Two Novel Disease-Causing Mutations in the LDLR of Familial Hypercholesterolemia

Analysis of low-density lipoprotein receptor gene mutations in a family with familial hypercholesterolemia

BACKGROUND

Familial hypercholesterolemia (FH) is a common monogenic autosomal dominant disorder, primarily mainly caused by pathogenic mutations in the low-density lipoprotein receptor (LDLR) gene. Through phenotypic-genetic linkage analysis, two LDLR pathogenic mutations were identified in FH families: c.G1027A (p.Gly343Ser) and c.G1879A (p.Ala627Thr).

MATERIALS AND METHODS

Whole exome sequencing was conducted on the proband with familial hypercholesterolemia to identify the target gene and screen for potential pathogenic mutations. The suspicious responsible mutation sites in 14 family members were analyzed using Sanger sequencing to assess genotype-phenotype correlations. Mutant and wild type plasmids were constructed and transfected into HEK293T cells to evaluate LDLR mRNA and protein expression. In parallel, bioinformatics tools were employed to predict structural and functional changes in the mutant LDLR.

RESULTS

Immunofluorescence analysis revealed no significant difference in the intracellular localization of the p.Gly343Ser mutation, whereas protein expression of the p.Ala627Thr mutation was decreased and predominantly localized in the cytoplasm. Western blotting has showed that protein expression levels of the mutant variants were markedly declined in both cell lysates and supernatants. Enzyme linked immunosorbent assay has demonstrated that LDLR protein levels in the supernatant of cell culture medium was not significant different from those of the wild-type group. However, LDLR protein levels in the cell lysate of both the Gly343Ser and Ala627Thr variants groups were significantly lower than those in the wild-type group. Bioinformatic predictions further suggested that these mutations may affect post-translational modifications of the protein, providing additional insight into the mechanisms underlying the observed reduction in protein expression.

CONCLUSIONS

In this study, we identified two heterozygous pathogenic variants in the LDLR gene, c.G1027A (p.Gly343Ser) and c.G1879A (p.Ala627Thr), in a family with familial hypercholesterolemia. We also conducted preliminary investigations into the mechanisms by which these mutations contribute to disease pathology.

Mouse models of atherosclerosis in translational research

Atherosclerotic cardiovascular disease (CVD), the major cause of premature human mortality, is a chronic and progressive metabolic and inflammatory disease in large- and medium-sized arteries. Mouse models are widely used to gain mechanistic insights into the pathogenesis of atherosclerosis and have facilitated the discovery of anti-atherosclerotic drugs. Despite promising preclinical studies, many drug candidates have not translated to clinical use because of the complexity of disease patho-mechanisms including lipid metabolic traits and inflammatory, genetic, and hemodynamic factors. We review the current preclinical utility and translation potential of traditional [apolipoprotein E (APOE)- and low-density lipoprotein (LDL) receptor (LDLR)-deficient mice] and emerging mouse models that include partial carotid ligation and AAV8-Pcsk9-D377Y injection in atherosclerosis research and drug discovery. This article represents an important resource in atherosclerosis research.

Evaluation of miRNA-27a/b expression in patients with familial hypercholesterolemia

Introduction

We aimed to evaluate the serum level of miRNA-27 expression in patients with familial hypercholesterolemia (FH).

Material and methods

miRNA-27a/b levels in serum were compared between 39 patients with heterozygous FH (HeFH = 20) and homozygous FH (HoFH = 19), and 20 healthy subjects (control group). The expression level of miRNA-27a/b was measured using real-time PCR.

Results

miRNA-27a/b expression in heFH patients (fold change: 2.21 ±0.69, p = 0.001) and in the subgroup of hoFH (fold change: 3 ±1.19, p = 0.001) was significantly higher compared to healthy people. In the comparison between HoFH and HeFH, the HoFH group had a significantly higher level of miRNA-27a/b expression (FC: 1.84 ±1.19, p = 0.009).

Conclusions

We observed higher miRNA-27a/b expression in patients with FH than in healthy individuals. In comparison with HoFH and HeFH groups, the former had a higher expression level of miRNA-27a/b, which indicates the potential of miRNA-27a/b as a candidate marker for the severity of disease in individuals with FH.