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Functional characterisation of rare genetic variants in the N-terminus of complement factor H in aHUS, C3G and AMD

Lookup NU author(s): Dr Edwin Wong, Thomas Hallam, Dr Vicky Brocklebank, Dr Patrick Walsh, Dr Kate Smith-Jackson, Victoria Shuttleworth, Tom Cox, Holly Anderson, Professor Kevin Marchbank, Professor Claire Harris, Professor David Kavanagh

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This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).


Abstract

Membranoproliferative glomerulonephritis (MPGN), C3 glomerulopathy (C3G) atypical haemolytic uraemic syndrome (aHUS) and age-related macular degeneration (AMD) have all been strongly linked with dysfunction of the alternative pathway (AP) of complement. A significant proportion of individuals with MPGN, C3G, aHUS and AMD carry rare genetic variants in the CFH gene that cause functional or quantitative deficiencies in the factor H (FH) protein, an important regulator of the AP. In silico analysis of the deleteriousness of rare genetic variants in CFH is not reliable and careful biochemical assessment remains the gold standard. Six N-terminal variants of uncertain significance in CFH were identified in patients with these diseases of the AP and selected for analysis. The variants were produced in Pichia Pastoris in the setting of FH CCPs 1-4, purified by nickel affinity chromatography and size exclusion and characterised by surface plasmon resonance and haemolytic assays as well as by cofactor assays in the fluid phase. A single variant, Q81P demonstrated a profound loss of binding to C3b with consequent loss of cofactor and decay accelerating activity. A further 2 variants, G69E and D130N, demonstrated only subtle defects which could conceivably over time lead to disease progression of more chronic AP diseases such as C3G and AMD. In the variants S159N; A161S; and M162V any functional defect was below the capacity of the experimental assays to reliably detect. This study further underlines the importance of careful biochemical assessment when assigning functional consequences to rare genetic variants that may alter clinical decisions for patients.


Publication metadata

Author(s): Wong EKS, Hallam T, Brocklebank V, Walsh P, Smith-Jackson K, Shuttleworth V, Cox T, Anderson H, Barlow PN, Marchbank KJ, Harris C, Kavanagh D

Publication type: Article

Publication status: Published

Journal: Frontiers in immunology

Year: 2021

Volume: 11

Print publication date: 01/01/2021

Online publication date: 14/01/2021

Acceptance date: 25/11/2020

Date deposited: 17/01/2021

ISSN (electronic): 1664-3224

Publisher: Frontiers Research Foundation

URL: https://doi.org/10.3389/fimmu.2020.602284

DOI: 10.3389/fimmu.2020.602284


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