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Establishing a Murine Superficial Bladder Cancer Model <em>via</em> an Intravesical Cell Administration Technique

This study presents an innovative method for establishing an orthotopic murine bladder tumor model with high efficiency and precise tumor localization. ...

Tianjin Institute of Urology

Genome-wide mapping of transcription factor (TF) binding sites is essential to identify a TF's direct target genes in kidney development and diseases. However, due to the cellular complexity of the kidney and limited numbers of a given cell type, it has been challenging to determine the binding sites of a TF . cAMP response element-binding protein (CREB) is phosphorylated and hyperactive in autosomal dominant polycystic kidney disease (ADPKD). We focus on CREB as an example to profile genomic loci bound by a TF and to identify its target genes using low numbers of specific kidney cells.

Integrative Cistromic and Transcriptomic Analyses Identify CREB Target Genes in Cystic Renal Epithelial Cells.

An impaired blood-retinal barrier (BRB) leads to diabetic macular edema (DME), which is a major complication of Diabetic retinopathy (DR). Mediators such as inflammation cause BRB breakdown. However, the explicit mechanism of its disruption is largely unknown. In this study, we identified tumor necrosis factor ligand-related molecule 1A (TL1A) as a crucial factor which protect retinal endothelial cells integrity in DR. By providing both human and mouse data, we show that TL1A is significantly decreased in the retinas of DME patients and diabetic rodents. We further demonstrate that the loss of TL1A accelerated diabetes-induced retinal barrier breakdown. TL1A supplementation protects the diabetic retina against BRB breakdown. Mechanistically, TL1A stabilize intracellular junctions and protect vascular integrity by blocking SHP1-Src-regulated VE-cadherin phosphorylation. Collectively, our findings reveal that loss of TL1A in the retina leads to increased vascular permeability in DR, and that TL1A treatment is of potential therapeutic interest for the treatment of DME.

Tumor necrosis factor ligand-related molecule 1A maintains blood-retinal barrier via modulating SHP-1-Src-VE-cadherin signaling in diabetic retinopathy.

Formation of biomolecular condensates by phase separation has recently emerged as a new principle for regulating gene expression in response to extracellular signaling. However, the molecular mechanisms underlying the coupling of signal transduction and gene activation through condensate formation, and how dysregulation of these mechanisms contributes to disease progression, remain elusive. Here, the authors report that CREB-regulated transcription coactivator 2 (CRTC2) translocates to the nucleus and forms phase-separated condensates upon activation of cAMP signaling. They show that intranuclear CRTC2 interacts with positive transcription elongation factor b (P-TEFb) and activates P-TEFb by disrupting the inhibitory 7SK snRNP complex. Aberrantly elevated cAMP signaling plays central roles in the development of autosomal dominant polycystic kidney disease (ADPKD). They find that CRTC2 localizes to the nucleus and forms condensates in cystic epithelial cells of both mouse and human ADPKD kidneys. Genetic depletion of CRTC2 suppresses cyst growth in an orthologous ADPKD mouse model. Using integrative transcriptomic and cistromic analyses, they identify CRTC2-regulated cystogenesis-associated genes, whose activation depends on CRTC2 condensate-facilitated P-TEFb recruitment and the release of paused RNA polymerase II. Together, their findings elucidate a mechanism by which CRTC2 nuclear condensation conveys cAMP signaling to transcription elongation activation and thereby promotes cystogenesis in ADPKD.

cAMP-Induced Nuclear Condensation of CRTC2 Promotes Transcription Elongation and Cystogenesis in Autosomal Dominant Polycystic Kidney Disease.

Renal tubular epithelial cells (TECs) can initiate an adaptive response to completely recover from mild acute kidney injury (AKI), whereas severe injury often leads to persistence of maladaptive repair and progression to kidney fibrosis. Through profiling of active DNA regulatory elements by ATAC-seq, we reveal widespread, dynamic changes in the chromatin accessibility of TECs after ischemia-reperfusion injury. We show that injury-specific domains of regulatory chromatin become accessible prior to gene activation, creating poised chromatin states to activate the consequent gene expression program and injury response. We further identify RXRα as a key transcription factor in promoting adaptive repair. Activation of RXRα by bexarotene, an FDA-approved RXRα agonist, restores the chromatin state and gene expression program to protect TECs against severe kidney injury. Together, our findings elucidate a chromatin-mediated mechanism underlying differential responses of TECs to varying injuries and identify RXRα as a therapeutic target of acute kidney injury.

Chromatin accessibility dynamics dictate renal tubular epithelial cell response to injury.

Cholangiocytes transit from quiescence to hyperproliferation during cystogenesis in polycystic liver disease (PLD), the severity of which displays prominent sex differences. Epigenetic regulation plays important roles in cell state transition. We aimed to investigate the sex-specific epigenetic basis of hepatic cystogenesis and to develop therapeutic strategies targeting epigenetic modifications for PLD treatment.

Multi-omics profiling of cholangiocytes reveals sex-specific chromatin state dynamics during hepatic cystogenesis in polycystic liver disease.

The formation of biomolecular condensates via phase separation has emerged as a fundamental principle underlying the spatiotemporal coordination of biological activities in cells. Aberrant biomolecular condensates often directly regulate key cellular process involved in the pathogenesis of human diseases, including kidney diseases.

Phase Separation in Kidney Diseases: Autosomal Dominant Polycystic Kidney Disease and Beyond.

Spatiotemporal regulation of gene expression is essential for maintaining cellular homeostasis throughout kidney development and disease progression. Transcription factors (TFs) and epigenetic modifications play pivotal roles in controlling gene expression. Profiling chromatin modifications across the genome, along with the distribution and target regulation by TFs in specific kidney cell types, is crucial for understanding the dynamic changes in gene expression. Here, we presented a comprehensive workflow for epigenomic, cistromic, and transcriptomic analyses of primary kidney tubular cells. Specifically, our methodologies included the isolation of primary kidney tubular epithelial cells, RNA extraction, assay for transposase-accessible chromatin using sequencing, ultra-low-input micrococcal nuclease-based native chromatin immunoprecipitation, cleavage under targets and release using nuclease, and subsequent bioinformatic analysis. This protocol provides a methodological framework for investigating the roles of TFs and epigenetic modifications in kidney development and diseases.

Zhiheng Liu

Tianjin Key Laboratory of Urology

Tianjin Institute of Urology

Establishing a Murine Superficial Bladder Cancer Model via an Intravesical Cell Administration Technique