Project description:Recent research has proposed that GIT2 (G protein-coupled receptor kinase interacting protein 2) acts as an integrator of the aging process through regulation of ‘neurometabolic’ integrity. One of the commonly accepted hallmarks of the aging process is thymic involution. At a relatively young age, 12 months of age, GIT2-/- mice present a prematurely distorted thymic structure and dysfunction compared to age-matched 12 month-old wild-type control (C57BL/6) mice. Disruption of thymic structure in GIT2-/- (GIT2KO) was associated with a significant reduction in the expression of the cortical thymic marker, Troma1 (cytokeratin 8). Double positive (CD4+CD8+) and single positive CD4+ T cells were also markedly reduced in 12 month-old GIT2KO mice compared to age-matched control wild-type mice. Coincident with the premature (12 months of age) thymic disruption in GIT2KO mice was the unique generation of a novel cervical ‘organ’, i.e. novel ‘parathymic lobes’. These novel organs did not exhibit classical peripheral lymph node-like characteristics but expressed high levels of T cell progenitors that were reflexively reduced in GIT2KO thymi. Using signaling pathway analysis of GIT2KO thymus and parathymic lobe transcriptomic data we found that the molecular signaling functions lost in the dysfunctional GIT2KO thymus were selectively reinstated in the novel parathymic lobe – suggestive of a compensatory effect for the premature thymic disruption. Broader inspection of high-dimensionality transcriptomic data from GIT2KO lymph nodes, spleen, thymus and parathymic lobes revealed a systemic alteration of multiple proteins (Dbp, Tef, Per1, Per2, Fbxl3, Ddit4, Sin3a) involved in the multidimensional control of cell cycle clock regulation, cell senescence, cellular metabolism and DNA damage. Altered cell clock regulation across both immune and non-immune tissues therefore may be responsible for the premature ‘aging’ phenotype of GIT2KO mice.
Project description:Thymic B cells have been recently shown the ability to be licensed to express Aire, a critical transcription factor involved in the expression of self-antigens in the thymus which are critical for clonal deletion of autoreactive T cells and maintenance of self-tolerance. Mutations in AIRE cause systemic autoimmunity in humans and autoimmunity with varying degrees of severity in different mouse strains. Thymic B cells have been studied in young animals, but studies of this population with age are lacking. Given the thymus undergoes age-associated atrophy in its stromal compartment, we hypothesized that aged thymic B cells may under go changes with age which may impact their ability to mediate clonal deletion of autoreactive T cells and may contribute to age-associated increases in autoimmune prevalence. By comparing the transcriptome of young and aged thymic B cells we find that Aire and transcriptional activators of Aire are signficantly decreased with age.
Project description:Thymic B cells have been recently shown the ability to be licensed to express Aire, a critical transcription factor involved in the expression of self-antigens in the thymus which are critical for clonal deletion of autoreactive T cells and maintenance of self-tolerance. Mutations in AIRE cause systemic autoimmunity in humans and autoimmunity with varying degrees of severity in different mouse strains. Thymic B cells have been studied in young animals, but studies of this population with age are lacking. Given the thymus undergoes age-associated atrophy in its stromal compartment, we hypothesized that aged thymic B cells may under go changes with age which may impact their ability to mediate clonal deletion of autoreactive T cells and may contribute to age-associated increases in autoimmune prevalence. By comparing the transcriptome of young and aged thymic B cells we find that Aire and transcriptional activators of Aire are signficantly decreased with age.
Project description:Vascular dysfunction is one of the typical characteristics of aging, but its contributing roles to systemic aging and the therapeutic potential is lacking experimental evidence. Accumulating data suggest that the mechanisms underlying aging are similar to those governing Hutchinson-Gilford progeria syndrome (HGPS), a premature aging disease, in which affected patients succumb to cardiovascular diseases (CVDs). Here, we generated a knock-in mouse model with the causative HGPS LmnaG609G mutation, called progerin. We crossed Lmnaf/f mice with a Tie2-Cre line to get Lmnaf/f;TC mice, which exhibit defective microvasculature and neovascularization, accelerated aging and shortened lifespan. Single-cell transcriptomic analysis of murine lung endothelial cells (MLECs) revealed a significant upregulation of inflammatory response. These data support endothelial dysfunction as a primary trigger of systemic aging and highlight gene therapy as a potential strategy for the clinical treatment of HGPS and age-related vascular dysfunction.
