Myelin plays a critical role in nervous system function and alteration
s in myelin-specific proteins cause a variety of neurologic disorders.
We isolated a novel cDNA from the CNS that shares little nucleotide s
equence homology with previously reported genes but appears to encode
a protein related to peripheral myelin protein-22 (PMP-22) based on it
s amino acid sequence, predicted structure, and cellular localization.
PMP-22 is important in peripheral myelination and Schwann cell prolif
eration, and mutations in its gene cause diseases of peripheral nerves
. The isolated cDNA is 1.8 kb in length with an open reading frame of
621 bp. Northern blot analysis detected hybridization of labeled cDNA
with a single 2.1-kb transcript only in the CNS. In situ hybridization
revealed expression of this cDNA in oligodendrocytes of brain and spi
nal cord as well as in oligodendrocyte-enriched cultures; therefore we
have named it oligodendrocyte-specific protein (OSP) cDNA. An OSP-spe
cific polyclonal antibody reacted with a single 22-kd protein present
in CNS myelin and oligodendrocytes. Developmental expression of OSP mR
NA in the spinal cord was similar to that of the mRNA for a major myel
in protein, proteolipid protein (PLP), and similar to PMP-22 in periph
eral nerves. Since OSP is localized to oligodendrocytes and myelin, ha
s a similar structure with PMP-22, and has a developmental pattern of
expression like other myelin proteins, it probably has an important ro
le in CNS myelinogenesis.