DEVELOPMENT OF A MICROSATELLITE-BASED APPROACH TO CO-SEGREGATION ANALYSIS OF FAMILIAL HYPERCHOLESTEROLEMIC KINDREDS

Co-segregation studies based on a selection of intragenic restriction fragment length polymorphisms of the low density lipoprotein receptor (LDLR) gene hare been used extensively both for research and diagnosti c studies of familial hypercholesterolaemia (FH) families, because dir ect mutation screening remains complex. Here we describe the developme nt and application of a more efficient approach to co-segregation stud ies based on highly informative dinucleotide and tetranucleotide repea ts flanking the LDLR gene. A series of microsatellites (D19S391, D19S3 94, D19S221 and D19S179) were selected for study on the basis of linka ge analysis in the CEPH families using intragenic polymorphisms for a TA repeat (exon 18) in the LDLR gene, and earlier data for a Pvu II po lymorphism (intron 15). A physical map of the region of chromosome 19 also contributed to this selection. One marker in particular, D19S394, sited 150 kilobases telomeric to the gene, was extremely useful, disp laying 90% heterozygosity, robust TCR of tetranucleotide repeats witho ut stutter bands, and no recombination with the LDLR gene (theta = 0, LOD 68). Use of this marker in the families of twenty-three FH proband s from Hampshire demonstrated co-segregation of the hyperlipidaemia ph enotype with the LDLR gene region, except in one family with defective apolipoprotein B-100, and a family turning out to display familial co mbined hyperlipidaemia. This approach should facilitate the search for any families where FH does not co-segregate with the LDLR gene, and w ill enhance the repertoire of molecular diagnostic tools available for FH.