AXONAL SWELLINGS AND DEGENERATION IN MICE LACKING THE MAJOR PROTEOLIPID OF MYELIN

Glial cells produce myelin and contribute to axonal morphology in the nervous system. Two myelin membrane proteolipids, PLP and DM20, were s hown to be essential for the integrity of myelinated axons. In the abs ence of PLP-DM20, mice assembled compact myelin sheaths but subsequent ly developed widespread axonal swellings and degeneration, associated predominantly with small-caliber nerve fibers. Similar swellings were absent in dysmyelinated shiverer mice, which lack myelin basic protein (MBP), but recurred in (MBPPLP)-P-star double mutants. Thus, fiber de generation, which was probably secondary to impaired axonal transport, could indicate that myelinated axons require local oligodendroglial s upport.