EXPRESSION OF THE DM-20 ISOFORM OF THE PLP GENE IN OLFACTORY NERVE ENSHEATHING CELLS - EVIDENCE FROM DEVELOPMENTAL STUDIES

The olfactory bulb is a specialized area of the CNS with well-defined areas containing both myelinated, and non-myelinated axons. The presen ce of plp gene transcripts has been demonstrated previously in the olf actory bulb, but no detailed description of plp gene activity in this complex area of the CNS is available. In this study we describe the de velopmental expression of the two plp gene isoforms, plp and dm-20, an d their products in the mouse olfactory bulb. plp gene activity was pr esent in the non-myelinated olfactory nerve layer of the bulb from E14 through to adult ages. Expression in the deeper layers of the bulb, a ssociated with myelination of the second order axons, was apparent fro m P10 onwards. dm-20 was the predominant isoform expressed at the tran script level in the olfactory nerve layer and was the only isoprotein demonstrable by immunostaining. This expression was associated with th e resident glial cell of the non-myelinated olfactory nerve layer, the olfactory nerve ensheathing cell. Selective expression of the DM-20 i soprotein in the non-myelin forming olfactory nerve ensheathing cells implies a role for DM-20 other than as a structural myelin protein. Fu rther study of this specialized glial cell may prove useful in elucida ting the specific function(s) of the DM-20 isoprotein.