Transcriptomic Phenotypes Research Articles

Multiplexed, image-based pooled screens in primary cells and tissues with PerturbView.

Optical pooled screening (OPS) is a scalable method for linking image-based phenotypes with cellular perturbations. However, it has thus far been restricted to relatively low-plex phenotypic readouts in cancer cell lines in culture due to limitations associated with in situ sequencing of perturbation barcodes. Here, we develop PerturbView, an OPS technology that leverages in vitro transcription to amplify barcodes before in situ sequencing, enabling screens with highly multiplexed phenotypic readouts across diverse systems, including primary cells and tissues. We demonstrate PerturbView in induced pluripotent stem cell-derived neurons, primary immune cells and tumor tissue sections from animal models. In a screen of immune signaling pathways in primary bone marrow-derived macrophages, PerturbView uncovered both known and novel regulators of NF-κB signaling. Furthermore, we combine PerturbView with spatial transcriptomics in tissue sections from a mouse xenograft model, paving the way to in situ screens with rich optical and transcriptomic phenotypes. PerturbView broadens the scope of OPS to a wide range of models and applications.

PerturbDB for unraveling gene functions and regulatory networks.

Perturb-Seq combines CRISPR (clustered regularly interspaced short palindromic repeats)-based genetic screens with single-cell RNA sequencing readouts for high-content phenotypic screens. Despite the rapid accumulation of Perturb-Seq datasets, there remains a lack of a user-friendly platform for their efficient reuse. Here, we developed PerturbDB (http://research.gzsys.org.cn/perturbdb), a platform to help users unveil gene functions using Perturb-Seq datasets. PerturbDB hosts 66 Perturb-Seq datasets, which encompass 4518521 single-cell transcriptomes derived from the knockdown of 10194 genes across 19 different cell lines. All datasets were uniformly processed using the Mixscape algorithm. Genes were clustered by their perturbed transcriptomic phenotypes derived from Perturb-Seq data, resulting in 421 gene clusters, 157 of which were stable across different cellular contexts. Through integrating chemically perturbed transcriptomes with Perturb-Seq data, we identified 552 potential inhibitors targeting 1409 genes, including an mammalian target of rapamycin (mTOR)signaling inhibitor, retinol, which was experimentally verified. Moreover, we developed a 'Cancer' module to facilitate the understanding of the regulatory role of genes in cancer using Perturb-Seq data. An interactive web interface has also been developed, enabling users to visualize, analyze and download all the comprehensive datasets available in PerturbDB. PerturbDB will greatly drive gene functional studies and enhance our understanding of the regulatory roles of genes in diseases such as cancer.

Single-cell analysis identifies distinct macrophage phenotypes associated with prodisease and proresolving functions in the endometriotic niche

Endometriosis negatively impacts the health-related quality of life of 190 million women worldwide. Novel advances in nonhormonal treatments for this debilitating condition are desperately needed. Macrophages play a vital role in the pathophysiology of endometriosis and represent a promising therapeutic target. In the current study, we revealed the full transcriptomic complexity of endometriosis-associated macrophage subpopulations using single-cell analyses in a preclinical mouse model of experimental endometriosis. We have identified two key lesion-resident populations that resemble i) tumor-associated macrophages (characterized by expression of Folr2, Mrc1, Gas6, and Ccl8+) that promoted expression of Col1a1 and Tgfb1 in human endometrial stromal cells and increased angiogenic meshes in human umbilical vein endothelial cells, and ii) scar-associated macrophages (Mmp12, Cd9, Spp1, Trem2+) that exhibited a phenotype associated with fibrosis and matrix remodeling. We also described a population of proresolving large peritoneal macrophages that align with a lipid-associated macrophage phenotype (Apoe, Saa3, Pid1) concomitant with altered lipid metabolism and cholesterol efflux. Gain of function experiments using an Apoe mimetic resulted in decreased lesion size and fibrosis, and modification of peritoneal macrophage populations in the preclinical model. Using cross-species analysis of mouse and human single-cell datasets, we determined the concordance of peritoneal and lesion-resident macrophage subpopulations, identifying key similarities and differences in transcriptomic phenotypes. Ultimately, we envisage that these findings will inform the design and use of specific macrophage-targeted therapies and open broad avenues for the treatment of endometriosis.

