Detection of senescence markers during mammalian embryonic development

Senescence-associated β-galactosidase (SAβ-gal) is a convenient histological technique used to identify senescent cells. Its ease of use is helpful to initially screen and detect senescent cells in heterogeneous cell populations both in vitro and in vivo. However, SAβ-gal staining is not an unequivocal marker of the senescent state, and diagnosis of such usually requires additional markers demonstrating an absence of proliferation and expression of cell-cycle inhibitors. Nonetheless, SAβ-gal remains one of the most widely used biomarkers of senescent cells. Recently, by measuring SAβ-gal activity, the expression of the cyclin-dependent kinase inhibitor p21 (waf1/cip1) and demonstrating a lack of proliferation, we identified senescent cells in the developing embryo. This chapter describes the methods for identifying cellular senescence in the embryo, detailing protocols for the detection of SAβ-gal activity in both sections and at the whole mount level, and immunohistochemistry protocols for the detection of additional biomarkers of senescence.This work was funded by Grants SAF2010-18829 and SAF2013-49082-P to W.M.K. from the Spanish Ministry for Economy and Competitiveness, the Agència de Gestió d’Ajuts Universitaris i de Recerca (AGAUR) from the Generalitat de Catalunya, and CRG core fundin

Age-associated inflammation inhibits epidermal stem cell function

Altered stem cell homeostasis is linked to organismal aging. However, the mechanisms involved remain poorly understood. Here we report novel alterations in hair follicle stem cells during skin aging, including increased numbers, decreased function, and an inability to tolerate stress. Performing high-throughput RNA sequencing on aging stem cells, cytokine arrays, and functional assays, we identify an age-associated imbalance in epidermal Jak-Stat signaling that inhibits stem cell function. Collectively, this study reveals a role for the aging epidermis in the disruption of cytokine and stem cell homeostasis, suggesting that stem cell decline during aging may be part of broader tumor-suppressive mechanisms.J.D. is supported by an EMBO long-term fellowship, and M.A.S. is funded by a La Caixa bank studentship. This work was funded in part by a Plan Nacional grant to W.M.K. from the Spanish/nMinistry for Science and Innovation (SAF2010-18829

Age-associated inflammation inhibits epidermal stem cell function

Altered stem cell homeostasis is linked to organismal aging. However, the mechanisms involved remain poorly understood. Here we report novel alterations in hair follicle stem cells during skin aging, including increased numbers, decreased function, and an inability to tolerate stress. Performing high-throughput RNA sequencing on aging stem cells, cytokine arrays, and functional assays, we identify an age-associated imbalance in epidermal Jak-Stat signaling that inhibits stem cell function. Collectively, this study reveals a role for the aging epidermis in the disruption of cytokine and stem cell homeostasis, suggesting that stem cell decline during aging may be part of broader tumor-suppressive mechanisms.J.D. is supported by an EMBO long-term fellowship, and M.A.S. is funded by a La Caixa bank studentship. This work was funded in part by a Plan Nacional grant to W.M.K. from the Spanish/nMinistry for Science and Innovation (SAF2010-18829

ΔNp63α promotes adhesion of metastatic prostate cancer cells to the bone through regulation of CD82

ΔNp63α is a critical mediator of epithelial development and stem cell function in a variety of tissues including the skin and breast, while overexpression of ΔNp63α acts as an oncogene to drive tumor formation and cancer stem cell properties in squamous cell carcinoma. However, with regards to the prostate, while ΔNp63α is expressed in the basal stem cells of the mature gland, during adenocarcinoma development, its expression is lost and its absence is used to clinically diagnose the malignant state. Surprisingly, here we identify a sub-population of bone metastatic prostate cancer cells in the PC3 cell line that express ΔNp63α. Interestingly, we discovered that ΔNp63α favors adhesion and stem-like growth of these cells in the bone microenvironment. In addition, we show that these properties require expression of the target gene CD82. Together, this work uncovers a population of bone metastatic prostate cancer cells that express ΔNp63α, and provides important information about the mechanisms of bone metastatic colonization. Finally, we identify metastasis-promoting properties for the tetraspanin family member CD82.We thank Roger Gomis and Marc Guiu for help with tumor imaging analysis, Jason Doles for help in the short hairpin design and the CRG Bioinformatics facility for assistance with microarray and sequencing data analysis. VDG was supported by a fellowship from ‘La Caixa’, and MP with an F.P.I. fellowship from the Spanish Ministry. This work was funded by Grants SAF2010-18829 (WMK) and SAF2013-49082-P (WMK) from the Ministerio de Economía y Competitividad and a Marie Curie International Reintegration Grant PIRG5-GA-2009-248262 (WMK)

