Novel LDLR variants affecting low density lipoprotein metabolism identified in familial hypercholesterolemia

Abstract

Background: Familial hypercholesterolemia (FH) is an autosomal dominant disease of lipid metabolism mainly caused by mutations in the low-density lipoprotein receptor (LDLR) gene. Genetic detection of patients with FH help with precise diagnosis and treatment, thus reducing the risk of coronary heart disease (CHD) and other related diseases. The study aimed to identify the causative gene mutations in a Chinese FH family and reveal the pathogenicity and the mechanism of these mutations. Methods and results: Whole exome sequencing was performed in a patient with severe lipid metabolism dysfunction seeking fertility guidance from a Chinese FH family. Two LDLR variants c.1875 C > G (p.N625K; novel variant) and c.1448G > A (p.W483*) were identified in the family. Wildtype and mutant LDLR constructs were established by the site-direct mutagenesis technique. Functional studies were carried out by cell transfection to evaluate the impact of detected variants on LDLR activity. The two variants were proven to affect LDL uptake and binding, resulting in cholesterol clearance reduction to different degrees. According to The American College of Medical Genetics and Genomics (ACMG) Standards and Guidelines, the W483* variant was classified as “Pathogenic”, while the N625K variant as “VUS”. Conclusions: Our results provide novel experimental evidence of functional alteration by LDLR variants identified in our study and expand the mutational spectrum of LDLR mutation induced FH.