Embryonic Pathways Research Articles

Bisphenol A induces apoptosis in response to DNA damage through c-Abl/YAPY357/ p73 pathway in P19 embryonal carcinoma stem cells

Bisphenol A (2,2-bis(4′-hydroxyphenyl) propane, BPA) is a well-known endocrine-disrupting compound that is widely used in various daily products and exhibits embryonic development toxicity and genotoxicity. However, the affected signaling pathways involved in embryonic development especially the interactions of involved proteins remain unclear. In our previous study (Ge et al., 2021), BPA induces DNA damage and apoptosis in Xenopus embryos, resulting in multiple malformations of larvae. However, the signaling pathways induced for apoptosis response to DNA damage are still not well elucidated. Here, we systematically elucidated the enriched pathways affected by BPA and illustrated the interactions of involved proteins. Results indicated that BPA affected multiple embryonic development pathways including Hippo, TGF-β, Wnt, and Notch pathways. Furthermore, the protein-protein interaction network suggested that the c-Abl/YAPY357/p73 pathway may play a key role in apoptosis induction in response to DNA damage. P19 embryonal carcinoma stem cells, as a developmental toxicity model, were treated with different BPA concentrations to establish an in vitro model to verify the role of the c-Abl/YAPY357/p73 pathway in apoptosis. BPA triggered DNA damage and significantly upregulated the expression levels of c-Abl, phosphorylated YAPY357, phosphorylated p73Y99, and cleaved caspase-3 protein (p < 0.05), thus decreasing cell viability and transcriptionally activating the p73 target genes Bax and Puma. These data suggested that BPA activated the c-Abl/YAPY357/p73 pathway in response to DNA damage. Imatinib, an inhibitor of tyrosine kinase c-Abl, significantly downregulated the elevated expression levels of p-YAPY357, p-p73Y99 and cleaved caspase-3 (p < 0.05) caused by BPA and then ameliorated the cell index of P19 cells in the BPA-treated group. Therefore, this substance restrained the phosphokinase activity of c-Abl and suppressed the c-Abl/YAPY357/p73 pathway. Results showed that the c-Abl/YAPY357/p73 pathway served as a mechanism for caspase-3 activation that induced the apoptosis response to DNA damage stress.

The role of the WNT signaling pathway in the maxillary sinus squamous cell carcinoma.

Paranasal sinus tumors are a rare type of cancer. Most of these tumors are of epithelial origin and 80% of them are maxillary sinus squamous cell carcinoma. The WNT signaling pathway is an essential embryonic regulatory pathway known to play an important role in many cancers, including head and neck cancers. However, the effect of this pathway in maxillary sinus tumors has not been studied before. The aim of the study was to determine the changes in the regulatory genes of the WNT signaling pathway in maxillary sinus tumors. For this purpose, total RNA was isolated from the pathological preparations of 85 patients who had previously been operated on for squamous cell maxillary sinus tumor, and gene expression changes were evaluated by real-time RT-qPCR. The interactions among proteins encoded by genes, whose expression levels were found to be decreased and increased, were determined by protein-protein interaction (PPI) network analysis using string database, and signaling pathways that they are involved in were examined by Reactome database. A significant decrease in the expression of 28 genes compared to the control (fold change < 2.00 and p-value < 0.05) and a significant increase in the expression of 23 genes (fold change < 2.00 and p-value < 0.05) were detected. According to in silico analysis results, Signal Transduction (REACTOME:R-HSA-162582) and Signaling by WNT (REACTOME:R-HSA-195721) pathways were determined as most regulated pathways and FZD4-LRP5 and BCL9-CTNNB1 were determined as the strongest interactions. The current study contributes to illuminating the genetic regulation of maxillary sinus carcinoma in which genetic knowledge is limited. Our findings take attention to the dysregulations of the WNT signaling pathway that may support maxillary sinus carcinogenesis. The results will pave the way for further studies that investigate the therapy target potential of the WNT signaling pathway in this rare cancer.

Regeneration of the larval sea star nervous system by wounding induced respecification to the Sox2 lineage.

