Whole Chromosome Instability induces senescence and promotes SASP.

Grasiella Angelina Andriani,Judith Campisi,Wanxia Li Tsai,Massimo Gadina,Jan Vijg,Francesca Faggioli,Laura Santambrogio,Vinnycius Pereira Almeida,Maurizio Mauro,Alexander Maslov,Cristina Montagna

doi:10.1038/srep35218

Abstract

Age-related accumulation of ploidy changes is associated with decreased expression of genes controlling chromosome segregation and cohesin functions. To determine the consequences of whole chromosome instability (W-CIN) we down-regulated the spindle assembly checkpoint component BUB1 and the mitotic cohesin SMC1A, and used four-color-interphase-FISH coupled with BrdU incorporation and analyses of senescence features to reveal the fate of W-CIN cells. We observed significant correlations between levels of not-diploid cells and senescence-associated features (SAFs). W-CIN induced DNA double strand breaks and elevated oxidative stress, but caused low apoptosis. SAFs of W-CIN cells were remarkably similar to those induced by replicative senescence but occurred in only 13 days versus 4 months. Cultures enriched with not-diploid cells acquired a senescence-associated secretory phenotype (SASP) characterized by IL1B, CXCL8, CCL2, TNF, CCL27 and other pro-inflammatory factors including a novel SASP component CLEC11A. These findings suggest that W-CIN triggers premature senescence, presumably to prevent the propagation of cells with an abnormal DNA content. Cells deviating from diploidy have the ability to communicate with their microenvironment by secretion of an array of signaling factors. Our results suggest that aneuploid cells that accumulate during aging in some mammalian tissues potentially contribute to age-related pathologies and inflammation through SASP secretion.

Highlights

Numerical whole chromosome instability (W-CIN) is a cellular state with a high propensity for chromosome mis-segregation generated by defects in the mitotic machinery and in cellular pathways controlling chromosome segregation, such as the Spindle Assembly Checkpoint (SAC) and sister chromatid cohesion[3,4]
We found that all mitotic components tested were significantly down-regulated at the mRNA level (p = 0.0219 for BUB1B, p = 0.0405 for BUB1, p = 0.0333 for structural maintenance of chromosomes 1A (SMC1A) and p = 0.0357 for BUB3) in SEN cells relative to proliferating cells (Fig. 1c)
Decrease in gene expression appeared SEN-specific, as non-mitotic quiescent cells did not significantly deregulate the expression of those targets (p = 0.3294 for BUB1B, p = 0.5093 for BUB1, p = 0.7947 for SMC1A and p = 0.6539 for BUB3) (Fig. 1c). Both BUB1B and BUB1 were down-regulated more than 10 fold in SEN when compared to proliferating cells (13 fold and 10 fold, respectively), while SMC1A and BUB3 were down-regulated to a lesser extent (3.9 and 3.1 fold, respectively). These results are in agreement with SAC and cohesin proteins being expressed at lower levels at older age[3,7,14,15], and suggest that the senescence-associated accumulation of ploidy changes in cultured fibroblasts could be a consequence of limited availability of those components

Summary

Introduction

Numerical whole chromosome instability (W-CIN) is a cellular state with a high propensity for chromosome mis-segregation generated by defects in the mitotic machinery and in cellular pathways controlling chromosome segregation, such as the Spindle Assembly Checkpoint (SAC) and sister chromatid cohesion[3,4]. Evidence for W-CIN activating the senescence response has emerged from studies suggesting that down-regulating genes that result in aneuploidy induces premature senescence in human cells[6,7,16,17]. Aneuploidy resulting from lagging chromosomes[13], or from a polyploid intermediate state[18,19], has been associated with senescence and premature aging in mice, reinforcing the potential role of W-CIN in age-related tissue degeneration. W-CIN induced the secretion of a growth factor, C-type lectin domain family 11 member A (CLEC11A/SCGF-b), which has not been previously associated with SASP and its secretion level is correlated with the frequency of not 2n cells. The present study proposes a model in which W-CIN triggers senescence arrest by multiple non-exclusive pathways, and suggests, for the first time, that cells deviating from diploidy can affect their microenvironment via secretion of SASP

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