Search

Intra-tumoral heterogeneity and diffuse infiltration are hallmarks of glioblastoma that challenge treatment efficacy. However, the mechanisms that set up both tumor heterogeneity and invasion remain poorly understood. Herein, we present a comprehensive spatiotemporal study that aligns distinctive intra-tumoral histopathological structures, oncostreams, with dynamic properties and a unique, actionable, spatial transcriptomic signature. Oncostreams are dynamic multicellular fascicles of spindle-like and aligned cells with mesenchymal properties, detected using ex vivo explants and in vivo intravital imaging. Their density correlates with tumor aggressiveness in genetically engineered mouse glioma models, and high-grade human gliomas. Oncostreams facilitate the intra-tumoral distribution of tumoral and non-tumoral cells, and the invasion of the normal brain. These fascicles are defined by a specific molecular signature that regulates their organization and function. Oncostreams structure and function depend on overexpression of COL1A1. COL1A1 is a central gene in the dynamic organization of glioma mesenchymal transformation, and a powerful regulator of glioma malignant behavior. Inhibition of COL1A1 eliminated oncostreams, reprogramed the malignant histopathological phenotype, reduced expression of the mesenchymal associated genes, induced changes in the tumor microenvironment and prolonged animal survival. Oncostreams represent a novel pathological marker of potential value for diagnosis, prognosis, and treatment.

Purpose Genomic reprogramming and cellular dedifferentiation are critical to the success of de novo tissue regeneration in lower vertebrates such as zebrafish and axolotl. In tissue regeneration following injury or disease, differentiated cells must retain lineage while assuming a progenitor-like identity in order to repopulate the damaged tissue. Understanding the epigenetic regulation of programmed cellular dedifferentiation provides unique insights into the biology of stem cells and cancer and may lead to novel approaches for treating human degenerative conditions. Methods Using a zebrafish in vivo model of adult muscle regeneration, we utilized chromatin immunoprecipitation followed by massively parallel DNA sequencing (ChIP-seq) to characterize early changes in epigenetic signals, focusing on three well-studied histone modifications-histone H3 trimethylated at lysine 4 (H3K4me3), and histone H3 trimethylated or acetylated at lysine 27 (H3K27me3 and H3K27Ac, respectively). Results We discovered that zebrafish myocytes undergo a global, rapid, and transient program to drive genomic remodeling. The timing of these epigenetic changes suggests that genomic reprogramming itself represents a distinct sequence of events, with predetermined checkpoints, to generate cells capable of de novo regeneration. Importantly, we uncovered subsets of genes that maintain epigenetic marks paradoxical to changes in expression, underscoring the complexity of epigenetic reprogramming. Conclusions Within our model, histone modifications previously associated with gene expression act for the most part as expected, with exceptions suggesting that zebrafish chromatin maintains an easily editable state with a number of genes paradoxically marked for transcriptional activity despite downregulation.

Gliomas are primary brain tumors characterized by their invasiveness and heterogeneity. Specific histological patterns such as pseudopalisades, microvascular proliferation, mesenchymal transformation and necrosis characterize the histological heterogeneity of high-grade gliomas. Our laboratory has demonstrated that the presence of high densities of mesenchymal cells, named oncostreams, correlate with tumor malignancy. We have developed a unique approach to understand the mechanisms that underlie glioma’s growth and invasion. Here, we describe a comprehensive protocol that utilizes laser capture microdissection (LMD) and RNA sequencing to analyze differential mRNA expression of intra-tumoral heterogeneous multicellular structures (i.e., mesenchymal areas or areas of tumor invasion). This method maintains good tissue histology and RNA integrity. Perfusion, freezing, embedding, sectioning, and staining were optimized to preserve morphology and obtain high-quality laser microdissection samples. The results indicate that perfusion of glioma bearing mice using 30% sucrose provides good morphology and RNA quality. In addition, staining tumor sections with 4% Cresyl violet and 0.5% eosin results in good nuclear and cellular staining, while preserving RNA integrity. The method described is sensitive and highly reproducible and it can be utilized to study tumor morphology in various tumor models. In summary, we describe a complete method to perform LMD that preserves morphology and RNA quality for sequencing to study the molecular features of heterogeneous multicellular structures within solid tumors.

