Combined deletion of MEN1, ATRX and PTEN triggers development of high-grade pancreatic neuroendocrine tumors in mice.

Pancreatic neuroendocrine tumors (PanNETs) are a heterogeneous group of tumors that exhibit an unpredictable and broad spectrum of clinical presentations and biological aggressiveness. Surgical resection is still the only curative therapeutic option for localized PanNET, but the majority of patients are diagnosed at an advanced and metastatic stage with limited therapeutic options. Key factors limiting the development of new therapeutics are the extensive heterogeneity of PanNETs and the lack of appropriate clinically relevant models. In that context, genomic sequencing of human PanNETs revealed recurrent mutations and structural alterations in several tumor suppressors. Here, we demonstrated that combined loss of MEN1, ATRX, and PTEN, tumor suppressors commonly mutated in human PanNETs, triggers the development of high-grade pancreatic neuroendocrine tumors in mice. Histopathological evaluation and gene expression analyses of the developed tumors confirm the presence of PanNET hallmarks and significant overlap in gene expression patterns found in human disease. Thus, we postulate that the presented novel genetically defined mouse model is the first clinically relevant immunocompetent high-grade PanNET mouse model.

Cytoskeleton remodeling induced by SMYD2 methyltransferase drives breast cancer metastasis.

Malignant forms of breast cancer refractory to existing therapies remain a major unmet health issue, primarily due to metastatic spread. A better understanding of the mechanisms at play will provide better insights for alternative treatments to prevent breast cancer cell dispersion. Here, we identify the lysine methyltransferase SMYD2 as a clinically actionable master regulator of breast cancer metastasis. While SMYD2 is overexpressed in aggressive breast cancers, we notice that it is not required for primary tumor growth. However, mammary-epithelium specific SMYD2 ablation increases mouse overall survival by blocking the primary tumor cell ability to metastasize. Mechanistically, we identify BCAR3 as a genuine physiological substrate of SMYD2 in breast cancer cells. BCAR3 monomethylated at lysine K334 (K334me1) is recognized by a novel methyl-binding domain present in FMNLs proteins. These actin cytoskeleton regulators are recruited at the cell edges by the SMYD2 methylation signaling and modulate lamellipodia properties. Breast cancer cells with impaired BCAR3 methylation lose migration and invasiveness capacity in vitro and are ineffective in promoting metastases in vivo. Remarkably, SMYD2 pharmacologic inhibition efficiently impairs the metastatic spread of breast cancer cells, PDX and aggressive mammary tumors from genetically engineered mice. This study provides a rationale for innovative therapeutic prevention of malignant breast cancer metastatic progression by targeting the SMYD2-BCAR3-FMNL axis.

Cytoskeleton remodeling induced by SMYD2 methyltransferase drives breast cancer metastasis.

Malignant forms of breast cancer refractory to existing therapies remain a major unmet health issue, primarily due to metastatic spread. A better understanding of the mechanisms at play will provide better insights for alternative treatments to prevent breast cancer cells dispersion. Here, we identify the lysine methyltransferase SMYD2 as a clinically actionable master regulator of breast cancer metastasis. While SMYD2 is overexpressed in aggressive breast cancers, we notice that it is not required for primary tumor growth. However, mammary-epithelium specific SMYD2 ablation increases mouse overall survival by blocking the primary tumor cells ability to metastasize. Mechanistically, we identify BCAR3 as a genuine physiological substrate of SMYD2 in breast cancer cells. BCAR3 monomethylated at lysine K334 (K334me1) is recognized by a novel methyl-binding domain present in FMNLs proteins. These actin cytoskeleton regulators are recruited at the cell edges by the SMYD2 methylation signaling and modulates lamellipodia properties. Breast cancer cells with impaired BCAR3 methylation loose migration and invasiveness capacity in vitro and are ineffective in promoting metastases in vivo . Remarkably, SMYD2 pharmacologic inhibition efficiently impairs the metastatic spread of breast cancer cells, PDX and aggressive mammary tumors from genetically engineered mice. This study provides a rationale for innovative therapeutic prevention of malignant breast cancer metastatic progression by targeting the SMYD2-BCAR3-FMNL axis.

