The naked mole rat (NMR) is the longest-lived rodent, resistant to multiple age-related diseases including neurodegeneration. However, the mechanisms underlying the NMR’s resistance to ...neurodegenerative diseases remain elusive. Here, we isolated oligodendrocyte progenitor cells (OPCs) from NMRs and compared their transcriptome with that of other mammals. Extracellular matrix (ECM) genes best distinguish OPCs of long- and short-lived species. Notably, expression levels of CD44, an ECM-binding protein that has been suggested to contribute to NMR longevity by mediating the effect of hyaluronan (HA), are not only high in OPCs of long-lived species but also positively correlate with longevity in multiple cell types/tissues. We found that CD44 localizes to the endoplasmic reticulum (ER) and enhances basal ATF6 activity. CD44 modifies proteome and membrane properties of the ER and enhances ER stress resistance in a manner dependent on unfolded protein response regulators without the requirement of HA. HA-independent role of CD44 in proteostasis regulation may contribute to mammalian longevity.
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•CD44 levels correlate with species maximum lifespan in OPCs, liver, skin, and fibroblasts•CD44 enhances basal ATF6 activity and ER stress resistance without the requirement of HA•CD44 localizes to the ER and alters ER proteome and ER membrane properties•CD44-dependent ER stress resistance is mediated by non-canonical activation of ATF6
Through comparative transcriptomics of short- and long-lived mammals, Takasugi et al. identified a correlation between longevity and CD44 levels. CD44 localizes to the ER and enhances basal ATF6 activity and ER stress resistance without HA. This HA-independent role of CD44 in proteostasis regulation may contribute to mammalian longevity.
Deregulation of receptor tyrosine kinase (RTK)-signaling is frequently observed in many human malignancies, making activated RTKs the promising therapeutic targets. In particular, activated ...RTK-signaling has a strong impact on tumor resistance to various DNA damaging agents, e.g., ionizing radiation and chemotherapeutic drugs. We showed recently that fibroblast growth factor receptor (FGFR)-signaling might be hyperactivated in imatinib (IM)-resistant gastrointestinal stromal tumors (GIST) and inhibition of this pathway sensitized tumor cells to the low doses of chemotherapeutic agents, such as topoisomerase II inhibitors. Here, we report that inhibition of FGFR-signaling in GISTs attenuates the repair of DNA double-strand breaks (DSBs), which was evidenced by the delay in γ-H2AX decline after doxorubicin (Dox)-induced DNA damage. A single-cell gel electrophoresis (Comet assay) data showed an increase of tail moment in Dox-treated GIST cells cultured in presence of BGJ398, a selective FGFR1-4 inhibitor, thereby revealing the attenuated DNA repair. By utilizing GFP-based reporter constructs to assess the efficiency of DSBs repair via homologous recombination (HR) and non-homologous end-joining (NHEJ), we found for the first time that FGFR inhibition in GISTs attenuated the homology-mediated DNA repair. Of note, FGFR inhibition/depletion did not reduce the number of BrdU and phospho-RPA foci in Dox-treated cells, suggesting that inhibition of FGFR-signaling has no impact on the processing of DSBs. In contrast, the number of Dox-induced Rad51 foci were decreased when FGFR2-mediated signaling was interrupted/inhibited by siRNA FGFR2 or BGJ398. Moreover, Rad51 and -H2AX foci were mislocalized in FGFR-inhibited GIST and the amount of Rad51 was substantially decreased in -H2AX-immunoprecipitated complexes, thereby illustrating the defect of Rad51 recombinase loading to the Dox-induced DSBs. Finally, as a result of the impaired homology-mediated DNA repair, the increased numbers of hypodiploid (i.e., apoptotic) cells were observed in FGFR2-inhibited GISTs after Dox treatment. Collectively, our data illustrates for the first time that inhibition of FGF-signaling in IM-resistant GIST interferes with the efficiency of DDR signaling and attenuates the homology-mediated DNA repair, thus providing the molecular mechanism of GIST's sensitization to DNA damaging agents, e.g., DNA-topoisomerase II inhibitors.
