Dynamic regulation of chromatin accessibility and transcription factors underlies distinct organ identity and function
Ontology highlight
ABSTRACT: After gut tube closure, different regional domains develop into uniquely functional organs. Our single cell analysis demonstrates that chromatin accessibility predicts lineage fate decisions, reflecting the transcriptional profiles of individual cells. Combining with bulk analyses, we have generated a comprehensive map of epigenetic changes over developmental time, revealing how chromatin accessibility and transcription factor (TF) binding cooperate to control organ identity and differentiation. Loss of the foregut and hindgut lineage-specific TFs, Sox2 and Cdx2, leads to the acquisition of accessibility profiles similar to neighbouring organs, while Sox2 overexpression in early development induces a loss of intestinal identity and pancreatic transformation into foregut fate precursors. Moreover, ectopic expression of Sox2 in normal adult and cancer intestinal and pancreatic tissues leads to lineage alterations, demonstrating its critical role in homeostasis and cancer. Together, these studies define the chromatin and transcriptional mechanisms of organ identity and lineage plasticity in development and disease.
Project description:USP7, a ubiquitin-specific peptidase (USP), plays an important role in many cellular processes through its catalytic deubiquitination of various substrates. However, its nuclear function to shape the transcriptional network in mouse embryonic stem cells (mESCs) remains poorly understood. Here, we report that USP7 maintains mESCs identity through both catalytic activity-dependent and -independent repression of lineage differentiation genes. Usp7 depletion attenuates SOX2 level and derepresses lineage differentiation genes thereby compromising mESCs pluripotency. Mechanistically, USP7 deubiquitinates and stabilizes SOX2 to repress mesoendodermal (ME) lineage genes. Moreover, USP7 assembles into RYBP-variant Polycomb repressive complex 1 and contributes to Polycomb chromatin-mediated repression of ME lineage genes in a catalytic activity-dependent manner. Importantly, USP7 deficient in its deubiquitination function is able to maintain RYBP binding to chromatin for repressing primitive endoderm-associated genes. Overall, our study demonstrates that USP7 harbors both catalytic and non-catalytic activity to repress different lineage differentiation genes thereby revealing a previously unrecognized role in controlling gene expression for maintaining mESCs identity.
Project description:MicroRNAs (miRNAs) are important post-transcriptional gene regulators in organ development. To explore candidate roles for miRNAs in prenatal SI lineage specification in humans, we used a multi-omic analysis strategy in a directed differentiation model that programs human pluripotent stem cells toward the SI lineage. We leveraged small RNA-seq to define the changing miRNA landscape, and integrated chromatin run-on sequencing (ChRO-seq) and RNA-seq to define genes subject to significant post-transcriptional regulation across the different stages of differentiation. Our analyses showed that the elevation of miR-182 and reduction of miR-375 are key events during SI lineage specification. We demonstrated that loss of miR-182 leads to an increase in the foregut marker SOX2. We also used single-cell analyses in murine adult intestinal crypts to support a life-long role for miR-375 in the regulation of Zfp36l2. We also uncovered opposing roles of SMAD4 and WNT signaling in regulating miR-375 expression during SI lineage specification. Beyond the mechanisms highlighted in this study, we also present a web-based application for exploration of post-transcriptional regulation and miRNA-mediated control in the context of early human SI development.
Project description:Formation of the hepato-pancreato-biliary organ system in mammals is a paradigm for organogenesis, whereby a small progenitor population of the ventral foregut gives rise to a multitude of different adult tissues, including liver, pancreas, gallbladder, and extra-hepatic bile ducts. The multipotent ventral foregut cell population undergoes an initial fate segregation into hepatic and pancreato-biliary progenitors in response to signaling cues from surrounding mesodermal tissues. Subsequently, pancreato-biliary progenitors give rise to ventral pancreatic and gallbladder progenitors. In this study, we used single-cell RNA sequencing to molecularly characterize progenitor populations in the ventral foregut that contribute to the formation of hepatic, pancreatic, and biliary organ rudiments throughout organogenesis.
Project description:The definitive endoderm germ layer is the provenance of multiple internal organs, including the lungs, liver, pancreas and intestines. Molecular events driving initial endoderm germ layer specification and subsequent anterior-posterior patterning of endoderm into distinct organ primordia remain largely cryptic. Through microarray analyses, we captured genome-wide transcriptional dynamics driving successive stages of endoderm development with the intent of identifying novel regulatory genes or diagnostic markers that respectively drive or mark endoderm committment. HES3 human embryonic stem cells (hESCs) were differentiated into highly homogeneous endodermal progenitor populations, and microarray analyses were conducted of six different populations at different tiers of the endodermal lineage hierarchy: undifferentiated hESCs, anterior primitive streak (day 1 of in vitro differentiation), definitive endoderm (day 3) and anterior foregut, posterior foregut or midgut/hindgut patterned endoderm populations (day 7). Additionally, we compared hESCs differentiated using two alternative endoderm induction protocols, serum-based or AFBLy-based differentiation (both day 3 of differentiation).
