MMP1 and systemic lupus erythematosus: In the absence of XIST, multiple XIST-regulated immune genes (e.g., TLR7, IRAK1, XIAP, TSC22D3, and MMP1) are overexpressed, resulting in the formation and expansion of CD11c + atypical memory B cells (ABCs, a unique B cell population indicating the onset of aging, infection, SLE or RA) (Yu et al. 2021; Karnell et al. 2017; Cancro 2020; Woodruff et al. 2020), B cell autoantibody production (Pyfrom et al. 2021), and overexpression of XIST-regulated genes during T cell maturation of SLE patients and mice, eventually contributing to SLE pathogenesis (Syrett et al. 2019).