EXPRESSION OF PO PROTEIN MESSENGER-RNA ALONG RAT SCIATIC-NERVE DURING DEVELOPMENT

The temporal and spatial expression of PO protein mRNA in the spinal nerve roots and in distal (popliteal trifurcation) segments of the developing rat sciatic nerve was examined using in situ hybridization. PO mRNA was undetectable in the PNS portions at day 16 post-fertilization (E16) but present in the roots as well as in the sciatic nerve by E18. While Schwann cells were labelled by in situ hybridization at E18, it was not until birth (Pi) that cells revealed the typical clusters of silver grains in a perinuclear distribution. Hybridization signal rose between P5 and P10, than decreased at P40, with no significant difference of PD mRNA levels between the different PNS portions at each age studied. These findings demonstrate the lack of proximo-distal gradient in abundance of PO mRNA during rat PNS development and add further insight in understanding the dynamics of axonal regulation of myelination in the PNS.