Genetic Risk Factors for Coronary Heart Disease in the Japanese Population

Our recent data on genes associated with premature coronary heart disease (CHD) or possibly involved in CHD in the Japanese population are described. Frequency distributions, mean values and median values of plasma lipoprotein (a) (Lp(a)) concentrations in a Japanese population are similar to those in most Caucasians. Preliminary data suggest that apolipoprotein (a) is also highly polymorphic in the Japanese population. Furthermore, in inactive plasminogen, phenotype M5, is polymorphic in the Japanese. Data obtained with polymerase chain reaction (PCR) and allele-specific oligonucleotide probes indicate that plasminogen M5 has a codon 601 missense mutation (GCT → ACT, Ala → Thr) and is identical with plasminogen Tochigi. As to apolipoprotein (apo) E polymorphisms, data obtained with PCR and allele-specific oligonucleotide probes suggest that many of apo E-2 have the codon 158 missense mutation (CGC → TGC, Arg → Cys) and that most, if not all, of apo E-4 have the codon 112 missense mutation (TGC → CGC, Cys → Arg) in the Japanese. The frequencies of alleles for apo E-2 and E-4, however, is lower in Japanese than in most Caucasians. As regarding familial hypercholesterolemia (FH), whose heterozygote frequency is estimated to be 1 in 500 persons in the Japanese, data obtained with family studies of the low density lipoprotein (LDL) receptor gene suggest that most, if not all, of relatively severe hereditary hypercholesterolemia associated with Achilles tendon xanthomas is caused by a defect of the LDL receptor gene, and that the origin of the mutant LDL receptor gene generally differs among different pedigrees in the Japanese population. On the other hand, data obtained by population and family studies suggest that hereditary moderate hypercholesterolemia due to abnormal gene(s) distinct from the abnormal LDL receptor gene may be more common than classic FH. As to the apolipoprotein A-I (apoA-I) gene, a mutant apoA-I gene with a codon 84 nonsense mutation which caused apoA-I deficiency, a marked reduction of HDL cholesterol and premature CHD is described. This finding suggests that a mutant apoA-I gene can act as a major gene for decreased levels of apoA-I and HDL cholesterol. Finally, application of genetic data for the prevention of premature CHD are discussed.