Gene mutations in low-density lipoprotein receptor in one Chinese padigree with homozygous familial hypercholesterolemia / 中华检验医学杂志

Objective To investigate low density lipoprotein receptor (LDLR)gene mutation in familial hypercholesterolemia (FH) patients. Methods The proband was given clinical diagnosis of homozygous FH based on marked features and blood lipid tests results. After apoB100R3500Q mutation was excluded, the promoter region and all of the 18 exons of LDLR gene were amplified by touch-downpolymerase chain reaction (PCR). The PCR products were analyzed by single-strand conformationalpolymorphism (SSCP). The PCR products with abnormal single strands were sequenced directly. Thesecondary structures of the mutational and wild type proteins were analyzed and compared byANTHEPROT5.0, and then the tertiary structures of the mutant and wild type LDLR were predicted atSWISS MODEL homepage online. Results A homozygous mutation A606T at exon 13 of the patients wasfound by SSCP and confirmed by DNA sequencing. GOR Ⅰ method in ANTHEPROT5.0 indicates that therandom coils and turns would replace some helixes at the mutation site. The online prediction from theSWISS MODEL homepage indicates the backbone structure of the mutant LDLR has no difference from thewild type one. Conclusion The results suggest the A606T mutation of LDLR gene is the cause of the FH inthis pedigree.

Mutation screening and functional analysis of low density lipoprotein receptor in a familial hypercholesterolemia family / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>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.</p><p><b>METHODS</b>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.</p><p><b>RESULTS</b>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.</p><p><b>CONCLUSION</b>It is possible that the W462X mutation of LDLR gene is the main cause for the disease in this family.</p>