Three novel small deletion mutations of the LDL receptor gene in Korean patients with familial hypercholesterolemia

Genetic Diagnosis of Familial Hypercholesterolemia in Asia

Familial hypercholesterolemia (FH) is a common genetic disease with an incidence of about 1 in 200-500 individuals. Genetic mutations markedly elevate low-density lipoprotein cholesterol and atherosclerotic cardiovascular disease (ASCVD) in FH patients. With advances in clinical diagnosis and genetic testing, more genetic mutations have been detected, including those in low-density lipoprotein receptor (LDLR), apolipoprotein B (APOB), proprotein convertase subtilisin/kexin type 9 (PCSK9), and so on. Globally, most FH patients remain undiagnosed, untreated, or inappropriately treated. Recently, there was a Global Call to Action by the Global Familial Hypercholesterolemia Community to reduce the health burden of FH. Asia, despite being the most populous continent with half of the global population, has low FH detection rates compared to Western countries. Therefore, we aimed to review the current status of FH genetic diagnosis in Asia to understand the gaps in FH diagnosis and management in this region.

Characteristics and Vascular Complications of Familial Hypercholesterolemia in Korea

Familial hypercholesterolemia (FH) is presently an important health issue worldwide. This condition shows phenotypic and genetic variations among affected people, and clinical and genetic data on FH are critical for effective diagnosis and management. Korean FH patients have relatively low levels of cholesterol and prevalence of xanthoma than patients from other countries, as determined by previous studies. The best predictive value of low-density lipoprotein cholesterol (LDL-C) for pathogenic mutations is suggested as 225 mg/dL. Many known and novel mutations on LDLR and some on APOB or PCSK9 have been identified in one-third of clinically diagnosed probands, and their locations on genes varied. Coronary artery disease was reported in 28% Korean FH patients, and traditional cardiovascular risk factors were associated with this complication. Aortic valve changes were also prevalent. However, the achievement rate of LDL-C target using lipid-lowering therapy is not satisfactory and is only 21%-44%. A further expanded registry and additional analysis may provide a more useful clinical tool for the diagnosis and treatment of Korean FH patients.

Mutations in low-density lipoprotein receptor gene as a cause of hypercholesterolemia in Taiwan

Familial hypercholesterolemia (FH) is inherited as an autosomal dominant trait that has been associated with more than 920 different mutations in the low-density lipoprotein receptor (LDLR) gene. To characterize LDLR gene mutations in the Chinese of Han descent with FH, we isolated genomic DNA from peripheral blood samples of 20 affected subjects and 50 healthy subjects with no family history of hypercholesterolemia. We used polymerase chain reaction and long polymerase chain reaction to amplify the 18 coding exons and the minimal promoter of the LDLR gene, and subjected amplicons to direct sequence analysis. We identified 6 mutations in LDLR gene, including heterozygous missense mutations I420T (ATC-->ACC), C660W (TGC-->TGG), H562Y (CAC-->TAC), and A606T (GCC-->ACC), and a heterozygous and a homozygous mutation in codon P664L (CCG-->CTG) as well as a homozygous large deletion of exons 6 to 8. The FH homozygotes manifested generalized xanthomatosis. One of the mutations we identified (C660W) was novel. In conclusion, we identified 5 missense mutations and 1 large deletion in LDLR gene, including 1 novel mutation in Han Chinese with FH in Taiwan.

Identification of four novel mutations of the low-density lipoprotein receptor gene in Korean patients with familial hypercholesterolemia

To obtain insight into the genetic variation of the low-density lipoprotein (LDL) receptor gene in Korean patients with familial hypercholesterolemia (FH), we used single-strand conformation polymorphism to screen all 18 exons and a promotor of the LDL receptor gene in 20 unrelated Korean FH patients. Four novel point mutations were detected in 5 FH patients and were characterized by sequence analysis. Of them, one is a nonsense mutation, a Glu-->Stop (CAG-->TAG) at codon 161, and results in a large deletion. The other three, which were a Ala-->Glu (GCG-->GAG) mutation at signal peptide, Cys-->Tyr (TGC-->TAC) at codon 210, and Pro-->Leu (CTG-->CCG) at codon 584, were novel missense mutations, which modified the highly conserved region of the LDL receptor gene. All these mutations were absent in normolipidemic controls and were associated in heterozygote carriers with clinical signs of FH. Identification of these novel mutations provides another example of the molecular heterogeneity of the LDL receptor gene mutations causing FH.