Cell communication, cell union, and initiation of meiosis in ciliate conjugation.
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MOTIVATION: Algorithms for ligand-receptor network inference have emerged as commonly used tools to estimate cell-cell communication from reference single-cell data. Many studies employ these algorithms to compare signaling between conditions and lack methods to statistically identify signals that are significantly different. We previously developed the cell communication inference algorithm Domino, which considers ligand and receptor gene expression in association with downstream transcription factor activity scoring. We developed the dominoSignal software to innovate upon Domino and extend its functionality to test statistically differential cellular signaling. RESULTS: This new functionality includes the compilation of active signals as linkages from multiple subjects in a single-cell data set and testing condition-dependent signaling linkage. The software is applicable for analysis of single-cell data sets with multiple subjects as biological replicates as well as with bootstrapped replicates from data sets with few or pooled subjects. We use simulation studies to benchmark the number of subjects in compared groups and cells within an annotated cell type sufficient to accurately identify differential linkages. We demonstrate the application of the Differential Cell Signaling Test (DCST) in the dominoSignal software to investigate consequences of cancer cell phenotypes and immunotherapy on cell-cell communication in tumor microenvironments. These applications in cancer studies demonstrate the ability of differential cell signaling analysis to infer changes to cell communication networks from therapeutic or experimental perturbations, which is broadly applicable across biological systems. AVAILABILITY: dominoSignal is available through Bioconductor at https://www.bioconductor.org/packages/release/bioc/html/dominoSignal.html.
MOTIVATION: Combining single-cell sequencing with ligand-receptor (LR) analysis paves the way for the characterization of cell communication events in complex tissues. In particular, directed weighted graphs naturally represent cell-cell communication events. However, current computational methods cannot yet analyze sample-specific cell-cell communication events, as measured in single-cell data produced in large patient cohorts. Cohort-based cell-cell communication analysis presents many challenges, such as the nonlinear nature of cell-cell communication and the high variability given by the patient-specific single-cell RNAseq datasets. RESULTS: Here, we present scACCorDiON (single-cell Analysis of Cell-Cell Communication in Disease clusters using Optimal transport in Directed Networks), an optimal transport algorithm exploring node distances on the Markov Chain as the ground metric between directed weighted graphs. Benchmarking indicates that scACCorDiON performs a better clustering of samples according to their disease status than competing methods that use undirected graphs. We provide a case study of pancreas adenocarcinoma, where scACCorDion detects a sub-cluster of disease samples associated with changes in the tumor microenvironment. Our study case corroborates that clusters provide a robust and explainable representation of cell-cell communication events and that the expression of detected LR pairs is predictive of pancreatic cancer survival. AVAILABILITY AND IMPLEMENTATION: The code of scACCorDiON is available at https://scaccordion.readthedocs.io/en/latest/. and https://doi.org/10.5281/zenodo.15267648. The survival analysis package can be found at https://github.com/CostaLab/scACCorDiON.su.
Rat ovarian granulosa cells and mouse myocardial cells respond to cell-specific hormones by cyclic AMP-dependent mechanisms. In coculture, these heterologous cells communicate by means of gap junctions. Exposure of the cocultures to a hormone specific for one cell type causes the heterologous cells to respond through a cell contact-dependent mechanism. These studies suggest that this cross-stimulation results from the intercellular communication of a mediator that is common to both cell types. The communicated mediator may be cyclic AMP.
Cell-to-cell communication was characterized in cumulus-oocyte complexes from rat ovarian follicles before and after ovulation. Numerous, small gap junctional contacts were present between cumulus cells and oocytes before ovulation. The gap junction are formed on the oocyte surface by cumulus cell processes that transverse the zona pellucida and contact the oolemma. The entire cumulus mass was also connected by gap junctions via cumulus-cumulus interactions. In the hours preceding ovulation, the frequency of gap junctional contacts between cumulus cells and the oocyte was reduced, and the cumulus was disorganized. Electrophysiological measurements indicated that bidirectional ionic coupling was present between the cumulus and oocyte before ovulation. In addition, iontophoretically injected fluorescein dye was tranferred between the oocyte and cumulus cells. Examination of the extent of ionic coupling in cumulus-oocyte specimens before and after ovulation revealed that ionic coupling between the cumulus and oocyte progressively decreased as the time of ovulation approached. In postovulatory specimens, no coupling was detected. Although some proteolytic mechanism may be involved in the disintegration of the cumulus-oocyte complex, neither the cumulus cells nor the oocyte produced detectable levels of plasminogen activator, a protease which is synthesized by membrana granulosa cells. In summary, cell communication is a characterisitc feature of the cumulus-oocyte complex, and this communication is terminated near the time of ovulation. This temporal pattern of the termination of communication between the cumulus and the oocyte may indicate that communication provides a mechanism for regulating the maturation of the oocyte during follicular development before ovulation.