Project description:The pancreas and liver arise from a common pool of progenitors in the foregut endoderm; however, the underlying molecular mechanisms driving this lineage diversification are not fully understood. We combined human pluripotent stem cell guided differentiation and sequential CRISPR-Cas9 loss-of-function screening to uncover regulators of pancreatic specification. Here we report the discovery of a cell-intrinsic requirement for HHEX, a transcription factor (TF) associated with diabetes susceptibility. HHEX promotes pancreatic differentiation through cooperation with pancreatic TFs as well as common TFs like FOXA2 that are shared by both pancreas and liver differentiation programs. Furthermore, HHEX restricts differentiation plasticity, and deletion of HHEX shifts FOXA2 interaction towards cooperation with HNF4A, driving liver differentiation. Therefore, HHEX safeguards pancreatic differentiation by promoting lineage specification while simultaneously restricting cell fate plasticity, demonstrating how organ domain demarcation requires fine tuning of TF cooperation.
Project description:The pancreas and liver arise from a common pool of progenitors in the foregut endoderm; however, the underlying molecular mechanisms driving this lineage diversification are not fully understood. We combined human pluripotent stem cell guided differentiation and sequential CRISPR-Cas9 loss-of-function screening to uncover regulators of pancreatic specification. Here we report the discovery of a cell-intrinsic requirement for HHEX, a transcription factor (TF) associated with diabetes susceptibility. HHEX promotes pancreatic differentiation through cooperation with pancreatic TFs as well as common TFs like FOXA2 that are shared by both pancreas and liver differentiation programs. Furthermore, HHEX restricts differentiation plasticity, and deletion of HHEX shifts FOXA2 interaction towards cooperation with HNF4A, driving liver differentiation. Therefore, HHEX safeguards pancreatic differentiation by promoting lineage specification while simultaneously restricting cell fate plasticity, demonstrating how organ domain demarcation requires fine tuning of TF cooperation.
Project description:Genome-wide transcriptional activity involves the binding of many transcription factors to thousands of sites in the genome. Determining which sites are directly driving transcription remains a challenge. Here we use acute protein depletion of the pioneer transcription factor SOX2 to establish its functionality in maintaining chromatin accessibility. We show that thousands of accessible sites are lost within an hour of protein depletion, indicating rapid turnover of these sites in the absence of pioneer factors. To understand the relationship with transcription we performed nascent transcription analysis and found that open chromatin sites that are maintained by SOX2 are highly predictive of gene expression, in contrast to all other SOX2 binding sites. We use CRISPR-Cas9 genome editing in the Klf2 locus to functionally validate a predicted regulatory element. We conclude that the regulatory activity of SOX2 is exerted largely at sites where it maintains accessibility and that other binding sites are largely dispensable for gene regulation.
Project description:We devised an improved assay for single cell profiling of chromatin accessibility with three-level combinatorial indexing (sci-ATAC-seq3). We applied this method to 53 fetal tissue samples representing 15 organs, altogether profiling approximately one million single cells. We leveraged cell types defined by gene expression in the same organs to annotate these data, and built a catalog of hundreds-of-thousands of candidate gene regulatory elements exhibiting cell type-specific accessibility. Our analyses focus on the properties of lineage-specific transcription factors, organ-specific specializations of broadly distributed cell types, and cell type-specific enrichments of complex trait heritability. Additional data formats are available at atlas.brotmanbaty.org.
Project description:Chromatin accessibility plays an essential role in controlling cellular identity and the therapeutic response of human cancers. However, the chromatin accessibility landscape and gene regulatory network of pancreatic cancer are largely uncharacterized. Here, we integrate the chromatin accessibility profiles of 84 pancreatic cancer organoid lines with whole-genome sequencing data, transcriptomic sequencing data and the results of drug sensitivity analysis of 283 epigenetic-related chemicals and 5 chemotherapeutic drugs. We identify distinct transcription factors that distinguish molecular subtypes of pancreatic cancer, predict numerous chromatin accessibility peaks associated with gene regulatory networks, discover novel regulatory noncoding mutations with potential as cancer drivers, and reveal the chromatin accessibility signatures associated with drug sensitivity. These results not only provide the chromatin accessibility atlas of pancreatic cancer but also suggest a systematic approach to comprehensively understand the gene regulatory network of pancreatic cancer in order to advance diagnosis and potential personalized medicine applications.
Project description:Chromatin accessibility plays an essential role in controlling cellular identity and the therapeutic response of human cancers. However, the chromatin accessibility landscape and gene regulatory network of pancreatic cancer are largely uncharacterized. Here, we integrate the chromatin accessibility profiles of 84 pancreatic cancer organoid lines with whole-genome sequencing data, transcriptomic sequencing data and the results of drug sensitivity analysis of 283 epigenetic-related chemicals and 5 chemotherapeutic drugs. We identify distinct transcription factors that distinguish molecular subtypes of pancreatic cancer, predict numerous chromatin accessibility peaks associated with gene regulatory networks, discover novel regulatory noncoding mutations with potential as cancer drivers, and reveal the chromatin accessibility signatures associated with drug sensitivity. These results not only provide the chromatin accessibility atlas of pancreatic cancer but also suggest a systematic approach to comprehensively understand the gene regulatory network of pancreatic cancer in order to advance diagnosis and potential personalized medicine applications.