Investigating the role of Runx2 in haematopoiesis

Thesis

Self-renewing multipotent haematopoietic stem cells (HSCs) are a rare but vital cell population supporting life-long homeostasis of the entire blood and immune system. Due to the paucity of HSCs and limitations in ex vivo HSC expansion, it has been difficult to comprehensively study the genetic regulators of the balancing of HSC self-renewal and differentiation.

Investigation of a genome-wide ex vivo CRISPR screen in mouse haematopoietic stem and progenitor cells (HSPCs) uncovered many putative negative regulators and essential genes which have previously been uncharacterised in HSCs. The RUNX transcription factor family were identified as putative negative regulators of HSC expansion. Runx1 and Runx2 loss promoted HSC expansion ex vivo and increased engraftment in vivo but had contrasting effects on the reconstitution of the broader haematopoietic system, therefore revealing nonredundant roles for Runx family members in haematopoiesis.

Runx2 was further validated as a potent regulator of haematopoiesis, using a haematopoieticspecific Runx2flox mouse. Heterozygosity of Runx2 was sufficient for increased HSC expansion ex vivo and increased engraftment in vivo. Runx2 was found to have a role in regulation of HSC self-renewal potential. Its loss, however, had no effect on steady-state haematopoiesis.

Runx2 loss also decreased T-cell output and partially blocked progression of early T-cell differentiation in the thymus. This supports a model where Runx2 regulates migration of lymphoid progenitor cells through T-cell differentiation, as Runx2-deficient lymphoid progenitor cells accumulated in the bone marrow and thymus.

In summary, the findings presented in this thesis demonstrated new roles for Runx2 in regulating T-cell output and self-renewal potential of HSCs.

Authors: Meaker, GA

• DOI: 10.5287/ora-wxzzxqyad
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Keywords: haematopoiesis; haematopoietic; transcription factor; genetics; gene; blood; runx2
• Subjects: Blood cells; Hematopoietic stem cells; Biology