This transgenic strain carries the Enhanced Green Fluorescent Protein (Clontech) driven by chicken beta-actin promoter and CMV intermediate early enhancer. The transgene was found to have integrated on the X chromosome. Mice of this strain, and cells derived from them, can be distinguished from wildtype on the basis of fluorescence. Transgene expression is seen as early as ~embryonic day 2.75, as morula stage embryos begin to compact. Expression of EGFP is spatiotemporally widespread, though levels differ between different lineages (e.g., expression is slightly higher in the heart). As the transgene is located on the X chromosome, transgenic males will exclusively transmit the EGFP transgene to their female offspring, providing the basis for a non-invasive sexing assay based on green fluorescence. The Donating Investigator reports that female homozygotes are not viable on this C57BL/6J congenic background. Hemizygous females on the congenic C57BL/6J background are viable and fertile. These mice may be useful for sex discrimination prior to overt sexual dimorphism (embryonic day 12.5), monitoring X-inactivation, and may be a source of fluorescently marked cells/tissues.
In an attempt to offer alleles on well-characterized or multiple genetic backgrounds, alleles are frequently moved to a genetic background different from that on which an allele was first characterized. This is the case for the strain above. It should be noted that the phenotype could vary from that originally described. We will modify the strain description if necessary as published results become available.