Intratumoral heterogeneity is a hallmark of high grade gliomas. However, whether heterogeneity is static or dynamic remains unknown. Here we demonstrate that gliomas’ core and border regions display areas of self-organized collective motion, which we have termed oncostreams. Histologically oncostreams appear as multicellular fascicles of elongated and aligned glioma cells with mesenchymal-like morphology, and their density correlates positively with tumor malignant behavior. Using time lapse confocal imaging of organotypic brain slices of experimental glioma we discovered oncostream dynamics, namely, as two self-organizing patterns of collective motion: streams (bidirectional motion) and flocks (unidirectional motion). Oncostreams were also present in human glioblastoma multiforme, and could also be detected using objective artificial indigent approaches. They were present in 47% of TCGA-GBM grade IV tumor tissues, in 8.6 % of TCGA-LGG grade III, and were absent in TCGA-LGG grade II. Oncostreams are heterogeneous, contain GFAP+ cells, Iba1+ microglia/macrophages cells, and ACTA2+ mesenchymal cells aligned along Sox2+ tumor cells. We propose that oncostreams function as highways possibly stimulating the spread of slower-moving glioma cells and/or non-tumor cells throughout the tumor mass, reinforcing a potential role of oncostreams in determining spatial heterogeneity and remodeling of the tumor microenvironment. To analyze the molecular landscape of oncostreams we used laser capture microdissection coupled to RNA-Seq and bioinformatics analysis: we detected the existence of genetic networks specific to oncostreams. Oncostreams were aligned along highly expressed extracellular matrix proteins, among them Col1a1 was the most differentially expressed. Genetic inhibition of Col1a1 dissembled oncostreams, decreased glioma heterogeneity and improved animal survival. We propose that oncostreams dynamics will be a promising avenue to understand glioma behavior, and treat these malignant tumors. Citation Format: Andrea Comba, Sebastien Motsch, Patrick Dunn, Todd Hollon, Daniel Zamler, Anna Argento, Alon Kahana, Phillip Kish, Maria Castro, Pedro Lowenstein. The dynamic tumor microenvironment: Oncostreams are self-organizing structures that modulate glioma progression and treatment [abstract]. In: Proceedings of the AACR Virtual Special Conference on the Evolving Tumor Microenvironment in Cancer Progression: Mechanisms and Emerging Therapeutic Opportunities; in association with the Tumor Microenvironment (TME) Working Group; 2021 Jan 11-12. Philadelphia (PA): AACR; Cancer Res 2021;81(5 Suppl):Abstract nr PR005.

Purpose The orbit displays unique vulnerability to inflammatory conditions. The most prevalent of these conditions, thyroid eye disease (TED), occurs in up to 50% of patients with Graves' disease (GD). Whereas the pathology of both TED and GD is driven by autoantibodies, it is unclear why symptoms manifest specifically in the orbit. Methods We performed retinoic acid treatment on both normal and TED patient-derived orbital fibroblasts (OFs) followed by mRNA and protein isolation, quantitative real-time polymerase chain reaction (qRT-PCR), enzyme-linked immunosorbent assay, RNA sequencing, and Western blot analyses. Results Both normal and TED patient-derived OFs display robust induction of monocyte chemoattractant protein 1 (MCP-1) upon retinoid treatment; TED OFs secrete significantly more MCP-1 than normal OFs. In addition, pretreatment of OFs with thiophenecarboxamide (TPCA-1) inhibits retinoid-induced MCP-1 induction, suggesting an NF-κB (nuclear factor kappa-light-chain-enhancer of activated B cells)-dependent mechanism. We also found that treatment with cholecalciferol (vitamin D3) mitigates MCP-1 induction, likely because of competition between retinoic acid receptors (RARs) and vitamin D receptors (VDR) for their common binding partner retinoid nuclear receptors (RXRs). Conclusions Retinoids that naturally accumulate in orbital adipose tissue can act on orbital fibroblasts to induce the expression of inflammation-associated genes. These data suggest a potential role for retinoids in sensitizing the orbit to inflammation.

Severely damaged adult zebrafish extraocular muscles (EOMs) regenerate through dedifferentiation of residual myocytes involving a muscle-to-mesenchyme transition. Members of the Twist family of basic helix-loop-helix transcription factors (TFs) are key regulators of the epithelial-mesenchymal transition (EMT) and are also involved in craniofacial development in humans and animal models. During zebrafish embryogenesis, twist family members (twist1a, twist1b, twist2, and twist3) function to regulate craniofacial skeletal development. Because of their roles as master regulators of stem cell biology, we hypothesized that twist TFs regulate adult EOM repair and regeneration. In this study, utilizing an adult zebrafish EOM regeneration model, we demonstrate that inhibiting twist3 function using translation-blocking morpholino oligonucleotides (MOs) impairs muscle regeneration by reducing myocyte dedifferentiation and proliferation in the regenerating muscle. This supports our hypothesis that twist TFs are involved in the early steps of dedifferentiation and highlights the importance of twist3 during EOM regeneration.