14 Natural killer cells have impaired cytotoxicity in advanced renal cell carcinoma

Abstract Background Natural killer (NK) cells are key mediators of anti-tumor activity in multiple cancers, including clear cell renal cell carcinoma (ccRCC). However, the phenotype and function of NK cells across different disease stages of ccRCC is incompletely characterized. Methods Single-cell RNA (scRNA)-sequencing (10x Genomics) data from tumor and adjacent normal kidney from ccRCC was analyzed at multiple clinical stages (localized – stage I/II/III; and advanced – stage IV). Graph-based clustering and lineage markers were used to identify distinct NK cell populations. Differential gene expression analysis was performed to further investigate NK cell phenotype and to derive a gene expression signature (GES). Gene signatures from NK cell subclusters of interest were used to interrogate bulk transcriptomic datasets and expression with clinical outcomes. Tumor-infiltrating NK cell function (cytokine production and cytotoxicity) was assessed by isolation of live NK cells from ccRCC tissue, co-culture with K562 target cells, and measurement of cytokine (IFNgamma) and cytotoxicity (CD107a) markers by flow cytometry. Results Single-cell transcriptomic data were analyzed from 13 patients with ccRCC (tumor and normal kidney), resulting in 21,139 high-quality NK cells. Patients with advanced/metastatic RCC had a lower proportion of NK cells versus total immune cells in the tumor microenvironment compared to normal kidney (p=0.036) and localized ccRCC (p=0.088). Clustering analysis revealed 6 distinct NK cell subsets. The C0.Bright-like NK cell cluster was significantly enriched in advanced ccRCC compared to localized ccRCC (p=0.048) and normal kidney (p=0.0059), expressed markers of tissue residency (ZNF683, ITGA1, CD9, ITGAE), and had decreased expression of cytotoxicity genes (GZMB, PRF1). A GES signature composed of genes upregulated in the dysfunctional C0.Bright-like NK cell cluster was used to interrogate bulk RNA-sequencing data from The Cancer Genome Atlas clear cell cohort, providing validation in a large, independent cohort, of an increase in this dysfunctional NK subset in advanced ccRCC compared to localized ccRCC (p=0.00039) and normal tissue (p=5.3e-05). To functionally confirm the decreased cytotoxicity of this dysfunctional NK population, CD45+CD56+CD3- NK cells were isolated from advanced ccRCC, and co-cultured with K562 target cells. Consistent with the transcriptomic phenotype, tumor-resident CD49a+CD9+ NK cells had cytokine production (IFNgamma) but decreased markers of cytotoxicity (CD107a) compared to CD49a-CD9- NK cells. By contrast, CD49a+CD9+ NK cells isolated from peripheral blood or normal kidney tissue maintained cytotoxic activity. Conclusions Among patients with ccRCC, a single-cell transcriptomic analysis revealed heterogeneous NK cell populations. A dysfunctional tumor resident NK cell phenotype was enriched among patients with advanced disease in ccRCC, and functionally confirmed to have diminished cytotoxicity. This study therefore provides insight into a new axis of immune dysfunction – decreased NK-mediated cytotoxicity – in advanced ccRCC. An improved understanding of NK cell dysfunction within ccRCC may provide a foundation for therapeutic restoration of NK-mediated anti-tumor activity in ccRCC. DOD CDMRP Funding: yes

Differential Responses to Aging Among the Transcriptome and Proteome of Mesenchymal Progenitor Populations.

The biological aging of stem cells (exhaustion) is proposed to contribute to the development of a variety of age-related conditions. Despite this, little is understood about the specific mechanisms which drive this process. In this study, we assess the transcriptomic and proteomic changes in 3 different populations of mesenchymal progenitor cells from older (50-70 years) and younger (20-40 years) individuals to uncover potential mechanisms driving stem cell exhaustion in mesenchymal tissues. To do this, we harvested primary bone marrow mesenchymal stem and progenitor cells (MPCs), circulating osteoprogenitors (COP), and adipose-derived stem cells (ADSCs) from younger and older donors, with an equal number of samples from men and women. These samples underwent RNA sequencing and label-free proteomic analysis, comparing the younger samples to the older ones. There was a distinct transcriptomic phenotype in the analysis of pooled older stem cells, suggestive of suppressed proliferation and differentiation; however, these changes were not reflected in the proteome of the cells. Analyzed independently, older MPCs had a distinct phenotype in both the transcriptome and proteome consistent with altered differentiation and proliferation with a proinflammatory immune shift in older adults. COP cells showed a transcriptomic shift to proinflammatory signaling but no consistent proteomic phenotype. Similarly, ADSCs displayed transcriptomic shifts in physiologies associated with cell migration, adherence, and immune activation but no proteomic change with age. These results show that there are underlying transcriptomic changes with stem cell aging that may contribute to a decline in tissue regeneration. However, the proteome of the cells was inconsistently regulated.

