Apolipoprotein EBethesda: A New Variant of Apolipoprotein E Associated with Type III Hyperlipoproteinemia

Apolipoprotein E (apoE) is associated with plasma lipoproteins and is important in modulating the catabolism of remnants of triglyceride-rich lipoproteins. ApoE is a polymorphic protein, and homozygosity for the E2 allele is associated with type III hyperlipoproteinemia. A variant of apoE, apoEBethesda, was found that migrates in the E1 position on isoelectric focusing. Evaluation of the proband and her family showed that both individuals with apoEBethesda had type III hyperlipoproteinemia, and the analysis was consistent with the concept that apoEBethesda was coded by a new E allele and that this allele was expressed in a codominant fashion. The discovery of apoEBethesda and its association with type III hyperlipoproteinemia provides additional evidence for the genetic heterogeneity of the E allele and suggests that a number of different structural mutations of the E apolipoprotein may be associated with the type III phenotype.