Tissue- and/or Temporal-Specific Mutations in Mice Using Conditional Alleles

Although many existing mutations are null alleles, multipurpose conditional alleles that can be used to delete gene function in a tissue- and/or temporal-specific manner are increasingly the alleles of choice. There are two distinct but related advantages: first, early lethal effects of the mutation can be bypassed by leaving the gene intact until later stages in development; second, indirect or secondary effects on an organ of interest can be eliminated by tissue- or organ-specific gene deletion. In this overview, we cover aspects of testing and using conditional alleles to ensure that the desired effect is obtained, including how to test the engineered conditional allele to ensure it functions as planned, and how to test any recombinase mouse strain used, including inducible transgenic or knock-in lines. Finally, we discuss how to use a conditional allele for maximum value in a phenotypic analysis.