ABSTRACT: Project 1, Quantitative analytical assessment of mouse embryo quality Embryo manipulation (e.g., cryopreservation and recovery, rederivation, genetic manipulation, etc) is central to the MMRRC mission. Today’s gold-standard evaluation of embryo quality relies on trained technicians visually evaluating morphology and overall appearance under light microscopy. Another mission of the MMRRC is to conduct research that increases the value of the repository to the scientific community. Genetic engineering technology offers the potential to modify existing lines or even generated specific new lines. The Ravata individual zygote electroporator (RIZE) is capable of sensing the electrical properties of the embryo and quantitatively evaluating embryo stage and health. The ability to quantitatively evaluate embryo health would establish a standardize protocol across all centers with minimized variability between technicians and centers. Further, the limitations in the ability to cryopreserve embryos post genetic manipulation prevent the ability of MMRRC centers to engineer lines and cryopreserve them for rederivation at a future date. These hurdles and roadblocks could all be overcome by using IVF-generated and frozen zygotes that are cryorecovered on the day of electroporation and then cryopreserved again after electroporation to await cryorecovery for embryo transfer at a later time. We have assembled a unique team of experts to advance the mission of the MMRRC and take these novel technologies and apply them to standardizing quantitative evaluation of cryopreserved embryos and genetically engineered embryos in the following aims. Specific Aim 1: Develop, establish, and validate a protocol for reliable and reproducible quantitative evaluation of cryorecovered IVF-derived embryos. The combination of our expertise in embryo manipulation in combination with the RIZE sensor enables us to investigate this novel quantitative method for assessing embryo health pre and post -cryopreservation prior to embryo transfer. Specific Aim 2: Apply quantitative evaluation to select IVF-derived embryos for CRISPR genome editing for embryo transfer. We will use the RIZE sensor to quantitatively assess the viability of embryos after CRISPR-EZ. Our expectation is that a quantitative method of evaluating embryo health will help to provide a means to standardize embryo quality assessment across centers, increase post thaw viability, and decrease variation between groups. Additionally, the MMRRC will be able to improve liveborn rates after embryo cryopreservation, CRISPR electroporation, and transfer. ABSTRACT: Project 2, Optimizing the rederivation of gut microbiota from MMRRC mice The MMRRC plays a pivotal role in archiving mouse models in publicly accessible repositories, provides numerous services to investigators and conducts novel research to enhance MMRRC services and improve the quality, reproducibility and robustness of mouse models. The MMRRC recognizes the imp...