Zebrafish extraocular muscles regenerate after severe injury. Injured myocytes dedifferentiate to a mesenchymal progenitor state and reenter the cell cycle to proliferate, migrate, and redifferentiate into functional muscles. A dedifferentiation process that begins with a multinucleated syncytial myofiber filled with sarcomeres and ends with proliferating mononucleated myoblasts must include significant remodeling of the protein machinery and organelle content of the cell. It turns out that autophagy plays a key role early in this process, to degrade the sarcomeres as well as the excess nuclei of the syncytial multinucleated myofibers. Because of the robustness of the zebrafish reprogramming process, and its relative synchrony, it can serve as a useful in vivo model for studying the biology of autophagy. In this chapter, we describe the surgical muscle injury model as well as the experimental protocols for assessing and manipulating autophagy activation.

Zebrafish extraocular muscles regenerate after severe injury. Injured myocytes dedifferentiate to a mesenchymal progenitor state and reenter the cell cycle to proliferate, migrate, and redifferentiate into functional muscles. A dedifferentiation process that begins with a multinucleated syncytial myofiber filled with sarcomeres and ends with proliferating mononucleated myoblasts must include significant remodeling of the protein machinery and organelle content of the cell. It turns out that autophagy plays a key role early in this process, to degrade the sarcomeres as well as the excess nuclei of the syncytial multinucleated myofibers. Because of the robustness of the zebrafish reprogramming process, and its relative synchrony, it can serve as a useful in vivo model for studying the biology of autophagy. In this chapter, we describe the surgical muscle injury model as well as the experimental protocols for assessing and manipulating autophagy activation.

Mesenchymal gliomas are the most aggressive tumors that carry the worst prognosis. The origins of mesenchymal cells within brain tumors, remains poorly understood. They could originate either from invading mesenchymal cells, from perivascular smooth muscle actin+ cells, or from a mesenchymal transformation of tumor cells. Identifying the origin and function of mesenchymal cells within gliomas is essential as these cells contribute to increased glioma aggressiveness and tumor progression. In this study we used human biopsies and implantable and genetically engineered mouse models (GEMM) of GBM to study tumor mesenchymal transformation. GBM implantable models were used to analyze the molecular landscape by laser microdissection followed by RNA-Seq and bioinformatics analysis. Time lapse confocal imagining was implemented to analyze GBM cells dynamics. Our results indicate the existence of a complex intratumoral and peritumoral dynamic organization of glioma cells (i.e., Oncostreams). Multicellular structures of elongated cells compatible with mesenchymal differentiation. These structures play important roles in intratumoral movements, peritumoral invasion of normal brain, and overall glioma progression. We also show that oncostreams are molecularly distinct and display increased expression of mesenchymal genes such as Col1a1. Knocking down of Col1a1 in a GEMM of aggressive gliomas reduced tumor progression and significantly increased animal survival. Histological examination confirmed absence of Col1a1, and absence of morphologically identifiable oncostreams. Our results show that tumor cells, especially within oncostreams, display a fibroblastic-like morphology and express proteins typical of mesenchymal cells. The knockout of Col1a1 from tumoral cells eliminated oncostreams from tumors and delayed tumor progression. These data suggest that tumor cells expressing mesenchymal genes regulate the organization of mesenchymal multicellular structures, and determine glioma progression. We propose that inhibiting mesenchymal transformation of glioma cells will assist in the treatment of glioblastoma.

Cell identity involves both selective gene activity and specialization of cytoplasmic architecture and protein machinery. Similarly, reprogramming differentiated cells requires both genetic program alterations and remodeling of the cellular architecture. While changes in genetic and epigenetic programs have been well documented in dedifferentiating cells, the pathways responsible for remodeling the cellular architecture and eliminating specialized protein complexes are not as well understood. Here, we utilize a zebrafish model of adult muscle regeneration to study cytoplasmic remodeling during cell dedifferentiation. We describe activation of autophagy early in the regenerative response to muscle injury, while blocking autophagy using chloroquine or Atg5 and Becn1 knockdown reduced the rate of regeneration with accumulation of sarcomeric and nuclear debris. We further identify Casp3/caspase 3 as a candidate mediator of cellular reprogramming and Fgf signaling as an important activator of autophagy in dedifferentiating myocytes. We conclude that autophagy plays a critical role in cell reprogramming by regulating cytoplasmic remodeling, facilitating the transition to a less differentiated cell identity.

