Rapid typing of apolipoprotein B DNA polymorphisms by DNA amplification. Association between Ag epitopes of human apolipoprotein B-100, a signal peptide insertion/deletion polymorphism, and a 3'flanking DNA variable number of tandem repeats polymorphism of the apolipoprotein B gene.
We present here rapid and efficient methods for the analysis of multiple variable apolipoprotein (apo) B loci using polymerase chain reaction based techniques. For illustrative purposes, we have applied these methods to establish an association between these polymorphisms and the apo B Ag immunological epitopes. The 5 DNA polymorphisms include 3 restriction endonuclease sites (for XbaI, EcoRI and MspI), a variable number of tandem repeat (VNTR) locus at the 3' end of the apo B gene, and an insertion/deletion polymorphism involving the signal peptide region of apo B. The latter two newly described polymorphisms are directly detectable following amplification and may have physiological effects on apo B expression because of their critical locations. All of these sites were typed using flanking oligonucleotides and the newly developed polymerase chain reaction. Amplification products were typed either directly (3' VNTR and signal peptide insertion/deletion alleles), or following specific enzyme digestion (for the restriction sites), or by allele specific oligonucleotides. The detailed methods presented will prove generally useful for rapidly typing DNA variation in the apo B gene. Using these techniques, we found a significant linkage disequilibrium between the Ag(t/z) locus and the 3' VNTR, and the Ag(c/g) locus and the signal peptide length polymorphism. Future association studies using these DNA polymorphisms should take into consideration that observed effects may be related to its linkage disequilibrium with the Ag loci and vice versa.