Multiplexed transcriptomic profiling of the fate of human CAR T cells in vivo via genetic barcoding with shielded small nucleotides.

The design of chimeric antigen receptor (CAR) T cells would benefit from knowledge of the fate of the cells in vivo. This requires the permanent labelling of CAR T cell products and their pooling in the same microenvironment. Here, we report a cell-barcoding method for the multiplexed longitudinal profiling of cells in vivo using single-cell RNA sequencing (scRNA-seq). The method, which we named shielded-small-nucleotide-based scRNA-seq (SSN-seq), is compatible with both 3' and 5' single-cell profiling, and enables the recording of cell identity, from cell infusion to isolation, by leveraging the ubiquitous Pol III U6 promoters to robustly express small-RNA barcodes modified with direct-capture sequences. By using SSN-seq to track the dynamics of the states of CAR T cells in a tumour-rechallenge mouse model of leukaemia, we found that a combination of cytokines and small-molecule inhibitors that are used in the ex vivo manufacturing of CAR T cells promotes the in vivo expansion of persistent populations of CD4+ memory T cells. By facilitating the probing of cell-state dynamics in vivo, SSN-seq may aid the development of adoptive cell therapies.

A differentiation roadmap of murine placentation at single-cell resolution.

The placenta is one of the most important yet least understood organs. Due to the limitations of conventional research approaches, we are still far from a comprehensive understanding of mouse placentation, especially regarding the differentiation of trophoblast lineages at the early developmental stage. To decipher cell compositions and developmental processes, we systematically profile the single-cell transcriptomes of trophoblast cells from extraembryonic tissues (embryonic day 7.5 (E7.5) and E8.5) and placentae (E9.5-E14.5) at one-day intervals. We identify distinct trophoblast cell types during mouse placentation, including unreported progenitor cells and intermediate precursor cells. An updated differentiation roadmap of mouse trophoblast lineages is presented following systematic transcriptome analyses. Based on transcriptomic regulatory network inference, we specify transcription factors responsible for the regulation of dynamic developmental processes during lineage diversification. We map lineage differentiation trajectories and find that sinusoid trophoblast giant cells arise from the subpopulation of ectoplacental cone cells. We provide a comprehensive single-cell data resource to shed light on future mechanistic studies of the gene regulatory networks governing hemochorial placentation.

Comprehensive molecular phenotyping of ARID1A-deficient gastric cancer reveals pervasive epigenomic reprogramming and therapeutic opportunities.

OBJECTIVE: Gastric cancer (GC) is a leading cause of cancer mortality, with ARID1A being the second most frequently mutated driver gene in GC. We sought to decipher ARID1A-specific GC regulatory networks and examine therapeutic vulnerabilities arising from ARID1A loss. DESIGN: Genomic profiling of GC patients including a Singapore cohort (>200 patients) was performed to derive mutational signatures of ARID1A inactivation across molecular subtypes. Single-cell transcriptomic profiles of ARID1A-mutated GCs were analysed to examine tumour microenvironmental changes arising from ARID1A loss. Genome-wide ARID1A binding and chromatin profiles (H3K27ac, H3K4me3, H3K4me1, ATAC-seq) were generated to identify gastric-specific epigenetic landscapes regulated by ARID1A. Distinct cancer hallmarks of ARID1A-mutated GCs were converged at the genomic, single-cell and epigenomic level, and targeted by pharmacological inhibition. RESULTS: We observed prevalent ARID1A inactivation across GC molecular subtypes, with distinct mutational signatures and linked to a NFKB-driven proinflammatory tumour microenvironment. ARID1A-depletion caused loss of H3K27ac activation signals at ARID1A-occupied distal enhancers, but unexpectedly gain of H3K27ac at ARID1A-occupied promoters in genes such as NFKB1 and NFKB2. Promoter activation in ARID1A-mutated GCs was associated with enhanced gene expression, increased BRD4 binding, and reduced HDAC1 and CTCF occupancy. Combined targeting of promoter activation and tumour inflammation via bromodomain and NFKB inhibitors confirmed therapeutic synergy specific to ARID1A-genomic status. CONCLUSION: Our results suggest a therapeutic strategy for ARID1A-mutated GCs targeting both tumour-intrinsic (BRD4-assocatiated promoter activation) and extrinsic (NFKB immunomodulation) cancer phenotypes.

