The Use of a Nonradioactive Digoxigenin Labeled Probe for Detection of Apo(a) Gene Size


Abstract: Elevated lipoprotein(a) [Lp(a)] concentrations are associated with premature coronary heart disease and early myocardial infarction. In the general human population the sizes of apolipoprotein [apo(a)] isoforms are inversely associated with lipoprotein(a) levels. Large isoforms are associated with low Lp (a) and small isoforms with high Lp(a) in the plasma. The size of the polymophism is directly correlated with the number of kringle-4 domains in apo(a). It has been shown by quantitative Southern blotting, and more recently by pulsed-field gel electrophoresis, that polymophism is the result of differences in the number of tandem kringle-4 repeats in the apo(a) gene. In our current study, we used a digoxigenin labeled MP-1 probe which is specific for the apo(a) gene and does not detect other genomic sequences under the blotting conditions. We determined plasma Lp(a) levels by ELISA and compared them with the size of the apo(a) gene. The latter were determined by dot blotting of plasma samples from 50 coronary artery disease patients (angiographically documented) and 50 healthy controls. Our results showed an inverse relation between the Lp(a) levels and the apo(a) gene size. This is consistent with the literature. Our method has no radioactive steps. It is rapid and easy to perform.

Keywords: Lp(a), coronary artery disease, dot blot analysis, DIG-labeling, apo(a) gene.

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