Biology subjects

Papadakis, A.

Publications and source records attributed to Papadakis, A..

4 recordsLinked to original sources

bioRxiv2026

Rare genetic variants in the IIS/mTOR signalling pathway identified in exceptionally long-lived individuals show shared in vitro effects associated with lifespan across species

BackgroundThe increase in human lifespan without a proportional increase in healthspan imposes a substantial burden on individuals and society. Exceptionally long-lived individuals and members of long-lived families exhibit compression of multi-morbidity. Genetics, and in particular rare protein-altering variants, appear to play an important role in their longevity. MethodsIn this study, we employed a targeted pathway approach to provide functional evidence of the significance of rare variants in the insulin/insulin-like growth factor 1 signalling - mechanistic target of rapamycin (IIS/mTOR) signalling pathway identified in long-lived individuals. To this end, we used CRISPR/Cas9 to introduce these rare genetic variants into mouse embryonic stem cells (mESCs). We subsequently assessed several functional readouts that have previously been associated with lifespan regulation in model organisms and/or IIS/mTOR and mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) signalling pathway activity. ResultsFunctional characterisation revealed that the variants exhibit both shared and distinct effects on the signalling pathways. Principal component analysis of omics-based datasets showed that the variants clustered into two groups, a distribution that corresponds with the grouping observed for a subset of functional readouts. All variant mESC lines exhibited a downregulation in IIS/mTOR and MAPK/ERK signalling pathway activity as well as an increase in Foxo3 expression and FOXO3 binding activity. We identified alterations in lipid and mitochondrial metabolism, including a reduction in mitochondrial DNA levels, which were mostly shared among all variants. All variant mESC lines exhibited a signature implying increased pluripotency. The effects on stress resistance and growth rate diverged between the two variant groups, with partially opposing effects. Group 1 demonstrated a reduced growth rate and increased resistance to a subset of stressors, while Group 2 demonstrated an increased growth rate and reduced resistance to a subset of stressors. ConclusionsHere, we provide evidence that rare genetic variants in the IIS/mTOR and MAPK/ERK signalling pathways identified in long-lived human individuals result in shared functional effects associated with longevity in model organisms. These insights can serve as a foundation to better understand the role of rare variants in the insulin signalling network in the regulation of human longevity. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=68 SRC="FIGDIR/small/728260v1_ufig1.gif" ALT="Figure 1"> View larger version (18K): org.highwire.dtl.DTLVardef@1ef36c3org.highwire.dtl.DTLVardef@1f44c96org.highwire.dtl.DTLVardef@1d0150forg.highwire.dtl.DTLVardef@16ab7d_HPS_FORMAT_FIGEXP M_FIG C_FIG

genetics↗

bioRxiv2023

Rapid and synchronous chemical induction of replicative-like senescence via a small molecule inhibitor

Cellular senescence is now acknowledged as a key contributor to organismal ageing and late-life disease. Although popular, the study of senescence in vitro can be complicated by the prolonged and asynchronous timing of cells committing to it and its paracrine effects. To address these issues, we repurposed the small molecule inhibitor inflachromene (ICM) to induce senescence to human primary cells. Within six days of treatment with ICM, senescence hallmarks, including the nuclear eviction of HMGB1 and -B2, are uniformly induced across IMR90 cell populations. By generating and comparing various high throughput datasets from ICM-induced and replicative senescence, we uncovered significant similarity of the two states. Notably though, ICM suppresses the proinflammatory secretome associated with senescence, thus alleviating most paracrine effects. In summary, ICM induces a senescence-like phenotype rapidly and synchronously thereby allowing the study of its core regulatory program without any confounding heterogeneity.

genomics↗

bioRxiv2022

ATAC-Seq and RNA-Seq combined analysis elucidates the impact of BORIS/CTCFL on melanoma progression, mediated by chromatin accessibility and gene expression alterations

Melanoma is the deadliest form of skin cancer, due to its tendency to metastasize early. Brother of Regulator of Imprinted Sites (BORIS), also known as CCCTC binding factor-Like (CTCFL), is a transcription regulator that becomes ectopically expressed in melanoma. We recently showed that BORIS contributes to melanoma phenotype switching by altering the gene expression program of proliferative melanoma cells in favor of a more invasive phenotype. However, how BORIS alters the transcriptome remains unclear. Here, ATAC-seq was used to study BORIS-mediated chromatin accessibility alterations in proliferative melanoma cells. Genes that gained promoter accessibility following ectopic BORIS expression, were enriched for melanoma-specific invasive genes as well as invasion-associated biological processes, while promoters of genes associated with proliferation show reduce accessibility. Integration of ATAC-Seq and RNA-Seq data demonstrates that increased chromatin accessibility is associated with transcriptional upregulation of genes involved in tumor progression processes, and the aberrant activation of oncogenic transcription factors, while reduced chromatin accessibility and downregulated genes, were associated with repressed activity of tumor suppressors. Together, these findings indicate that BORIS mediates transcriptional reprogramming in melanoma cells by altering chromatin accessibility and gene expression, shifting the cellular transcription landscape of proliferative melanoma cells towards a pro-invasive genetic signature. SignificanceWe recently reported that BORIS contributes to melanoma phenotype switching by altering the transcriptional landscape of melanoma cells from a proliferative to an invasive state. In this study, using ATAC-Seq, we demonstrate that ectopic BORIS expression in proliferative melanoma cells leads to increased chromatin accessibility at promoters of upregulated invasion-associated genes. Importantly, by integrating the ATAC-Seq data with RNA-Seq data, we were able to identify key cancer-associated transcription factors that become aberrantly activated or repressed following ectopic BORIS expression. Taken together, this study sheds light on the mechanisms by which BORIS mediates phenotype switching in melanoma cells.

cancer biology↗

bioRxiv2019

HMGB1 as a rheostat of chromatin topology and RNA homeostasis on the path to senescence

Spatial organization and gene expression of mammalian chromosomes are maintained and regulated in conjunction with cell cycle progression. This is however disturbed once cells enter senescence and the highly abundant HMGB1 protein is depleted from senescent cell nuclei to act as an extracellular proinflammatory stimulus. Despite its physiological importance, we know little about the positioning of HMGB1 on chromatin or about its roles in the nucleus. To address this, we mapped HMGB1 binding genome-wide in different primary cells using a tailored protocol. We integrated ChIP-seq and Hi-C data with a graph theory approach to uncover HMGB1 demarcation of a subset of topologically-associating domains (TADs) that harbor genes required for paracrine senescence. Moreover, using sCLIP, knock-down and overexpression experiments, we now show that HMGB1 is a bona fide RNA-binding protein (RBP) bound to senescence-relevant mRNAs and affecting splicing. HMGB1 also has an interactome rich in RBPs, many of which are implicated in senescence regulation. The mRNAs of many of these RBPs are directly bound by HMGB1 and concertedly regulate the availability of SASP-relevant transcripts. Our findings highlight a broader than hitherto assumed role for HMGB1. It coordinates chromatin folding and RNA homeostasis as part of a feedforward loop controlling both cell-autonomous and paracrine senescence inside and outside of cells.

genomics↗