Below is an instruction from Human. Write a response.
    ### Instruction:
    What causes Pelizaeus-Merzbacher disease ?
    ### Response:
    What causes Pelizaeus-Merzbacher disease? Pelizaeus-Merzbacher disease is caused by mutations in the PLP1 gene. This gene provides instructions for producing proteolipid protein 1 and a modified version (isoform) of proteolipid protein 1, called DM20. Proteolipid protein 1 and DM20 are primarily located in the central nervous system and are the main proteins found in myelin, the fatty covering that insulates nerve fibers.
    