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An individual with a healthy phenotype in spite of a pathogenic LDL receptor mutation (C240F)

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Author

Summary, in English

Familial hypercholesterolemia (FH) is caused by a defect in the function of the low density lipoprotein (LDL) receptor and inherited in an autosomal, codominant way. In this study we present a 13-year-old girl, compound heterozygote for the LDL receptor mutations C240F and Y167X. Fibroblasts from the patient showed very low cholesterol esterification rate, LDL uptake, and degradation compared to normal fibroblasts (< 2%, 8%, and < 2%, respectively). The C240F mutant was expressed in LDL receptor deficient CHOMldlA7 cells. Analysis of cell extracts by immunoblotting demonstrated delayed processing of the mutated LDL receptor, which was accumulated as a precursor protein of normal size. A high molecular weight form of the receptor was also detectable in these cells, which probably reflects cross-linking through the unpaired cysteine residue in the binding domain. Cells expressing the C240F mutant protein were unable to mediate uptake and degradation of LDL. The two siblings of the index case also carried the C240F mutation, but surprisingly one of them (a 17-year-old brother) showed no signs of hypercholesterolemia. This observation is consistent with the view that there may be cholesterol lowering mechanisms that can be activated, perhaps by mutations in known or hitherto unknown genes.

Publishing year

1999

Language

English

Pages

332-339

Publication/Series

Clinical Genetics

Volume

55

Issue

5

Document type

Journal article

Publisher

Wiley-Blackwell

Topic

  • Medical Genetics

Keywords

  • expression
  • LDL receptor
  • familial hypercholesterolemia
  • mutation
  • phenotype

Status

Published

ISBN/ISSN/Other

  • ISSN: 0009-9163