Mutation Analysis of Exon 3 of the LDL Receptor Gene in Patients with Severe Hypercholesterolemia

Single-strand conformation polymorphism analysis was used to screen for mutations in exon 3 of the low density lipoprotein receptor gene in a group of 218 unrelated patients with severe hypercholesterolemia (low density lipoprotein cholesterol > 6.7 mmol/l) living in the Cologne area of Germany. Including the complementary primers the fragment studied had a length of 176 bp. An abnormal single-strand conformation polymorphism pattern was observed in eight patients, four of whom had an identical abnormal fragment pattern indicating that five different mutations were present. By direct DNA sequencing, the underlying mutations could be confirmed (Cys54-->Tyr, Trp66-->Gly, Glu80-->Lys, 2 bp insertion (AT between codon 44 and 45, 9 bp deletion (codons 65 to 67)). The analysis of the pathogenicity indicates that all mutations were causative for the low density lipoprotein cholesterol elevation. The Trp66-->Gly and Glu80-->Lys mutations were previously described in a French-Canadian population and in an English population, respectively. The 2 bp insertion was detected in four unrelated patients and is one of the most frequent mutations detected up to now in the German population.