The enteric nervous system (ENS) coordinates essential intestinal functions through the concerted action of diverse enteric neurons (ENs). However, integrated molecular knowledge of EN subtypes is ...lacking. To compare human and mouse ENs, we transcriptionally profiled healthy ENS from adult humans and mice. We aimed to identify transcripts marking discrete neuron subtypes and visualize conserved EN subtypes for humans and mice in multiple bowel regions.
Human myenteric ganglia and adjacent smooth muscle were isolated by laser-capture microdissection for RNA sequencing. Ganglia-specific transcriptional profiles were identified by computationally subtracting muscle gene signatures. Nuclei from mouse myenteric neurons were isolated and subjected to single-nucleus RNA sequencing, totaling more than 4 billion reads and 25,208 neurons. Neuronal subtypes were defined using mouse single-nucleus RNA sequencing data. Comparative informatics between human and mouse data sets identified shared EN subtype markers, which were visualized in situ using hybridization chain reaction.
Several EN subtypes in the duodenum, ileum, and colon are conserved between humans and mice based on orthologous gene expression. However, some EN subtype–specific genes from mice are expressed in completely distinct morphologically defined subtypes in humans. In mice, we identified several neuronal subtypes that stably express gene modules across all intestinal segments, with graded, regional expression of 1 or more marker genes.
Our combined transcriptional profiling of human myenteric ganglia and mouse EN provides a rich foundation for developing novel intestinal therapeutics. There is congruency among some EN subtypes, but we note multiple species differences that should be carefully considered when relating findings from mouse ENS research to human gastrointestinal studies.
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Objective
To determine interrelationships between the expression of long intergenic (noncoding) RNA–p21 (lincRNA‐p21), NF‐κB activity, and responses to methotrexate (MTX) in rheumatoid arthritis (RA) ...by analyzing patient blood samples and cell culture models.
Methods
Expression levels of long noncoding RNA and messenger RNA (mRNA) were determined by quantitative reverse transcription–polymerase chain reaction. Western blotting and flow cytometry were used to quantify levels of intracellular proteins. Intracellular NF‐κB activity was determined using an NF‐κB luciferase reporter plasmid.
Results
Patients with RA expressed reduced basal levels of lincRNA‐p21 and increased basal levels of phosphorylated p65 (RelA), a marker of NF‐κB activation. Patients with RA who were not treated with MTX expressed lower levels of lincRNA‐p21 and higher levels of phosphorylated p65 compared with RA patients treated with low‐dose MTX. In cell culture using primary cells and transformed cell lines, MTX induced lincRNA‐p21 through a DNA‐dependent protein kinase catalytic subunit (DNA PKcs)–dependent mechanism. Deficiencies in the levels of PRKDC mRNA in patients with RA were also corrected by MTX in vivo. Furthermore, MTX reduced NF‐κB activity in tumor necrosis factor α–treated cells through a DNA PKcs–dependent mechanism via induction of lincRNA‐p21. Finally, we observed that depressed levels of TP53 and lincRNA‐p21 increased NF‐κB activity in cell lines. Decreased levels of lincRNA‐p21 did not alter NFKB1 or RELA transcripts; rather, lincRNA‐p21 physically bound to RELA mRNA.
Conclusion
Our findings support a model whereby depressed levels of lincRNA‐p21 in RA contribute to increased NF‐κB activity. MTX decreases basal levels of NF‐κB activity by increasing lincRNA‐p21 levels through a DNA PKcs–dependent mechanism.
WDR5 nucleates the assembly of histone-modifying complexes and acts outside this context in a range of chromatin-centric processes. WDR5 is also a prominent target for pharmacological inhibition in ...cancer. Small-molecule degraders of WDR5 have been described, but most drug discovery efforts center on blocking the WIN site of WDR5, an arginine binding cavity that engages MLL/SET enzymes that deposit histone H3 lysine 4 methylation (H3K4me). Therapeutic application of WIN site inhibitors is complicated by the disparate functions of WDR5, but is generally guided by two assumptions-that WIN site inhibitors disable all functions of WDR5, and that changes in H3K4me drive the transcriptional response of cancer cells to WIN site blockade. Here, we test these assumptions by comparing the impact of WIN site inhibition versus WDR5 degradation on H3K4me and transcriptional processes. We show that WIN site inhibition disables only a specific subset of WDR5 activity, and that H3K4me changes induced by WDR5 depletion do not explain accompanying transcriptional responses. These data recast WIN site inhibitors as selective loss-of-function agents, contradict H3K4me as a relevant mechanism of action for WDR5 inhibitors, and indicate distinct clinical applications of WIN site inhibitors and WDR5 degraders.
