Changes in expression of mRNA specific for cell adhesion molecules (L1 and NCAM) in the transected peripheral nerve of the adult rat

Abstract

The relative amounts of transcripts specific for the adhesive molecule L1 and the neural cell adhesion molecule (NCAM) in the distal stump of transected rat sciatic nerves were determined by quantitative Northern blot analysis during the first four weeks after injury. Two days after operation, transcript levels were approximately 50% lower in the lesioned than in the unsevered control nerve reaching maximum values 2 and 3 times over control for L1 and NCAM mRNAs, respectively, after 3 weeks. In contrast, expression of the mRNAs specific for the myelin-associated glycoprotein (MAG) and for the major myelin protein of the peripheral nervous system, P0, dropped to 10% or less of the control after nerve injury and did not exceed 30 and 20%, respectively, 3 weeks after the lesion. The up-regulation of L1- and NCAM-specific mRNAs in distal nerve stump parallels the induction of L1 and NCAM protein expression by Schwann cells of lesioned nerves as revealed by previous immunocytochemical studies and may reflect the Schwann cells' capacity to recapitulate development and to promote axonal regrowth.