Spinal Anesthesia Prior to Laparoscopic Hysterectomy Resulted in Decreased Postoperative Pain and Opioid Use.

Study Objective: To determine if a pre-operative morphine/bupivacaine spinal injection prior to laparoscopic hysterectomy reduced postoperative pain and resulted in less opioid consumption during the hospital stay. Methods: A retrospective cohort study (Canadian Task Force Classification II-2) was conducted at a single institution regional referral center (community hospital) in North Carolina. Three hundred nineteen patients met criteria for inclusion: 192 received spinal anesthesia and 127 did not. Baseline demographics were similar between the two groups. Median pain scores were significantly lower in the treatment than the control group on day of surgery (DOS) (2 vs. 6; P < 0.001) and postoperative day 1 (POD1) (2 vs. 4; P < 0.001). Results: Primary outcomes were pain scores on DOS and POD1 and inpatient opioid use. Pain scores were obtained using the 0 to 10 Numerical Rating Scale. Opioids were converted to oral morphine milliequivalents (OME). Median opioid use was also significantly lower in the treatment than the control group on DOS (0 vs. 15.00 OME; P < 0.001) and POD1 (0 vs. 7.5 OME; P < 0.001). Median length of stay between the groups was not significantly different. Conclusion: Pre-operative morphine spinal injection for laparoscopic hysterectomy led to significantly lower pain scores and inpatient opioid consumption. Pre-operative spinal anesthesia for benign laparoscopic hysterectomy appears helpful for enhancing the postoperative experience.

Elevated NSD3 histone methylation activity drives squamous cell lung cancer.

Amplification of chromosomal region 8p11-12 is a common genetic alteration that has been implicated in the aetiology of lung squamous cell carcinoma (LUSC)1-3. The FGFR1 gene is the main candidate driver of tumorigenesis within this region4. However, clinical trials evaluating FGFR1 inhibition as a targeted therapy have been unsuccessful5. Here we identify the histone H3 lysine 36 (H3K36) methyltransferase NSD3, the gene for which is located in the 8p11-12 amplicon, as a key regulator of LUSC tumorigenesis. In contrast to other 8p11-12 candidate LUSC drivers, increased expression of NSD3 correlated strongly with its gene amplification. Ablation of NSD3, but not of FGFR1, attenuated tumour growth and extended survival in a mouse model of LUSC. We identify an LUSC-associated variant NSD3(T1232A) that shows increased catalytic activity for dimethylation of H3K36 (H3K36me2) in vitro and in vivo. Structural dynamic analyses revealed that the T1232A substitution elicited localized mobility changes throughout the catalytic domain of NSD3 to relieve auto-inhibition and to increase accessibility of the H3 substrate. Expression of NSD3(T1232A) in vivo accelerated tumorigenesis and decreased overall survival in mouse models of LUSC. Pathological generation of H3K36me2 by NSD3(T1232A) reprograms the chromatin landscape to promote oncogenic gene expression signatures. Furthermore, NSD3, in a manner dependent on its catalytic activity, promoted transformation in human tracheobronchial cells and growth of xenografted human LUSC cell lines with amplification of 8p11-12. Depletion of NSD3 in patient-derived xenografts from primary LUSCs containing NSD3 amplification or the NSD3(T1232A)-encoding variant attenuated neoplastic growth in mice. Finally, NSD3-regulated LUSC-derived xenografts were hypersensitive to bromodomain inhibition. Thus, our work identifies NSD3 as a principal 8p11-12 amplicon-associated oncogenic driver in LUSC, and suggests that NSD3-dependency renders LUSC therapeutically vulnerable to bromodomain inhibition.

