IDENTIFICATION OF AN EMBRYONIC ISOFORM OF MYELIN BASIC-PROTEIN THAT IS EXPRESSED WIDELY IN THE MOUSE EMBRYO

We have identified a myelin basic protein (MBP) isoform in mouse embry os that includes an exon up-stream of the usual transcription initiati on site. This isoform, embryonic-neonatal MBP (E-MBP), is expressed at the protein level in the embryonic nervous system at a time when othe r MBP isoforms are not detected. In addition to the central and periph eral nervous systems of the embryo and neonate, the thymus, spleen, an d testes also express E-MBP at the protein level. The expression of E- MBP in cell types distinct from the nervous system strongly suggests t hat this MBP isoform has a role apart from the formation of myelin.