Differential expression of collapsin response mediator proteins (CRMP/ULIP) in subsets of oligodendrocytes in the postnatal rodent brain

The family of collapsin response mediator protein/Unc-33-like protein (CRMP /Ulip), composed of four homologous members, is specifically and highly exp ressed in the nervous system during embryonic neuronal development and dram atically down-regulated in the adult. Members of this family have been prop osed to be part of the semaphorins signal transduction pathway involved in axonal outgrowth. Here, we show by in situ hybridization and immunohistoche mistry that CRMP2/Ulip2, and to a lesser extent CRMP3/Ulip4, are expressed in immature and mature oligodendrocytes, but not in astrocytes. Transcripts encoding the other CRMP/Ulip members are also detectable by RT-PCR in high ly purified mature oligodendrocytes. Interestingly, in the adult, the prote in CRMP2/Ulip2 is mainly detectable in subsets of oligodendrocytes distribu ted according to an increasing rostrocaudal gradient, with the largest numb er of positive cells being present in the brain stem and spinal cord. In cu ltures of highly purified oligodendrocytes, however, CRMP2/Ulip2 was detect able in all the cells. Addition of Sema3A in the culture medium completely inhibited the emergence of oligodendrocyte processes suggesting that, as in neurons, a Sema3A signaling pathway mediated via CRMP2/Ulip2 may be involv ed in the regulation of oligodendroglial process outgrowth.