Genotyping and Endocrinology Clinical Services: Apolipoprotein E (ApoE) Assay Procedures__ Genotyping The genotyping (isotyping) method performed by The Laboratory of Endocrinology, Aging and Disease (LEAD) differentiates the three different alleles of ApoE by nucleotide differences that change the amino acid in positions 112 and 158. The e3 allele is the most common and is differentiated by a cysteine at position 112 and an arginine at position 158 in the receptor-binding region of ApoE. The e4 allele differs from e3 and e2 by having arginine at position 112 and 158. E2 isoform contains a cysteine at position 112 and 158 (see Figure below).  Sample Preparation Genotyping is performed on DNA extracted from leukocytes (serum/plasma), or buffy coat. DNA can also be shipped for ApoE analysis. Blood should be spun in BD Vacutainer CPT Tubes available from Fisher Scientific for best results. For samples from research or clinical trials, we recommend storage at –80°C prior to transport on dry ice to the laboratory. DNA extracted from samples is subjected to PCR and digestion in order to determine individual genotype. Each experiment is run with standards for quality control. |