The ability to restore lost body parts following traumatic injury is a fascinating area of biology that challenges current understanding of the ontogeny of differentiation. The origin of new cells needed to regenerate lost tissue, and whether they are pluripotent or have de- or trans-differentiated, remains one of the most important open questions . Additionally, it is not known whether developmental gene regulatory networks are reused or whether regeneration specific networks are deployed. Echinoderms, including sea stars, have extensive ability for regeneration, however, the technologies for obtaining transgenic echinoderms are limited and tracking cells involved in regeneration, and thus identifying the cellular sources and potencies has proven challenging. In this study, we develop new transgenic tools to follow the fate of populations of cells in the regenerating larva of the sea star Patiria miniata. We show that the larval serotonergic nervous system can regenerate following decapitation. Using a BAC-transgenesis approach we show that expression of the pan ectodermal marker, sox2, is induced in previously sox2 minus cells , even when cell division is inhibited. sox2+ cells give rise to new sox4+ neural precursors that then proceed along an embryonic neurogenesis pathway to reform the anterior nervous systems. sox2+ cells contribute to only neural and ectoderm lineages, indicating that these progenitors maintain their normal, embryonic lineage restriction. This indicates that sea star larval regeneration uses a combination of existing lineage restricted stem cells, as well as respecification of cells into neural lineages, and at least partial reuse of developmental GRNs to regenerate their nervous system.

Epithelial-endothelial transition and endothelial-mesenchymal transition.

The movement of continuous sheets of epithelial cells occurs during embryonic development, tissue repair, and cancer. Common to cellular and molecular principles of collective cell migration, invading cancers seem to reactivate embryonic pathways and patterns of cell movement. Epithelial cells possess the capability to become mesenchymal cells in a process called epithelial mesenchymal transition (EMT), which has been extensively studied and described. The aim of this article is to summarize the most recent literature data concerning less known epithelial-endothelial transition and endothelial-mesenchymal transition.

Physiological Functions of Thiol Peroxidases (Gpx1 and Prdx2) during Xenopus laevis Embryonic Development.

Glutathione peroxidase 1 (Gpx1) and peroxiredoxin 2 (Prdx2) belong to the thiol peroxidase family of antioxidants, and have been studied for their antioxidant functions and roles in cancers. However, the physiological significance of Gpx1 and Prdx2 during vertebrate embryogenesis are lacking. Currently, we investigated the functional roles of Gpx1 and Prdx2 during vertebrate embryogenesis using Xenopus laevis as a vertebrate model. Our investigations revealed the zygotic nature of gpx1 having its localization in the eye region of developing embryos, whereas prdx2 exhibited a maternal nature and were localized in embryonic ventral blood islands. Furthermore, the gpx1-morphants exhibited malformed eyes with incompletely detached lenses. However, the depletion of prdx2 has not established its involvement with embryogenesis. A molecular analysis of gpx1-depleted embryos revealed the perturbed expression of a cryba1-lens-specific marker and also exhibited reactive oxygen species (ROS) accumulation in the eye regions of gpx1-morphants. Additionally, transcriptomics analysis of gpx1-knockout embryos demonstrated the involvement of Wnt, cadherin, and integrin signaling pathways in the development of malformed eyes. Conclusively, our findings indicate the association of gpx1 with a complex network of embryonic developmental pathways and ROS responses, but detailed investigation is a prerequisite in order to pinpoint the mechanistic details of these interactions.

Expression of the Sonic Hedgehog Embryonic Signalling Pathway Components in Matched Pre-Treatment and Relapsed Small Cell Lung Cancer Biopsies

