A proof‐of‐concept study in mice with defects in ERK signaling and, as a result, reduced DNA methylation in CD4 T cells resulted in overexpression of several X‐linked genes such as Cd11a, Cd70, and Cd40l and SLE development; further estrogen addition exacerbated the disease. The gene discussed is CD4; the disease is systemic lupus erythematosus.