during ageing
and subversion of normal differentiation in hematological malignancies.
The current program has 3 aims: In the first aim we will use CRISPR/Cas9-based gene perturbation and
ectopic expression to identify the transcriptional regulators of key lineage bifurcations, and subsequently combine
proteomics and high-throughput perturbation of regulatory elements to identify physical and regulatory transcription
factor cross-talk and the resulting gene regulatory networks (GRNs) involved in myelo-erythroid lineage
specification. This will include measuring the effect of known leukemogenic mutations on protein-protein
interactions and GRN activity, in order to identify putative therapeutic intervention points.
In the second aim we will study how HSC fitness and susceptibility to clonal expansion is regulated by
ageing. In particular, we will develop improved mouse models of clonal hematopoiesis (CH) that allow reproducible
and temporally controlled sub-stoichiometric introduction of relevant mutations (Dnmt3a, Tet2) into HSC. These
models will be used to study the role of ageing in clonal hematopoiesis and identify extrinsic cues that promote
expansion of mutant HSCs as a strategy to ameliorate CH.
In the third aim we will use the sub-stoichiometric introduction of mutations into HSCs to generate an
accurate model of myelofibrosis (MF), and in addition use HSC subtype-specific Cre drivers to determine the role of platelet-biased HSCs in disease initiation. In these models the role of the aged micro-environment in MF
progression will be studied, and putative extrinsic regulators identified and evaluated for their therapeutic potential
in iPSC-based organoid models.
IPR from the new CH and models will be protected and commercialised where possible. New putative
molecular targets will be explored using MHU spin-offs (e.g. Alethiomics)