Functional analysis of six novel LDLR mutations in the Argentinian population

TOSCANINI U; HELMAN L; CUNIBERTI L; KAESER L; GIUNTA G; COLOMBO R; PONTOGLIO A; GÓMEZ A

Milán

Congreso; European Society of Human Genetics; 2018

Introduction: Mutations in the gene encoding the low-density lipoprotein receptor (LDLR) are involved in the molecular etiology of autosomaldominant familial hypercholesterolemia (FH), an hereditary condition associated with coronary heart disease and the risk of prematuredeath. Based on FH prevalence among Caucasians, it is expected that >80,000 cases are present in Argentina, less than 1% of which havebeen identified so far. Previously, in a cohort of Argentinian FH patients we detected eight unreported LDLR single nucleotide variants(SNVs). Six of them are located in the coding regions of the gene and lead to an amino acid substitution. To assess the pathogenicity ofeach SNV, we performed a functional investigation of the corresponding variant of the receptor proteins.Materials and Methods: Binding, uptake, and degradation of 125-I-labeled LDL by cultured CHO cells expressing wild-type and mutantLDLR proteins were compared in the presence and absence of an excess of unlabelled LDL. Levels of LDLR mRNA expression weredetermined by qRT-PCR 48 h after transfection with plasmids.Results: Four out of the six LDLR mutants showed a markedly reduced in vitro receptor activity, suggesting their role in the pathogenesis ofFH.Conclusions: According to in silico predictions and conservation analysis in multiple species, two of the six identified LDLR variants arelikely benign SNVs. The remaining four variants can be categorized as ?pathogenic variants? that expand the spectrum of FH-linked LDLRmutations in the Argentinian population.