The senotherapeutic drug ABT-737 disrupts aberrant p21 expression to restore liver regeneration in adult mice

Young mammals possess a limited regenerative capacity in some tissues, which is lost upon maturation. We investigated whether cellular senescence might play a role in such loss during liver regeneration. We found that following partial hepatectomy, the senescence-associated genes p21, p16Ink4a, and p19Arf become dynamically expressed in different cell types when regenerative capacity decreases, but without a full senescent response. However, we show that treatment with a senescence-inhibiting drug improves regeneration, by disrupting aberrantly prolonged p21 expression. This work suggests that senescence may initially develop from heterogeneous cellular responses, and that senotherapeutic drugs might be useful in promoting organ regeneration.Work in the Keyes lab was funded in part by grants from the Spanish Ministry for Economy and Competitiveness (SAF2013-49082-P), La Fondation Recherche Medicale (FRM) (AJE20160635985), Fondation ARC (PJA20181208104), IDEX Attractivité-University of Strasbourg (IDEX2017), and La Fondation Schlumberger pour l'Education et la Recherche (FSER) (FSER 19-Year 2018), and ANR (ANR-19-CE13-0023-03). Work was also supported by grant ANR-10-LABX-0030-INRT, a French State fund managed by the Agence Nationale de la Recherche under the frame program Investissements d'Avenir (ANR-10-IDEX-0002-02

Senescence is a developmental mechanism that contributes to embryonic growth and patterning

Senescence is a form of cell-cycle arrest linked to tumor suppression and aging. However, it remains controversial and has not been documented in nonpathologic states. Here we describe senescence as a normal developmental mechanism found throughout the embryo, including the apical ectodermal ridge (AER) and the neural roof plate, two signaling centers in embryonic patterning. Embryonic senescent cells are nonproliferative and share features with oncogene-induced senescence (OIS), including expression of p21, p15, and mediators of the senescence-associated secretory phenotype (SASP). Interestingly, mice deficient in p21 have defects in embryonic senescence, AER maintenance, and patterning. Surprisingly, the underlying mesenchyme was identified as a source for senescence instruction in the AER, whereas the ultimate fate of these senescent cells is apoptosis and macrophage-mediated clearance. We propose that senescence is a normal programmed mechanism that plays instructive roles in development, and that OIS is an evolutionarily adapted reactivation of a developmental process.M.S. and V.D.G. are funded by ‘‘La Caixa’’ fellowships, and M.P. by an FPI fellowship from the Spanish Ministry. This work was funded in part by a Plan Nacional grant to W.M.K. from the Spanish Ministry for Science and Innovation (SAF2010-18829) and CRG core fundin

Chromatin-bound IκB-alpha regulates a subset of polycomb target genes in differentiation and cancer

IκB proteins are the primary inhibitors of NF-κB. Here, we demonstrate that sumoylated and phosphorylated IκBα accumulates in the nucleus of keratinocytes and interacts with histones H2A and H4 at the regulatory region of HOX and IRX genes. Chromatin-bound IκBα modulates Polycomb recruitment and imparts their competence to be activated by TNF-alpha. Mutations in the Drosophila IκBα gene cactus enhance the homeotic phenotype of Polycomb mutants, which is not counteracted by mutations in dorsal/NF-κB. Oncogenic transformation of keratinocytes results in cytoplasmic IκBα translocation associated with a massive activation of Hox. Accumulation of cytoplasmic IκBα was found in squamous cell carcinoma (SCC) associated with IKK activation and HOX upregulation