Use of a biotinylated probe and in situ hybridization for light and electron microscopic localization of Po mRNA in myelin-forming Schwann cells.

A biotinylated Po glycoprotein cDNA was hybridized in situ to aldehyde-fixed vibratome sections and to aldehyde-fixed thin sections of Lowicryl-embedded trigeminal ganglia of 15 day old rats. Alkaline phosphatase and peroxidase detectors were used for light microscopic (LM) studies and peroxidase or colloidal gold were employed for electron microscopic (EM) detection. In both LM and EM sections, probe was found in cytoplasmic areas of myelin-forming Schwann cells that were enriched in granular endoplasmic reticulum, demonstrating that these regions contain Po mRNA. Interestingly, Po mRNA tended to cluster in regions close to the developing myelin sheath. Relatively simple methods are here described for EM detection of mRNA with reasonable tissue preservation and high resolution. These methods may be useful for developmental and disease-related studies of specific mRNAs in mammalian tissues.