Epigenetic changes in human model KMT2A leukemias highlight early events during leukemogenesis

Chromosomal translocations involving KMT2A gene are one of the most common genetic alterations found in pediatric acute myeloid leukemias (AML) although the molecular mechanisms that initiate the disease remain incompletely defined. To elucidate these initiating events we have used a human model system of AML driven by the KMT2A-MLLT3 (KM3) fusion. More specifically, we investigated changes in DNA methylation, histone modifications, and chromatin accessibility at each stage of our model system and correlated these with expression changes. We observe the development of a profound hypomethylation phenotype in the early stages of leukemic transformation after KM3 addition along with loss of expression of stem cell associated genes along with skewed expression in other genes such as S100A8/9 implicated in leukemogenesis. In addition, early increases in the expression of the lysine demethylase KDM4B was functionally linked to these expression changes as well as other key transcription factors. Remarkably, our ATAC-seq data showed that there were relatively few leukemiaspecific changes and the vast majority corresponded to open chromatin regions and transcription factor clusters previously observed in other cell types. Integration of the gene expression and epigenetic changes revealed the adenylate cyclase gene ADCY9 as an essential gene in KM3-AML, and suggest the potential for autocrine signalling through the chemokine receptor CCR1 and CCL23 ligand. Together, our results suggest that KM3 induces subtle changes in the epigenome while co-opting the normal transcriptional machinery to drive leukemogenesis.

Predicting cell-to-cell communication networks using NATMI

Development of high throughput single-cell sequencing technologies has made it cost-effective to profile thousands of cells from diverse samples containing multiple cell types. To study how these different cell types work together, here we develop NATMI (Network Analysis Toolkit for Multicellular Interactions). NATMI uses connectomeDB2020 (a database of 2293 manually curated ligand-receptor pairs with literature support) to predict and visualise cell-to-cell communication networks from single-cell (or bulk) expression data. Using multiple published single-cell datasets we demonstrate how NATMI can be used to identify (i) the cell-type pairs that are communicating the most (or most specifically) within a network, (ii) the most active (or specific) ligand-receptor pairs active within a network, (iii) putative highly-communicating cellular communities and (iv) differences in intercellular communication when profiling given cell types under different conditions. Furthermore, analysis of the Tabula Muris (organism-wide) atlas confirms our previous prediction that autocrine signalling is a major feature of cell-to-cell communication networks, while also revealing that hundreds of ligands and their cognate receptors are co-expressed in individual cells suggesting a substantial potential for self-signalling.

TGF-β Regulates Collagen Type I Expression in Myoblasts and Myotubes via Transient Ctgf and Fgf-2 Expression

Transforming Growth Factor β (TGF-β) is involved in fibrosis as well as the regulation of muscle mass, and contributes to the progressive pathology of muscle wasting disorders. However, little is known regarding the time-dependent signalling of TGF-β in myoblasts and myotubes, as well as how TGF-β affects collagen type I expression and the phenotypes of these cells. Here, we assessed effects of TGF-β on gene expression in C2C12 myoblasts and myotubes after 1, 3, 9, 24 and 48 h treatment. In myoblasts, various myogenic genes were repressed after 9, 24 and 48 h, while in myotubes only a reduction in Myh3 expression was observed. In both myoblasts and myotubes, TGF-β acutely induced the expression of a subset of genes involved in fibrosis, such as Ctgf and Fgf-2, which was subsequently followed by increased expression of Col1a1. Knockdown of Ctgf and Fgf-2 resulted in a lower Col1a1 expression level. Furthermore, the effects of TGF-β on myogenic and fibrotic gene expression were more pronounced than those of myostatin, and knockdown of TGF-β type I receptor Tgfbr1, but not receptor Acvr1b, resulted in a reduction in Ctgf and Col1a1 expression. These results indicate that, during muscle regeneration, TGF-β induces fibrosis via Tgfbr1 by stimulating the autocrine signalling of Ctgf and Fgf-2.

Natriuretic peptide system expression in murine and human submandibular salivary glands: a study of the spatial localisation of ANB, BNP, CNP and their receptors

The natriuretic peptide (NP) system comprises of three ligands, the Atrial Natriuretic Peptide (ANP), Brain Natriuretic peptide (BNP) and C-type Natriuretic peptide (CNP), and three natriuretic peptide receptors, NPRA, NPRB and NPRC. Here we present a comprehensive study of the natriuretic peptide system in healthy murine and human submandibular salivary glands (SMGs). We show CNP is the dominant NP in mouse and human SMG and is expressed together with NP receptors in ducts, autonomic nerves and the microvasculature of the gland, suggesting CNP autocrine signalling may take place in some of these glandular structures. These data suggest the NP system may control salivary gland function during homeostasis through the regulation of electrolyte re-absorption, neural stimulation and/or blood vessel wall contraction/relaxation. We also show abnormal expression of NPRA in the stroma of a subset of human SMGs resected from patients diagnosed with oral squamous cell carcinoma (OSCC) of non-salivary gland origin. This finding warrants further research to investigate a possible correlation between early OSCC invasion and NPRA overexpression.

