DAPI Staining of Whole-Mount Mouse Embryos or Fetal Organs.

Mouse embryos and fetal organs have no pigmentation except for the retinal pigmented epithelium of the eye at subsequent stages of development. This makes it difficult to visualize and photodocument embryonic structures using conventional light microscopy. A simple method is provided here that uses fluorescent nuclear stains. At the relatively low magnifications of dissecting microscopes, the nuclei of embryonic tissues essentially become "pixels" of fluorescence that "paint" the embryo, providing images similar to those obtained by low-magnification scanning electron microcopy (SEM). This method can be applied to standardly fixed whole embryos at least up to embryonic Day 14.5 (E14.5), and to embryos that have been processed for whole-embryo in situ hybridization and immunostaining. Dissected tissues and organs (e.g., palate, heart, lungs, gastrointestinal tract) may also be stained and visualized with this technique.