A novel TC deletion resulting in Pro(260)-> Stop in the human LCAT gene isassociated with a dominant effect on HDL-cholesterol

Human lecithin:cholesterol acyltransferase (LCAT) plays a key role in the b iogenesis of circulating high-density lipoprotein-cholesterol (HDL-C) and r everse cholesterol efflux. We investigated the molecular defect in the LCAT gene in a family with low levels of HDL-C. The proband. a 53-year-old woma n from Oklahoma City. had a HDL-C level of 0.21 mmol/l. The LCAT activity i n the proband was 5 nmol/ml/h and cholesterol esterification rate was 54.2 nmol/ml/h, consistent with LCAT deficiency. Analysis of polymerase chain re action (PCR) amplified subgenomic fragments of LCAT DNA on polyacrylamide g els revealed heteroduplex bands in the proband and three other affected ind ividuals in exon 6 DNA sequence analyses of the proband's LCAT gene identif ied a 2 base pair deletion (TC) (base pairs 4544-4545. corresponding to ami no acid 255) in the heteroduplex allele, thereby converting Pro(260) to a p remature stop codon and a predicted truncated protein of 260 amino acids. T his is approximately 60% of the length of the normal translated protein. Th e heterozygous individuals also revealed significant reduction in apolipopr otein A-1 levels compared with the unaffected family members (n = 4). The m arked reduction in HDL-C in the proband and sibling suggests a dominant eff ect of this mutation on HDL-C levels. Furthermore, because the deletion res ults in a heterozygous allele that can be detected by a simple PCR reaction and polyacrylamide gel-size fractionation, it may be possible to rapidly s creen susceptible individuals for the presence of this mutation. (C) 2001 E lsevier Science Ireland Ltd. All rights reserved.