Tubulin detyrosination promotes human trophoblast syncytium formation.

Human trophoblast syncytialization is one of the most important yet least understood events during placental development. In this study, we found that detyrosinated α-tubulin (detyr-α-tub), which is negatively regulated by tubulin tyrosine ligase (TTL), was elevated during human placental cytotrophoblast fusion. Correspondingly, relatively high expression of TTL protein was observed in first-trimester human placental cytotrophoblast cells, but fusing trophoblast cells exhibited much lower levels of TTL. Notably, fusion of preeclamptic cytotrophoblast cells was compromised but could be partially rescued by knockdown of TTL levels. Mechanistically, chronic downregulation of TTL in trophoblast cells resulted in significantly elevated expression of detyr-α-tub. Restoration of detyr-α-tub thus contributed to the cell surface localization of the fusogenic protein Syncytin-2 and the gap junction protein Connexin 43 (Cx43), which in turn promoted successful fusion between trophoblast cells. Taken together, the results suggest that tubulin detyrosination plays an essential role in human trophoblast fusogenic protein aggregation and syncytialization. Insufficient tubulin detyrosination leads to defects in syncytialization and potentially to the onset of preeclampsia.

Zinc finger E-box-binding homeobox 1 (ZEB1) is required for neural differentiation of human embryonic stem cells.

Human pluripotent stem cells hold great promise for improving regenerative medicine. However, a risk for tumor formation and difficulties in generating large amounts of subtype derivatives remain the major obstacles for clinical applications of stem cells. Here, we discovered that zinc finger E-box-binding homeobox 1 (ZEB1) is highly expressed upon differentiation of human embryonic stem cells (hESCs) into neuronal precursors. CRISPR/Cas9-mediated ZEB1 depletion did not impede neural fate commitment, but prevented hESC-derived neural precursors from differentiating into neurons, indicating that ZEB1 is required for neuronal differentiation. ZEB1 overexpression not only expedited neural differentiation and neuronal maturation, which ensured safer neural cell transplantation, but also facilitated the generation of excitatory cortical neurons, which were valuable for managing certain neurological disorders, such as Parkinson's disease (PD) and amyotrophic lateral sclerosis (ALS). Our study provides useful information on how human neural cells are generated, which may help in forming strategies for developing and improving replacement therapies for treating patients with neurological diseases.

Single-cell RNA-seq reveals the diversity of trophoblast subtypes and patterns of differentiation in the human placenta.

The placenta is crucial for a successful pregnancy and the health of both the fetus and the pregnant woman. However, how the human trophoblast lineage is regulated, including the categorization of the placental cell subtypes is poorly understood. Here we performed single-cell RNA sequencing (RNA-seq) on sorted placental cells from first- and second-trimester human placentas. New subtypes of cells of the known cytotrophoblast cells (CTBs), extravillous trophoblast cells (EVTs), Hofbauer cells, and mesenchymal stromal cells were identified and cell-type-specific gene signatures were defined. Functionally, this study revealed many previously unknown functions of the human placenta. Notably, 102 polypeptide hormone genes were found to be expressed by various subtypes of placental cells, which suggests a complex and significant role of these hormones in regulating fetal growth and adaptations of maternal physiology to pregnancy. These results document human placental trophoblast differentiation at single-cell resolution and thus advance our understanding of human placentation during the early stage of pregnancy.

Fine-Tuned and Cell-Cycle-Restricted Expression of Fusogenic Protein Syncytin-2 Maintains Functional Placental Syncytia.

