Mouse Genetics Laboratory Shared Resource Summary The Mouse Genetics Laboratory (MGL) Shared Resource provides Masonic Cancer Center (MCC) and Office of Academic Clinical Affairs (OACA) members with access to state-of-the-art technologies required to create and efficiently study genetically modified mice. Genetically modified mice have been vital tools for cancer studies for many years, enabling researchers to determine the roles of specific genes in cancer-relevant traits such as immune evasion, tumor initiation, and metastasis. MGL meets this need through the following specific aims: 1) Produce transgenic and knockout mice, 2) Cryopreserve mouse sperm and embryos, 3) Assist with mouse embryo manipulation, and 4) Provide scientific consultation and specialized services. These services provide MCC members convenient, cost-effective access to genetically modified mice. Access to these mice and associated technologies is critical to the ongoing work of MCC, particularly to members of the Genetic Mechanisms, Immunology, and Cellular Mechanisms Programs. MGL is led by Dr. Timothy Hallstrom, who has 15 years of experience with mouse genetics research. He is the PI of a research laboratory focused on the cellular mechanisms controlling the retinoblastoma protein. Day-to- day operations of MGL are managed by Yun You, PhD, who also educates users of the laboratory on policies, protocols, and maintenance of transgenic mouse strains. During the current period of support, MGL was able to rapidly respond to investigators’ needs during the COVID-19 outbreak by processing many different lines for sperm cryopreservation. We introduced a new service that allows 2-cell embryos to be frozen for later rederivation. This circumvents the usual need for sometimes complex breeding encountered after standard frozen embryo derivation. We have also worked with the Genome Engineering Shared Resource to significantly improve the efficacy of CRISPR with large DNA constructs by using adeno-associated virus for CRISPR delivery of large insertions (~4.5 kb). Services offered internally by MGL are often more cost-effective and efficient than using external providers. MGL is supported by the University as well as CCSG funds, and MCC members are given priority over other users. In fiscal year 2022, 34 researchers used MGL services, of whom 27 were MCC members.