Biology subjects

Janiszewski, A.

Publications and source records attributed to Janiszewski, A..

8 recordsLinked to original sources

bioRxiv2022

A deep learning approach for improved detection of homologous recombination deficiency from shallow genomic profiles

Homologous Recombination Deficiency (HRD) is a predictive biomarker of poly-ADP ribose polymerase 1 inhibitors (PARPi) response. Most HRD detection methods are based on genome wide enumeration of scarring events and require deep genome sequence profiles (> 30x). The cost and workflow-specific biases introduced by these genome profiling methods currently limits clinical adoption of HRD testing. We introduce the Genomic Integrity Index (GII), a Convolutional Neuronal Network, that leverages features from low pass (1x) Whole Genome Sequencing data to distinguish HRD positive and negative samples. In a cohort of 230 ovarian and breast cancer, we found GII supports accurate stratification of samples yielding results that are highly concordant with state-of-the-art HRD detection methods (0.865<AUC<0.996) which require 50x deeper coverage. We conclude that the deep learning framework supporting GII allows accurate detection of HRD from shallow genome profiles, reducing biases and data generation costs making it uniquely suited for clinical applications.

cancer biology↗

bioRxiv2022

The Wnt/TCF7L1 transcriptional repressor axis drives primitive endoderm formation by antagonizing naive and formative pluripotency

Early during preimplantation development and in heterogeneous mouse embryonic stem cells (mESC) culture, pluripotent cells are specified towards either the primed epiblast or the primitive endoderm (PE) lineage. Canonical Wnt signaling is crucial for safeguarding naive pluripotency and embryo implantation, yet the role and relevance of canonical Wnt inhibition during early mammalian development remains unknown. Here, we demonstrate that transcriptional repression exerted by Wnt/TCF7L1 promotes PE differentiation of mESCs and in preimplantation inner cell mass. Time-series RNA sequencing and promoter occupancy data reveal that TCF7L1 binds and represses genes encoding essential naive pluripotency factors and indispensable regulators of the formative pluripotency program, including Otx2 and Lef1. Consequently, TCF7L1 promotes pluripotency exit and suppresses epiblast lineage formation, thereby driving cells into PE specification. Conversely, deletion of Tcf7l1 abrogates PE differentiation without restraining epiblast priming. Taken together, our study underscores the importance of transcriptional Wnt inhibition in regulating lineage segregation in ESCs and preimplantation embryo development as well as identifies TCF7L1 as key regulator of this process.

developmental biology↗

bioRxiv2020

Revealing the Key Regulators of Cell Identity in the Human Adult Pancreas

Cellular identity during development is under the control of transcription factors that form gene regulatory networks. However, the transcription factors and gene regulatory networks underlying cellular identity in the human adult pancreas remain largely unexplored. Here, we integrate multiple single-cell RNA-sequencing datasets of the human adult pancreas, totaling 7393 cells, and comprehensively reconstruct gene regulatory networks. We show that a network of 142 transcription factors forms distinct regulatory modules that characterize pancreatic cell types. We present evidence that our approach identifies regulators of cell identity in the human adult pancreas. We predict that HEYL, BHLHE41 and JUND are active in acinar, beta and alpha cells, respectively, and show that these proteins are present in the human adult pancreas as well as in human induced pluripotent stem cell (hiPSC)-derived islet cells. Using single-cell transcriptomics, we found that JUND represses beta cell genes in hiPSC-alpha cells. Both BHLHE41 and JUND depletion seemed to increase the number of sc-enterochromaffin cells in hiPSC-derived islets. The comprehensive gene regulatory network atlas can be explored interactively online. We anticipate our analysis to be the starting point for a more sophisticated dissection of how transcription factors regulate cell identity in the human adult pancreas. Furthermore, given that transcription factors are major regulators of embryo development and are often perturbed in diseases, a comprehensive understanding of how transcription factors work will be relevant in development and disease. HIGHLIGHTSO_LIReconstruction of gene regulatory networks for human adult pancreatic cell types C_LIO_LIAn interactive resource to explore and visualize gene expression and regulatory states C_LIO_LIPrediction of putative transcription factors that drive pancreatic cell identity C_LIO_LIBHLHE41 depletion in primary islets induces apoptosis C_LI

bioinformatics↗

bioRxiv2020

Defining totipotency using criteria of increasing stringency

Totipotency is the ability of a single cell to give rise to all the differentiated cells that build the conceptus, yet how to capture this property in vitro remains incompletely understood. Defining totipotency relies upon a variety of assays of variable stringency. Here we describe criteria to define totipotency. We illustrate how distinct criteria of increasing stringency can be used to judge totipotency by evaluating candidate totipotent cell types in the mouse, including early blastomeres and expanded or extended pluripotent stem cells. Our data challenge the notion that expanded or extended pluripotent states harbor increased totipotent potential relative to conventional embryonic stem cells under in vivo conditions.

cell biology↗

bioRxiv2019

Temporal resolution of global gene expression and DNA methylation changes in the final phases of reprogramming towards induced pluripotency.

