Cell type–specific spatiotemporal control of GFP-tagged protein degradation in mice

Loss-of-function studies are a central approach to understanding gene/protein function. In mice, this often relies upon heritable recombination at the DNA level. This approach is slow and nonreversible, which limits both spatial and temporal resolution of analysis. Recently, degron techniques that directly target proteins for degradation have been successfully used to quickly and reversibly knock down proteins. Currently, these systems have been limited by lack of tissue/cell type specificity. Here, we generated mice that allow spatial and temporal control of GFP-tagged protein degradation. This DegronGFP line leads to degradation of GFP-tagged proteins in different cellular compartments and in distinct cell types. Further, it is rapid and reversible. We used DegronGFP to probe the function of the glucocorticoid receptor in the epidermis and demonstrate that it has distinct functions in proliferative and differentiated cells-an analysis that would not have been possible with traditional recombination approaches. We propose that the ability to use GFP knock-in lines for loss-of-function analysis will provide additional motivation for generation of these useful tools.