IDENTIFICATION OF A COMMON LOW-DENSITY-LIPOPROTEIN RECEPTOR MUTATION (C163Y) IN THE WEST OF SCOTLAND

Familial hypercholesterolaemia (FH) is an autosomal codominant disorde r characterised by high levels of LDL cholesterol and a high incidence of coronary artery disease. Our aims were to track the low density li poprotein receptor (LDLR) gene in individual families with phenotypic FH and to identify and characterise any mutations of the LDLR gene tha t may be common in the west of Scotland FH population using single str and conformational polymorphism analysis (SSCP). Patient samples consi sted of 80 heterozygous probands with FH, 200 subjects who were relate d to the probands, and a further 50 normal, unrelated control subjects . Tracking of the LDLR gene was accomplished by amplification of a 19 allele tetranucleotide microsatellite that is tightly Linked to the LD LR gene locus. Primers specific for exon 4 of the LDLR gene were used to amplify genomic DNA and used for SSCP analysis. Any PCR products wi th different migration patterns as assessed by SSCP were then sequence d directly In addition to identifying probands with a common mutation, family members were screened using a forced restriction site assay an d analysed using microplate array diagonal gel electrophoresis (MADGE) . Microsatellite D19S394 analysis was informative in 20 of 23 families studied. In these families there was no inconsistency with segregatio n of the FH phenotype with the LDLR locus. Of the FH probands, 15/80 h ad a mutant allele as assessed by SSCP using three pairs of primers co vering the whole of exon 4 of the LDLR gene. Direct DNA sequencing sho wed that 7/15 of the probands had a C163Y mutation. Using a PCR induce d restriction site assay for the enzyme RsaI and MADGE, it was determi ned that the C163Y mutation cosegregated with the FH phenotype in fami ly members of the FH probands. This mutant allele was not present in a ny of the control subjects. Microsatellite analysis has proven useful in tracking the LDLR gene and could be used in conjunction with LDL ch olesterol levels to diagnose FH, especially in children and young adul ts where phenotypic diagnosis can be difficult.