Many types of multinucleated cells (syncytia) generated by cell-cell fusion are post-mitotic, but it remains unclear how this state is maintained and why. Here, we utilized the fluorescent ubiquitination-based cell-cycle indicator (Fucci) reporter system to show that human placental trophoblast cells were all in the G0 phase before they fuse. Expression of the fusogenic protein (fusogen) Syncytin-2 was confined to G0 cells. Overexpression of Syncytin-2 in cycling cells overrode the cell-cycle restriction and enabled fusion of cells in the S/G2/M phases but resulted in the unstable syncytia retaining mitotic features. The Syncytin-2-induced syncytia were functionally compromised with respect to pathogen defense and hormone secretion. We found that, during trophoblast fusion, the cell-cycle inhibitor p21 interacted with the GCM1 transcription factor, and this complex bound to the promoter of Syncytin-2 and promoted its transcription. These findings demonstrate that G0-restricted Syncytin-2 expression is a prerequisite for development of functional post-mitotic syncytia.

The zinc finger E-box-binding homeobox 1 (Zeb1) promotes the conversion of mouse fibroblasts into functional neurons.

The zinc finger E-box-binding transcription factor Zeb1 plays a pivotal role in the epithelial-mesenchymal transition. Numerous studies have focused on the molecular mechanisms by which Zeb1 contributes to this process. However, the functions of Zeb1 beyond the epithelial-mesenchymal transition remain largely elusive. Using a transdifferentiation system to convert mouse embryonic fibroblasts (MEFs) into functional neurons via the neuronal transcription factors achaete-scute family bHLH (basic helix-loop-helix) transcription factor1 (Ascl1), POU class 3 homeobox 2 (POU3F2/Brn2), and neurogenin 2 (Neurog2, Ngn2) (ABN), we found that Zeb1 was up-regulated during the early stages of transdifferentiation. Knocking down Zeb1 dramatically attenuated the transdifferentiation efficiency, whereas Zeb1 overexpression obviously increased the efficiency of transdifferentiation from MEFs to neurons. Interestingly, Zeb1 improved the transdifferentiation efficiency induced by even a single transcription factor (e.g. Asc1 or Ngn2). Zeb1 also rapidly promoted the maturation of induced neuron cells to functional neurons and improved the formation of neuronal patterns and electrophysiological characteristics. Induced neuron cells could form functional synapse in vivo after transplantation. Genome-wide RNA arrays showed that Zeb1 overexpression up-regulated the expression of neuron-specific genes and down-regulated the expression of epithelial-specific genes during conversion. Taken together, our results reveal a new role for Zeb1 in the transdifferentiation of MEFs into neurons.

Deep RNA sequencing analysis of syncytialization-related genes during BeWo cell fusion.

The syncytiotrophoblast (STB) plays a key role in maintaining the function of the placenta during human pregnancy. However, the molecular network that orchestrates STB development remains elusive. The aim of this study was to obtain broad and deep insight into human STB formation via transcriptomics. We adopted RNA sequencing (RNA-Seq) to investigate genes and isoforms involved in forskolin (FSK)-induced fusion of BeWo cells. BeWo cells were treated with 50 µM FSK or dimethylsulfoxide (DMSO) as a vehicle control for 24 and 48 h, and the mRNAs at 0, 24 and 48 h was sequenced. We detected 28,633 expressed genes and identified 1,902 differentially expressed genes (DEGs) after FSK treatment for 24 and 48 h. Among the 1,902 DEGs, 461 were increased and 395 were decreased at 24 h, while 879 were up-regulated and 763 were down-regulated at 48 h. When the 856 DEGs identified at 24 h were traced individually at 48 h, they separated into 6 dynamic patterns via a K-means algorithm, and most were enriched in down-even and up-even patterns. Moreover, the Gene Ontology (GO) terms syncytium formation, cell junction assembly, cell fate commitment, calcium ion transport, regulation of epithelial cell differentiation and cell morphogenesis involved in differentiation were clustered, and the MAPK pathway was most significantly regulated. Analyses of alternative splicing isoforms detected 123,200 isoforms, of which 1,376 were differentially expressed. The present deep analysis of the RNA-Seq data of BeWo cell fusion provides important clues for understanding the mechanisms underlying human STB formation.