The generation of induced pluripotent stem cells (iPSCs) involves activation of the endogenous pluripotency circuitry and global DNA demethylation late in reprogramming, but temporal resolution of these events using existing markers is insufficient. Here, we generated murine transgenic lines harboring dual fluorescent reporters reflecting cell-state specific expression of the master pluripotency factor Oct4 and the 5-methylcytosine dioxygenase Tet1. By assessing reprogramming intermediates based on dual reporter patterns, we identified a sequential order of Tet1 and Oct4 gene activation at proximal and distal regulatory elements following pluripotency entry. Full induction of Tet1 marks a pivotal late intermediate stage occurring after a phase of global gene repression, and preceding full activation of Oct4 along with late naive pluripotency and germline-specific genes. Sequential activation of Tet1 further distinguishes two waves of global DNA demethylation, targeting distinct genomic features and largely uncoupled from transcriptional changes, with dynamics unique to iPSC reprogramming. Moreover, we demonstrate that loss of Tet1 is compatible with reprogramming towards full Oct4 gene activation, but generates iPSCs with aberrant DNA methylation, chromosomal instability during lineage priming and defective differentiation potential. Therefore, the transcriptional logic of Tet1 expression signals a deterministic epigenetic roadmap towards generation of high quality iPSCs.

cell biology↗

bioRxiv2019

Dynamic Erasure of Random X-Chromosome Inactivation during iPSC Reprogramming

BackgroundInduction and reversal of chromatin silencing is critical for successful development, tissue homeostasis and the derivation of induced pluripotent stem cells (iPSCs). X-chromosome inactivation (XCI) and reactivation (XCR) in female cells represent chromosome-wide transitions between active and inactive chromatin states. While XCI has long been studied and provided important insights into gene regulation, the dynamics and mechanisms underlying the reversal of stable chromatin silencing of X-linked genes are much less understood. Here, we use allele-specific transcriptomic approaches to study XCR during mouse iPSC reprogramming in order to elucidate the timing and mechanisms of chromosome-wide reversal of gene silencing. ResultsWe show that XCR is hierarchical, with subsets of genes reactivating early, late and very late. Early genes are activated before the onset of late pluripotency genes activation and the complete silencing of the long non-coding RNA (lncRNA) Xist. These genes are located genomically closer to genes that escape XCI, unlike those reactivating late. Interestingly, early genes also show increased pluripotency transcription factor (TF) binding. We also reveal that histone deacetylases (HDACs) restrict XCR in reprogramming intermediates and that the severe hypoacetylation state of the Xi persists until late reprogramming stages. ConclusionsAltogether, these results reveal the timing of transcriptional activation of mono-allelically repressed genes during iPSC reprogramming, and suggest that allelic activation involves the combined action of chromatin topology, pluripotency transcription factors and chromatin regulators. These findings are important for our understanding of gene silencing, maintenance of cell identity, reprogramming and disease.

developmental biology↗

bioRxiv2019

Autologous micrograft accelerates endogenous wound healing response via ERK-induced cell migration

Defective fibroblast migration causes delayed wound healing (WH) and chronic skin lesions. Autologous micrograft (AMG) therapies have recently emerged as a new effective treatment able to improve wound healing capacity. However, the molecular mechanisms connecting their beneficial outcomes with the wound healing process are still unrevealed. Here, we show that AMG modulates primary fibroblast migration and accelerates skin re-epithelialization without affecting cell proliferation. We demonstrate that AMG is enriched in a pool of WH-associated growth factors that may provide the initiation signal for a faster endogenous wound healing response. This, in turn leads to increased cell migration rate by elevating activity of extracellular signal-regulated kinase (ERK) pathway and subsequent activation of matrix metalloproteinase expression and their extracellular enzymatic activity. Moreover, AMG-treated wounds showed increased granulation tissue formation and organized collagen content. Overall, we shed light on AMG molecular mechanism supporting its potential to trigger a highly improved wound healing process.

molecular biology↗

bioRxiv2018

Two Active X-chromosomes Modulate the Growth, Pluripotency Exit and DNA Methylation Landscape of Mouse Naive Pluripotent Stem Cells through Different Pathways

During early mammalian development, the two X-chromosomes in female cells are active. Dosage compensation between XX female and XY male cells is then achieved by X-chromosome inactivation in female cells. Reprogramming female mouse somatic cells into induced pluripotent stem cells (iPSCs) leads to X-chromosome reactivation. The extent to which increased X-chromosome dosage (X-dosage) in female iPSCs leads to differences in the molecular and cellular properties of XX and XY iPSCs is still unclear. We show that chromatin accessibility in mouse iPSCs is modulated by X-dosage. Specific sets of transcriptional regulator motifs are enriched in chromatin with increased accessibility in XX or XY iPSCs. We show that the transcriptome, growth and pluripotency exit are also modulated by X-dosage in iPSCs. To understand the mechanisms by which increased X-dosage modulates the molecular and cellular properties of mouse pluripotent stem cells, we used heterozygous deletions of the X-linked gene Dusp9 in XX embryonic stem cells. We show that X-dosage regulates the transcriptome, open chromatin landscape, growth and pluripotency exit largely independently of global DNA methylation. Our results uncover new insights into X-dosage in pluripotent stem cells, providing principles of how gene dosage modulates the epigenetic and genetic mechanisms regulating cell identity.

developmental biology↗