The manatee variational autoencoder model for predicting gene expression alterations caused by transcription factor perturbations

We present the Manatee variational autoencoder model to predict transcription factor (TF) perturbation-induced transcriptomes. We demonstrate that the Manatee in silico perturbation analysis recapitulates target transcriptomic phenotypes in diverse cellular lineage transitions. We further propose the Manatee in silico screening analysis for prioritizing TF combinations targeting desired transcriptomic phenotypes.

Mapping the Single-Cell Differentiation Landscape of Osteosarcoma.

The genetic intratumoral heterogeneity observed in human osteosarcomas poses challenges for drug development and the study of cell fate, plasticity, and differentiation, which are processes linked to tumor grade, cell metastasis, and survival. To pinpoint errors in osteosarcoma differentiation, we transcriptionally profiled 31,527 cells from a tissue-engineered model that directs mesenchymal stem cells toward adipogenic and osteoblastic fates. Incorporating preexisting chondrocyte data, we applied trajectory analysis and non-negative matrix factorization to generate the first human mesenchymal differentiation atlas. This "roadmap" served as a reference to delineate the cellular composition of morphologically complex osteosarcoma tumors and quantify each cell's lineage commitment. Projecting a bulk RNA-sequencing osteosarcoma dataset onto this roadmap unveiled a correlation between a stem-like transcriptomic phenotype and poorer survival outcomes. Our study quantifies osteosarcoma differentiation and lineage, a prerequisite to better understanding lineage-specific differentiation bottlenecks that might someday be targeted therapeutically.

Abstract PS06-09: Fragmentomic analysis of a circulating tumor DNA targeted cancer gene panel discriminates ER status in metastatic breast cancer liquid biopsies

Abstract Background: Circulating tumor DNA (ctDNA) isolated from the peripheral blood of patients with cancer is now routinely used in the clinic to detect tumor somatic mutations, with multiple ctDNA-targeted sequencing panels commercially available for Food and Drug Administration (FDA)-approved biomarker indications to guide targeted therapy options. More recently, it has been appreciated that ctDNA fragmentation patterns are influenced by the chromatin structure of the cell of origin, with greater diversity in fragment size in areas with open chromatin and less diversity in fragment size in areas with closed chromatin. In consequence, multiple studies have found that ctDNA fragmentation patterns can be used to accurately infer epigenomic and transcriptomic phenotypes from their tumor cells of origin. However, these analyses have previously relied on whole-genome sequencing (WGS), and it is not feasible to identify FDA-approved biomarker indications in a cost-effective manner with WGS. Methods: Peripheral blood was collected from a cohort of 90 patients with metastatic HER2-negative breast cancer (ER-positive n=71, ER-negative n=19). Cell-free DNA was extracted from plasma and sequenced using a custom 822 gene pan-cancer targeted sequencing panel (IDT). Shannon entropy of first coding exon fragment sizes (E1SE) was used to quantify fragmentation patterns. Higher diversity of fragment sizes, leading to a higher E1SE, are expected in ctDNA derived from areas of the genome with more open chromatin. A machine learning model utilizing the E1SE metric across all genes in the targeted panel was developed to distinguish between ER-positive and ER-negative disease. Results: Training cross-validated accuracy of the machine learning model was 87.8% with AUC of 0.91 to distinguish between ER-positive and ER-negative disease, despite a median ctDNA fraction of only 0.02. E1SE metrics for ESR1 and CCND1 were significantly higher in ER-positive than ER-negative samples, while E1SE metrics for EGFR, c-Kit and members of the MAP kinase family were significantly higher in ER-negative than ER-positive samples, consistent with anticipated differences in gene expression between ER-positive and ER-negative triple negative breast cancers. In contrast, HER2 E1SE was similar between groups, as expected in this clinically HER2-negative cohort. Conclusions: We have shown for the first time that sequencing from standard targeted ctDNA panels can be utilized to infer phenotypic information through analysis of ctDNA fragmentation patterns in patients with metastatic breast cancer. This expands the depth of potential biologic data that can be extracted from targeted ctDNA sequencing panels in addition to DNA mutation status in a cost-effective manner. In the future, this approach can be exploited to expand ctDNA-based biomarker development beyond DNA mutation status. Citation Format: Kyle Helzer, Jamie Sperger, Yue Shi, Viridiana Carreno, Hannah Krause, Katherine Kaufmann, Leilani Mora-Rodriguez, Matthew Bootsma, Mark Burkard, Ruth O'Regan, Kari Wisinski, Joshua Lang, Shuang (George) Zhao, Malinda West, Marina Sharifi. Fragmentomic analysis of a circulating tumor DNA targeted cancer gene panel discriminates ER status in metastatic breast cancer liquid biopsies [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PS06-09.

