Protocol for an in vivo CRISPR screen for germinal center B cells in mice using ecotropic retrovirus

The lack of an in vitro model that recapitulates germinal center (GC) B cell biology necessitates the use of animal models for genetic studies. Here, we present a protocol for an in vivo CRISPR screen for GC B cells in mice using an ecotropic retrovirus. We describe steps for constructing a single guide (sgRNA) library and performing a genetic screen in a mouse model of protein immunization, including procedures for sequencing and data analysis.