Long-lived rodents have become an attractive model for the studies on aging. To understand evolutionary paths to long life, we prepare chromosome-level genome assemblies of the two longest-lived ...rodents, Canadian beaver (Castor canadensis) and naked mole rat (NMR, Heterocephalus glaber), which were scaffolded with in vitro proximity ligation and chromosome conformation capture data and complemented with long-read sequencing. Our comparative genomic analyses reveal that amino acid substitutions at “disease-causing” sites are widespread in the rodent genomes and that identical substitutions in long-lived rodents are associated with common adaptive phenotypes, e.g., enhanced resistance to DNA damage and cellular stress. By employing a newly developed substitution model and likelihood ratio test, we find that energy and fatty acid metabolism pathways are enriched for signals of positive selection in both long-lived rodents. Thus, the high-quality genome resource of long-lived rodents can assist in the discovery of genetic factors that control longevity and adaptive evolution.
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•Improved genome assemblies of the naked mole rat and Canadian beaver•Substitutions at disease-causing sites could be adaptive•Unique substitutions in long-lived rodents support stress resistance•Genome resource for studies of long-lived rodents
Zhou et al. generate “chromosome-level” genome assemblies for the Canadian beaver and naked mole rat. They characterize genome features and identify common substitutions in long-lived rodents that support enhanced tolerance of cells to DNA damage. The study also provides a valuable genome resource for aging research.
OBJECTIVES/GOALS: The major objective of this project is two points. First, is to repeat and confirm previous observations that there is elevated cytosolic Line1 DNA in the cytoplasm of cells derived ...from old mice compared to young. Second is to identify which Line1s in the genome are contributing to this free DNA and test if targeting them rescues the age-related phenotype. METHODS/STUDY POPULATION: This project will focus on data collected from both tissues and primary cells derived from multiple tissues. Using cellular/tissue fractionation kits, we isolate specifically from the cytoplasm. This specificity is confirmed by western blotting. Measurement of the Line1 levels is measured by quantitative PCR. Subsequently, these cytoplasmic samples are sent off for sequencing in order to quantify the length of the free DNA in the cytoplasm and to identify which Line1 genomic families the cytosolic DNA originates. Additionally, FISH is utilized to visualize Line1 DNA in the cytoplasm of aged versus young cells RESULTS/ANTICIPATED RESULTS: We anticipate this research to confirm the hypothesis that extranuclear Line1 DNA accumulates with age in both tissues and primary fibroblasts. Additionally, we expect to be able to determine which specific families of genomic Line1 is driving this extranuclear DNA, which would suggest the active retrotransopable elements that are directly involved in this aging related phenotype. Assuming successful identification of such families, we can then target and silence these specific elements to determine not only if cytoplasmic Line1 in aged mice decreases, but additionally if the healthspan and/or lifespan of these mice improves DISCUSSION/SIGNIFICANCE: Dereoressed Line1s have been shown to be involved in detrimental phenotypes, including autoimmune disease, cancer, and inflammaging. Targeting retrotransposons, either directly through degradation of transcriptional product of LINE1s or indirectly by improving function of regulators, will be crucial in ablating aging phenotypes
Descriptions of karyotypes of many animal species are currently available. In addition, there has been a significant increase in the number of sequenced genomes and an ever-improving quality of ...genome assembly. To close the gap between genomic and cytogenetic data we applied fluorescent in situ hybridization (FISH) and Hi-C technology to make the first full chromosome-level genome comparison of the guinea pig (Cavia porcellus), naked mole-rat (Heterocephalus glaber), and human. Comparative chromosome maps obtained by FISH with chromosome-specific probes link genomic scaffolds to individual chromosomes and orient them relative to centromeres and heterochromatic blocks. Hi-C assembly made it possible to close all gaps on the comparative maps and to reveal additional rearrangements that distinguish the karyotypes of the three species. As a result, we integrated the bioinformatic and cytogenetic data and adjusted the previous comparative maps and genome assemblies of the guinea pig, naked mole-rat, and human. Syntenic associations in the two hystricomorphs indicate features of their putative ancestral karyotype. We postulate that the two approaches applied in this study complement one another and provide complete information about the organization of these genomes at the chromosome level.
