These Col1a1-tetO-H2B-mcherry mutant mice contain a tet-responsive element (tetO) and a histone H2B-mCherry fusion protein, targeted to the collagen, type I, alpha 1 (Col1a1) locus. Homozygous are viable, fertile, and normal is size. Animals have a subtle kink in the tail. When bred with another mouse expressing reverse tetracycline-controlled transactivator protein (rtTA) or tetracycline-controlled transactivator protein (tTA), expression of mCherry can be regulated with the tetracycline analog doxycycline (dox) in the resulting double mutant offspring. Specifically, breeding Col1a1-tetO-H2B-mcherry mice with R26-rtTA mice (see Stock No. 006965) results in double mutant mice which express mCherry in embryonic stem (ES) cells, and differentiated trophoblast stem (TS) cells after administration of dox. These mice may be useful for visualizing pluripotent cells. The Jackson Laboratory 2024, used with permission.