Abstract Cancer stem cells may be responsible for tumour regrowth and acquisition of resistance in small cell lung cancer (SCLC). The Hedgehog pathway regulates survival and proliferation of tissue progenitor and stem cell populations, promoting the expression of stem cell related and proliferative genes. We evaluated the Sonic Hedgehog (Shh) embryonic signalling pathway in relapsed SCLC. Expression levels of Shh related genes GLI1, SMO, SUFU, PTCH1, HHIP, BCL2, BMI, ZEB1, ZEB2, N-MYC, Twist1 were analysed by qRT-PCR in matched pre-treatment and relapsed tumour fresh frozen biopsies of three SCLC patients. Expression of each gene was compared using the paired samples t-test, as well as comparison of mean expression levels was done. Data were statistically interpreted using the MedCalc version 10.2.0.0 software. 2.9-fold lower mean mRNA expression of the major Hedgehog activation indicator GLI1 was observed in relapsed samples (p = 0.0529). Mean expression of six Shh inducible genes, PTCH1, HHIP, N-MYC, ZEB2, Twist1, ZEB1, was also downregulated by 2.6-, 2.2-, 1.9-, 1.8-, 1.2-, 1.1-fold, respectively (p = 0.4252, p = 0.1268, p = 0.2480, p = 0.1169, p = 0.1480, p = 0.7595, respectively). 1.8-fold mean expression decrease was found for Gli activator Smo (p = 0.4111). Only the Shh pathway inhibitor SUFU and two other examined Hedgehog signalling inducible genes BCL2 and BMI in relapsed SCLC showed 0.8-, 0.9-,and 0.8-fold increase of expression, respectively (p = 0.3074, p = 0.7921, and p = 0.3822, respectively). To our knowledge, this is the first report of comparison of Shh signalling in matched pre-treatment and relapsed SCLC biopsies. Our data show decreased activity for majority of Shh pathway components in relapsed SCLC, although difference did not reach statistical significance.

Novel Classification System and Surgical Algorithm for Facial Congenital Melanocytic Nevi

Background Congenital melanocytic nevus (CMN) is characterized by pigmented skin patches. Large CMN affects 1 in 20,000 newborns globally and runs the risk of melanoma transformation. A classification system for CMN patterns has been previously established for the trunk and extremities. However, there is no classification system for facial CMN to date. This study proposes a facial CMN classification scheme that can help guide management decisions. Methods Facial CMN images were retrieved from public repositories. The outline of the facial CMNs were extracted and transposed onto a standardized 3D model. To identify distinct patterns, the CMN images of anatomic sub-regions of the face were clustered and heat-maps were generated. The clinical features of the CMNs were standardized based on previously published criteria. Results The study identified 291 images of facial CMNs. The CMNs could be categorized into seven distinct patterns based on anatomic distribution. Each CMN could be further characterized according to estimated size category, color heterogeneity, rugosity, nodularity, and degree of hypertrichosis. Discussion The study proposes a novel classification scheme for facial CMN to characterize the variability in the anatomic distribution. Researchers further aim to test the validity of their scheme on a CMN image dataset from collaborating institutions. Conclusion A better understanding of the patterns of facial CMNs can glean insights into the embryonic pathways of melanocytic migration on the face. Grouping of facial CMNs by patterns may guide the development of treatment strategies to best preserve the esthetics and functionality of a child's face. Congenital melanocytic nevus (CMN) is characterized by pigmented skin patches. Large CMN affects 1 in 20,000 newborns globally and runs the risk of melanoma transformation. A classification system for CMN patterns has been previously established for the trunk and extremities. However, there is no classification system for facial CMN to date. This study proposes a facial CMN classification scheme that can help guide management decisions. Facial CMN images were retrieved from public repositories. The outline of the facial CMNs were extracted and transposed onto a standardized 3D model. To identify distinct patterns, the CMN images of anatomic sub-regions of the face were clustered and heat-maps were generated. The clinical features of the CMNs were standardized based on previously published criteria. The study identified 291 images of facial CMNs. The CMNs could be categorized into seven distinct patterns based on anatomic distribution. Each CMN could be further characterized according to estimated size category, color heterogeneity, rugosity, nodularity, and degree of hypertrichosis. The study proposes a novel classification scheme for facial CMN to characterize the variability in the anatomic distribution. Researchers further aim to test the validity of their scheme on a CMN image dataset from collaborating institutions. A better understanding of the patterns of facial CMNs can glean insights into the embryonic pathways of melanocytic migration on the face. Grouping of facial CMNs by patterns may guide the development of treatment strategies to best preserve the esthetics and functionality of a child's face.

