Nuclear GTPase found in germinal center B-cells, where it may inhibit function of the activation-induced cytidine deaminase AICDA (By similarity). Reduces somatic hypermutation in B-cells which may enhance genome stability (PubMed:22833677). B-cell and T-cell development is unaffected, and germinal centers form normally. Class-switch recombination in B-cells is not affected. B-cells in older mice (3 months onwards) show significantly increased somatic hypermutation near the immunoglobulin heavy chain locus, mainly at G:C base pairs. Other loci also show increased rates of somatic hypermutation.