A mutation (T-45C) in the promoter region of the low-density-lipoprotein (LDL)-receptor gene is associated with a mild clinical phenotype in a patient with heterozygous familial hypercholesterolaemia (FH).
We have identified a rare mutation (T-45C) in the low density lipoprotein (LDL)-receptor gene in a Welsh patient with a clinical diagnosis of heterozygous familial hypercholesterolaemia (FH). The mutation is in the proximal Sp1 binding site in repeat 3 of the 42 bp region of the promoter required for sterol-dependent regulation of transcription, but the substituted nucleotide is not a strongly conserved base in the consensus sequence for Sp1 binding. Normal and mutant promoter fragments (from base -600 to -5) were linked to a luciferase reporter gene, and transient expression in COS cells showed that the mutation reduced transcriptional activity to approximately 43% of normal in the presence, and 25% in the absence of sterols in the medium. Competitive gel-shift mobility assays showed that the mutation reduced the binding affinity for transcription factor Sp1. Analysis of a neutral polymorphism in the LDL-receptor mRNA from the patient's lymphoblasts showed that expression of one allele was reduced. Since Southern blotting of genomic DNA and sequencing of the entire coding region of the LDL-R gene did not reveal any other potential defects, we infer that the T-45 C mutation is the underlying cause of hypercholesterolaemia in the proband.
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Medical Research Council Lipoprotein Team, Royal Postgraduate Medical School, Hammersmith Hospital, London, UK.
Neuwirth
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Wade
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Knight
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Soutar
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D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002460:Cell Line; D004247:DNA; D005260:Female; D006579:Heterozygote; D006801:Humans; D006938:Hyperlipoproteinemia Type II / Q000235:genetics*; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D009154:Mutation; D010375:Pedigree; D010641:Phenotype; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000378:metabolism; D011973:Receptors, LDL / Q000235:genetics*; D016329:Sp1 Transcription Factor / Q000378:metabolism; D014162:Transfection
D012333:RNA, Messenger; D011973:Receptors, LDL; D016329:Sp1 Transcription Factor; D004247:DNA