This gene encodes a transmembrane proteolipid protein that is the predominant myelin protein present in the central nervous system. It may play a role in the compaction, stabilization, and maintenance of myelin sheaths, as well as in oligodendrocyte development and axonal survival. Mutations in this gene cause X-linked Pelizaeus-Merzbacher disease and spastic paraplegia type 2. Alternatively spliced transcript variants encoding distinct isoforms or having different 5' UTRs, have been identified for this gene. [provided by RefSeq, Jul 2008]