Familial hypercholesterolemia: A single-nucleotide variant (SNV) in mosaic at the low density lipoprotein receptor (LDLR).

Background And Aims: Familial hypercholesterolemia is most frequently caused by genetic variants in the LDLR gene. Most of LDLR pathogenic variants are missense, followed by splicing and deletion/insertions variants. Mosaicism is a genetic condition in which an individual shows more than one clone of cells with different genotypes. The objective of this article was the molecular characterization of a patient with hypercholesterolemia.

Methods And Results: Genetic analysis of DNA from peripheral blood and saliva was performed by NGS, Sanger sequencing and pyrosequencing technologies. NGS analysis detected the pathogenic variant LDLR:c.1951G > T:p.(Asp651Tyr) in 9%-12% of reads. The presence of the variant was confirmed by pyrosequencing analysis. The variant found was functional characterized using an in vitro model (CHO-ldlA7 cells). Activity and expression of cell surface LDLR were measured by flow cytometry. Colocalization LDLR-Dil-LDL was detected by immunofluorescence. The LDLR activity showed 80% uptake, 50% binding and 53% expression of cell surface LDLR regarding wild type.

Conclusions: Herein, we report the first case of a mosaic single nucleotide variant affecting the LDLR gene in a patient with familial hypercholesterolemia. As it has been described for other pathologies, mosaicism could be underestimated in FH and its detection will improve with the introduction of NGS technologies in the diagnostic routine.