Abstract
Acridine orange (AO) was shown to be an effective probe for the ultrastructural localization of gene expression in embryonic epithelial and ectomesenchymal cells during rabbit incisor tooth organogenesis. A concentration of 10 −2 M AO provided high-resolution localization of intranuclear binding sites indicative of “transcriptively active” euchromatin portions of the cell nucleus. This method was combined with an analysis of the distribution of silver grains resulting from the incorporation of labeled uridine into ribonucleic acid molecules as evaluated by RNAse T 1 and actinomycin D sensitivity. Comparisons of the spatial distribution patterns of (1) electron-dense reaction products resulting from AO binding to euchromatin, and (2) silver grains resulting from the incorporation of uridine into newly synthesized RNA molecules, localized several discrete “transcriptively active” regions in the cervical loop of progenitor ectomesenchymal and adjacent epithelial cell prior to overt cell differentiation. The results justify further investigations of acridine orange and other related molecules as ultrastructural probes for gene expression during embryonic epithelial-mesenchymal interactions associated with epidermal organogenesis.
Published Version
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