Hyaluronan goes to great length Gorbunova, Vera; Takasugi, Masaki; Seluanov, Andrei
Cell Stress,
07/2020, Letnik:
4, Številka:
9
Journal Article
Recenzirano
Odprti dostop
Hyaluronan is a major non-protein component of extracellular matrix that affects biomechanical properties of tissues and interacts with cell receptors. Hyaluronan is a linear glycosaminoglycan ...composed of repeating disaccharides of (β, 1-4)-glucuronic acid (GlcUA) and (β, 1-3)-N-acetyl glucosamine (GlcNAc). The length of hyaluronan can range from an oligomer to an extremely long form up to millions of daltons. The concept that emerged in the field is that high (HMW-HA) and low (LMW-HA) molecular weight hyaluronans have different biological properties and trigger different signaling cascades within the cells. LMW-HA is associated with inflammation, tissue injury and metastasis, while HMW-HA improves tissue homeostasis and has anti-inflammatory and antimetastatic properties. HMW-HA is used in the clinic to treat arthritis, and as a filler in surgery and in the form of rinses to treat local inflammation. However, HMW-HA products used in the clinic come in a range of sizes between 0.5-6 mDa that are used interchangeably. Remarkably, the tissues of a long-lived and cancer-resistant rodent, the naked mole rat, contain abundant HA of very high molecular weight. While human fibroblasts secrete HA up to 2 MDa, naked mole rat fibroblasts produce HA of 6-12 MDa. Does this very high HMW-HA (vHMW-HA) differ functionally from HMW-HA? We found that vHMW-HA has superior cytoprotective properties compared to HMW-HA, and interacts differently with the CD44 receptor leading to distinct transcriptional changes (Takasugi
(2020), Nat Commun). These results indicate that vHMW-HA has greater therapeutic benefits than the standard HMW-HA.
TRF2 (telomeric repeat binding factor 2) is an essential component of the telomeric cap, where it forms and stabilizes the T-loop junctions. TRF2 forms the T-loops by stimulating strand invasion of ...the 3' overhang into duplex DNA. TRF2 also has been shown to localize to nontelomeric DNA double-strand breaks, but its functional role in DNA repair has not been examined. Here, we present evidence that TRF2 is involved in homologous recombination (HR) repair of nontelomeric double-strand breaks. Depletion of TRF2 strongly inhibited HR and delayed the formation of Rad51 foci after γ-irradiation, whereas overexpression of TRF2 stimulated HR. Depletion of TRF2 had no effect on nonhomologous end-joining, and overexpression of TRF2 inhibited nonhomologous end-joining. We propose, based on our results and on the ability of TRF2 to mediate strand invasion, that TRF2 plays an essential role in HR by facilitating the formation of early recombination intermediates.
Naked mole rat (NMR) is the long-lived and tumor-resistant rodent. NMRs possess multiple adaptations that may contribute to longevity and cancer-resistance. However, whether NMRs have more efficient ...DNA repair have not been directly tested. Here we compared base excision repair (BER) and nucleotide excision repair (NER) systems in extracts from NMR and mouse fibroblasts after UVC irradiation. Transcript levels of the key repair enzymes demonstrated in most cases higher inducibility in the mouse vs the NMR cells. Ratios of repair enzymes activities in the extracts somewhat varied depending on post-irradiation time. NMR cell extracts were 2-3-fold more efficient at removing the bulky lesions, 1.5-3-fold more efficient at removing uracil, and about 1.4-fold more efficient at cleaving the AP-site than the mouse cells, while DNA polymerase activities being as a whole higher in the mouse demonstrate different patterns of product distribution. The level of poly(ADP-ribose) synthesis was 1.4-1.8-fold higher in the NMR cells. Furthermore, NMR cell extracts displayed higher binding of PARP1 to DNA probes containing apurinic/apyrimidinic site or photo-reactive DNA lesions. Cumulatively, our results suggest that the NMR has more efficient excision repair systems than the mouse, which may contribute to longevity and cancer resistance of this species.
Are DNA damage and mutations possible causes or consequences of aging? This question has been hotly debated by biogerontologists for decades. The importance of DNA damage as a possible driver of the ...aging process went from being widely recognized to then forgotten, and is now slowly making a comeback. DNA double strand breaks (DSBs) are particularly relevant to aging because of their toxicity, increased frequency with age and the association of defects in their repair with premature aging. Recent studies expand the potential impact of DNA damage and mutations on aging by linking DNA DSB repair and age-related chromatin changes. There is overwhelming evidence that increased DNA damage and mutations accelerate aging. However, an ultimate proof of causality would be to show that enhanced genome and epigenome stability delays aging. This is not an easy task, as improving such complex biological processes is infinitely more difficult than disabling it. We will discuss the possibility that animal models with enhanced DNA repair and epigenome maintenance will be generated in the near future.
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