Fig 2: Expression profiling of A2m in BM and phenotypic impacts of its loss of function in mice. (A–F) Body composition phenotypic assays of BMD (A), bone mineral content (B), bone area (C), body length (D), lean (E) and fat mass (F) in 8 female and 7 male 13-week-old homozygous mutant (HOM) A2mtm1b(NCOM)Mfgc mice and 226 female and 209 male wild type mice. Data are from the International Mouse Phenotypic Consortium. p-values determined by unpaired Student’s t-test. (G) Methylation status of 27,578 unique CpG sites in human BM-MSCs from young (≤25 years old) vs. elderly (≥50 years old) donors (GSE17448) and used to quantify the extent of A2M promoter methylation plotted as the intensity ratio between methylated and unmethylated alleles (β-values). Values range from 0 to 1 with 0 being unmethylated. **p < 0.01 by unpaired Student’s t-test. (H) Color coded visualization of tSNE analysis of single cell RNA-Seq of bone marrow niche cells. (n = 17,347 cells). P1, P2, P3, and P4 are subpopulation clusters of LEPR+ SSCs wherein P1, P3, P4 represent osteogenic skewed populations, and P2 represents adipogenic-skewed cells. Expression landscape of Lepr, Lrp1, and A2m are shown. O1, O2, and O3 represent osteoblast and V1 and V2 endothelial cells. Data and visualization taken from publicly available online source of single cell RNA seq analysis of the bone marrow niche cells called niche explorer (https://compbio.nyumc.org/niche/).

Fig 3: A2m is downregulated in Lin-LEPR+ SSPCs from elderly vs. mature mice. (A) Heat map of the top 1000 expressed transcripts in Lin−LEPR+ SSPCs enriched from the BM of mature (3-month) vs. elderly (24-month) male mice based on RNA-Seq analysis. Colors correspond to per-gene z-score computed across each row. (B) PCA analysis of data from (A). (C) Gene sets contributing to PC1 and PC2 based on data from (B). (D) Volcano plot showing Log2 fold-change (FC) values for DEGs and their corresponding p-values in Lin−LEPR+ cells from (A). (E) Transcripts per million counts (TPM) of A2M in Lin−LEPR+ cells from mature vs. elderly mice. Plotted data are mean ± SD and p-value by paired Student’s t-test. (F) Top gene ontology (GO) terms based on p-value identified by GSEA of DEGs in Lin−LEPR+ cells from (D). (G) Most significantly changed Reactome pathways based on DEGs from (D).