Molecular basis of an apolipoprotein[a] null allele: A splice site mutation is associated with deletion of a single exon

Laura A. Cox, Catherine Jett, James E. Hixson

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    Apolipoprotein[a] (apo[a]), a unique component of atherogenic lipoprotein[a], is highly polymorphic in human and nonhuman primates. Null alleles, producing no detectable circulating Lp[a] or apo[a] isoforms, are found at high frequencies. The molecular basis of null alleles is not yet known. In baboons, approximately two-thirds of null alleles do not produce detectable hepatic transcripts (transcript negative nulls), and one-third of null alleles produce normal amounts of apo[a] transcripts (transcript positive nulls). We have cloned apo[a] cDNA from a baboon carrying a transcript positive null allele defective in secretion from primary hepatocytes. Compared with wild-type cDNA, the null allele contained an in- frame 47 amino acid deletion in the protease domain corresponding to one exon of the apo[a] gene. The null allele contains an A→T substitution in the third nucleotide position of the intron downstream of the deleted exon which alters the donor splice site consensus sequence. Thus, this null is likely due to a mutation that prevents normal mRNA splicing, yielding a shortened protein that may be defective in intramolecular interactions required for normal processing and secretion of apo[a]. This is the first report of a molecular basis for apo[a] null alleles.

    Original languageEnglish (US)
    Pages (from-to)1319-1326
    Number of pages8
    JournalJournal of lipid research
    Issue number7
    Publication statusPublished - Jul 1 1998



    • Lipid metabolism
    • Plasminogen
    • Protein secretion
    • Transcript processing

    ASJC Scopus subject areas

    • Biochemistry
    • Endocrinology
    • Cell Biology

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