Lung organogenesis requires precise timing and coordination to effect spatial organization and function of the parenchymal cells. To provide a systematic broad-based view of the mechanisms governing ...the dynamic alterations in parenchymal cells over crucial periods of development, we performed a single-cell RNA-sequencing time-series yielding 102,571 epithelial, endothelial and mesenchymal cells across nine time points from embryonic day 12 to postnatal day 14 in mice. Combining computational fate-likelihood prediction with RNA in situ hybridization and immunofluorescence, we explore lineage relationships during the saccular to alveolar stage transition. The utility of this publicly searchable atlas resource (www.sucrelab.org/lungcells) is exemplified by discoveries of the complexity of type 1 pneumocyte function and characterization of mesenchymal Wnt expression patterns during the saccular and alveolar stages - wherein major expansion of the gas-exchange surface occurs. We provide an integrated view of cellular dynamics in epithelial, endothelial and mesenchymal cell populations during lung organogenesis.
Abstract
WDR5 is a highly-conserved nuclear protein that performs multiple scaffolding functions in the context of chromatin. WDR5 is also a promising target for pharmacological inhibition in cancer, ...with small molecule inhibitors of an arginine-binding pocket of WDR5 (the ‘WIN’ site) showing efficacy against a range of cancer cell lines in vitro. Efforts to understand WDR5, or establish the mechanism of action of WIN site inhibitors, however, are stymied by its many functions in the nucleus, and a lack of knowledge of the conserved gene networks—if any—that are under its control. Here, we have performed comparative genomic analyses to identify the conserved sites of WDR5 binding to chromatin, and the conserved genes regulated by WDR5, across a diverse panel of cancer cell lines. We show that a specific cohort of protein synthesis genes (PSGs) are invariantly bound by WDR5, demonstrate that the WIN site anchors WDR5 to chromatin at these sites, and establish that PSGs are bona fide, acute, and persistent targets of WIN site blockade. Together, these data reveal that WDR5 plays a predominant transcriptional role in biomass accumulation and provide further evidence that WIN site inhibitors act to repress gene networks linked to protein synthesis homeostasis.
Flow cytometry studies on injured kidney tubules are complicated by the low yield of nucleated single cells. Furthermore, cell-specific responses such as cell cycle dynamics in vivo have ...conventionally relied on indirect immunohistochemistry and proximal tubule markers that may be downregulated in injury. Here, we report a new tissue dissociation protocol for the kidney with an early fixation step that greatly enhances the yield of single cells. Genetic labeling of the proximal tubule with either mT/mG "tomato" or R26Fucci2aR (Fucci) cell cycle reporter mice allows us to follow proximal tubule-specific changes in cell cycle after renal injury. Image-based flow cytometry (FlowSight) enables gating of the cell cycle and concurrent visualization of the cells with bright field and fluorescence. We used the Fucci mouse in conjunction with FlowSight to identify a discrete polyploid population in proximal tubules after aristolochic acid injury. The tissue dissociation protocol in conjunction with genetic labeling and image-based flow cytometry is a tool that can improve our understanding of any discrete cell population after injury.
The SNF5 subunit of the SWI/SNF chromatin remodeling complex has been shown to act as a tumor suppressor through multiple mechanisms, including impairing the ability of the oncoprotein transcription ...factor MYC to bind chromatin. Beyond SNF5, however, it is unknown to what extent MYC can access additional SWI/SNF subunits or how these interactions affect the ability of MYC to drive transcription, particularly in SNF5-null cancers. Here, we report that MYC interacts with multiple SWI/SNF components independent of SNF5. We show that MYC binds the pan-SWI/SNF subunit BAF155 through the BAF155 SWIRM domain, an interaction that is inhibited by the presence of SNF5. In SNF5-null cells, MYC binds with remaining SWI/SNF components to essential genes, although for a purpose that is distinct from chromatin remodeling. Analysis of MYC-SWI/SNF target genes in SNF5-null cells reveals that they are associated with core biological functions of MYC linked to protein synthesis. These data reveal that MYC can bind SWI/SNF in an SNF5-independent manner and that SNF5 modulates access of MYC to core SWI/SNF complexes. This work provides a framework in which to interrogate the influence of SWI/SNF on MYC function in cancers in which SWI/SNF or MYC are altered.
Common genetic variants confer substantial risk for chronic lung diseases, including pulmonary fibrosis. Defining the genetic control of gene expression in a cell-type-specific and context-dependent ...manner is critical for understanding the mechanisms through which genetic variation influences complex traits and disease pathobiology. To this end, we performed single-cell RNA sequencing of lung tissue from 66 individuals with pulmonary fibrosis and 48 unaffected donors. Using a pseudobulk approach, we mapped expression quantitative trait loci (eQTLs) across 38 cell types, observing both shared and cell-type-specific regulatory effects. Furthermore, we identified disease interaction eQTLs and demonstrated that this class of associations is more likely to be cell-type-specific and linked to cellular dysregulation in pulmonary fibrosis. Finally, we connected lung disease risk variants to their regulatory targets in disease-relevant cell types. These results indicate that cellular context determines the impact of genetic variation on gene expression and implicates context-specific eQTLs as key regulators of lung homeostasis and disease.
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