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Fine mapping and conditional analysis identify a new mutation in the autoimmunity susceptibility gene BLK that leads to reduced half-life of the BLK protein

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Author

  • Angelica M. Delgado-Vega
  • Mikhail G. Dozmorov
  • Manuel Bernal Quiros
  • Ying-Yu Wu
  • Belen Martinez-Garcia
  • Sergey V. Kozyrev
  • Johan Frostegard
  • Lennart Truedsson
  • Enrique de Ramon
  • Maria F. Gonzalez-Escribano
  • Norberto Ortego-Centeno
  • Bernardo A. Pons-Estel
  • Sandra D'Alfonso
  • Gian Domenico Sebastiani
  • Torsten Witte
  • Bernard R. Lauwerys
  • Emoke Endreffy
  • Laszlo Kovacs
  • Carlos Vasconcelos
  • Berta Martins da Silva
  • Jonathan D. Wren
  • Javier Martin
  • Casimiro Castillejo-Lopez
  • Marta E. Alarcon-Riquelme
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Summary, in English

Objectives To perform fine mapping of the autoimmunity susceptibility gene BLK and identify functional variants involved in systemic lupus erythematosus (SLE). Methods Genotyping of 1163 European SLE patients and 1482 controls and imputation were performed covering the BLK gene with 158 single-nucleotide polymorphisms. Logistic regression analysis was done using PLINK and conditional analyses using GENABEL's test score. Transfections of BLK constructs on HEK293 cells containing the novel mutation or the wild type form were analysed for their effect on protein half-life using a protein stability assay, cycloheximide and western blot. CHiP-qPCR for detection of nuclear factor. B (NFkB) binding. Results Fine mapping of BLK identified two independent genetic effects with functional consequences: one represented by two tightly linked associated haplotype blocks significantly enriched for NF kappa B-binding sites and numerous putative regulatory variants whose risk alleles correlated with low BLK mRNA levels. Binding of NFkBp50 and p65 to an associated 1.2 Kb haplotype segment was confirmed. A second independent genetic effect was represented by an Ala71Thr, low-frequency missense substitution with an OR = 2.31 (95% CI 1.38 to 3.86). The 71Thr decreased BLK protein half-life. Conclusions These results show that rare and common regulatory variants in BLK are involved in disease susceptibility and both, albeit independently, lead to reduced levels of BLK protein.

Publishing year

2012

Language

English

Pages

1219-1226

Publication/Series

Annals of the Rheumatic Diseases

Volume

71

Issue

7

Document type

Journal article

Publisher

BMJ Publishing Group

Topic

  • Rheumatology and Autoimmunity

Status

Published

ISBN/ISSN/Other

  • ISSN: 1468-2060