Functional Analysis of 3′UTR Variants at the LDLR and PCSK9 Genes in Patients with Familial Hypercholesterolemia

Familial hypercholesterolemia (FH) is an autosomal dominant disease with an estimated prevalence of 1 in 200-250 individuals. Patients with FH are at increased risk of premature coronary artery disease. Early diagnosis and treatment are essential for improving clinical outcomes. In many cases, however, the genetic diagnosis is not confirmed. At present, routine genetic testing does not analyze the 3^′UTR regions of LDLR and PCSK9. However, 3^′UTR-single nucleotide variants could be of interest because they can modify the target sequence of miRNAs that regulate the expression of these genes. Our study fully characterizes the 3^′UTR regions of LDLR and PCSK9 in 409 patients with a suspected diagnosis of FH using next-generation sequencing. In 30 of the 409 patients, we found 21 variants with an allelic frequency of <1%; 14 of them at 3^′UTR-LDLR and 8 at 3^′UTR-PCSK9. The variants’ pathogenicity was studied in silico; subsequently, a number of the variants were functionally validated using luciferase reporter assays. LDLR:c.^∗653G > C showed a 41% decrease in luciferase expression, while PCSK9:c.^∗950C > T showed a 41% increase in PCSK9 expression, results that could explain the hypercholesterolemia phenotype. In summary, the genetic analysis of the 3^′UTR regions of LDLR and PCSK9 could improve the genetic diagnosis of FH.