Abstract
This article contains detailed protocols for the localization of mRNA transcripts within whole Drosophila embryos. The procedures are based on the use of digoxigenin-, fluorescein-, and biotin-labeled antisense RNA probes for nonradioactive detection of transcripts. The labels are visualized in situ by differently colored water-insoluble precipitates using alkaline phosphatase- or beta-galactosidase-based immunoassays. First, a basic method is described that allows detection of transcript distribution(s) of one or more genes using the same color precipitate. Second, a sequential alkaline phosphatase detection method is presented that permits the visualization of two or three independent transcript patterns in multiple colors in the same embryo. Third, a shortened two-color in situ hybridization protocol is provided that employs a combination of beta-galactosidase and alkaline phosphatase colorimetric reactions for differential detection. The two-color in situ hybridization methods work equally well in Drosophila and zebrafish embryos and may therefore also be adaptable to other species.
