Project description:To investigate the global transcriptome changes in mouse hematopoietic stem cell aging, we performed high-throughput sequencing of Poly A+ RNA (RNA-Seq) from purified 4 month, and 24 month-old HSCs (SP-KSL-CD150+). With biological duplicates, more than 200 million reads in total for each age of HSC were obtained. Comparison of the young and old HSC transcriptomes revealed that 1,337 genes that were up-regulated, and 1,297 genes were down-regulated with HSC aging. The most highly represented upstream regulator was growth factor TGFB1, accounting for ~ 19% of differential gene expression in young versus old HSC (p-value = 1.96E-33). Gene ontology (GO) analyses indicated that up-regulated genes in 24mo HSCs are highly enriched in Regulation of Cell Adhesion, Regulation of Cell Proliferation and Ribosome, while down-regulated genes are enriched in DNA Base Excision Repair, DNA replication and Cell Cycle. RNA-seq also allowed us to examine alternative isoforms with aging including alternative splicing, promoter usage and pre-mRNA abundance. Mouse hematopoietic stem cell mRNA profiles of 4 month and 24 month old WT mice were generated generated by deep sequencing, in duplicate, using Illumina Hiseq 2000
Project description:To investigate the global DNA methylation changes in mouse hematopoietic stem cell aging, we performed whole-genome bisulfite sequencing (WGBS). We generated 1,494 million (4mo HSCs), and 1,493 million (24mo HSCs) raw reads; about 82.6% and 84.3%, respectively, were successfully aligned to either strand of the reference genome (mm9). Of all the cytosines present in the reference genome sequence, about 93% of Cs and 99% of CGs were covered in both datasets, with an average coverage of 46-fold (4mo) and 50-fold (24mo). In contrast to the age-associated hypomethylation observed in studies of somatic cells, mentioned above, HSCs showed an increase of methylation with age. The average methylation level over all 16 million covered CpGs increased from 83.5% in young (4mo) HSC to 84.6% in old (24mo) HSC. We observed a total of 448,166 differentially methylated CpGs (DMCs), defined as those having a 20% or more difference in methylation ratio, of which 38.5% (172,609) were hypomethylated (hypo-DMCs) and 61.5% (275,557) were hypermethylated (hyper-DMCs) with aging. For different genomic features, a slightly greater DNA methylation ratio increase was observed for the gene body, LINEs and SINEs, while CGIs and promoters showed balanced increases and decreases. Localization analysis of DMCs indicates that DNA encoding for ribosome RNA (rDNA) is primarily a hotspot for hypo-DMCs, while promoters without CpG islands, CpG island shores and LINE repetitive elements exhibit both hypo- and hyper-DMCs. Mouse hematopoietic stem cell DNA methylation profiles of 4 month and 24 month old WT mice were generated generated by deep sequencing, in duplicate, using Illumina Hiseq 2000.
Project description:To investigate the global transcriptome changes in mouse hematopoietic stem cell aging, we performed high-throughput sequencing of Poly A+ RNA (RNA-Seq) from purified 4 month, and 24 month-old HSCs (SP-KSL-CD150+). With biological duplicates, more than 200 million reads in total for each age of HSC were obtained. Comparison of the young and old HSC transcriptomes revealed that 1,337 genes that were up-regulated, and 1,297 genes were down-regulated with HSC aging. The most highly represented upstream regulator was growth factor TGFB1, accounting for ~ 19% of differential gene expression in young versus old HSC (p-value = 1.96E-33). Gene ontology (GO) analyses indicated that up-regulated genes in 24mo HSCs are highly enriched in Regulation of Cell Adhesion, Regulation of Cell Proliferation and Ribosome, while down-regulated genes are enriched in DNA Base Excision Repair, DNA replication and Cell Cycle. RNA-seq also allowed us to examine alternative isoforms with aging including alternative splicing, promoter usage and pre-mRNA abundance.
