Mutation type classification and pathogenicity assignment of sixteen missense variants located in the EGF-precursor homology domain of the LDLR

The primary genetic cause of familial hypercholesterolemia (FH) is related to mutations in the LDLR gene encoding the Low-density Lipoprotein Receptor. LDLR structure is organized in 5 different domains, including an EGF-precursor homology domain that plays a pivotal role in lipoprotein release and receptor recycling. Mutations in this domain constitute 51.7% of the total missense variants described in LDLR. The aim of the present work was to analyse how clinically significant variants in the EGF-precursor homology domain impact LDLR. The activity of sixteen LDLR variants was functionally characterized by determining LDLR expression by Western blot and LDLR expression, LDL binding capacity and uptake, and LDLR recycling activity by flow cytometry in transfected CHO-ldlA7 cells. Of the analysed variants, we found six non-pathogenic LDLR variants and ten pathogenic variants distributed as follow: three class 3 variants; four class 2 variants; and three class 5 variants. These results can be incorporated into clinical management of patients by helping guide the appropriate level of treatment intensity depending on the extent of loss of LDLR activity. This data can also contribute to cascade-screening for pathogenic FH variants.We thank Prof. Monty Krieger for kindly providing CHO-ldlA7 cells. We sincerely thank Haziq Siddiqi (Harvard Medical School) for his critical reading and editing of this manuscript and Professor Katrine T. Schjoldager (Copenhagen Center for Glycomics) for her invaluable research assistance on glycosylation analysis of p.(Ser584Pro) LDLR variant. This work was supported by the Basque Government (Grupos Consolidados IT-1264-19). A.B.-V. was supported by a grant PIF (2014–2015), Gobierno Vasco and DOKBERRI 2019-I. S.J. was supported by a grant PIF (2017–2018), Gobierno Vasco. U.G-G. and R.A-E. were supported by Fundación Biofísica Bizkai