Compound Heterozygotes for a Novel Mutation, Apo E1 Nagoya (Arg142Ser) and Apo E2 (Arg158Cys), with Severe Type III Hyperlipoproteinemia and Familial Hypercholesterolemia

AIM: A patient with severe type III hyperlipoproteinemia and familial hypercholesterolemia (FH) was previously reported (Metabolism, 44,1995:460-465). In the current study, the patient's apolipoprotein (apo) E gene was analyzed. METHODS: An apo E isoform analysis was performed using isoelectric focusing and immunoblotting. In addition, after DNA preparation, a restriction fragment length polymorphism analysis and DNA sequence analysis were performed. RESULTS: The patient's apo E phenotype was E2/E1, and the genotype was e2/e2. The sequence analysis of the patient's DNA revealed a new variant of apo E, which involves a single substitution of one serine (AGC) for one arginine (CGC) at position 142, thereby adding one negatively charged unit to apo E2. Therefore, the patient was compound heterozygous for apo E1 (Arg142Ser) and apo E2 (Arg158Cys). CONCLUSIONS: A novel mutation, apo E1 Nagoya (Arg142Ser) in a patient with severe type III hyperlipoproteinemia with heterozygous FH was characterized. Since the presence of arginine at the amino acid residue 142 of apo E is considered to play an important role in binding to LDL receptors, the mutation apo E1 Nagoya (Arg142Ser) likely contributed to the expression of severe type III hyperlipoproteinemia in this patient.