From transplantation to transgenics: mouse models of developmental hematopoiesis

The mouse is integral to our understanding of hematopoietic biology. Serving as a mammalian model system, the mouse has allowed for the discovery of self-renewing multipotent stem cells, provided functional assays to establish hematopoietic stem cell identity and function, and has become a tool for understanding the differentiation capacity of early hematopoietic progenitors. The advent of genetic technology has strengthened the use of mouse models for identifying critical pathways in hematopoiesis. Full genetic knockout models, tissue-specific gene deletion, and genetic overexpression models create a system for the dissection and identification of critical cellular and genetic processes underlying hematopoiesis. However, the murine model has also introduced perplexity in understanding developmental hematopoiesis. Requisite in utero development paired with circulation has historically made defining sites of origin and expansion in the murine hematopoietic system challenging. However, the genetic accessibility of the mouse as a mammalian system has identified key regulators of hematopoietic development. Technological advances continue to generate extremely powerful tools that when translated to the murine system provide refined in vivo spatial and temporal control of genetic deletion or overexpression. Future advancements may add the ability of reversible genetic manipulation. In this review, we describe the major contributions of the murine model to our understanding of hematopoiesis.