Targeted sequencing of a gene panel in patients with Familial Hypercholesterolemia from Southern Poland

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 sequencing (NGS) technology. PATIENTS AND METHODS: The study involved 90 unrelated adults (age range, 18-70 years) with FH diagnosed 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.