Use of the single strand conformational polymorphism (SSCP) technique to identify mutations in the LDL-receptor gene

Abstract

In the majority of patients with a clinical diagnosis of familial hypercholesterolaemia (FH), the disorder is caused by one of (probably) several hundred different mutations in the gene coding for the LDL-receptor. We have developed the SSCP technique, to petit identification of the specific mutation in most patients within a few wcxks. New methods to achieve high throughput will he presented, which are currently being used to screen 800 FH patients at the rate of one exon per wezk for the entire sample. Once the specific mutation has been identified in a patient, an unequivocal genetic test can be developed to allow screening of the patient’s relatives, and data will be presented on the efficiency of such family-based case finding to identify new patients with FH. We have investigated the possibility that patients with different mutations (or classes of mutations) have different plasma lipid levels and thus a different prognosis for CAD. In a sample of 31 I patients with FH, 6 different mutations have been identified in exon 4 of the gene in 29 patients (9.3%). and as a group these have levels of LDL-cbolesterol considerably higher than those with mutations in any other part of the gene (9.4 v 7.8mmol respwtively, p<O.Ol). In addition, patients with any mutation causing a “defective protein” have a faster rise in chol&orol levels with age than those with a “null allele” mutation, where no receptor protein is produced. Thus patients with mutations either in exon 4 or those causing a defective protein may be at greaater risk of CAD.