Older HSCs develop an IL-1–dependent immune-inflammatory transcriptional signature. (A) Principal component analysis (PCA) plot of LT-HSCs (LKS CD34^–Flt3^–CD48^–CD150⁺) from 2mo, n = 4 WT; n = 3 IL-1R1KO) and 2y, n = 4 WT; n = 5 IL-1R1KO) WT SPF and IL-1R1KO SPF mice, based on RNA-sequencing (RNA-seq) expression values fragments per kilobase million. (B) Venn diagram depicting DEGs in HSCs from 2mo and 2y mice, which are unique to WT, unique to IL-1R1KO, or shared between the 2 groups. (C) Overrepresented GO terms (maximum of 15 terms) for upregulated (UP) and downregulated (DOWN) DEGs, unique to older WT LT-HSCs, unique to older IL-1R1KO LT-HSCs, or shared between the 2 groups. All displayed GO terms are significant (FDR < 0.05). GO terms related to hematopoiesis, immunity, or inflammation are indicated in bold. Abbreviations: dephospho, dephosphorylation; dev., development; diff., differentiation; elect., electron; mig., migration; mitATP, mitochondrial ATP; neg., negative; pos., positive; reg., regulatory; resp., response; transp., transport. (D) Heatmap showing expression of genes associated with GO terms. Response to cytokine (GO: 0034097) and genes which were previously described as being associated with lymphoid, myeloid, and megakaryocytic development. Column Z-scores are normalized. All genes displayed are significantly different in pairwise group comparison (WT_2mo_1-4, 2mo WT vs WT_2y_1-4, 2y SPF WT; IL-1R1KO_2mo_1-3, 2mo IL-1R1KO vs IL-1R1KO_2y_1-5, 2y IL-1R1KO) with FDR < 0.05. (*) not significant.