Neuromodulatory co-expression in cardiac vagal motor neurons of the Dorsal Motor Nucleus of the Vagus

Dorsal Motor Nucleus of the Vagus (DMV) activity is required for cardioprotection from physiological interventions such as remote ischemic pre-conditioning (RIPC). Herein, we discover the transcriptomic phenotypes of cardioprotective DMV neurons, by combining high throughput transcriptomics, 3D anatomical mapping, and neural tracing in 12 week old male and female Sprague Dawley rats. We find that DMV neurons appear to participate in neuromodulatory co-expression, including those that project to the heart. To distinguish potential mechanisms of cardioprotection, we highlight the functional significance of several transcripts in cardiac-projecting DMV neurons and we begin to validate these findings at the protein level. In our sc-RNAseq data we find that Snca (α-synuclein), the cardioprotective neuromodulator Adcyap1 (PACAP), and the neuropeptide Cartpt (CART) are enriched in cardiac-projecting DMV neurons. To contrast our molecular findings in cardioprotective DMV neurons, we have also collected single neuron HT-RTqPCR data from the other source of cardiac vagal motoneurons, the Nucleus Ambiguus (NA). Catecholaminergic transcripts, including Slc18a2 (VMAT2), Ddc, and Th, are enriched in cardiac-projecting DMV neurons relative to those of the NA. These findings implicate catecholaminergic processes, synuclein, and these secreted neuropeptides in cardioprotection. At the protein level, we found PACAP, CART, SNCA and TH enrichment, as well as co-localization of PACAP, TH, and ChAT, in cardiac-projecting DMV neurons. There is consistency between our findings from three spatial transcriptomics techniques and across sexes. Based on these results, we propose a 3D anatomical and molecular map of cardiac vagal motoneurons. This work fills a major gap in the understanding of the cellular mechanisms by which parasympathetic drive provides cardioprotection and provides a future translational path to emulating the positive vagal neuromodulatory effects on heart health. Funding was provided by the R01 HL161696 grant through National Heart, Lung, and Blood institute and the National Institutes of Health Common Fund SPARC Program Grant OT2OD030534. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Single-cell spatial transcriptomics reveals a dystrophic trajectory following a developmental bifurcation of myoblast cell fates in facioscapulohumeral muscular dystrophy.

Facioscapulohumeral muscular dystrophy (FSHD) is linked to abnormal derepression of the transcription activator DUX4. This effect is localized to a low percentage of cells, requiring single-cell analysis. However, single-cell/nucleus RNA-seq cannot fully capture the transcriptome of multinucleated large myotubes. To circumvent these issues, we use multiplexed error-robust fluorescent in situ hybridization (MERFISH) spatial transcriptomics that allows profiling of RNA transcripts at a subcellular resolution. We simultaneously examined spatial distributions of 140 genes, including 24 direct DUX4 targets, in in vitro differentiated myotubes and unfused mononuclear cells (MNCs) of control, isogenic D4Z4 contraction mutant and FSHD patient samples, as well as the individual nuclei within them. We find myocyte nuclei segregate into two clusters defined by the expression of DUX4 target genes, which is exclusively found in patient/mutant nuclei, whereas MNCs cluster based on developmental states. Patient/mutant myotubes are found in "FSHD-hi" and "FSHD-lo" states with the former signified by high DUX4 target expression and decreased muscle gene expression. Pseudotime analyses reveal a clear bifurcation of myoblast differentiation into control and FSHD-hi myotube branches, with variable numbers of DUX4 target-expressing nuclei found in multinucleated FSHD-hi myotubes. Gene coexpression modules related to extracellular matrix and stress gene ontologies are significantly altered in patient/mutant myotubes compared with the control. We also identify distinct subpathways within the DUX4 gene network that may differentially contribute to the disease transcriptomic phenotype. Taken together, our MERFISH-based study provides effective gene network profiling of multinucleated cells and identifies FSHD-induced transcriptomic alterations during myoblast differentiation.

Abstract 270: Dissecting the effects of p53 mutation and p53 loss on pancreatic tumor microenvironment

