A novel apolipoprotein E5 variant with a 24-bp insertion causing hyperlipidemia

A tandem 24-bp insertion in the apolipoprotein E (apo E) gene was detected in a patient with elevated triglyceride, apolipoprotein (apo) CII, and apo CIII levels. This novel variant, apo E5ss, showed in position apo E5 by isoelectric focusing and was of larger molecular weight than apo E3 during two-dimensional gel electrophoresis. Polymerase chain reaction-single strand conformation polymorphism analysis using the primer pairs that cover all the coding regions was useful for rapid detection of the variant of the apo E allele. Apo E5ss may have a 24-bp insertion caused by slipped mispairing, resulting in a tandem duplication of amino acid residues 135-142 [APOE, 24-BP INS, DUP CODONS 135-142]. The proband was the only person with apo E5ss among the 806 Japanese males that we examined. We inspected six other reported apo E5 variants in the literature.