A 10-bp deletion in the apolipoprotein {epsilon} gene causing apolipoprotein E deficiency and severe type III hyperlipoproteinemia
- Medizinische Universitaetsklinik Heidelberg (Germany); and others
Type III hyperlipoproteinemia (HLP) is usually associated with homozygosity for apolipoprotein (apo) E2. We identified a 30-year-old male German of Hungarian ancestry with severe type III HLP and apo E deficiency. The disease was expressed in an extreme phenotype with multiple cutaneous xanthomas. Apo E was detectable only in trace amounts in plasma but not in the different lipoprotein fractions. Direct sequencing of PCR-amplified segments of the apo {epsilon} gene identified a 10-bp deletion in exon 4 (bp 4037-4046 coding for amino acids 209-212 of the mature protein). The mutation is predictive for a reading frameshift introducing a premature stop codon (TGA) at amino acid 229. By western blot analysis, we found small amounts of a truncated apo E in the patient`s plasma. Family analysis revealed that the proband was homozygous - and 10 of 24 relatives were heterozygous - for the mutation. Heterozygotes had, as compared to unaffected family members, significantly higher triglycerides (TG), very low-density lipoprotein (VLDL) cholesterol and a significantly higher VLDL cholesterol-to-serum TG ratio, which is indicative of a delayed remnant catabolism. We propose that the absence of a functionally active apo E is the cause of the severe type III HLP in the patient and that the mutation, even in a single dose in heterozygotes, predisposes in variable severity to the phenotypic expression of the disease. 37 refs., 8 figs., 2 tab.
- OSTI ID:
- 219858
- Journal Information:
- American Journal of Human Genetics, Vol. 58, Issue 2; Other Information: PBD: Feb 1996
- Country of Publication:
- United States
- Language:
- English
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