Independent parental contributions initiate zygote polarization in Arabidopsis thaliana

Embryogenesis of flowering plants is initiated by polarization of the zygote, a prerequisite for correct axis formation in the embryo. The daughter cells of the asymmetric zygote division form the pro-embryo and the mostly extra-embryonic suspensor.1 The suspensor plays a pivotal role in nutrient and hormone transport and rapid growth of the embryo.2,3 Zygote polarization is controlled by a MITOGEN-ACTIVATING PROTEIN (MAP) kinase signaling pathway including the MAPKK kinase (MAP3K) YODA (YDA)4 and the upstream membrane-associated proteins BRASINOSTEROID SIGNALING KINASE 1 (BSK1) and BSK2.5,6 Furthermore, suspensor development is controlled by cysteine-rich peptides of the EMBRYO SURROUNDING FACTOR 1 (ESF1) family.7 While they act genetically upstream of YDA, the corresponding receptor to perceive these potential ligands is unknown. In other developmental processes, such as stomata development, YDA activity is controlled by receptor kinases of the ERECTA family (ERf).8-12 While the receptor kinases upstream of BSK1/2 in the embryo have so far not been identified,1 YDA is in part activated by the sperm cell-derived BSK family member SHORT SUSPENSOR (SSP) that represents a naturally occurring, constitutively active variant of BSK1.5,13 It has been speculated that SSP might be a paternal component of a parental tug-of-war controlling resource allocation toward the embryo.2,13 Here, we show that in addition to SSP, the receptor kinase ERECTA plays a crucial role in zygote polarization as a maternally contributed part of the embryonic YDA pathway. We conclude that two independent parental contributions initiate zygote polarization and control embryo development.

Intrauterine Growth Restriction Causes Abnormal Embryonic Dentate Gyrus Neurogenesis in Mouse Offspring That Leads to Adult Learning and Memory Deficits.

Human infants who suffer from intrauterine growth restriction (IUGR), which is a failure to attain their genetically predetermined weight, are at increased risk for postnatal learning and memory deficits. Hippocampal dentate gyrus (DG) granule neurons play an important role in memory formation; however, it is unknown whether IUGR affects embryonic DG neurogenesis, which could provide a potential mechanism underlying abnormal postnatal learning and memory function. Using a mouse model of the most common cause of IUGR, induced by hypertensive disease of pregnancy, we first assessed adult learning and memory function. We quantified the percentages of embryonic hippocampal DG neural stem cells (NSCs) and progenitor cells and developing glutamatergic granule neurons, as well as hippocampal volumes and neuron cell count and morphology 18 and 40 d after delivery. We characterized the differential embryonic hippocampal transcriptomic pathways between appropriately grown and IUGR mouse offspring. We found that IUGR offspring of both sexes had short-term adult learning and memory deficits. Prenatally, we found that IUGR caused accelerated embryonic DG neurogenesis and Sox2+ neural stem cell depletion. IUGR mice were marked by decreased hippocampal volumes and decreased doublecortin+ neuronal progenitors with increased mean dendritic lengths at postnatal day 18. Consistent with its known molecular role in embryonic DG neurogenesis, we also found evidence for decreased Wnt pathway activity during IUGR. In conclusion, we have discovered that postnatal memory deficits are associated with accelerated NSC differentiation and maturation into glutamatergic granule neurons following IUGR, a phenotype that could be explained by decreased embryonic Wnt signaling.

CLL-348: STAT3 Induces the Expression of GLI1 in Chronic Lymphocytic Leukemia Cells

The glioma associated oncogene-1 (GLI1), a downstream effector of the embryonic Hedgehog pathway, was detected in chronic lymphocytic leukemia (CLL), but not normal adult cells. GLI1-activating mutations were identified in 10% of patients with CLL. However, what induces GLI1 expression in GLI1-unmutated CLL cells is unknown. Because signal transducer and activator of transcription 3 (STAT3) is constitutively activated in CLL cells, and sequence analysis detected putative STAT3-binding sites in the GLI1 gene promoter, we hypothesized that STAT3 induces the expression of GLI1. Western immunoblotting detected GLI1 in CLL cells from 7 of 7 patients, flow cytometry analysis confirmed that CD19+/CD5+ CLL cells co-express GLI1, and confocal microscopy showed co-localization of GLI1 and phosphorylated STAT3. Chromatin immunoprecipitation showed that STAT3 protein co-immunoprecipitated GLI1, as well as other STAT3-regulated genes. Transfection of CLL cells with STAT3-shRNA induced a mark decrease in GLI1 levels, suggesting that STAT3 binds to and induces the expression of GLI1 in CLL cells. An electromobility shift assay confirmed that STAT3 binds, and a luciferase assay showed that STAT3 activates the GLI1 gene. Transfection with GLI1-siRNA significantly increased the spontaneous apoptosis rate of CLL cells, suggesting that GLI1 inhibitors might provide therapeutic benefit to patients with CLL.

