Fluorescence in situ hybridization of interphase nuclei isolated from whole blood of transgenic mice.

Homozygosity in transgenic mice is typically confirmed by the time-consuming practice of breeding suspected homozygotes to non-transgenics and looking for 100% transmittance of the transgene to offspring. We have devised a simple reproducible method for isolating white blood cell nuclei from small quantities of mouse whole blood and have utilized fluorescence in situ hybridization to confirm the presence of one (hemizygous) or two (homozygous) copies of the transgene locus in interphase nuclei fixed to microscope slides. This method should have other applications where in situ hybridization of interphase nuclei is desirable.