Fibroblast growth factors (Fgfs) regulate critical biological processes such as embryonic development, tissue homeostasis, wound healing, and tissue regeneration. In zebrafish, Fgf signaling plays an important role in the regeneration of the spinal cord, liver, heart, fin, and photoreceptors, although its exact mechanism of action is not fully understood. Utilizing an adult zebrafish extraocular muscle (EOM) regeneration model, we demonstrate that blocking Fgf receptor function using either a chemical inhibitor (SU5402) or a dominant-negative transgenic construct (dnFGFR1a:EGFP) impairs muscle regeneration. Adult zebrafish EOMs regenerate through a myocyte dedifferentiation process, which involves a muscle-to-mesenchyme transition and cell cycle reentry by differentiated myocytes. Blocking Fgf signaling reduced cell proliferation and active caspase 3 levels in the regenerating muscle with no detectable levels of apoptosis, supporting the hypothesis that Fgf signaling is involved in the early steps of dedifferentiation. Fgf signaling in regenerating myocytes involves the MAPK/ERK pathway: inhibition of MEK activity with U0126 mimicked the phenotype of the Fgf receptor inhibition on both muscle regeneration and cell proliferation, and activated ERK (p-ERK) was detected in injured muscles by immunofluorescence and western blot. Interestingly, following injury, ERK2 expression is specifically induced and activated by phosphorylation, suggesting a key role in muscle regeneration. We conclude that the critical early steps of myocyte dedifferentiation in EOM regeneration are dependent on Fgf signaling.

PURPOSE The homeobox transcription factor PITX2 is a known regulator of mammalian ocular development, and human PITX2 mutations are associated with Axenfeld-Rieger syndrome (ARS). However, the treatment of patients with ARS remains mostly supportive and palliative. METHODS The authors used molecular genetic, pharmacologic, and embryologic techniques to study the biology of ARS in a zebrafish model that uses transgenes to mark neural crest and muscle cells in the head. RESULTS The authors demonstrated in vivo that pitx2 is a key downstream target of retinoic acid (RA) in craniofacial development, and this pathway is required for coordinating neural crest, mesoderm, and ocular development. pitx2a knockdown using morpholino oligonucleotides disrupts jaw and pharyngeal arch formation and recapitulates ocular characteristics of ARS, including corneal and iris stroma maldevelopment. These phenotypes could be rescued with human PITX2A mRNA, demonstrating the specificity of the knockdown and evolutionary conservation of pitx2a function. Expression of the ARS dominant negative human PITX2A K50E allele also caused ARS-like phenotypes. Similarly, inhibition of RA synthesis in the developing eye (genetic or pharmacologic) disrupted craniofacial and ocular development, and human PITX2A mRNA partially rescued these defects. CONCLUSIONS RA regulation of pitx2 is essential for coordinating interactions among neural crest, mesoderm, and developing eye. The marked evolutionary conservation of Pitx2 function in eye and craniofacial development makes zebrafish a potentially powerful model of ARS, amenable to in vivo experimentation and development of potential therapies.

OBJECTIVES/SPECIFIC AIMS: Oncostreams represent a novel growth pattern of GBM. In this study we uncovered the cellular and molecular mechanism that regulates the oncostreams function in GBM growth and invasion. METHODS/STUDY POPULATION: We studied oncostreams organization and function using genetically engineered mouse gliomas models (GEMM), mouse primary patient derived GBM model and human glioma biopsies. We evaluated the molecular landscape of oncostreams by laser capture microdissection (LCM) followed by RNA-Sequencing and bioinformatics analysis. RESULTS/ANTICIPATED RESULTS: Oncostreams are multicellular structures of 10-20 cells wide and 2-400 μm long. They are distributed throughout the tumors in mouse and human GBM. Oncostreams are heterogeneous structures positive for GFAP, Nestin, Olig2 and Iba1 cells and negative for Neurofilament. Using GEMM we found a negative correlation between oncostream density and animal survival. Moreover, examination of patient’s glioma biopsies evidenced that oncostreams are present in high grade but no in low grade gliomas. This suggests that oncostreams may play a role in tumor malignancy. Our data also indicated that oncostreams aid local invasion of normal brain. Transcriptome analysis of oncostreams revealed 43 differentially expressed (DE) genes. Functional enrichment analysis of DE genes showed that “collagen catabolic processes”, “positive regulation of cell migration”, and “extracellular matrix organization” were the most over-represented GO biological process. Network analysis indicated that Col1a1, ACTA2, MMP9 and MMP10 are primary target genes. These genes were also overexpressed in more malignant tumors (WT-IDH) compared to the less malignant (IDH1- R132H) tumors. Confocal time lapse imagining of 3D tumor slices demonstrated that oncostreams display a collective motion pattern within gliomas that has not been seen before. DISCUSSION/SIGNIFICANCE OF IMPACT: In summary, oncostreams are anatomically and molecularly distinctive, regulate glioma growth and invasion, display collective motion and are regulated by the extracellular matrix. We propose oncostreams as novel pathological markers valuable for diagnosis, prognosis and designing therapeutics for GBM patients.

