Innovative Strategies

Production of sex-sorted blastocysts

By mating wildtype females with male mice carrying an X-linked GFP transgene, we can produce blastocysts that can be sorted by sex (female embryos are fluorescent but male embryos are not).  When such blastocysts are injected with ES cells to make chimeric mice and the resulting pups are sexed at birth, we can immediately see if any sex conversion has taken place (e.g., by male ES cells being injected into female embryos, or vice versa), which is a strong indication of germline capability.