Abstract Pancreatic ductal adenocarcinoma (PDAC) is a devastating malignant disease with a dismal prognosis. In the past decades, a plethora of genetically engineered mouse models (GEMMs) with autochthonous pancreatic tumor development have greatly facilitated the studies of pancreatic cancer. Commonly used GEMMs of PDAC often harbor the oncogenic KRAS driver mutation (KrasG12D), in combination with either p53 mutation by knock-in strategy (Trp53R172H) or p53 loss by conditional knockout (Trp53cKO) strategy, in pancreatic cell lineages. However, the systematic comparison of the tumor microenvironment between KrasG12D; Trp53R172H (KPmut) mouse models and KrasG12D; Trp53cKO (KPloss) mouse models is still lacking. In this study, we conducted cross-dataset single-cell RNA-sequencing (scRNA-seq) analyses to compare the pancreatic tumor microenvironment from KPmut mouse models and KPloss mouse models, especially focusing on the cell compositions and transcriptomic phenotypes of major cell types including cancer cells, B cells, T cells, granulocytes, myeloid cells, cancer-associated fibroblasts, and endothelial cells. We identified the similarities and differences between KPmut and KPloss mouse models, revealing the effects of p53 mutation and p53 loss on oncogenic KRAS-driven pancreatic tumor progression. Citation Format: Yang Chen. Dissecting the effects of p53 mutation and p53 loss on pancreatic tumor microenvironment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 270.

Abstract 3778: Comprehensive analysis of single disseminated cancer cells identifies a stem-like phenotype with strong prognostic impact

Abstract Introduction: Recent studies on disseminated cancer cells (DCCs) in Non-Small-Cell Lung Cancer (NSCLC) patients demonstrated their clinical relevance even in early tumor stages. However, their molecular and phylogenetic link to the primary tumor is currently unclear. Certain genetic alterations, such as TP53 or KRAS mutations, have been proposed to be clonal events and drivers of dissemination and metastasis. In this study, we analyzed the genome and transcriptome of single DCCs to identify the characteristics of early DCCs and their translational clinical value. Materials and methods: From 2011 to 2019 we prospectively collected and analyzed bone marrow aspirates and lymph node samples from 296 newly diagnosed NSCLC patients undergoing tumor resection with curative intention. Presence of DCC was examined by i) immunocytology (IC) for Cytokeratin (clone A45-B/B3, bone marrow, BM-DCCs) or EpCAM (clone BerEp4, lymph node, LN-DCCs) and ii) immunofluorescent (IF) staining for EpCAM in a live cell suspension (clone HEA-125) from BM or LN. Single cells were isolated using micromanipulation and subjected to Whole Genome Amplification or combined Whole Genome/Transcriptome Amplification for IC and IF, respectively. Sanger sequencing for known hotspot mutations in TP53 and KRAS was performed on single DCCs. Gene expression profiles of DCCs were analyzed by single cell RNA sequencing and the results were compared with clinical data with a mean follow-up of 2.93 years (range 0.03-7.22). Results: LN-DCCs were found in 44.8% and 59.6% by IC and IF, respectively. CKIC pos BM-DCCs were found in 45.2%, while EpCAMIF pos BM-DCCs were present in 52.8%. LN-DCCs correlated with reduced tumor-specific survival (TSS, p=0.009) and progression-free survival (PFS, p=0.025). EpCAMIF pos, but not CKIC pos BM-DCCs correlated with reduced TSS (p=0.003) and PFS (p=0.083). Genetic analysis of single DCCs revealed that TP53 or KRAS mutations could be found in 3.6% and 2.8% of analyzed BM-DCCs and 5.0% and 29.3% of LN-DCCs for IF and IC, respectively. Single cell RNA-seq showed distinct transcriptomic profiles for LN- and BM-DCCs, and identified a DCC phenotype with high stemness score in the bone marrow. Further analysis of potential transcriptome-based biomarkers identified a novel candidate marker for activated EpCAMpos BM-DCCs that strongly correlates with PFS and TSS (p<0.001). Conclusions: DCCs in early-stage NSCLC have high prognostic value and predict reduced PFS and TSS. While genetic alterations in the TP53 and KRAS gene were not detected in the majority of analyzed DCCs, transcriptomic phenotypes provided relevant information and identified a subset of activated DCCs that correlate strongly with relapse and poor outcome. Citation Format: Tobias Mederer, Daniel Spitzl, Felix Elsner, Bernhard Polzer, Michael Ried, Reiner Neu, Tobias Robold, Hans-Stefan Hofmann, Christoph A. Klein. Comprehensive analysis of single disseminated cancer cells identifies a stem-like phenotype with strong prognostic impact [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3778.

Transcriptotype-Driven Discovery of Apigenin as a Therapy against Cholestatic Liver Fibrosis: Through Inhibition of PANoptosis and Following Type-I Interferon Responses.

