Axonal modulation of myelin gene expression in the peripheral nerve

✍ Scribed by A. C. LeBlanc; Dr. J. F. Poduslo

• Publisher: John Wiley and Sons
• Year: 1990
• Tongue: English
• Weight: 951 KB
• Volume: 26
• Category: Article
• ISSN: 0360-4012
• DOI: 10.1002/jnr.490260308

✦ Synopsis

Myelin gene expression (Po, MBP, P,, and MAG) was investigated during Wallerian degeneration and in the presence or absence of subsequent axonal regeneration and remyelination. The steady state levels of mRNA and protein were assessed in the crushed or permanently transected rat sciatic nerve at 0, 1, 4, 7, 10, 12, 14, 21, and 35 days after injury. The mRNA and protein steady state levels of the myelin specific genes, Po and the MBPs, decreased to low yet detectable levels during Wallerian degeneration and returned to normal levels with subsequent axonal regeneration. The steady state level of P, protein also followed a similar pattern of expression. The steady state level of MAG mRNA decreased to undetectable levels by 4 days of injury in the permanently transected nerve. After crush injury, re-expression of MAG to levels comparable to those of normal nerves preceded that of P, by 2 days and that of Po and the MBPs by 3 weeks during axonal regeneration and remyelination. These results support the proposed roles for MAG in the formation of initial Schwann cell-axonal contact required for myelin assembly, for P, in fatty acid transport during myelination, and for Po and the MBPs in the maintenance of the integrity and compactness of the myelin sheath. In addition, these results indicate that the expression of the myelin specific genes, P , and MBP, is constitutive and that the level of myelin specific mRNAs is modulated by axonal contact and myelin assembly.