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 significantly elevated LDL-cholesterol and premature ischemic heart disease. FH is caused by mutations in LDLR, APOB and PCSK9 genes, however, they account for about 40% of FH cases. In order to obtain a FH genetic diagnosis, the 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 region of Southern Poland, using a targeted next generation sequencing (NGS) technology.

PATIENTS AND METHODS: 90 unrelated adults (aged 18-70) with clinically diagnosed FH according to the Simon Broome Register criteria. A custom designed capture assay and Illumina MiSeq platform were used. The panel included exons and exon/intron boundaries of known FH-causing genes: LDLR, APOB, PCSK9 and genes previously associated with high cholesterol: APOE, ABCG5, ABCG8, LPL, NPC1, LDLRAP1, LIPC, STAP1, CELSR2. Genetic variants were classified based on in silico predictions and ClinVar reports.

RESULTS: We detected 4 subjects with variants in the LDL receptor and APOB gene, that have not been previously linked to FH in ClinVar. We found APOB 100 mutations outside the common LDL-receptor binding region in exon 26 and 29. Interestingly, the high frequency of pathogenic variants of APOE rs7412, probably damaging (4 patients) and benign rs429358 (16 persons) in exon 4 of APOE gene was observed.

CONCLUSIONS: NGS is a useful and reliable method to detect new variants in genes related to familial hypercholesterolemia. In addition, the results allow to detect FH phenocopies and introduce appropriate treatment.