MPN-383: GLI1 Promotes the Pro-Fibrotic Function of Monocyte-Derived Fibrocytes in Myelofibrosis

Primary myelofibrosis (MF), post-polycythemia vera (PV) MF, and post-essential thrombocytosis MF are myeloproliferative neoplasms (MPNs) characterized by progressive bone marrow (BM) fibrosis. A recent study suggested that glioma-associated oncogene-1 (GLI1), a downstream effector of the embryonic Hedgehog pathway, is implicated in the pathogenesis of BM fibrosis in MF. Because we and other investigators have found that monocyte-derived fibrocytes, rather than mesenchymal stromal cells (MSCs), induce BM fibrosis in MF, we sought to determine the role of GLI1 in MF fibrocytes. To do this, we analyzed BM biopsy sections of patients with MF using multiplex fluorescence immunohistochemistry and detected high levels of GLI1 in CD45+/CD68+/procollagen I+ fibrocytes and low levels of GLI1 in CD90+/CD105+ MSCs (<i>P</i>=0.009 and <i>P</i>=0.002, respectively). Using immunostaining, RNA <i>in situ</i> hybridization, gene expression, and western immunoblotting analyses of cultured BM fibrocytes or MSCs, we observed significantly higher levels of GLI1 and GLI1-induced matrix metalloproteases (MMP) 2 and 9 in MF fibrocytes than in MF MSCs or normal BM-derived fibrocytes (<i>P</i><0.05 each). Next, by transplanting human MF BM cells into NSG mice, we found that the engrafted cells differentiated into GLI1-expressing cells that induced BM fibrosis. Inhibition of GLI using non-specific GLI antagonist 61 (GANT61) decreased the formation of both MF fibrocytes and normal fibrocytes (<i>P</i><0.05). However, GLI1 silencing using small interfering RNA specifically induced apoptosis of MF fibrocytes and fibrocyte-forming cells (<i>P</i>=0.008 and <i>P</i><0.001, respectively) and increased fragmentation of MF fibrocyte DNA. In addition, GLI1 knockdown reduced MMP2, MMP9, SMAD2/3, and procollagen I gene expression (<i>P</i><0.05) and protein levels. Finally, because we recently found that GLI1 expression in leukemic cells is induced by constitutively activated signal transducer and activator of transcription 3 (STAT3), we performed chromatin immunoprecipitation, luciferase, and STAT3-silencing assays on MF fibrocytes and found that STAT3 binds and activates GLI1 gene promoter in these cells. In conclusion, GLI1, triggered by constitutively activated STAT3, activates pro-fibrotic signaling pathways in MF fibrocytes. Downregulation of GLI1 hampers fibrocyte survival and function, suggesting that GLI1 inhibition might alleviate BM fibrosis in patients with MF.

Transcriptome Analysis Identifies Doublesex and Mab-3 Related Transcription Factor (DMRT3) in Nasal Polyp Epithelial Cells of Patients Suffering from Non-Steroidal Anti-Inflammatory Drug-Exacerbated Respiratory Disease (AERD).

