A New Family of Transcripts of the Myelin Basic Protein Gene: Expression in Brain and in Immune System

Abstract

A cDNA clone (MBP2) corresponding to a novel mouse myelin basic protein (MBP) mRNA has been isolated from an adult mouse bone marrow cDNA library. It contains the MBP exons la-7 except exon 5. Using PCR experiments we have determined that this MBP2 mRNA belongs to a new MBP mRNA family initiated upstream from exon 1b. Their 5’end extends into exon la and/or the region O’previously described. These mRNAs are generated by alternative splicing of the primary transcript involving excision of exon la, 1b, 2, 5, or 6. Thus, these new mRNAs are produced from a promoter(s) located upstream from the major promoter 1b. They are expressed in brain (at least from embryonic day 15), in bone marrow, and in other hemolymphoppietic tissues, particularly in macrophage cells. As their expression is not restricted to myelinating cells, the function of these novel MBP mRNAs and putative proteins might not be related to myelination.