Twist1 is involved in trophoblast syncytialization by regulating GCM1.

INTRODUCTION: The multinucleated syncytiotrophoblast (STB) is maintained and regenerated by the fusion of underlying cytotrophoblast cells (CTBs) and is responsible for a number of functions in the human placenta. Deficiencies in this structure may result in pregnancy-associated diseases. However, the detailed mechanisms underlying trophoblast syncytialization await further investigation. METHODS: The location of the transcription factor Twist1 in human placental tissues was identified by immunohistochemistry. The expression of Twist1 and glial cells missing-1 (GCM1) was evaluated by qPCR or western blotting in two cell-fusion models including forskolin-induced fusion of BeWo cells and spontaneous syncytialization of CTBs. The key role of Twist1 in trophoblast differentiation was identified using BeWo cells transfected with Twist1-specific siRNA. We investigated the effect of hypoxia on the expression of Twist1 and GCM1 in primary CTBs cultured with 2% oxygen. The Twist1 binding region in the GCM1 gene was detected by chromatin-immunoprecipitation. RESULTS: Twist1 was expressed in human placental tissues, and the expression of Twist1 and GCM1 increased in a time-dependent manner during spontaneous syncytialization of primary CTBs and forskolin-induced fusion of BeWo cells. A reduction in Twist1 and GCM1 expression was observed under hypoxic conditions and was accompanied by inhibition of trophoblast syncytialization. Moreover, siRNA-mediated silencing of Twist1 resulted in inhibition of BeWo cells fusion and down-regulation of GCM1 expression. Furthermore, Twist1 was found to bind to the E-box-enriched region in intron 2 of the GCM1 gene during forskolin-induced fusion of BeWo cells. DISCUSSION: The above results suggest that Twist1 is required during trophoblast syncytialization. Twist1 may promote trophoblast syncytialization by regulating the expression of GCM1.

Effects of individually silenced N-glycosylation sites and non-synonymous single-nucleotide polymorphisms on the fusogenic function of human syncytin-2.

The placental syncytiotrophoblast, which is formed by the fusion of cytotrophoblast cells, is indispensable for the establishment and maintenance of normal pregnancy. The human endogenous retrovirus envelope glycoprotein syncytin-2 is the most important player in mediating trophoblast cell-cell fusion as a fusogen. We constructed expression plasmids of wild-type and 21 single-amino-acid substitution mutants of syncytin-2, including 10 N-glycosylation sites individually silenced by mutagenizing N to Q, 1 naturally occurring single-nucleotide polymorphism (SNP) N118S that introduced an N-glycosylation site, and another 10 non-synonymous SNPs located within important functional domains. We observed that syncytin-2 was highly fusogenic and that the mutants had different capacities in merging 293T cells. Of the 21 mutants, N133Q, N312Q, N443Q, C46R (in the CXXC motif) and R417H (in the heptad repeat region and immunosuppressive domain) lost their fusogenicity, whereas N332Q, N118S, T367M (in the fusion peptide), V483I (in the transmembrane domain) and T522M (in the cytoplasmic domain) enhanced the fusogenic activity. We also proved that N133, N146, N177, N220, N241, N247, N312, N332 and N443 were all glycosylated in 293T cells. A co-immunoprecipitation assay showed compromised interaction between mutants N443Q, C46R, T367M, R417H and the receptor MFSD2A, whereas N118S was associated with more receptors. We also sequenced the coding sequence of syncytin-2 in 125 severe pre-eclamptic patients and 272 normal pregnant Chinese women. Surprisingly, only 1 non-synonymous SNP T522M was found and the frequencies of heterozygous carriers were not significantly different. Taken together, our results suggest that N-glycans at residues 133, 312, 332 and 443 of syncytin-2 are required for optimal fusion induction, and that SNPs C46R, N118S, T367M, R417H, V483I and T522M can alter the fusogenic function of syncytin-2.