ESR8: “The impact of genome instability in cellular senescence and ageing”

TAU (Yosef Shiloh group): The impact of genome instability in cellular senescence and ageing.

i. Objective of research: To dissect the link between genome instability and senescence at the organismal, cellular and molecular levels.

ii. Current state of the artGenome instability is a molecular hallmark of ageing. The main axis in maintaining genome stability is the DNA damage response (DDR), a complex signalling network. Genetic loss of key DDR players usually leads to severe diseases that often include premature ageing. We believe that in addition to these rare disorders, numerous combinations of sequence alterations in DDR genes account for a continuum of variation in genome stability in the general population that affects public health on a large scale, including the pace and nature of ageing. This conviction, together with mounting evidence that cell senescence in body tissues affects the ageing process, underlie our work on the link between genetically determined genome instability, cell senescence and ageing at the organismal, tissue and individual cell levels. We use for this purpose mouse models that we generated and derived cell lines. The DDR is vigorously activated by DNA double-strand breaks (DSBs). The DSB response is mobilized by the ATM protein kinase, whose loss leads to the severe genome instability syndrome, ataxia-telangiectasia (A-T). Another important component of the DDR network is the WRN helicase-nuclease, which is involved in numerous DNA transactions and whose loss leads in humans to the premature ageing disorder, Werner syndrome (WS). We conjectured that appropriate mouse models for our work should be based on combinations of wild-type and null alleles in the murine Atm and Wrn genes.

iii. Research methodology and approach: We found the double-knockout (dKO) genotype (Atm-/-/Wrn-/-) be embryonic lethal due to severe developmental retardation. All other Atm/Wrn genotypic combinations (including the double heterozygotes, Atm+/-/Wrn+/-) which represent a genotype that exists in humans) are born alive and exhibit various degrees of premature ageing. We can induce the dKO genotype in cultured cells by introducing 4-hydroxytamoxifen to fibroblast lines from adult mice that are homozygous for floxed Atm and Wrn null alleles and express a Cre(ERT) transgene. Notably, this action induces rapid cell senescence without treatment with DNA damaging agents. We will follow morbidity, senescence and ageing parameters associated with these genotypes at the organismal and tissue levels. Molecular analysis will include hallmarks of genome stability and ‘spontaneous’ DNA damage. Analysis of cell lines derived from these genotypes (including the induced dKO system) will culminate in monitoring transcriptome dynamics and pathway analysis.

iv. Originality and innovative aspects of the ESR project: We have established a unique experimental system that allows investigation of the genome instability-cell senescence-ageing link at various levels, with expected new, deep insights into this link.

v. Integration of the ESR project to the overall research programme: Our ESR will work with the Genevia on RNA-seq data analysis algorithms, with the ProtATonce on identifying the secretome of dKO cells and with LXRepair on the development of miniaturized DSB repair assays.