Background: Aspirin-exacerbated respiratory disease (AERD) is a syndrome characterised by chronic rhinosinusitis, nasal polyps, asthma and aspirin intolerance. An imbalance of eicosanoid metabolism with anover-production of cysteinyl leukotrienes (CysLTs) has been associated with AERD. However, the precise mechanisms underlying AERD are unknown. Objective: To establish the transcriptome of the nasal polyp airway epithelial cells derived from AERD patients to discover gene expression patterns in this disease. Methods: Nasal airway epithelial cells were isolated from 12 AERD polyps and 8 AERD non-polyp nasal mucosa samples as controls from the same subjects. Utilising the Illumina HiSeq 2500 platform, RNA samples were sequenced. Potential gene candidate DMRT3 was selected from the differentially-expressed genes for validation. Results: Comparative transcriptome profiling of nasal epithelial cells was accomplished in AERD. A total of 20 genes had twofold mean regulation expression differences or greater. In addition, 8 genes were upregulated, including doublesex and mab-3 related transcription factor 3 (DMRT3), and 12 genes were downregulated. Differentially regulated genes comprised roles in inflammation, defence and immunity. Metabolic process and embryonic development pathways were significantly enriched. Enzyme-linked immune sorbent assay (ELISA) results of DMRT3 in AERD patients were significantly upregulated compared to controls (p = 0.03). Immunohistochemistry (IHC) of AERD nasal polyps localised DMRT3 and was predominantly released in the airway epithelia. Conclusion: Findings suggest that DMRT3 could be potentially involved in nasal polyp development in AERD patients. Furthermore, several genes are downregulated, hinting at the dedifferentiation phenomenon in AERD polyps. However, further studies are imperative to confirm the exact mechanism of polyp formation in AERD patients.

ETV4 and ETV5 drive synovial sarcoma through cell cycle and DUX4 embryonic pathway control

Synovial sarcoma is an aggressive malignancy with no effective treatments for patients with metastasis. The synovial sarcoma fusion SS18-SSX, which recruits the SWI/SNF-BAF chromatin remodeling and polycomb repressive complexes, results in epigenetic activation of FGF receptor (FGFR) signaling. In genetic FGFR-knockout models, culture, and xenograft synovial sarcoma models treated with the FGFR inhibitor BGJ398, we show that FGFR1, FGFR2, and FGFR3 were crucial for tumor growth. Transcriptome analyses of BGJ398-treated cells and histological and expression analyses of mouse and human synovial sarcoma tumors revealed prevalent expression of two ETS factors and FGFR targets, ETV4 and ETV5. We further demonstrate that ETV4 and ETV5 acted as drivers of synovial sarcoma growth, most likely through control of the cell cycle. Upon ETV4 and ETV5 knockdown, we observed a striking upregulation of DUX4 and its transcriptional targets that activate the zygotic genome and drive the atrophy program in facioscapulohumeral dystrophy patients. In addition to demonstrating the importance of inhibiting all three FGFRs, the current findings reveal potential nodes of attack for the cancer with the discovery of ETV4 and ETV5 as appropriate biomarkers and molecular targets, and activation of the embryonic DUX4 pathway as a promising approach to block synovial sarcoma tumors.

Misregulation of Drosophila Sidestep Leads to Uncontrolled Wiring of the Adult Neuromuscular System and Severe Locomotion Defects.

Holometabolic organisms undergo extensive remodelling of their neuromuscular system during metamorphosis. Relatively, little is known whether or not the embryonic guidance of molecules and axonal growth mechanisms are re-activated for the innervation of a very different set of adult muscles. Here, we show that the axonal attractant Sidestep (Side) is re-expressed during Drosophila metamorphosis and is indispensable for neuromuscular wiring. Mutations in side cause severe innervation defects in all legs. Neuromuscular junctions (NMJs) show a reduced density or are completely absent at multi-fibre muscles. Misinnervation strongly impedes, but does not completely abolish motor behaviours, including walking, flying, or grooming. Overexpression of Side in developing muscles induces similar innervation defects; for example, at indirect flight muscles, it causes flightlessness. Since muscle-specific overexpression of Side is unlikely to affect the central circuits, the resulting phenotypes seem to correlate with faulty muscle wiring. We further show that mutations in beaten path Ia (beat), a receptor for Side, results in similar weaker adult innervation and locomotion phenotypes, indicating that embryonic guidance pathways seem to be reactivated during metamorphosis.

