MOLECULAR-BASIS OF FISH-EYE DISEASE IN A PATIENT FROM SPAIN - CHARACTERIZATION OF A NOVEL MUTATION IN THE LCAT GENE AND LIPID ANALYSIS OF THE CORNEA

The genetic and biochemical basis of fish-eye disease (FED) was invest igated in a 63-year-old female proband with low plasma HDL cholesterol . Analyses of corneal and plasma lipids of the proband were consistent with impaired lecithin:cholesterol acyltransferase (LCAT) activity. F ree cholesterol and phospholipid levels were elevated relative to cont rol values, whereas cholesteryl ester levels were greatly reduced. Fat ty acid compositions of corneal lipids from the proband and control su bjects differ from the respective fatty acid compositions of their pla sma lipids. This suggests that the metabolic pathwaays and acyl chain specificities for phospholipid, cholesteryl ester, and triglyceride me tabolism within the cornea are distinct from those of plasma. Sequenci ng of the LCAT gene from the proband revealed a novel mutation at nucl eotide 399, corresponding to an Arg(99)-->Cys substitution. Secretion of LCAT (Arg(99)-->Cys) by transfected COS-6 cells was approximate to 50% of that of the wildtype, but its specific activity against reassem bled HDL was 93% lower than that of wild-type LCAT. The specific activ ities of wild-type and LCAT (Arg(99)-->Cys) against LDL were reduced s imilarly, suggesting that the appearance of the FED phenotype does not require enhanced activity against LDL. Our data support the hypothesi s that FED is a partial LCAT deficiency in which poor esterification i n specific types of HDL particles may contribute to the appearance of the corneal opacities.