Whole-mount in situ hybridization (WISH) is a method to visualize gene expression through hybridization of in vitro synthesized riboprobes to cellular mRNAs. WISH has been used in developmental biology for decades and was adapted to many species, especially for model organisms of developmental biology. The method has evolved, from analyzing small embryo batches to large-scale gene expression screenings, using: (1) manual or automated protocols, (2) colorimetric or fluorescent detection of the hybridized riboprobes, and (3) individual or systemic image acquisition and storage. As for bovine embryo staging, the in situ hybridization of whole embryonic discs has both proved useful and efficient, provided that a few improvements were brought to the in vitro riboprobe synthesis.
