Variant-specific quantification of factor H in plasma identifies null alleles associated with atypical hemolytic uremic syndrome

Hakobyan, Svetlana, Tortajada, Agustín, Harris, Claire Louise, de Córdoba, Santiago R and Morgan, Bryan Paul ORCID: https://orcid.org/0000-0003-4075-7676 2010. Variant-specific quantification of factor H in plasma identifies null alleles associated with atypical hemolytic uremic syndrome. Kidney International 78 (8) , pp. 782-788. 10.1038/ki.2010.275

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Abstract

Atypical hemolytic uremic syndrome (aHUS) is associated with complement alternative pathway defects in over half the cases. Point mutations that affect complement surface regulation are common in factor H (CFH); however, sometimes individuals have null mutations in heterozygosis. The latter are difficult to identify, although a consistently low plasma factor H (fH) concentration is suggestive; definitive proof requires demonstration that the mutant sequence is not expressed in vitro. Here, novel reagents and assays that distinguish and individually quantify the common factor H-Y402H polymorphic variants were used to identify alleles of the CFH gene, resulting in low or null expression of full-length fH and also normal or increased expression of the alternative splice product factor H-like-1 (FHL-1). Our assay identified three Y402H heterozygotes with low or absent fH-H402 but normal or increased FHL-1-H402 levels in a cohort of affected patients. Novel mutations explained the null phenotype in two cases, which was confirmed by family studies in one. In the third case, family studies showed that a known mutation was present on the Y allele. The cause of reduced expression of the H allele was not found, although the data suggested altered splicing. In each family, inheritance of low expression or null alleles for fH strongly associated with aHUS. Thus, our assays provide a rapid means to identify fH expression defects without resorting to gene sequencing or expression analysis.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Medicine Systems Immunity Research Institute (SIURI)
Subjects:	R Medicine > R Medicine (General)
Uncontrolled Keywords:	complement, family history, hemolytic uremic syndrome, polymorphisms
Publisher:	Nature Publishing Group
ISSN:	0085-2538
Last Modified:	06 Nov 2022 14:37
URI:	https://orca.cardiff.ac.uk/id/eprint/29965

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