Somatic mutations and single-cell transcriptomes reveal the root of malignant rhabdoid tumours

Malignant rhabdoid tumour (MRT) is an often lethal childhood cancer that, like many paediatric tumours, is thought to arise from aberrant fetal development. The embryonic root and differentiation pathways underpinning MRT are not firmly established. Here, we study the origin of MRT by combining phylogenetic analyses and single-cell mRNA studies in patient-derived organoids. Comparison of somatic mutations shared between cancer and surrounding normal tissues places MRT in a lineage with neural crest-derived Schwann cells. Single-cell mRNA readouts of MRT differentiation, which we examine by reverting the genetic driver mutation underpinning MRT, SMARCB1 loss, suggest that cells are blocked en route to differentiating into mesenchyme. Quantitative transcriptional predictions indicate that combined HDAC and mTOR inhibition mimic MRT differentiation, which we confirm experimentally. Our study defines the developmental block of MRT and reveals potential differentiation therapies.

STAT3 induces the expression of GLI1 in chronic lymphocytic leukemia cells

The glioma associated oncogene-1 (GLI1), a downstream effector of the embryonic Hedgehog pathway, was detected in chronic lymphocytic leukemia (CLL), but not normal adult cells. GLI1 activating mutations were identified in 10% of patients with CLL. However, what induces GLI1 expression in GLI1-unmutated CLL cells is unknown. Because signal transducer and activator of transcription 3 (STAT3) is constitutively activated in CLL cells and sequence analysis detected putative STAT3-binding sites in the GLI1 gene promoter, we hypothesized that STAT3 induces the expression of GLI1. Western immunoblotting detected GLI1 in CLL cells from 7 of 7 patients, flow cytometry analysis confirmed that CD19+/CD5+ CLL cells co-express GLI1 and confocal microscopy showed co-localization of GLI1 and phosphorylated STAT3. Chromatin immunoprecipitation showed that STAT3 protein co-immunoprecipitated GLI1 as well as other STAT3-regulated genes. Transfection of CLL cells with STAT3-shRNA induced a mark decrease in GLI1 levels, suggesting that STAT3 binds to and induces the expression of GLI1 in CLL cells. An electromobility shift assay confirmed that STAT3 binds, and a luciferase assay showed that STAT3 activates the GLI1 gene. Transfection with GLI1-siRNA significantly increased the spontaneous apoptosis rate of CLL cells, suggesting that GLI1 inhibitors might provide therapeutic benefit to patients with CLL.

Linkage-specific deubiquitylation by OTUD5 defines an embryonic pathway intolerant to genomic variation.

Reversible modification of proteins with linkage-specific ubiquitin chains is critical for intracellular signaling. Information on physiological roles and underlying mechanisms of particular ubiquitin linkages during human development are limited. Here, relying on genomic constraint scores, we identify 10 patients with multiple congenital anomalies caused by hemizygous variants in OTUD5, encoding a K48/K63 linkage-specific deubiquitylase. By studying these mutations, we find that OTUD5 controls neuroectodermal differentiation through cleaving K48-linked ubiquitin chains to counteract degradation of select chromatin regulators (e.g., ARID1A/B, histone deacetylase 2, and HCF1), mutations of which underlie diseases that exhibit phenotypic overlap with OTUD5 patients. Loss of OTUD5 during differentiation leads to less accessible chromatin at neuroectodermal enhancers and aberrant gene expression. Our study describes a previously unidentified disorder we name LINKED (LINKage-specific deubiquitylation deficiency-induced Embryonic Defects) syndrome and reveals linkage-specific ubiquitin cleavage from chromatin remodelers as an essential signaling mode that coordinates chromatin remodeling during embryogenesis.

Differential Expression Profiling Reveals Stress-Induced Cell Fate Divergence in Soybean Microspores.

Stress-induced microspore embryogenesis is a widely employed method to achieve homozygosity in plant breeding programs. However, the molecular mechanisms that govern gametophyte de- and redifferentiation are understood poorly. In this study, RNA-Seq was used to evaluate global changes across the microspore transcriptome of soybean (Glycine max [L.] Merrill) as a consequence of pretreatment low-temperature stress. Expression analysis revealed more than 20,000 differentially expressed genes between treated and control microspore populations. Functional enrichment illustrated that many of these genes (e.g., those encoding heat shock proteins and cytochrome P450s) were upregulated to maintain cellular homeostasis through the mitigation of oxidative damage. Moreover, transcripts corresponding to saccharide metabolism, vacuolar transport, and other pollen-related developmental processes were drastically downregulated among treated microspores. Temperature stress also triggered cell wall modification and cell proliferation—characteristics that implied putative commitment to an embryonic pathway. These findings collectively demonstrate that pretreatment cold stress induces soybean microspore reprogramming through suppression of the gametophytic program while concomitantly driving sporophytic development.