Project description:Regulation of quiescence is essential for adult stem cell maintenance, longevity and sustained regeneration potential. Our studies have uncovered that physiological and transient changes in mitochondrial shape regulate the quiescent state of adult muscle stem cells (MuSCs). We show that mitochondria in MuSCs rapidly fragment in response to an activation stimulus, via a systemic HGF/mTOR mechanism, to drive the exit from deep quiescence. Deletion of the mitochondrial fusion protein OPA1 and forced mitochondrial fragmentation is sufficient to transition MuSCs into G-alert quiescence causing premature activation and depletion upon a stimulus. Loss of OPA1 activates a glutathione (GSH) redox signaling pathway that promotes cell-cycle progression, myogenic gene expression and commitment. MuSCs with chronic OPA1 loss and mitochondrial fragmentation, leading to mitochondrial dysfunction, continue to reside in a primed state but acquire severe cell cycle defects. Additionally, we provide evidence that OPA1 decline and impaired mitochondrial dynamics may contribute to age-related MuSC dysfunction. These findings reveal a fundamental role for OPA1 and mitochondrial dynamics in establishing the quiescent state and activation potential of adult stem cells.
Project description:Sepsis-associated encephalopathy (SAE) is a major and frequent complication in patients with sepsis resulting in delirium and premature death. Sepsis survivors commonly suffer from long-term cognitive impairment causing immense burden on patients, caregivers, and economic health systems. Underlying pathophysiology of SAE related cognitive deficits is largely unresolved, Thus treatment options are missing. We report that experimental polymicrobial sepsis in mice induces synaptic pathology in the central nervous system underlying defective long-term potentiation and cognitive dysfunction. Analysis of differentially expressed genes revealed severely affected downregulation of genes related to neuronal and synaptic signaling in the brain, e.g. of the activity-regulated cytoskeleton-associated protein (Arc ), of the transcription-regulatory EGR family, and of the dual-specificity phosphatase 6 (Dusp6). On the protein level, ARC expression and mitogen-activated protein (MAP) kinase signaling in the brain was disturbed during SAE. For targeted rescue of dysregulated synaptic signaling and plasticity, we overexpressed ARC in the hippocampus by bilateral in-vivo stereotactic microinjection of an adeno-associated virus containing a neuron-specific plasmid of the Arc transgene. Hereby, defective synaptic plasticity and signaling in the hippocampus were restored and memory function improved. Accordingly, synaptic plasticity, neuronal spine pathology, and memory dysfunction also improved when post-septic mice were subjected to enriched environment demonstrating the potential for activity-induced recovery of long-term cognitive dysfunction. Together, we identified synaptic pathology of neurocognitive dysfunction after severe systemic infection and provide a proof-of-concept approach to interfere with SAE pathomechanisms leading to cognitive improvement.
Project description:Microarray Analysis of Space-flown Murine Thymus Tissue Reveals Changes in Gene Expression Regulating Stress and Glucocorticoid Receptors. We used microarrays to detail the gene expression of space-flown thymic tissue and identified distinct classes of up-regulated genes during this process. We report here microarray gene expression analysis in young adult C57BL/6NTac mice at 8 weeks of age after exposure to spaceflight aboard the space shuttle (STS-118) for a period of 13 days. Upon conclusion of the mission, thymus lobes were extracted from space flown mice (FLT) as well as age- and sex-matched ground control mice similarly housed in animal enclosure modules (AEM). mRNA was extracted and an automated array analysis for gene expression was performed. Examination of the microarray data revealed 970 individual probes that had a 1.5 fold or greater change. When these data were averaged (n=4), we identified 12 genes that were significantly up- or down-regulated by at least 1.5 fold after spaceflight (p≤0.05). Together, these data demonstrate that spaceflight induces significant changes in the thymic mRNA expression of genes that regulate stress, glucocorticoid receptor metabolism, and T cell signaling activity. These data explain, in part, the reported systemic compromise of the immune system after exposure to the microgravity of space.