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Emerging evidence indicates that coagulation-related molecular programs are associated with thrombosis, tumor progression, and molecular dysregulation in gastric cancer (GC). However, thrombosis-associated molecular features in GC and their potential links to inherited susceptibility remain insufficiently understood. Integrated analyses of transcriptomic data from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) datasets were performed to identify thrombosis-associated genes and establish a machine learning-based prognostic signature. Genome-wide association study (GWAS), expression quantitative trait loci (eQTL), transcriptome-wide association study (TWAS), and Mendelian randomization (MR) analyses were conducted to investigate susceptibility-associated transcriptional programs in GC. Functional assays were used to evaluate candidate genes associated with malignant phenotypes. Single-cell RNA sequencing (scRNA-seq) and cell-cell communication analyses were further performed to characterize cell-type-specific expression patterns and potential intercellular interactions. A total of 22 differentially expressed thrombosis-associated genes were identified, and a prognostic signature comprising 14 genes was established. The signature stratified patients into high- and low-risk groups and showed prognostic performance in both the training and validation cohorts. Integrative GWAS, eQTL, and TWAS analyses identified susceptibility-associated transcriptional programs that were positively correlated with the thrombosis-associated risk score. Silencing ACTN2 and CRYAB significantly reduced GC cell migration and invasion. scRNA-seq analysis revealed relatively high CRYAB expression in neutrophils, and CellChat analysis suggested potential neutrophil-B cell interactions involving COLLAGEN-related signaling. This integrative multi-omics study identified a thrombosis-associated molecular signature linked to prognosis and germline susceptibility-associated transcriptional programs in GC. ACTN2 and CRYAB may represent candidate genes associated with GC cell migration and invasion, while single-cell analysis suggested potential immune-related communication features.
BACKGROUND: Alcohol-associated liver disease (ALD) is a major cause of alcohol-associated mortality. Previously, we identified KDM5B as a sex-specific mediator of ALD development; however, the mechanism behind KDM5B-induced pathological changes is not established. METHODS: Kdm5b flox/flox female mice were fed a western diet and 20% alcohol in the drinking water for 8-16 weeks (WDA). To induce KO, mice received 2×1011 genome copies of AAV8-CMV-Cre, AAV8-TBG-Cre, or AAV8-control. To test the role of myeloid C/EBPβ, Cebpbfl/fl, or Cebpbfl/fl Lyz2-Cre mice were fed WDA for 16 weeks. RESULTS: We found that Kdm5b KO prevented alcohol-induced liver fibrosis and liver inflammation in female mice. These changes were in part mediated by hepatocyte-to-non-parenchymal cell communication changes. KDM5B in hepatocytes promoted pro-inflammatory and pro-fibrotic changes in liver macrophages, endothelial cells, and stellate cells. Moreover, KDM5B promoted alcohol-induced early increase in EpCAM-positive liver progenitors and loss of liver function at later time points of alcohol feeding. We found that loss of liver function was dependent on a hepatocyte-to-macrophage communication feedback loop. KDM5B in hepatocytes inhibited macrophage C/EBPβ expression, which in turn resulted in loss of the mature KCs phenotype and prevented the ability of KCs to support hepatocyte differentiation, ultimately leading to loss of liver synthetic function. CONCLUSIONS: KDM5B activation in hepatocytes drives pathogenic cell-cell communication, leading to alcohol-induced loss of liver function in ALD.
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Osteoblasts were investigated by two methods, electrical conductance and dye injection. Current injection into one cell caused a change in the recorded transmembrane potential of a second cell, indicating high conductance pathways between the two cells. Dyes injected into a single osteoblast were transmitted to numerous surrounding cells.
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At the surface of aggregating cells of the slime mould, Dictyostelium discoideum, two different sites interacting with extracellular cAMP are detectable: binding sites and cycl-nucleotide phosphodiesterase. Both sites are developmentally regulated. An adequate stimulus for the chemoreceptor system in D. discoideum is the change of cAMP concentration in time, rather than concentration per se: long-term binding of cAMP causes only short-term response. The system is, consequently, adapted to the recognition of pulses rather than to steady-state concentrations of cAMP. The ce,lls are, nevertheless, able to sense stationary spatial gradients and to respond to them by chemotactic orientation. The possibility is discussed that they do so by transforming spatial concentration changes into temporal ones, using extending pseudopods as sensors. The cAMP recognition system is part of a molecular network involved in the generation of spatio-temporal patterns of cellular activities. This system controls the periodic formation of chemotactic signals and their propagation from cell to cell. The phosphodiesterase limits the duration of the cAMP pulses and thus sharply separates the periods of signalling; the binding sites at the cell surface are supposed to be the chemoreceptors. The control of cellular activities via cAMP receptors can be studied with biochemical techniques with cell suspensions in which spatial inhomogeneities are suppressed by intense stirring, whereas the temporal aspect of the spatiotemporal pattern is preserved. Under these conditions it can be shown that the extracellular cAMP concentration changes periodically, and that the phase of the cellular oscillator can be shifted by external pulses of cAMP. It can also be shown that small cAMP pulses induce a high output of cAMP, which demonstrates signal amplification, a function necessary for a cellular relay system.
A system has been developed to study cellular interactions between cells of complementary mating types prior to mating in the ciliate, Euplotes crassus. The presumptive mates were distinguished by using singlet and doublet cells of appropriate mating types in the mixtures. Cells of a given mating type were prelabelled with [3H]leucine and mixed with unlabelled complementary cells. Exchange of [3H]leucine-labelled material from donor to recipient cells was monitored through the various stages of the preconjugant interaction. A label transfer between the mating type complementary cells was detected from the beginning of the visible mating reaction, which occurs after a waiting period from the time of cell mixing and involves ciliary agglutination prior to cell body fusion. Complementary cells which were prevented from physically contacting each other and cells which were not competent to mate appeared unable to take up the labelled material. It is suggested that this material consists of some substance(s) playing an important role in the preconjugant cell-to-cell interactions of E. crassus.