Haplotypes of the human apoprotein AI-CIII-AIV gene cluster in coronary atherosclerosis.

Restriction fragment length polymorphisms of the apoprotein AI-CIII-AIV gene cluster (on the long arm of chromosome 11) were investigated in a group of Caucasian survivors of myocardial infarction, using genomic hybridisation analysis. Four common haplotypes were identified at this locus, M1P1S1, M2P1S1, M1P2S1, and M2P1S2; where M1 and M2 are the common and uncommon alleles defined using the restriction enzyme MspI, P1 and P2 are the common and uncommon alleles defined by the enzyme PstI, and S1 and S2 are the common and uncommon alleles defined by the enzyme SstI. Seven genotype combinations were observed of approximate frequencies; a/a 0.70 (33/47), a/d 0.15 (7/47), a/b 0.04 (2/47), d/d 0.04 (2/47), a/c 0.02 (1/47), b/c 0.02 (1/47), and c/d 0.02 (1/47). In contrast the corresponding values for normotriglyceridaemic Caucasian controls, without a personal or family history of atherosclerotic heart disease were; 0.83 (40/48), 0.02 (1/48), 0.06 (3/48), 0, 0.04 (2/48), 0.04 (2/48), and 0. The relative incidence of the d haplotype, characterised by the presence of a cleavage site for the enzyme SstI in the fourth exon of the ApoCIII gene, was significantly higher in the patient group (P less than 0.01). However, because of the tight linkage between the polymorphic loci studied, it was not possible to identify haplotypes associated with any greater risk of premature atherosclerosis than when the SstI polymorphism was considered in isolation.