Cholangiopathies lack effective medicines and can progress into end-stage liver diseases. Mining natural product transcriptome databases for bioactive ingredients, which can reverse disease-associated transcriptomic phenotypes, holds promise as an effective approach for drug discovery. To identify disease-associated transcriptomic changes, we performed RNA-sequencing on bile duct ligation (BDL)-induced cholestatic liver fibrosis mice, as well as PBC and PSC patients, and found that PANoptosis and activation of type-I interferon (IFN) signaling were observed in BDL mice and patients with PBC and PSC. We then established a transcriptotype-driven screening system based on HERB and ITCM databases. Among 283 natural ingredients screened, apigenin (Api), which is widely distributed in varieties of food and medicinal plants, was screened out by our screen system since it reversed the expression pattern of key genes associated with PANoptosis and type-I IFN responses. In BDL, Abcb4-/-, and DDC-fed mice, Api effectively ameliorated liver injuries, inflammation, and fibrosis. It also protected cholangiocytes from bile acid-stimulated PANoptosis, thus alleviating damage-associated molecular pattern-mediated activation of TBK1-NF-κB in macrophages. Additionally, Api directly inhibited type-I IFN-induced downstream inflammatory responses. Our study demonstrated the pathogenic roles of PANoptosis and type-I IFN signaling in cholestatic liver fibrosis and verified the feasibility of transcriptotype-based drug screening. Furthermore, this study revealed a novel anti-inflammatory mechanism of Api and identified it as a promising candidate for the treatment of cholestatic liver fibrosis.

RNA Sequencing in Disease Diagnosis.

RNA sequencing (RNA-seq) enables the accurate measurement of multiple transcriptomic phenotypes for modeling the impacts of disease variants. Advances in technologies, experimental protocols, and analysis strategies are rapidly expanding the application of RNA-seq to identify disease biomarkers, tissue- and cell-type-specific impacts, and the spatial localization of disease-associated mechanisms. Ongoing international efforts to construct biobank-scale transcriptomic repositories with matched genomic data across diverse population groups are further increasing the utility of RNA-seq approaches by providing large-scale normative reference resources. The availability of these resources, combined with improved computational analysis pipelines, has enabled the detection of aberrant transcriptomic phenotypes underlying rare diseases. Further expansion of these resources, across both somatic and developmental tissues, is expected to soon provide unprecedented insights to resolve disease origin, mechanism of action, and causal gene contributions, suggesting the continued high utility of RNA-seq in disease diagnosis.

DNA hypomethylation promotes the expression of CASPASE-4 which exacerbates inflammation and amyloid-β deposition in Alzheimer’s disease

Alzheimer’s disease (AD) is the sixth leading cause of death in the USA. It is established that neuroinflammation contributes to the synaptic loss, neuronal death, and symptomatic decline of AD patients. Accumulating evidence suggests a critical role for microglia, innate immune phagocytes of the brain. For instance, microglia release pro-inflammatory products such as IL-1β which is highly implicated in AD pathobiology. The mechanisms underlying the transition of microglia to proinflammatory promoters of AD remain largely unknown. To address this gap, we performed reduced representation bisulfite sequencing (RRBS) to profile global DNA methylation changes in human AD brains compared to no disease controls. We identified differential DNA methylation of CASPASE-4 (CASP4), which when expressed promotes the generation of IL-1β and is predominantly expressed in immune cells. DNA upstream of the CASP4 transcription start site was hypomethylated in human AD brains, which was correlated with increased expression of CASP4. Furthermore, microglia from a mouse model of AD (5xFAD) express increased levels of CASP4 compared to wild-type (WT) mice. To study the role of CASP4 in AD, we developed a novel mouse model of AD lacking the mouse ortholog of CASP4 and CASP11, which is encoded by mouse Caspase-4 (5xFAD/Casp4−/−). The expression of CASP11 was associated with increased accumulation of pathologic protein aggregate amyloid-β (Aβ) and increased microglial production of IL-1β in 5xFAD mice. Utilizing RNA-sequencing, we determined that CASP11 promotes unique transcriptomic phenotypes in 5xFAD mouse brains, including alterations of neuroinflammatory and chemokine signaling pathways. Notably, in vitro, CASP11 promoted generation of IL-1β from macrophages in response to cytosolic Aβ through cleavage of downstream effector Gasdermin D (GSDMD). Therefore, here we unravel the role for CASP11 and GSDMD in the generation of IL-1β in response to Aβ and the progression of pathologic inflammation in AD. Overall, our results demonstrate that overexpression of CASP4 due to differential DNA methylation in AD microglia contributes to the progression of AD pathobiology. Thus, we identify CASP4 as a potential target for immunotherapies for the treatment and prevention of AD.

