TP53 and systemic lupus erythematosus: Of note, when we compared the cell-cycle state of control and SLE HSPCs in clusters 3 and 4, we observed that the vast majority of SLE HSPCs in cluster 4 was in the S/G2-M phase (Figure 3E), whereas the gene expression and the frequency of cells expressing the cell-cycle-associated genes CDK4, CDK6, CCND2, and TP53 were increased in SLE HSPCs within cluster 4 compared with healthy HSPCs although these changes did not reach statistical significance (Figure 3F).