Project description:To investigate the global DNA methylation changes in mouse hematopoietic stem cell aging, we performed whole-genome bisulfite sequencing (WGBS). We generated 1,494 million (4mo HSCs), and 1,493 million (24mo HSCs) raw reads; about 82.6% and 84.3%, respectively, were successfully aligned to either strand of the reference genome (mm9). Of all the cytosines present in the reference genome sequence, about 93% of Cs and 99% of CGs were covered in both datasets, with an average coverage of 46-fold (4mo) and 50-fold (24mo). In contrast to the age-associated hypomethylation observed in studies of somatic cells, mentioned above, HSCs showed an increase of methylation with age. The average methylation level over all 16 million covered CpGs increased from 83.5% in young (4mo) HSC to 84.6% in old (24mo) HSC. We observed a total of 448,166 differentially methylated CpGs (DMCs), defined as those having a 20% or more difference in methylation ratio, of which 38.5% (172,609) were hypomethylated (hypo-DMCs) and 61.5% (275,557) were hypermethylated (hyper-DMCs) with aging. For different genomic features, a slightly greater DNA methylation ratio increase was observed for the gene body, LINEs and SINEs, while CGIs and promoters showed balanced increases and decreases. Localization analysis of DMCs indicates that DNA encoding for ribosome RNA (rDNA) is primarily a hotspot for hypo-DMCs, while promoters without CpG islands, CpG island shores and LINE repetitive elements exhibit both hypo- and hyper-DMCs.
Project description:We investigate the aging changes for Histone marks H3K4me3, H3K27me3 and H3K36me3 for mouse hematopoietic stem cells. Mouse hematopoietic stem cell histone methylation profiles of 4 month and 24month old WT mice were generated generated by deep sequencing, in duplicate, using Illumina Hiseq 2000
Project description:BackgroundThe decline of hematopoietic stem cell (HSC) function upon aging contributes to aging-associated immune remodeling and leukemia pathogenesis. Aged HSCs show changes to their epigenome, such as alterations in DNA methylation and histone methylation and acetylation landscapes. We previously showed a correlation between high Cdc42 activity in aged HSCs and the loss of intranuclear epigenetic polarity, or epipolarity, as indicated by the specific distribution of H4K16ac.ResultsHere, we show that not all histone modifications display a polar localization and that a reduction in H4K16ac amount and loss of epipolarity are specific to aged HSCs. Increasing the levels of H4K16ac is not sufficient to restore polarity in aged HSCs and the restoration of HSC function. The changes in H4K16ac upon aging and rejuvenation of HSCs are correlated with a change in chromosome 11 architecture and alterations in nuclear volume and shape. Surprisingly, by taking advantage of knockout mouse models, we demonstrate that increased Cdc42 activity levels correlate with the repression of the nuclear envelope protein LaminA/C, which controls chromosome 11 distribution, H4K16ac polarity, and nuclear volume and shape in aged HSCs.ConclusionsCollectively, our data show that chromatin architecture changes in aged stem cells are reversible by decreasing the levels of Cdc42 activity, revealing an unanticipated way to pharmacologically target LaminA/C expression and revert alterations of the epigenetic architecture in aged HSCs.
Project description:BACKGROUND:Differentiation of induced pluripotent stem cells (iPSCs) toward hematopoietic progenitor cells (HPCs) raises high hopes for disease modeling, drug screening, and cellular therapy. Various differentiation protocols have been established to generate iPSC-derived HPCs (iHPCs) that resemble their primary counterparts in morphology and immunophenotype, whereas a systematic epigenetic comparison was yet elusive. RESULTS:In this study, we compared genome-wide DNA methylation (DNAm) patterns of iHPCs with various different hematopoietic subsets. After 20 days of in vitro differentiation, cells revealed typical hematopoietic morphology, CD45 expression, and colony-forming unit (CFU) potential. DNAm changes were particularly observed in genes that are associated with hematopoietic differentiation. On the other hand, the epigenetic profiles of iHPCs remained overall distinct from natural HPCs. Furthermore, we analyzed if additional co-culture for 2 weeks with syngenic primary mesenchymal stromal cells (MSCs) or iPSC-derived MSCs (iMSCs) further supports epigenetic maturation toward the hematopoietic lineage. Proliferation of iHPCs and maintenance of CFU potential was enhanced upon co-culture. However, DNAm profiles support the notion that additional culture expansion with stromal support did not increase epigenetic maturation of iHPCs toward natural HPCs. CONCLUSION:Differentiation of iPSCs toward the hematopoietic lineage remains epigenetically incomplete. These results substantiate the need to elaborate advanced differentiation regimen while DNAm profiles provide a suitable measure to track this process.