FIG. 3.
Genic expression of XP and XM in the early embryo. (A) RNA/DNA FISH to confirm the specificity of RNA FISH signals. To ensure that nascent RNA signals originated from the corresponding genes, images were captured, cell coordinates marked, and slides denatured for subsequent DNA FISH using the same BAC probe (labeled with a different fluorophore). Note that RNA and DNA signals were perfectly coincident, confirming the specificity of RNA FISH. A representative experiment is shown. (B, D, G, and I) Nascent RNA FISH of indicated genes combined with Xist RNA FISH. Representative nuclei are shown. For all images, z sections were taken through the nucleus and merged into one plane to view all signals. (C, F, H, and J) Summary of all RNA FISH data from female (F) and male (M) embryos of the indicated stage. n, number of nuclei examined; the number of embryos analyzed is in parentheses. (E) Example of skewed expression in which the XP RNA shows fewer nascent transcripts at the four-cell stage.