Epigenetic priming targets tumor heterogeneity to shift transcriptomic phenotype of pancreatic ductal adenocarcinoma towards a Vitamin D susceptible state

As a highly heterogeneous tumor, pancreatic ductal adenocarcinoma (PDAC) exhibits non-uniform responses to therapies across subtypes. Overcoming therapeutic resistance stemming from this heterogeneity remains a significant challenge. Here, we report that Vitamin D-resistant PDAC cells hijacked Vitamin D signaling to promote tumor progression, whereas epigenetic priming with glyceryl triacetate (GTA) and 5-Aza-2′-deoxycytidine (5-Aza) overcame Vitamin D resistance and shifted the transcriptomic phenotype of PDAC toward a Vitamin D-susceptible state. Increasing overall H3K27 acetylation with GTA and reducing overall DNA methylation with 5-Aza not only elevated the Vitamin D receptor (VDR) expression but also reprogrammed the Vitamin D-responsive genes. Consequently, Vitamin D inhibited cell viability and migration in the epigenetically primed PDAC cells by activating genes involved in apoptosis as well as genes involved in negative regulation of cell proliferation and migration, while the opposite effect of Vitamin D was observed in unprimed cells. Studies in genetically engineered mouse PDAC cells further validated the effects of epigenetic priming for enhancing the anti-tumor activity of Vitamin D. Using gain- and loss-of-function experiments, we further demonstrated that VDR expression was necessary but not sufficient for activating the favorable transcriptomic phenotype in respond to Vitamin D treatment in PDAC, highlighting that both the VDR and Vitamin D-responsive genes were prerequisites for Vitamin D response. These data reveal a previously undefined mechanism in which epigenetic state orchestrates the expression of both VDR and Vitamin D-responsive genes and determines the therapeutic response to Vitamin D in PDAC.

Grade 2, 3 and Dedifferentiated Chondrosarcomas: A Comparative Study of Isocitrate Dehydrogenase-Mutant and Wild-Type Tumors with Implications for Prognosis and Therapy.

Grade 2 and 3 and dedifferentiated chondrosarcomas (CS) are frequently associated with isocitrate dehydrogenase (IDH) mutations and often exhibit a poor clinical outcome. Treatment is limited mainly to surgery. Defining IDH status (wild type (WT) and mutant) and the associated transcriptome may prove useful in determining other therapeutic options in these neoplasms. Formalin-fixed paraffin-embedded material from 69 primary and recurrent grade 2, 3 and dedifferentiated CS was obtained. DNA sequencing for IDH1 and IDH2 mutations (n = 47) and RNA sequencing via Nextseq 2000 (n = 14) were performed. Differentially expressed genes (DEGs) were identified and used to predict aberrant biological pathways with Ingenuity Pathway Analysis (IPA) software (Qiagen). Gene Set Enrichment Analyses (GSEA) using subsets C3, C5 and C7 were performed. Differentially expressed genes were validated by immunohistochemistry. Outcome analysis was performed using the Wilcoxon test. A set of 69 CS (28 females, 41 males), average age 65, distributed among femur, pelvis, humerus, and chest wall were identified from available clinical material. After further selection based on available IDH status, we evaluated 15 IDH WT and 32 IDH mutant tumors as part of this dataset. Out of 15 IDH WT tumors, 7 involved the chest wall/scapula, while 1 of 32 mutants arose in the scapula. There were far more genes overexpressed in IDH WT tumors compared to IDH mutant tumors. Furthermore, IDH WT and IDH mutant tumors were transcriptomically distinct in the IPA and GSEA, with IDH mutant tumors showing increased activity in methylation pathways and endochondral ossification, while IDH WT tumors showed more activity in normal matrix development pathways. Validation immunohistochemistry demonstrated expression of WT1 and AR in IDH WT tumors, but not in IDH mutants. SATB2 was expressed in IDH mutant tumors and not in WT tumors. Outcome analysis revealed differences in overall survival between mutant and WT tumors (p = 0.04), dedifferentiated mutant and higher-grade (2, 3) mutant tumors (p = 0.03), and dedifferentiated mutant and higher-grade (2, 3) WT tumors (p = 0.03). The longest survival times were observed in patients with higher-grade WT tumors, while patients with dedifferentiated mutant tumors showed the lowest survival. Generally, patients with IDH WT tumors displayed longer survival in both the higher-grade and dedifferentiated groups. Grade 2, 3 and dedifferentiated chondrosarcomas are further characterized by IDH status, which in turn informs transcriptomic phenotype and overall survival. The transcriptome is distinct depending on IDH status, and implies different treatment targets.

A compendium of genetic regulatory effects across pig tissues

The Farm Animal Genotype-Tissue Expression (FarmGTEx) project has been established to develop a public resource of genetic regulatory variants in livestock, which is essential for linking genetic polymorphisms to variation in phenotypes, helping fundamental biological discovery and exploitation in animal breeding and human biomedicine. Here we show results from the pilot phase of PigGTEx by processing 5,457 RNA-sequencing and 1,602 whole-genome sequencing samples passing quality control from pigs. We build a pig genotype imputation panel and associate millions of genetic variants with five types of transcriptomic phenotypes in 34 tissues. We evaluate tissue specificity of regulatory effects and elucidate molecular mechanisms of their action using multi-omics data. Leveraging this resource, we decipher regulatory mechanisms underlying 207 pig complex phenotypes and demonstrate the similarity of pigs to humans in gene expression and the genetic regulation behind complex phenotypes, supporting the importance of pigs as a human biomedical model.

