Targeted exome sequencing in anti-factor H antibody negative HUS reveals multiple variations
Genetic susceptibility to atypical hemolytic uremic syndrome (aHUS) may lie within genes regulating or activating the alternate complement and related pathways converging on endothelial cell activation.
We tested 32 Indian patients of aHUS negative for antibodies to complement factor H for genetic variations in a panel of 15 genes, i.e., CFH, CFHR1-5, CFI, CFB, C3, CD46, MASP2, DGKE, ADAMTS13, THBD and PLG using next-generation DNA sequencing and for copy number variation in CFHR1-3.
Despite absence of a public database of exome variations in the Indian population and limited functional studies, we could establish a genetic diagnosis in 6 (18.8%) patients using a stringent scheme of prioritization. One patient carried a likely pathogenic variation. The number of patients carrying possibly pathogenic variation was as follows: 1 variation: 5 patients, 2 variations: 9 patients, 3 variations: 5 patients, 4 variations: 9 patients, 5 variations: 2 patients and 6 variations: 2 patients. Homozygous deletion of CFHR1-3 was present in five patients; none of these carried a diagnostic genetic variation. Patients with or without diagnostic variation did not differ significantly in terms of enrichment of genetic variations that were rare/novel or predicted deleterious, or for possible environmental triggers.
We conclude that genetic testing for multiple genes in patients with aHUS negative for anti-FH antibodies reveals multiple candidate variations that require prioritization. Population data on variation frequency of the Indian population and supportive functional studies are likely to improve diagnostic yield.
KeywordsHemolytic uremic syndrome Next-generation sequencing Multiplex ligation-dependent probe amplification
The authors wish to acknowledge the contributions of the following colleagues: Savita Saini from the Division of Nephrology, Department of Pediatrics, All India Institute of Medical Sciences, New Delhi; Arti Yadav, Jyotsna Singh, and Debasis Dash from the CSIR-Institute of Genomics and Integrative Biology, New Delhi.
Compliance with ethical standards
Conflict of interest
There are no conflicts of interest.
The study was supported by Centre Franco-Indien pour la Promotion de la Recherche Avancée (CEFIPRA) vide Project Code no. 4703-1.
Human and animal rights
The study was approved by the Institute Ethics Committee vide IEC/NP-162/10.04.2015.
Informed consent was obtained from all participants. Identifying details of the participants have not been included in the manuscript.
- 25.Exome Variant Server, NHLBI GO Exome Sequencing Project (ESP), Seattle, WA. http://evs.gs.washington.edu/EVS/. Accessed 15 Apr 2016
- 26.Saunders RE, Abarrategui-Garrido C, Frémeaux-Bacchi V, Goicoechea de Jorge E, Goodship THJ, López Trascasa M, et al. The interactive factor H-atypical hemolytic uremic syndrome mutation database and website: update and integration of membrane cofactor protein and factor I mutations with structural models. Hum Mutat. 2007;28:222–34.CrossRefPubMedGoogle Scholar
- 30.Esparza-Gordillo J, Goicoechea de Jorge E, Buil A, Carreras Berges L, López-Trascasa M, Sánchez-Corral P, et al. Predisposition to atypical hemolytic uremic syndrome involves the concurrence of different susceptibility alleles in the regulators of complement activation gene cluster in 1q32. Hum Mol Genet. 2005;14:703–12.CrossRefPubMedGoogle Scholar
- 38.Richards S, Aziz N, Bale S, Bick D, Das S, Gastier-Foster J, et al. Standards and guidelines for the interpretation of sequence variants: a joint consensus recommendation of the American College of Medical Genetics and Genomics and the Association for Molecular Pathology. Genet Med. 2015;17:405–23.CrossRefPubMedPubMedCentralGoogle Scholar