The oligodendrocyte-myelin glycoprotein gene is highly expressed during the late stages of myelination in the rat central nervous system.

Oligodendrocyte-myelin glycoprotein (OMgp) is expressed on the surface of oligodendrocytes and neurones and is thought to inhibit axonal regeneration after brain injury in adult, like Nogo and myelin-associated glycoprotein (MAG). We previously observed that the OMgp gene locus on chromosome 17 could be associated with autism, a developmental disorder. The aim of the present study was to characterise the developmental expression of OMgp mRNA in the central nervous system. First we determined the rat OMgp gene sequence and compared it with the human and mouse sequences. Several regions, putative sites for the fixation of transcription factors, are conserved between these three species in the unique intron of this gene. Using quantitative and semi-quantitative RT-PCR, we studied OMgp gene expression in rat brain during post-natal development. We found that OMgp mRNA expression was developmentally regulated, with a peak of expression in the late stages of myelination. We observed a similar profile in oligodendrocyte cultures, in absence of neurones, suggesting that OMgp mRNA expression by oligodendrocytes was independent of axonal influence. Our observations suggest that OMgp is a late marker of myelination, which could be implicated in the arrest of oligodendrocyte proliferation, arrest of myelination or compaction of myelin.