Low-cost camera-based estrous tracking enables transgenesis in Peromyscus leucopus, the primary reservoir for Lyme disease

CRISPR/Cas9 technology has revolutionized the production of animal models by reducing experimental timelines, slashing costs and streamlining gene editing, leading to a rapid expansion in the number of unique models for the study of human disease and gene function. However, most non-model animals, many of which are important in cancer and aging research, remain recalcitrant to genome engineering due to our limited understanding of their reproductive biology. Many wild rodents that transmit human diseases remain particularly challenging to engineer due to low pregnancy rates, the lack of external copulatory plugs, and susceptibility to premature termination of pregnancy. Here, we present low-cost activity-based estrous tracking for the efficient generation of timed pregnant and pseudopregnant white-footed mice and extend this tracking method to both lab mice and hamsters. Leveraging this technology, we demonstrate the generation of engineered Peromyscus leucopus, the primary reservoir for Lyme disease-causing bacteria and a putative model organism for studies of aging. These tools have broad implications for biomedical research and ecological engineering. ### Competing Interest Statement JB, EJC, CD and KME are the authors of multiple provisional applications filed by MIT on the method. JB is a director of the Mice Against Ticks nonprofit.