The history of MISTRG

MISTRG mice have been developed, from 2005 to 2014, in a collaborative effort between the labs of Pr. Richard A. Flavell (Yale University), Pr. Markus G. Manz (University of Zürich) and Regeneron Pharmaceuticals, with funding from the Bill and Melinda Gates Foundation.

What are MISTRG mice?

MISTRG are used for the efficient generation of "humanized mice", i.e. mice repopulated with a human immune system.

MISTRG are highly immunodeficient mice that lack T and B lymphocytes and NK cells, preventing immun erejection of the human graft. They express the human SIRPa protein, a "don't-eat-me" signal, that protects human cells from phagocytosis. Finally, several cytokine-encoding genes are humanized by knock-in replacement, resulting in defects in mouse cell populations and support for human cells. These cytokines are M-CSF, IL-3, GM-CSF and Thrombopoietin.

MISTRG is an acronym for the 7 modified genes in the genome of these mice: M-CSF^h/h IL-3/GM-CSF^h/h SIRPa^h/h TPO^h/h RAG2^-/- IL2Rg^-/-

What are the characteristics of humanized MISTRG?

• Hematopoietic Stem Cells: MISTRG support the engraftment of human hematopoietic and progenitor cells (HSPCs) of fetal, newborn and adult origin. In serial transplantation experiments, the most stringent assay of HSPC maintenance, we have detected transplantation of human cells up to quaternary recipient mice. This result is approaching the maintenance of mouse HSPCs in mouse hosts.
• Monocytes and macrophages: MISTRG mice support the development of diverse subsets of functional circulating monocytes and tissue macrophages. This is a unique feature of MISTRG compared to other humanized mouse models.
• NK cells: Human macrophages produce IL-15, a cytokine that supports the development of functional human NK cells.
• MISTRG support the engraftment of hematopoietic diseases, such as acute myeloid leukemia (AML) or myelodysplastic syndromes (MDS)

What are the limitations of MISTRG?

• Anemia: The presence of human macrophages results in the phagocytosis of mouse red blood cells. Experimental conditions need to be optimized to limit the lethal consequences of anemia.
• Adaptive immunity: Like in other humanized mouse models, antigen-specific adaptive immune responses are inefficient in humanized MISTRG. This is due to the selection of a T cell repertoire in a mouse thymus and the imperfect organization of lymphoid structure. However, T and B cells respond normally to polyclonal stimulation.

Any question?

Feel free to email us at rongvaux@fredhutch.org, we will be happy to share our lab protocols.

References

Development and function of human innate immune cells in a humanized mouse model. A. Rongvaux, Tim Willinger, J. Martinek, T. Strowig, S.V. Gearty, L.L. Teichmann, Y. Saito, F. Marches, S. Halene, A.K. Palucka, M.G. Manz, R.A. Flavell. 2014. Nature Biotechnology. 32(4):364-72.
News and Views by: H. Spits. New models of human immunity. Nature Biotechnology. 32:335-6.