GBM remains the deadliest primary malignant brain tumor. Given the importance of invading cells, less attention has been paid to the tumor mass, even if such a mass eventually kills the patient. We previously demonstrated that human and mouse transplantable or GEMM gliomas display regular anatomical multicellular structures containing elongated cells which we named ‘oncostreams’. Oncostreams are 10–20 cells wide, 2–400 um long, and are distributed throughout the tumors. Furthermore, we uncovered a negative correlation between oncostream density and animal survival suggesting that oncostreams play a role in tumor malignancy. Further data indicate that oncostreams aid local invasion of normal brain. Co-implantation experiments demonstrated that oncostreams facilitate the intratumoral spread of slow migrating cells. To determine a possible molecular distinctiveness of oncostreams we used laser capture microdissection followed by RNA-Seq, bioinformatics and network analysis. Evaluation of the transcriptome demonstrated differential expression (DE) of genes between oncostreams and adjacent tumor. Functional enrichment of DE genes showed that “collagen catabolic processes”, “positive regulation of cell migration”, and “extracellular matrix organization” were the most over-represented gene ontologies. Network analysis indicated that Col1a1, ACTA2, MMP9, MMP10 and ADAMTS2, genes important for cell migration and ECM interactions, are part of these networks. IHC and PCR were used to validate RNA-Seq expression changes. To understand the cellular dynamics in our system we used time lapse imagining and evaluated the results using high level statistical analyses. The following tests, i.e., velocity distribution, pair-wise correlation of local position, velocity correlation, etc. were used to characterize the dynamics of cellular intratumoral motility. These data demonstrate the existence of collective motion within glioma tumors. Taken together, our results show that oncostreams, move by collective motion, are anatomically and molecularly distinct, reveal the existence of glioma self-organization, and regulate glioma growth and invasion. Targeting oncostreams is a candidate therapeutic strategy.

Heat shock is a common technique for inducible gene expression system in a variety of organisms. Heat shock treatment of adult zebrafish is more involved and generally consists of manually transferring fish between housing rack tanks and preheated water tanks or the use of timed heaters in stand-alone aquaria. To avoid excessive fish handling and to take advantage of the continuous flow of a standard housing rack, proposed modifications consisted of installing an aquarium heater inside each tank, manually setting the heater to reach heat shocking temperatures (37°C) and, after that, testing that every tank responded equally. To address the limitations in the existing systems, we developed a novel modification of standard zebrafish housing racks to perform heat shock treatment in conditions of continuous water flow. By adding an extra manifold to the housing rack and connecting it to a recirculating bath to create a parallel water flow system, we can increase the temperature from standard conditions (28.5°C) to heat shock conditions with high precision (38.0-38.3°C, mean ± SD = 38.1°C ± 0.14°C) and minimal variation among experimental tanks (coefficient of variation [CV] = 0.04%). This means that there is virtually no need for laborious pretreatment calibrations or continuous adjustments to minimize intertank variation. To test the effectiveness of our design, we utilized this system to induce enhanced green fluorescent protein (EGFP) expression in hsp70-EGFP fish and performed a fin regeneration experiment with hsp70l:dnfgfr1-EGFP fish to confirm that heat-induced gene expression reached physiological levels. In summary, our newly described aquatic heat shock system minimizes effort during heat shock experiments, while ensuring the best water quality and fish welfare and facilitating large heat shock settings or the use of multiple transgenic lines for both research and teaching experiments.

Cidofovir-based compounds having an amino acid, dipeptide or tripeptide attached to a cidofovir or cyclic cidofovir framework. The compounds show enhanced oral bioavailability and increased binding to the PepT1 transporter. The present invention also provides compositions and methods for treating virus infections, and a method of preparing cidofovir.

Insulin-like growth factors (Igfs) are key regulators of key biological processes such as embryonic development, growth, and tissue repair and regeneration. The role of Igf in myogenesis is well documented and, in zebrafish, promotes fin and heart regeneration. However, the mechanism of action of Igf in muscle repair and regeneration is not well understood. Using adult zebrafish extraocular muscle (EOM) regeneration as an experimental model, we show that Igf1 receptor blockage using either chemical inhibitors (BMS754807 and NVP-AEW541) or translation-blocking morpholino oligonucleotides (MOs) reduced EOM regeneration. Zebrafish EOMs regeneration depends on myocyte dedifferentiation, which is driven by early epigenetic reprogramming and requires autophagy activation and cell cycle reentry. Inhibition of Igf signaling had no effect on either autophagy activation or cell proliferation, indicating that Igf signaling was not involved in the early reprogramming steps of regeneration. Instead, blocking Igf signaling produced hypercellularity of regenerating EOMs and diminished myosin expression, resulting in lack of mature differentiated muscle fibers even many days after injury, indicating that Igf was involved in late re-differentiation steps. Although it is considered the main mediator of myogenic Igf actions, Akt activation decreased in regenerating EOMs, suggesting that alternative signaling pathways mediate Igf activity in muscle regeneration. In conclusion, Igf signaling is critical for re-differentiation of reprogrammed myoblasts during late steps of zebrafish EOM regeneration, suggesting a regulatory mechanism for determining regenerated muscle size and timing of differentiation, and a potential target for regenerative therapy.

