Whole-mount in situ hybridization (WISH) optimized for gene expression analysis in mouse embryos and embryoid bodies

Whole-mount in situ hybridization (WISH) is a technique widely used in developmental biology to study the localization of RNA sequences in intact tissues or whole organisms. In this chapter we present a detailed protocol that was optimized for gene expression analysis in early stage mouse embryos (5.5-10.5 days post-coitum) and embryoid bodies formed by differentiating embryonic stem cells and can be used for the detection of up to two distinct RNA sequences simultaneously. The initial steps of the procedure are the generation of the labeled riboprobe(s) and the embryo or embryoid body preparation, which can be completed in less than 2 days. The actual WISH procedure, comprised of the hybridization, the post-hybridization washes, and the immunological staining, can be completed in 3 days.