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Nucleotide sequences of two mRNAs for rat brain myelin proteolipid protein

R J Milner, C Lai, K A Nave

    Cell
    |October 1, 1985
    PubMed

    Insights

    Rat brain proteolipid protein (PLP) mRNAs, crucial for central nervous system myelin, show variations but encode identical proteins highly conserved across mammals. The 1600 nucleotide mRNA may not be functionally necessary.

    Area of Science:

    • Neuroscience
    • Molecular Biology
    • Genetics

    Background:

    • Proteolipid protein (PLP) is the primary protein in central nervous system myelin.
    • PLP is encoded by a single gene and plays a critical role in myelin structure and function.

    Purpose of the Study:

    • To investigate the heterogeneity of rat brain PLP mRNAs.
    • To compare the protein products and evolutionary conservation of PLP.
    • To assess the functional necessity of different PLP mRNA variants.

    Main Methods:

    • Analysis of rat brain mRNA sequences (3200 and 1600 nucleotides).
    • Amino acid sequence comparison between rat and bovine PLP.
    • Comparative analysis of PLP mRNA usage in mouse and monkey.

    Main Results:

    • Rat brain exhibits two distinct PLP mRNA variants (3200 and 1600 nucleotides) with different 5' ends and 3' polyadenylation sites.
    • Both mRNA variants encode identical 277 amino acid proteins, showing 99% identity to bovine PLP, indicating high conservation.
    • Post-translational removal of the amino-terminal methionine suggests no signal peptide is required for membrane insertion.
    • Mouse and monkey primarily use the larger (3200 nucleotide) mRNA, implying the smaller variant might not be essential.

    Conclusions:

    • Rat brain PLP mRNA exhibits significant heterogeneity, yet produces a highly conserved protein essential for myelin.
    • The high degree of conservation suggests a critical functional role for PLP throughout mammalian evolution.
    • The differential usage of PLP mRNA variants across species indicates potential redundancy or species-specific functional requirements.

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