Journal of Lipid Research, Vol 37, 35-44, Copyright © 1996 by Lipid Research, Inc.
A new molecular defect in the lecithin: cholesterol acyltransferase (LCAT) gene associated with fish eye disease
C Contacos, DR Sullivan, KA Rye, H Funke and G Assmann
Department of Clinical Biochemistry, Royal Prince Alfred Hospital, Camperdown, New South Wales, Australia.
We report a new genetic defect in the lecithin:cholesterol acyltransferase
(LCAT) gene associated with classical clinical and biochemical features of
fish eye disease. The 63-year-old Australian female proband also suffers
from non-insulin-dependent (type II) diabetes mellitus. She presented with
corneal opacities, markedly reduced HDL-cholesterol (0.1 mmol/L; < 10%
of normal controls), and elevated plasma triglycerides. The presence of
diabetes did not explain the lipoprotein profile, which differed markedly
in comparison to two female hypertriglyceridemic diabetic subjects.
Cholesterol esterification in HDL-like particles was minimal but plasma
cholesterol esterification was maintained due to LCAT activity in non-HDL-
containing lipoprotein fractions. DNA sequence analysis of the proband's
LCAT gene showed two C to T transitions resulting in the substitution of
Thr123 with Ile and Tyr144 with Cys. Allele-specific PCR amplification
procedures were used to confirm the presence of the mutations in this
proband and to screen for additional carriers in her family. Three first
degree relatives (mother, brother, son) were heterozygous for the Thr123
--> Ile mutation and her daughter had the Tyr144 --> Cys mutation.
Apart from a reduction in HDL-cholesterol levels to half the normal
concentration and a 20% reduction in apoA-I levels, their plasma lipids
were unremarkable. The proband's son and daughter were further
investigated. Both had normal cholesterol esterification rates in plasma
and VLDL/LDL-depleted plasma, but reduced LCAT activity (50% that of
normal). Thus, the biochemical and phenotypic expression for fish eye
disease in the heterozygote subjects was similar, irrespective of the
underlying LCAT mutation.