Identification of homozygosity for a human apolipoprotein A-I variant.

An apolipoprotein (apo) A-I variant, previously described in two Norwegian families (Schamaun et al. 1983. Hum. Genet. 64: 380-383), represents a mutation in apoA-I in which a single amino acid substitution of lysine for glutamic acid has taken place at residue 136. An offspring resulting from inter- marriage between the two families is genotypically homozygous for this variant. He is the first individual discovered to be homozygous for any of the apoA-I variants. Analysis of lipid data collected from these families indicates one or more lipid abnormalities. The low density lipoproteins (LDL) of subjects having this apoA-I variant demonstrate a compositional abnor- mality. The plasma cholesterol concentration in the homozygous subject is low because of the extremely reduced levels of LDL and apoB, a property shared by some of his first-degree relatives. However, because of the presence of apoE2 in this family, it is not possible to definitively link these lipid abnormalities to the presence of the A-I variant. -Rall, S. C., Jr., K. H. Weisgraber, R. W. Mahle)., C. Ehnholm, 0. Schamaun, B. Olaisen, J. P. Blomhoff, and P. Teisberg. Identification of homozygosity for a human apolipoprotein A-I variant. J. Lipid Res. 1986. 27: 436-441.