title: Multiple crm- mutations in familial hypercholesterolemia. Evidence for 13 alleles, including four deletions.
abstract: The low density lipoprotein (LDL) receptors in fibroblasts from 132 subjects with the clinical syndrome of homozygous familial hypercholesterolemia were analyzed by immunoprecipitation with an anti-LDL receptor monoclonal antibody. 16 of the 132 cell strains (12%) synthesized no immunodetectable LDL receptor protein, indicating the presence of two mutant genes that failed to produce cross-reacting material (crm- mutations). DNA and mRNA from 15 of the 16 crm- patients, representing 30 crm- genes, were available for further study. Haplotype analysis based on 10 restriction fragment length polymorphisms (RFLPs) suggested that the 30 crm- genes represent 13 mutant alleles. Four of the alleles produced no mRNA. Three of these four mRNA- alleles had large deletions ranging from 6 to 20 kb that eliminated the promoter region of the gene. The fourth mRNA- allele did not contain any deletion or alteration in the promoter sequence; the reason for the mRNA- phenotype was not apparent. Nine alleles were positive for mRNAs, of which three encoded mRNAs of abnormal size. One of the abnormal mRNAs was produced by a gene harboring a deletion, and another was produced by a gene with a complex rearrangement. The third abnormal-sized mRNA (3.1 kb larger than normal) was produced by an allele that had no detectable alterations as judged by Southern blotting. The other six mRNA+ alleles appeared normal by Southern blotting and produced normal-sized mRNA but no receptor protein. The current studies demonstrate that mRNA analysis coupled with haplotype determination by Southern blot analysis can be used to classify crm- mutations at a genetic locus where multiple alleles exist.
authors.affiliation: Department of Molecular Genetics, University of Texas Health Science Center, Dallas 75235.
authors.forename: H H
authors.initials: HH
authors.lastname: Hobbs
authors.forename: E
authors.initials: E
authors.lastname: Leitersdorf
authors.forename: J L
authors.initials: JL
authors.lastname: Goldstein
authors.forename: M S
authors.initials: MS
authors.lastname: Brown
authors.forename: D W
authors.initials: DW
authors.lastname: Russell
mesh_terms: D000293:Adolescent; D000328:Adult; D000483:Alleles; D000818:Animals; D002648:Child; D002675:Child, Preschool; D002872:Chromosome Deletion; D003001:Cloning, Molecular; D003429:Cross Reactions; D005260:Female; D005347:Fibroblasts / Q000032:analysis; D006720:Homozygote; D006801:Humans; D006938:Hyperlipoproteinemia Type II / Q000235:genetics* / Q000276:immunology; D008077:Lipoproteins, LDL / Q000235:genetics / Q000378:metabolism; D008297:Male; D051379:Mice; D009154:Mutation; D011973:Receptors, LDL / Q000235:genetics / Q000276:immunology
chemical_list: D008077:Lipoproteins, LDL; D011973:Receptors, LDL