TLR7 escapes X chromosome inactivation in immune cells

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Science Immunology  26 Jan 2018:
Vol. 3, Issue 19, eaap8855
DOI: 10.1126/sciimmunol.aap8855

The X chromosome link to lupus

Nine of 10 individuals who develop systemic lupus erythematosus (SLE) are women. Furthermore, individuals with Klinefelter syndrome (47,XXY) also have increased incidence of SLE, suggesting that X chromosome dosage could be an important risk factor in SLE. Using sensitive quantification methods, Souyris et al. demonstrate that Toll-like receptor 7 (TLR7) that is encoded from the X chromosome escapes X inactivation in B cells and myeloid cells in females and Klinefelter individuals. TLR7 binds single-stranded RNA and activates type I interferon signaling, a pathway that is also activated in SLE patients. On the basis of this, the authors propose that biallelic expression of TLR7 contributes to greater SLE risk in individuals with two X chromosomes.

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