Association of DNA-haplotypes in the human LDL-receptor gene with normal serum cholesterol levels.

For the low density lipoprotein receptor (LDLR), many mutations have been characterized which identify this gene as one with an important role in lipid metabolism in patients with familial hypercholesterolemia (FH). Genetic heterogeneity at this locus raises the possibility that the LDLR may also contribute to variation in cholesterol levels in the normocholesterolemic population. We have determined genotypes at the LDLR locus using restriction fragment length polymorphisms (RFLPs) detected with the enzymes StuI, ApalI, PvuII and NcoI in 324 normocholesterolemic individuals from Germany. A significant association (p less than 0.01) was detected between the cutting site for the PvuII RFLP and lower cholesterol levels, and variation associated with this polymorphism explains 3% of the sample variance in cholesterol levels. In family studies we have determined four-RFLP haplotypes of 148 independent LDLR genes and have observed 9 haplotypes in the population. Three of these haplotypes containing the cutting site for PvuII are associated with a reduction in plasma LDL-cholesterol levels. Phylogenetic analysis indicates that these three haplotypes are related by evolutionary history, and this suggests that a single functionally important sequence change in the LDLR explains our observations. Our data confirm other reports and strongly suggest that the LDLR locus may be one of those genes involved in determining serum cholesterol levels in the normal population.