Targeted sequencing of a gene panel in patients with familial hypercholesterolemia from Southern Poland

Abstract

INTRODUCTION Familial hypercholesterolemia (FH) is an autosomal dominant monogenic lipid metabolism disorder characterized by a significantly elevated level of low‑density lipoprotein (LDL) cholesterol and leading to premature ischemic heart disease. FH is caused by mutations in the LDLR, APOB, and PCSK9 genes; however, these mutations account for only about 40% of FH cases. In order to obtain a genetic diagnosis of FH, sequencing of other genes involved in the lipid metabolism might be useful. OBJECTIVES This study aimed to describe genetic variants in genes associated with FH in a group of patients from the Małopolska province in Southern Poland, using the targeted next generation sequenc‑ ing (NGS) technology. PATIENTS AND METHODS The study involved 90 unrelated adults (age range, 18–70 years) with FH di‑ agnosed clinically according to the Simon Broome Register criteria. A custom‑designed capture assay and the Illumina MiSeq platform were used. The panel included exons and exon / intron boundaries of known FH‑causing genes: LDLR, APOB, and PCSK9, as well as genes previously associated with high cholesterol levels: APOE, ABCG5, ABCG8, LPL, NPC1, LDLRAP1, LIPC, STAP1, and CELSR2. Genetic variants were classified based on in silico predictions and ClinVar reports. RESULTS We detected 4 patients with variants in the LDLR and APOB genes that had not been previously linked to FH in ClinVar. We also found APOB mutations outside the common LDL receptor–binding region, in exons 26 and 29. Interestingly, we observed a high frequency of pathogenic variants in exon 4 of the APOE gene: rs7412, probably damaging (4 patients) and rs429358, benign (16 patients). CONCLUSIONS NGS is a useful and reliable method to detect new variants in genes related to FH. In addition, the results enable the detection of FH phenocopies and introduction of appropriate treatment.