Fluorescent latex microparticles: A non-invasive short-term cell lineage marker suitable for use in the mouse early embryo.

We have examined the potential of fluorescent latex microparticles for use as a short term cell lineage marker in the mouse preimplantation embryo. Isolated blastomeres and intact embryos rapidly adsorb and subsequently endocytose the particles (0.2 μm diameter) from a monodisperse suspension in normal medium, so that cytoplasmic endocytic organelles, but not the cytosol itself, becomes labelled. Latex fluorescence, either within intact embryos, disaggregated cells or thick resin sections, is stable during UV irradiation. The development of labelled embryos, both in terms of sequential morphological changes and their time of expression, was comparable to controls and resulted in blastocysts with normal cell numbers and capacity for tissue differentiation. Latex fluorescence is preserved within all the progeny of labelled blastomeres over several cell cycles (e.g. from 8-cell stage to 64-cell stage) and is not transmitted to unlabelled cells either by exocytosis or via midbodies. The particles are particularly suitable for labelling exclusively the entire population of outside cells in the intact embryo from the 16-cell stage onwards.