Human low-grade gliomas represent a population of brain tumors that remain a therapeutic challenge. Preclinical evaluation of agents, to test their preventive or therapeutic efficacy in these tumors, requires the use of animal models. Spontaneous gliomas develop in models of chemically induced carcinogenesis, such as in the transplacental N-ethyl-N-nitrosourea (ENU) rat model. However, without the ability to detect initial tumor formation, multiplicity or to measure growth rates, it is difficult to test compounds for their interventional or preventional capabilities. In this study Fisher-334 rats, treated transplacentally with ENU, underwent magnetic resonance imaging (MRI) examination in order to evaluate this approach for detection of tumor formation and growth. ENU-induced intracranial cerebral tumors were first observable in T2-weighted images beginning at 4 months of age and grew with a mean doubling time of 0.487 +/- 0.112 months. These tumors were found histologically to be predominately mixed gliomas. Two therapeutic interventions were evaluated using MRI, vitamin A (all-trans retinol palmitate, RP), as a chemopreventative agent and the anti-angiogenic drug SU-5416. RP was found to significantly delay the time to first tumor observation by one month (P = 0.05). No differences in rates of tumor formation or growth rates were observed between control and RP-treated groups. MRI studies of rats treated with SU-5416 resulted in reduction in tumor growth rates compared to matched controls. These results show that MRI can be used to provide novel information relating to the therapeutic efficacy of agents against the ENU-induced tumor model.

It is our hypothesis that low grade gliomas are the glial counterparts of other precancerous lesions such as colon polyps and, therefore, suitable targets for chemoprevention. Steps in the molecular progression of gliomas have been described, indicating that an accumulation of abnormalities is required for progression to a high grade and interruption of this progression might be possible. An animal model of chemical glial carcinogenesis was used to test this hypothesis. Pregnant rats were injected intravenously with ENU (ethylnitrosourea) on the 18th day of gestation to induce gliomas in the offspring, which were randomized to receive control diet, diet supplemented with vitamin A palmitate, or diet supplemented with N-acetylcysteine. Animals exposed to ENU and receiving a control diet developed brain tumors and had a shortened life expectancy compared with rats unexposed to ENU. The animals treated with NAC showed no statistically significant delay in the time to tumor and no change in the histologic grade of the tumors when compared with animals receiving control diet, but the time to death from any cause of NAC treated animals differed significantly from untreated animals. Animals receiving high dose VA had statistically significantly prolonged time to tumor, survived significantly longer than untreated animals, but had no reduction in the total number of tumors or change in the histologic grade of their tumors. The theoretical basis of these results is likely due to the putative mechanism of action of these agents. These data indicate that glioma chemoprevention is possible and deserves further exploration.

Cancer stem cells (CSCs) are those cells within a malignant tumor that can self-renew and initiate new tumors, with the ability to produce all the cell lineages that comprise the tumor. Recent studies have revealed that cancer treatments that target the tumor without addressing CSCs might reduce the tumor load but be unable to achieve a cure. Generation and maintenance of CSCs through genetic and epigenetic reprogramming is essential for tumor maintenance and resistance to therapy. Therefore, developing therapies targeted at CSCs is critical to achieving cures for cancer1. Yet the biology of CSCs, and particularly the process of cellular reprogramming, is still not well understood, in part because of the many mutations carried by these cells, only a few of which are deterministic. In order to develop a better understanding of the mechanistic underpinnings of adult cell dedifferentiation, we developed a zebrafish model that utilizes adult myocyte reprogramming in the context of muscle regeneration. Our model utilizes the lateral rectus muscle of the eye, which can recover from >50% myectomy by reprogramming the residual (i.e. “post-mitotic”) myocytes to reenter the cell cycle, remodel the extracellular matrix, proliferate, migrate and then redifferentiate into myocytes that reform a functional muscle (as determined by an optokinetic response). The proliferative burst of reprogrammed myocytes is particularly robust, with >70% of cells undergoing mitosis during the regeneration process. Such a robust in vivo model of cell dedifferentiation represents a unique opportunity to study the cellular, genetic and epigenetic processes involved. We find that the dedifferentiation process begins with activation of epigenetic regulators to remodel chromatin, followed by activation of autophagy to remodel the cytoplasm, followed by cell cycle reentry. Epigenetic changes include changes in DNA and histone methylation, along with activation of genes encoding transcription factors that are frequently found to be involved with oncogenesis, such as myc, jun, fos, and twist. A transcriptome analysis using deep sequencing reveals significant similarities between the genetic signatures of dedifferentiated zebrafish myocytes and human cancer cells. This analysis also identifies long non-coding RNAs that are induced early during the dedifferentiation process, and work is ongoing to annotate these lncRNAs with reference to human cancer. In summary, an in vivo zebrafish non-cancer model of cancer can provide unique mechanistic insights into the biology of CSCs. In addition, as an aquatic species this model is particularly well suited for drug screening, providing an innovative new approach to developing drugs that target reprogramming/dedifferentiating cells. Citation Format: Ke’ale Louie, Alfonso Saera-Vila, Phillip E. Kish, Alon Kahana. Zebrafish adult cell dedifferentiation as a noncancer model of cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2541.

