Cell cyclin kinase inhibitor Cdkn2c regulates B cell homeostasis and function in the NZM2410-derived murine lupus susceptibility locus Sle2c1

Sle2c1 is an NZM2410-derived lupus susceptibility locus that induces an expansion of the B1a cell compartment. B1a cells have a repertoire enriched for autoreactivity, and an expansion of this B cell subset occurs in several mouse models of lupus. Here we showed that expression of Sle2c1 enhances NZB cellular phenotypes that have been associated with autoimmune pathogenesis. A combination of genetic mapping and candidate gene analysis presents Cdkn2c, a gene encoding for cyclin kinase inhibitor p18INK4c (p18), as the top candidate gene for inducing the Slec2c1 associated expansion of B1a cells. A novel SNP in the Cdkn2c promoter is associated with a significantly reduced Cdkn2c expression in the splenic B cells and B1a cells from Sle2c1-carrying mice, which leads to defective G1 cell cycle arrest in splenic B cells and increased proliferation of Pc B1a cells. As cell cycle is differentially regulated in B1a and B2 cells, these results suggest that Cdkn2c play a critical role in B1a cell self renewal, and that its impaired expression leads to an accumulation of these cells with high autoreactive potential.

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Xu Z, Potula HH, Vallurupalli A, Perry D, Baker H, Croker BP, Dozmorov I, Morel L