A genetically modified mouse or genetically engineered mouse model (GEMM) is a mouse that has had its genome altered through the use of genetic engineering techniques. Genetically modified mice are commonly used for research or as animal models of human diseases and are also used for research on genes. Together with patient-derived xenografts (PDXs), GEMMs are the most common in vivo models in cancer research. Both approaches are considered complementary and may be used to recapitulate different aspects of disease. GEMMs are also of great interest for drug development, as they facilitate target validation and the study of response, resistance, toxicity and pharmacodynamics.

Rudolf Jaenisch is a Professor of Biology at MIT and a founding member of the Whitehead Institute for Biomedical Research. He is a pioneer of transgenic science, in which an animal’s genetic makeup is altered. Jaenisch has focused on creating genetically modified mice to study cancer, epigenetic reprogramming and neurological diseases.