Po Glycoprotein mRNA distribution in myelin-forming Schwann cells of the developing rat trigeminal ganglion

Abstract

A biotinylated P0 cDNA was hybridized in situ to aldehyde-fixed vibratome sections of trigeminal ganglia from day 2, day 7, day 15, day 30 and adult rats. Nickel-enhanced horseradish peroxidase (HRP) was used in an antibody sandwich method to detect hybridization. After postfixation in osmium tetroxide, the sections were dehydrated in ethanol and embedded in epon. At each age, some vibratome sections were used to count the HRP-positive and HRP-negative myelin-forming Schwann cells. The percentage of HRP-positive myelin-forming Schwann cells in ganglia from day 2, 7, 15, 30, and adult rats were 31%, 56%, 47%, 12% and 3%. In sections of ganglia from 2-day-old rats, studied by light and electron microscopy, peroxidase reaction product localizing hybridized P0 mRNA was found on profiles of granular (rough) endoplasmic reticulum (RER) in perinuclear regions of Schwann cells which had formed two to three compact myelin lamellae. Peroxidase deposits were larger and more numerous in the cytoplasm cells with thicker myelin sheaths. At day 7, some Schwann cells had long external mesaxons; the cytoplasm between these mesaxons and the cell surface often contained abundant HRP-stained profiles of RER. In sections from day 7 and day 15 ganglia, substantially more reaction product was found. In each myelin-forming Schwann cell, the amount was generally proportional to the size of the newly formed myelin sheath. HRP deposits were observed all along the outer surfaces of myelin segments at these ages, and their distribution corresponded to that of the RER.(ABSTRACT TRUNCATED AT 250 WORDS)