Enteric glial cell network function is required for epithelial barrier restitution following intestinal ischemic injury in the early postnatal period.

Ischemic damage to the intestinal epithelial barrier, such as in necrotizing enterocolitis or small intestinal volvulus, is associated with higher mortality rates in younger patients. We have recently reported a powerful pig model to investigate these age-dependent outcomes in which mucosal barrier restitution is strikingly absent in neonates but can be rescued by direct application of homogenized mucosa from older, juvenile pigs by a yet-undefined mechanism. Within the mucosa, a postnatally developing network of enteric glial cells (EGCs) is gaining recognition as a key regulator of the mucosal barrier. Therefore, we hypothesized that the developing EGC network may play an important role in coordinating intestinal barrier repair in neonates. Neonatal and juvenile jejunal mucosa recovering from surgically induced intestinal ischemia was visualized by scanning electron microscopy and the transcriptomic phenotypes were assessed by bulk RNA sequencing. EGC network density and glial activity were examined by Gene Set Enrichment Analysis, three-dimensional (3-D) volume imaging, and Western blot and its function in regulating epithelial restitution was assessed ex vivo in Ussing chamber using the glia-specific inhibitor fluoroacetate (FA), and in vitro by coculture assay. Here we refine and elaborate our translational model, confirming a neonatal phenotype characterized by a complete lack of coordinated reparative signaling in the mucosal microenvironment. Furthermore, we report important evidence that the subepithelial EGC network changes significantly over the early postnatal period and demonstrate that the proximity of a specific functional population of EGC to wounded intestinal epithelium contributes to intestinal barrier restitution following ischemic injury.NEW & NOTEWORTHY This study refines a powerful translational pig model, defining an age-dependent relationship between enteric glia and the intestinal epithelium during intestinal ischemic injury and confirming an important role for enteric glial cell (EGC) activity in driving mucosal barrier restitution. This study suggests that targeting the enteric glial network could lead to novel interventions to improve recovery from intestinal injury in neonatal patients.

Fluid and imaging amyloid‐beta biomarkers discordant individuals present different blood transcriptomic phenotypes

AbstractBackgroundCerebrospinal fluid (CSF) and Positron emission tomography (PET) amyloid‐β biomarkers are commonly used interchangeably to measure amyloid‐β deposition, an early event in the development of Alzheimer’s disease (AD). However, it is not uncommon to find individuals with discordant measurements of amyloid‐β CSF and PET. It has been hypothesized that this discordance may be an intermediate step between the CSF and brain amyloid deposition, and that discordant individuals might be in different disease stages or have different disease phenotypes. Here, we applied blood transcriptomic analysis to evaluate differences in amyloid‐β CSF and PET discordant and concordant individuals.MethodWe analyzed the blood transcriptome of 200 individuals from the ADNI cohort who had measurements of both CSF amyloid‐β42 and [18F]Florbetapir PET at baseline and at 2‐year follow‐up. The demographic characteristics of the sample are presented in table 1. Our analysis yielded four groups: CSF+/PET‐ (n = 18), CSF‐/PET+ (n = 19), CSF+/PET+ (n = 76), and CSF‐/PET‐ (n = 87). The latter was the control group for all analyses. Differentially expressed genes (DEGs, uncorrected p‐value < 0.01) were used for gene set enrichment analysis (GSEA) to identify group‐specific altered biological pathways.ResultCSF+/PET‐, CSF‐/PET+ and CSF+/PET+ individuals showed a great proportion of unshared DEGs (Figure 1). The CSF+/PET‐ group, which is thought to represent a very early stage in the disease, presented the highest number of unshared DEGs (273) with upregulated GO terms involved mainly in metabolic processes. The CSF‐/PET+ group possessed 113 unique DEGs, while the CSF+/PET+ possessed 47. Interestingly, these groups presented similar alterations in biological processes, representing mainly alterations in immune response and inflammation.ConclusionOur results highlight the differences in the blood transcriptomic phenotype between CSF and PET amyloid‐β concordant and discordant individuals. Importantly, individuals very early in the AD continuum (CSF+/PET‐) presented the most distinct phenotype. Our results suggest that blood transcriptomics are able to capture subtle changes in brain amyloid‐β and might help identify individuals in different stages of AD.