Classical LCAT deficiency resulting from a novel homozygous dinucleotide deletion in exon 4 of the human lecithin: cholesterol acyltransferase gene causing a frameshift and stop codon at residue 144

Lecithin: cholesterolacyltransferase (LCAT) transacylates the fatty acid at the sn-2 position of lecithin to the 3 beta-OH group of cholesterol formin g lysolecithin and the majority of cholesteryl ester found in plasma. LCAT participates in the reverse cholesterol transport pathway in man where it e sterifies tissue-derived cholesterol following efflux from peripheral cells into HDL. Only 38 unique mutations in the human LCAT ene have been reporte d worldwide. Our French female proband presented with corneal opacity and n o detectable plasma LCAT activity using either endogenous or exogenous assa ys. Her total plasma cholesterol and HDL cholesterol were low (2.34 mmol/l and 0.184 mmol/l, respectively) with a very high cholesterol/cholesteryl es ter molar ratio (10.9:1). Plasma triglycerides were 0.470 mmol/l with low a po B (40.5 mg:dl), apo A-I (14.7 mg/dl), apo A-II (6.8 mg/dl) and apo E (2. 1 mg/dl) levels. Plasma lipoprotein analysis by ultracentrifugation showed very low HDL concentrations and a characteristic shift of the lipoprotein p rofile towards larger, less dense particles. No proteinuria, renal dysfunct ion or signs of atherosclerosis were noted at age 45. Sequence analysis of her LCAT gene showed a novel homozygous TG-deletion at residues 138-139 tha t resulted in a frameshift causing the generation of a stop codon and prema ture termination of the LCAT protein at amino acid residue 144, Western blo tting of the patient's plasma using a polyclonal IgY primary antibody again st human LCAT failed to demonstrate the presence of a truncated LCAT protei n. A 53 bp mismatched PCR primer was designed to generate an Fsp 1 restrict ion site in the wild type sequence of exon 4 where the mutation occurred. T he 155 bp PCR product from the wild type allele produced a 103 bp and 52 bp fragment with Fsp 1 and no cleavage products with the mutant allele thus p ermitting rapid screening for this novel mutation. (C) 1999 Elsevier Scienc e Ireland Ltd. All rights reserved.