OLIGODENDROCYTE PROGENITORS IN THE EMBRYONIC SPINAL-CORD EXPRESS DM-20

Oligodendrocyte progenitors, originating in the ventral ventricular zo ne of the embryonic rodent spinal cord, migrate and differentiate into the oligodendrocytes myelinating the future white matter. Transcripts for the dm-20 isoform of the proteolipid protein (plp) gene are detec table initially in cells of the ventral ventricular region of the embr yonic cental canal and subsequently throughout the white matter. The d m-20+ cells are present several days before oligodendrocytes or myelin sheaths are detectable. The purpose of the present study was to deter mine if DM-20 protein is present and whether DM-20+ cells can be linke d to the oligodendrocyte lineage in the mouse spinal cord. Expression of plp and dm-20 transcripts and product ws monitored using reverse tr anscription polymerase chain reaction (RT-PCR), and in situ hybridizat ion and immunostaining of cryosections and associated cultures. Cell i dentification was performed using antigenic markers characterizing dif ferent stages of oligodendrocyte differentiation. We show a temporal a nd spatial progression of cells expressing dm-20 transcripts and produ ct from the ventral ventricular zone at embryonic day 13 (E13.0), via the lateral borders of the floor plate to the ventral pa and white mat ter. The cells, initially devoid of myelin basic protein (MBP) and PLP , co-express these myelin proteins at approximately E16.5/17.0. Some D M-20+ cells co-label with definitive markers of th early oligodendrocy te lineage, are capable of mitosis and subsequently differentiate into oligodendrocytes. Other DM-20+ cells may represent earlier precursor cells. The expression of DM-20 in oligodendrocyte progenitors is consi stent with a postulated role in glial cell development.