Pathogenicity of the LDLR c.97C>T (p.Gln33Ter) Mutation in Familial Hypercholesterolemia

Abstract

Background: Familial hypercholesterolemia (FH) is a hereditary disease caused mainly by mutations in the gene encoding the low-density lipoprotein receptor (LDLR). This study aimed to confirm the pathogenicity of the LDLR c.97C>T (p.Gln33Ter) mutation through in vitro functional validation and determine whether this nonsense mutation induces nonsense-mediated mRNA decay (NMD).

Methods: The proband and his family were included in accordance with Chinese Expert Consensus on FH screening. The disease-causing mutations were fund using whole-exome sequencing and were confirmed using bidirectional Sanger sequencing. The pathogenicity of the mutation was predicted using in silico analysis. The LDLR c.97C>T (p.Gln33Ter) mutation was generated using site-directed mutagenesis and expressed in HEK293T cells lacking endogenous LDLR expression. The effects of this alteration on LDLR expression and LDL uptake were assessed using flow cytometry, quantitative polymerase chain analysis, western blotting, and confocal laser scanning microscopy.

Results: The mutation that causes FH in this family was LDLR c.97C>T (p.Gln33Ter), and family members with this mutation exhibited elevated levels of low-density lipoprotein cholesterol (LDL-C). The cell experiment results showed that this mutation prevented the synthesis of LDLR protein and caused the cells to lose their LDL uptake ability.

Conclusion: LDLR c.97C>T (p.Gln33Ter) is a pathogenic FH mutation. However, this nonsense mutation did not induce NMD.

Keywords: familial hypercholesterolemia; low‐density lipoprotein receptor; nonsense mutation; whole‐exome sequencing.