Our recent studies have shown that telomeric 10p is frequently deleted in both low and high grade gliomas. Other studies have shown an invariant association of erb-b amplification and loss of chromosome 10. It has not been determined whether this association was specific for a particular locus on chromosome 10. We sought to assess this by examining tumors, for both 10p loss and gene amplification. 55% of tumors showed some degree of allelic imbalance at 10p15. Amplification of erb-b, c-myc, and a mitochondrial cDNA probe, recently found to be amplified in diverse grades of gliomas was assessed. erb-b and the mitochondrial cDNA probe showed amplification in 28% of the tumors; c-myc gene was amplified in only one astrocytoma. No significant association was noted when comparing the presence of a specific amplified gene, and loss of loci on chromosome. Chromosome 10p15 shows significant loss in glial tumors, and is independent of the chromosome 10 region associated with erb-b amplification. The region at 10p15 is distinct in harboring a putative tumor suppressor gene in gliomas, and is involved earlier in the multi-step pathway to glial tumor malignancy.

Binocular vision requires intricate control of eye movement to align overlapping visual fields for fusion in the visual cortex, and each eye is controlled by 6 extraocular muscles (EOMs). Disorders of EOMs are an important cause of symptomatic vision loss. Importantly, EOMs represent specialized skeletal muscles with distinct gene expression profile and susceptibility to neuromuscular disorders. We aim to investigate and describe the anatomy of adult zebrafish extraocular muscles (EOMs) to enable comparison with human EOM anatomy and facilitate the use of zebrafish as a model for EOM research. Using differential interference contrast (DIC), epifluorescence microscopy, and precise sectioning techniques, we evaluate the anatomy of zebrafish EOM origin, muscle course, and insertion on the eye. Immunofluorescence is used to identify components of tendons, basement membrane and neuromuscular junctions (NMJs), and to analyze myofiber characteristics. We find that adult zebrafish EOM insertions on the globe parallel the organization of human EOMs, including the close proximity of specific EOM insertions to one another. However, analysis of EOM origins reveals important differences between human and zebrafish, such as the common rostral origin of both oblique muscles and the caudal origin of the lateral rectus muscles. Thrombospondin 4 marks the EOM tendons in regions that are highly innervated, and laminin marks the basement membrane, enabling evaluation of myofiber size and distribution. The NMJs appear to include both en plaque and en grappe synapses, while NMJ density is much higher in EOMs than in somatic muscles. In conclusion, zebrafish and human EOM anatomy are generally homologous, supporting the use of zebrafish for studying EOM biology. However, anatomic differences exist, revealing divergent evolutionary pressures.

Summary: The formation and invagination of the optic stalk coincides with the migration of cranial neural crest (CNC) cells, and a growing body of data reveals that the optic stalk and CNC cells communicate to lay the foundations for periocular and craniofacial development. Following migration, the interaction between the developing eye and surrounding periocular mesenchyme (POM) continues, leading to induction of transcriptional regulatory cascades that regulate craniofacial morphogenesis. Studies in chick, mice, and zebrafish have revealed a remarkable level of genetic and mechanistic conservation, affirming the power of each animal model to shed light on the broader morphogenic process. This review will focus on the role of the developing eye in orchestrating craniofacial morphogenesis, utilizing morphogenic gradients, paracrine signaling, and transcriptional regulatory cascades to establish an evolutionarily-conserved facial architecture. We propose that in addition to the forebrain, the eye functions during early craniofacial morphogenesis as a key organizer of facial development, independent of its role in vision. genesis 49:222–230, 2011. V C 2011 Wiley-Liss, Inc.

