Authors: Christopher A. Odhams, Amy L. Roberts, Susan K. Vester, Carolina S. T. Duarte, Charlie T. Beales, Alexander J. Clarke, Sonja Lindinger, Samuel J. Daffern, Antonino Zito, Lingyan Chen, Leonardo L. Jones, Lora Boteva, David L. Morris, Kerrin S. Small, Michelle M. A. Fernando, Deborah S. Cunninghame Graham & Timothy J. Vyse
Systemic lupus erythematosus (SLE) is an autoimmune disease, characterised by increased expression of type I interferon (IFN)-regulated genes and a striking sex imbalance towards females. Through combined genetic, in silico, in vitro, and ex vivo approaches, we define CXorf21, a gene of hitherto unknown function, which escapes X-chromosome inactivation, as a candidate underlying the Xp21.2 SLE association. We demonstrate that CXorf21 is an IFN-response gene and that the sexual dimorphism in expression is magnified by immunological challenge. Fine-mapping reveals a single haplotype as a potential causal cis-eQTL for CXorf21. We propose that expression is amplified through modification of promoter and 3′-UTR chromatin interactions. Finally, we show that the CXORF21 protein colocalises with TLR7, a pathway implicated in SLE pathogenesis. Our study reveals modulation in gene expression affected by the combination of two hallmarks of SLE: CXorf21 expression increases in a both an IFN-inducible and sex-specific manner.