Connexin-43-dependent ATP release mediates macrophage activation during sepsis

Bacterial spillage into a sterile environment following intestinal hollow-organ perforation leads to peritonitis and fulminant sepsis. Outcome of sepsis critically depends on macrophage activation by extracellular ATP-release and associated autocrine signalling via purinergic receptors. ATP-release mechanisms, however, are poorly understood. Here, we show that TLR-2 and −4 agonists trigger ATP-release via Connexin-43 hemichannels in macrophages leading to poor sepsis survival. In humans, Connexin-43 was upregulated on macrophages isolated from the peritoneal cavity in patients with peritonitis but not in healthy controls. Using a murine peritonitis/sepsis model, we identified increased Connexin-43 expression in peritoneal and hepatic macrophages. Conditional Lyz2cre/creGja1flox/flox mice were developed to specifically assess Connexin-43 impact in macrophages. Both macrophage-specific Connexin-43 deletion and pharmacological Connexin-43 blockade were associated with reduced cytokine secretion by macrophages in response to LPS and CLP, ultimately resulting in increased survival. In conclusion, inhibition of autocrine Connexin-43-dependent ATP signalling on macrophages improves sepsis outcome.

71 The Effect of Two Different In Vitro Culture Media and Mice Embryo Groupings on Hatchability After 24 Hours of Culture

Mammalian blastocysts must hatch out from the zona pellucida before implantation. In vitro embryo culture and grouping of mice blastocysts are conducive options of assisted reproductive technologies (ART) to speed up the hatching rate of mice embryos. The number of embryos per unit volume has the greatest impact on hatching rates due to autocrine signalling. The study aimed to determine the effect of two in vitro culture (IVC) media (TCM-199 and Ham’s F10) and embryo groupings (1, 2, 3, and 4 embryos per 50-µL droplet) after 24 h of culture on hatching rate. Breeds of C57BL/6 (n = 10) and BALB/c (n = 10) were raised until they reached maturity and bred naturally to produce the first filial generation. The photoperiod was 14 h of light followed by 10 h of darkness in the breeding house, and feed and water were provided ad libitum. Female mice were superovulated using eCG and hCG. The first filial generations from 2 breeds were used for the collection of 160 blastocysts and randomly allocated into 2 IVC media (80 embryos for TCM-199 and 80 embryos for Ham’s F10) and again subjected to 4 embryo groupings (1, 2, 3, and 4 embryos per droplet) treatments. Four replicates were done per treatment group. The general linear model of Minitab version 17 (Minitab Inc., State College, PA, USA) was used to analyse the data. The hatching rate of blastocyst stage was significantly higher for TCM-199 (56.9 ± 27.2) compared with Ham’s F10 (50.0 ± 35.1%). The comparison of all embryo groupings, 1 (20.0 ± 40.5), 2 (28.8 ± 29.7), 3 (59.1 ± 38.8), and 4 (43.8 ± 32.4%) per 50-µL droplet showed significant differences, irrespective of IVC medium and breed. In TCM-199, groupings of 1 (20.0 ± 41.0), 2 (30.0 ± 29.9), 3 (63.3 ± 40.3), and 4 (42.5 ± 33.5%) had a significant difference on blastocyst hatching percent. In Ham’s F10, groupings of 1 (20.0 ± 41.0), 2 (27.5 ± 30.2), 3 (55.0 ± 37.9), and 4 (45.0 ± 32.0%) were significantly different on blastocyst hatching rate. However, an increase in hatching rate was observed for the interaction of media and embryo groupings and especially when embryos were increased per droplet in all breeds. In conclusion, the use of TCM-199 and grouping of 3 embryos per 50-µL droplet during culture had the highest hatching rate compared with the use of Ham’s F10.

Modelling of macrophage interactions by partial differential equations

The recruitment of macrophages at the tumor sites is the earliest immune response takes place during tumor progression. In breast cancer, experimental studies reveals that the tumor cells are capable of taking advantage on the plasticity of macrophages. Tumor cells respond to epidermal growth factor, EGF that released by macrophages while macrophages respond to colony stimulating factor 1, CSF-1 that released by tumor cells. This chains continues and results a paracrine signalling loop. Consequently, tumor cells and macrophages will aggregate and invade to other tissues or organ. Tumor cells also receive their own signals, adding a new feature of interaction called autocrine signalling loop. By considering in vitro interactions, a system of partial differential equations that incorporate the saturating functions for secretion terms was developed. This functions describes the production of chemical signals saturates with increasing cell density. Stability analysis are then performed to investigate the conditions for aggregation. For a given average of cells density, the homogeneous steady state is non-trivial and the concentration of CSF-1 and EGF are produced in the saturated production. Stability results show that regions for instability are reduced, compared to previous model which assumes the production rates are linear with increasing cell density. Besides, the inclusion of autocrine signalling loop increase the occurrence of aggregation. Decreasing the production rates and chemotaxis sensitivity, together with increasing the decay rates are required to impede the aggregation from initiated. This results should provide valuable clinical suggestions in guiding medical experts during drug designs.