Mutation screening of the codon 3500 region of the apolipoprotein B gene by denaturing gradient-gel electrophoresis.

Familial defective apolipoprotein B (FDB) is a clinical condition resembling familial hypercholesterolemia. The underlying genetic defects are mutations in the apolipoprotein B-100 (apo B-100) gene. Two mutations (Arg3500 --> Gln and Arg3531 --> Cys) are known to date. We designed a denaturing gradient-gel electrophoresis (DGGE) technique to detect sequence variations in codons 3456-3553 of the apo B-100 gene. In 46 heterozygous FDB patients with the predominant codon 3500 mutation, a uniform four-band DGGE pattern was seen, whereas 57 non-FDB patients showed the uniform single-band pattern expected in normal homozygotes. The recently described codon 3531 mutation and a previously unpublished Arg --> Pro mutation in codon 3480 showed unique DGGE patterns, allowing unambiguous differentiation of the three mutations. The DGGE method thus both detects known FDB mutations and screens for other mutations in codons 3456-3553 of the low-density lipoprotein receptor binding region of apo B-100; it can be used as a first-line screening method for FDB.