Identification of novel variants in the <i>LDLR</i> gene in Russian patients with familial hypercholesterolemia using targeted sequencing
В. В. Мирошникова, Olga Romanova, О.Н. Иванова, Mikhail А. Fedyakov, Alexandra Panteleeva, Yury A. Barbitoff, M. V. Muzalevskaya, S. A. Urazgildeevа, В. С. Гуревич, Stanislav P. Urazov, Sergey G. Scherbak, Аndrey М. Sarana, Наталя Семенова, И. В. Анисимова, Daria Guseva, Sofya Pchelina, Аndrey S. Glotov, Ekaterina Zakharova, Oleg S. Glotov
Abstract
Familial hypercholesterolemia (FH) is caused by mutations in various genes, including the <em>LDLR</em>, <em>APOB</em> and <em>PSCK9</em> genes; however, the spectrum of these mutations in Russian individuals has not been fully investigated. In the present study, mutation screening was performed on the <em>LDLR</em> gene and other FH‑associated genes in patients with definite or possible FH, using next‑generation sequencing. In total, 59 unrelated patients were recruited and sorted into two separate groups depending on their age: Adult (n=31; median age, 49; age range, 23‑70) and children/adolescent (n=28; median age, 11; age range, 2‑21). FH‑associated variants were identified in 18 adults and 25 children, demonstrating mutation detection rates of 58 and 89% for the adult and children/adolescent groups, respectively. In the adult group, 13 patients had FH‑associated mutations in the <em>LDLR</em> gene, including two novel variants [NM_000527.4: c.433_434dupG p.(Val145Glyfs*35) and c.1186G>C p.(Gly396Arg)], 3 patients had APOB mutations and two had ABCG5/G8 mutations. In the children/adolescent group, 21 patients had FH‑causing mutations in the LDLR gene, including five novel variants [NM_000527.4: c.325T>G p.(Cys109Gly), c.401G>C p.(Cys134Ser), c.616A>C p.(Ser206Arg), c.1684_1691delTGGCCCAA p.(Pro563Hisfs*14) and c.940+1_c.940+4delGTGA], and 2 patients had APOB mutations, as well as <em>ABCG8</em> and <em>LIPA</em> mutations, being found in different patients. The present study reported seven novel <em>LDLR</em> variants considered to be pathogenic or likely pathogenic. Among them, four missense variants were located in the coding regions, which corresponded to functional protein domains, and two frameshifts were identified that produced truncated proteins. These variants were observed only once in different patients, whereas a splicing variant in intron 6 (c.940+1_c.940+4delGTGA) was detected in four unrelated individuals. Previously reported variants in the <em>LDLR, APOB, ABCG5/8</em> and <em>LIPA</em> genes were observed in 33 patients. The <em>LDLR</em> p.(Gly592Glu) variant was detected in 6 patients, representing 10% of the FH cases reported in the present study, thus it may be a major variant present in the Russian population. In conclusion, the present study identified seven novel variants of the <em>LDLR</em> gene and broadens the spectrum of mutations in FH‑related genes in the Russian Federation.