A high glucose concentration during early stages of in vitro equine embryo development alters expression of genes involved in glucose metabolism.

Equineembryos exhibit an unusual pattern of glucose tolerance in vitro and are currently cultured in hyperglycaemic conditions. Our main objective was to analyse the effect of different glucose concentrations on in vitro-produced equine embryo development and quality. Experiments comparing in vitro and in vivo produced embryos. Oocytes (n=641) were collected from post-mortem ovaries, matured in vitro and fertilised by intracytoplasmic sperm injection (ICSI). Embryo culture was divided from Day 0 to Day 4 and from Day 4 to Day 9 in three groups: 5-10 (5 and 10mmol/L glucose respectively; n=87); 5-17 (5 and 17.5mmol/L; n=66); and 10-17 (10 and 17.5mmol/L; n=117). A control group of 20 in vivo produced blastocysts was included. Cleavage and blastocyst rates were evaluated and embryos were snap-frozen for analysis of the relative mRNA expression of genes related to mitochondrial function, DNA methylation, apoptosis, glucose transport and metabolism. No differences were observed in the cleavage or blastocyst rates among in vitro groups. Under high glucose conditions in vitro (10-17 group), BAX/BCL2 was higher, and PFKP, LDHA and COX2 were overexpressed compared to all other groups. The two groups with 5mmol/L glucose concentration during the first culture stage (5-10 and 5-17) displayed similar patterns which differed to the 10-17 group. Conclusions related to embryo quality are based on gene expression patterns. Transfer of in vitro-produced embryos would reveal whether the observed differences improve embryo developmental competence. Five mM glucose during the first days of culture seems to be preferable to avoid over-activation of embryonic glycolytic pathways. Further studies are necessary to determine whether this improves embryo developmental competence.

Abstract 115: Hedgehog signaling pathway promotes breast cancer adaptation to hypoxia

Abstract Breast cancer is the most commonly diagnosed cancer in women in the US. Metastasis accounts for the majority of breast cancer-related deaths. Rapidly proliferating primary tumors experience oxygen levels that are lower in comparison to the normal tissue. The proportions of these hypoxic tumor cells in breast cancer strongly correlate to the incidence of metastasis. Around 70% of breast cancers present with bone metastasis. Tumor cells that metastasize to the bone can lead to an imbalance in bone homeostasis, often leading to osteolysis. Our lab has previously reported that the activation of Hedgehog (Hh) signaling, one of the embryonic developmental pathways found to be abnormally activated in breast cancer, leads to increased osteolysis in vivo. The incidence of osteolytic metastasis at the tibio-femoral junction was significantly reduced in the Hh signaling-deficient mice. Since a hypoxic microenvironment is prevalent in bone, it is imperative to understand how Hh signaling drives tumor cell adaptation to hypoxia. The hypoxic tumor microenvironment in the primary tumor might select for metastatic cells that are better able to metastasize to the bone. We hypothesize that Hh signaling enables the adaptation of breast cancer cells to hypoxia and consequently their metastatic potential. Hh signaling can be canonically activated through smoothened (SMO)-dependent activation of the transcriptional regulator GLI. Cellular response to hypoxia is mediated by the hypoxia-inducible factors (HIFs). To understand the importance of Hh signaling activation in hypoxic condition, we inhibited the Hh signaling pathway using GLI and SMO inhibitors. Additionally, we knocked-down GLI1 in breast cancer cell lines. We have identified a feed-forward mechanism between Hh signaling and HIF signaling in hypoxic conditions leading to sustained hypoxia response by stabilization of HIF-1α. Future investigations will address the significance of Hh signaling inhibition in a murine model of TNBC. This study will help determine the therapeutic benefit of hedgehog inhibitors in controlling hypoxia-mediated metastasis and tumorigenesis. Citation Format: Tshering D. Lama-Sherpa, Sarah C. Kammerud, Lalita A. Shevde. Hedgehog signaling pathway promotes breast cancer adaptation to hypoxia [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 115.