IDENTIFICATION OF EMBRYONIC-CELL LINEAGES IN HISTOLOGICAL SECTIONS OF M-MUSCULUS [--] M-CAROLI CHIMERAS

Abstract

An in situ cell marker system was developed which allows identification of M. caroli and M. musculus cells in interspecific chimeras. A radioactively labeled, cloned DNA probe to M. musculus satellite DNA was hybridized in situ to sections of M. musculus and M. caroli adult tissues. Autoradiography revealed high levels of hybridization to the nuclei of M. musculus cells, but little or no label bound to M. caroli cells. The DNA probe could also distinguish M. musculus and M. caroli cells in the same tissue section. Patches of labeled and unlabeled cells were clearly identified in sections of adult chimeric tissues and also in the embryonic ectoderm of 6.5-day embryonic chimeras. The ability to recognize M. musculus and M. caroli cells in sections of chimeras should provide a powerful new tool in analyses of cell lineages in both embryonic and adult mouse chimeras. The marker system has several advantages over other marker systems so far developed, the most important of which is its ubiquity. Since it is a nuclear marker, only cells without nuclei should be unsuited to its use. The potential of the marker system was shown by its use in demonstrating directly for the first time the postimplantation derivatives of inner cell mass and trophectoderm in blastocysts, reconstituted with M. musculus trophectoderm and M. caroli inner cell mass.