ABSTRACT The goal of the International Mouse Phenotyping Consortium (IMPC) is to develop a resource of null allele lines for every protein-coding gene in the mouse genome and, through standardized, broad-based phenotyping, catalog the biological function of each targeted gene. The NIH-funded Knockout Mouse Phenotyping Project (KOMP2) has supported two previous phases of null allele production and phenotyping, contributing to more than half of the null allele lines made and characterized by the IMPC. This application describes our plan for Baylor College of Medicine (BCM) to continue as a KOMP2 site during a third phase of funding. We propose to produce, cryopreserve, and phenotype null allele mouse lines for 600 protein coding genes. We have developed a bioinformatics approach to identify and prioritize genes with known or putative human disease associations but little-to-no in vivo functional annotation for null allele mouse line production. We will generate and validate null alleles using established CRISPR genome editing approaches and quality control procedures, cryopreserve all null allele lines using accepted techniques, and deliver germplasm to the MMRRC repositories for community- wide distribution. These null allele lines represent a gold standard resource for the scientific community and an important foundation for future research and translational studies. We will utilize our established pipelines to perform broad-based, standardized adult phenotyping on all mutant lines and assess homozygous lethal and subviable lines in an embryonic phenotyping pipeline. The phenotyping data we generate will provide fundamental new insights into mammalian biology as well as the genetic bases of human disease. All allele and phenotype data will be submitted in real time to the Data Coordination Center, ensuring the rapid dissemination of all BCM data to the wider biomedical scientific community. We will continue our production and phenotyping technology development programs, developing our own new approaches and adopting new methodologies from the community as they arise. The BCM KOMP2 team has the established expertise, experience, and resources to meet the proposed phase 3 goals in an efficient and cost-effective manner.