Project description:The purpose of this study was to determine gene expression changes in hematopoietic stem cells (HSCs) in young and old BALB/c mice, and the impact of Sirt1 gene knockout on HSC aging.
Project description:Sirtuin 1 (SIRT1) is involved in both aging and circadian-clock regulation, yet the link between the two processes in relation to SIRT1 function is not clear. Using Sirt1-deficient mice, we found that Sirt1 and Period 2 (Per2) constitute a reciprocal negative regulation loop that plays important roles in modulating hepatic circadian rhythmicity and aging. Sirt1-deficient mice exhibited profound premature aging and enhanced acetylation of histone H4 on lysine16 (H4K16) in the promoter of Per2, the latter of which leads to its overexpression; in turn, Per2 suppresses Sirt1 transcription through binding to the Sirt1 promoter at the Clock/Bmal1 site. This negative reciprocal relationship between SIRT1 and PER2 was also observed in human hepatocytes. We further demonstrated that the absence of Sirt1 or the ectopic overexpression of Per2 in the liver resulted in a dysregulated pace of the circadian rhythm. The similar circadian rhythm was also observed in aged wild type mice. The interplay between Sirt1 and Per2 modulates aging gene expression and circadian-clock maintenance. To investigate hepatic SIRT1-dependent aging related genes, livers from wild type mice at 3 months (young), 12 months (middle age), and 19 months (old) of age, as well as Sirt1-deficient mice at 3 months of age were snap frozen and subject to RNA isolation and microarray analysis.
Project description:SIRT1 is involved in both aging and circadian clock regulation, yet the link between the two processes in relation to SIRT1 function is unclear. Analyzing SIRT1-deficient cells and mice, we demonstrated that SIRT1 and Per2 constitute a reciprocal negative regulation loop that plays important roles in modulating circadian rhythmicity, metabolism and aging. SIRT1-deficient mice exhibit profound premature aging and enhanced H4K16 acetylation in the promoter of Per2 leading to its overexpression; in turn, Per2 suppresses SIRT1 transcription through binding to SIRT1 promoter at the CLOCK/BMAL1 site. We further demonstrated that absence of SIRT1 or ectopic overexpression of Per2 in the liver resulted in an accelerated pace of circadian rhythm and dysregulated amplitude, mimicking the natural process of circadian shortening in aged mice. Thus the interplay between SIRT1 and Per2 provides a link between the life-long sequence of aging and circadian clock maintenance.
Project description:Loss of immune function and an increased incidence of myeloid leukemia are two of the most clinically significant consequences of aging of the hematopoietic system. To better understand the mechanisms underlying hematopoietic aging, we evaluated the cell intrinsic functional and molecular properties of highly purified long-term hematopoietic stem cells (LT-HSCs) from young and old mice. We found that LT-HSC aging was accompanied by cell autonomous changes, including increased stem cell self-renewal, differential capacity to generate committed myeloid and lymphoid progenitors, and diminished lymphoid potential. Expression profiling revealed that LT-HSC aging was accompanied by the systemic down-regulation of genes mediating lymphoid specification and function and up-regulation of genes involved in specifying myeloid fate and function. Moreover, LT-HSCs from old mice expressed elevated levels of many genes involved in leukemic transformation. These data support a model in which age-dependent alterations in gene expression at the stem cell level presage downstream developmental potential and thereby contribute to age-dependent immune decline, and perhaps also to the increased incidence of leukemia in the elderly.
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:Sirtuin 1 (SIRT1) is involved in both aging and circadian-clock regulation, yet the link between the two processes in relation to SIRT1 function is not clear. Using Sirt1-deficient mice, we found that Sirt1 and Period 2 (Per2) constitute a reciprocal negative regulation loop that plays important roles in modulating hepatic circadian rhythmicity and aging. Sirt1-deficient mice exhibited profound premature aging and enhanced acetylation of histone H4 on lysine16 (H4K16) in the promoter of Per2, the latter of which leads to its overexpression; in turn, Per2 suppresses Sirt1 transcription through binding to the Sirt1 promoter at the Clock/Bmal1 site. This negative reciprocal relationship between SIRT1 and PER2 was also observed in human hepatocytes. We further demonstrated that the absence of Sirt1 or the ectopic overexpression of Per2 in the liver resulted in a dysregulated pace of the circadian rhythm. The similar circadian rhythm was also observed in aged wild type mice. The interplay between Sirt1 and Per2 modulates aging gene expression and circadian-clock maintenance.