Structure and expression of the mouse myelin proteolipid protein gene.

The gene for the mouse myelin proteolipid protein has been isolated and the seven exons have been sequenced. Since the sequence of a rat proteolipid protein cDNA and partial sequence of the human proteolipid protein gene have been determined, it was possible to demonstrate a very high degree of conservation for the proteolipid protein gene exons among species. While there are some nucleotide changes, the protein coding region of the mouse gene encodes protein that is totally conserved relative to both rat and human proteolipid proteins. The regulatory and noncoding regions of the proteolipid protein gene are also highly conserved. The upstream regulatory and 5'-noncoding region of the gene is 92% homologous to the comparable region of the human proteolipid protein gene, and the 3'-noncoding region of the mouse gene is approximately 90% homologous to a rat proteolipid protein cDNA through 2,200 nucleotides of 3'-noncoding DNA. S1 nuclease protection experiments indicated that the major 5'-end for proteolipid protein mRNAs from mouse, rat, human, or baboon is approximately 147-160 nucleotides upstream from the initial methionine codon of the protein coding region. Other S1 nuclease protection experiments indicated the possible existence of an alternative splice site within exon 3, which may produce mRNA for DM20. This mRNA is approximately 100 nucleotides shorter than that for the proteolipid protein, and it is missing the latter half of exon 3, that is, amino acids 116-150 of the proteolipid protein sequence.