[Mutation screening and functional analysis of low density lipoprotein receptor in a familial hypercholesterolemia family].
OBJECTIVE
To screen the mutations of the low density lipoprotein receptor (LDLR) gene in a familial hypercholesterolemia (FH) family, and analyze the LDL-uptaking function of LDLR on lymphocytes of patients.


METHODS
Genomic DNA was extracted from four affected members in a Chinese FH family. The presence of apoB100 gene R3500Q mutation which results in familial defective apolipoprotein B100 (FDB) was excluded first. Fragments of the LDLR gene were amplified by touch-down polymerase chain reaction (Touch-down PCR) and analyzed by single-strand conformational polymorphism (SSCP). The suspect fragments of the LDLR gene were cloned and sequenced. Furthermore, the lymphocytes bounded with fluorescent-labeled LDL (DiI-LDL) were measured by fluorescence flow cytometry.


RESULTS
A nonsense mutation was identified in exon 10 of LDLR gene. This mutation gave rise to a premature stop codon (W462X), resulting in the absence of most of the LDLR domains. It was detected in all the affected members of the FH family. The ratios of functional LDLR in lymphocytes from patients and normal controls were 63.7% and 77.3% respectively. As a result, the activity of the functional LDLR in patients was just 82.4% of that in the normal controls.


CONCLUSIONS
It is possible that the W462X mutation of LDLR gene is the main cause for the disease in this family.
Cheng
Xiao-huan
XH
Zhongnan Hospital, Wuhan University, Wuhan, Hubei, 430071 People's Republic of China.
Zheng
Fang
F
Zhou
Xin
X
Xiong
Chen-ling
CL
Ding
Junfa
J
Chen
Yong-mei
YM
D000328:Adult; D053299:Apolipoprotein B-100 / Q000235:genetics; D001483:Base Sequence; D016022:Case-Control Studies; D004252:DNA Mutational Analysis; D003850:Deoxyribonuclease I / Q000378:metabolism; D005091:Exons / Q000235:genetics; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D006938:Hyperlipoproteinemia Type II / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D008077:Lipoproteins, LDL / Q000378:metabolism; D008214:Lymphocytes / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D009154:Mutation; D010375:Pedigree; D011973:Receptors, LDL / Q000235:genetics* / Q000378:metabolism*
D053299:Apolipoprotein B-100; D008077:Lipoproteins, LDL; D011973:Receptors, LDL; D003850:Deoxyribonuclease I