Binocular vision requires intricate control of eye movement by 6 pairs of extraocular muscles (EOMs). Congenital and acquired strabismus secondary to EOM dysfunction cause misaligned binocular inputs, which can lead to amblyopia (neurologic vision loss) or diplopia, collectively affecting as much as 5% to 10% of the US population.1,2 More broadly, skeletal muscle injury and degenerative conditions are common and debilitating and represent important causes of morbidity and mortality worldwide.3,4 Mammalian myonuclei are defined as being postmitotic, and muscle growth and repair are achieved by myogenic progenitor cells termed satellite cells.5–11 These cells are identified by expression of the paired box transcription factor family members Pax7 and/or Pax3. Pax7 is expressed by most adult muscle satellite cells, whereas Pax3 is present only in satellite cells of particular muscles and is transiently expressed by activated satellite cells.12–15 Muscle injury can be a focal injury (e.g., stab wound) or a major injury with significant tissue loss and every degree of injury in between. Response to focal injury would require a local repair process, whereas significant tissue loss would require more extensive tissue generation (i.e., “whole-organ” regeneration). In mammals, muscle repair following focal injury involves the proliferation of satellite cells to form myoblasts that express the transcription factor MyoD. Some myoblasts maintain MyoD expression, downregulate Pax7, and commit to differentiation by activation of myogenin. These differentiated myoblasts fuse to form myocytes. Other myoblasts maintain Pax7 expression, downregulate MyoD, and eventually withdraw from the cell cycle to maintain the satellite cell population of the muscle.14,16,17 In contrast, whole-organ muscle regeneration is much more limited in mammals despite the presence of satellite cells. In salamanders, limb amputation is followed by limb regeneration in which Pax7-positive cells play an important role in some but not all salamander species.18 Pax7-positive satellite cells have also been described in mammalian EOMs.19 Additionally, progenitor cells that express PITX2 have been described.20 EOMs are a specialized form of skeletal muscle derived from branchial and cephalic mesoderm,21–23 and EOM satellite cells may have certain distinguishing features compared to their somitic counterparts. However, published results are somewhat inconsistent. Some results suggest that the EOM stem cell niche is protected from aging and disease24,25 and maintains proliferative potential longer than somitic muscles.26 Other results argue that aged EOM stem cells lose their ability to fuse to form multinucleated myotubes.26 This disagreement in published conclusions may be the result of using different species and/or different experimental approaches. To investigate the potential for adult whole-organ skeletal muscle regeneration, we exploited the well-documented regenerative capacity of adult zebrafish. With its genome nearly fully sequenced and with well-developed molecular tools, the zebrafish (Danio rerio) has become an important model for human disease research. In particular, adult zebrafish have robust regenerative capacity in organs as diverse as the brain, retina, fins, and heart.27–32 In regenerating complex tissues, zebrafish use both resident stem cells (e.g., melanocyte precursors in fins33) and lineage-restricted dedifferentiated cells (e.g., cardiac myocytes,34 retinal Muller glia,31,35 and osteoblasts32,36), suggesting that zebrafish might be an ideal model for studying de novo whole-organ muscle regeneration. Our model uses a large EOM myectomy in sexually mature adult zebrafish. We focused on the lateral rectus (LR) muscle because of its anatomic isolation from the other EOMs37 and its surgical accessibility and the ability to assess its function using horizontal gaze eye movement. Here we report that, following myectomy of approximately 50% of the LR muscle, adult zebrafish regenerated an anatomically correct and functional muscle. Unlike embryonic EOM development, the regeneration process appears to be independent of pax7-positive satellite cells, as classic satellite cells are not detectable in zebrafish adult EOMs by electron microscopy or immunofluorescence techniques. Instead, our data reveal that residual EOM myocytes undergo dedifferentiation to form myoblasts, followed by robust myoblast proliferation and redifferentiation into functional muscle fibers. We propose that the ability of residual EOM myocytes to dedifferentiate following severe injury underlies their whole-organ regenerative capacity in zebrafish, compared with other species in which dedifferentiation is actively blocked. Furthermore, adult zebrafish EOM regeneration via dedifferentiation offers a powerful model for studying the mechanistic underpinnings of cellular reprogramming and dedifferentiation.

We have previously reported the occurrence of two endogenous protein phosphorylation systems in mammalian brain that are enhanced in the presence of 3-phosphoglycerate (3PG) and ATP. We present here a study of one of these systems, the phosphorylation of the 72-kDa protein (3PG-PP72). This system was separated into the substrate, 3PG-PP72, and a kinase by ammonium sulfate fractionation, hydroxyapatite chromatography, and hydrophobic interaction HPLC. The substrate protein was shown to be directly phosphorylated with [1-32P]1,3-bisphosphoglycerate [( 1-32P]1,3BPG) with an apparent Km of 1.1 nM. Nonradioactive 1,3BPG inhibited 32P incorporation in the presence of [gamma-32P]ATP and 3PG. Phosphopeptide mapping and phosphoamino acid analyses indicated that the site of phosphorylation of 3PG-PP72 observed in the presence of 3PG and ATP is a serine residue identical to that observed with [1-32P]1,3BPG. Moreover, [32P]phosphate incorporated into 3PG-PP72 in the presence of 3PG and ATP was removed by subsequent incubation with glucose-1-phosphate or glucose-6-phosphate. Finally, 3PG-PP72 showed chromatographic behaviors identical to those of glucose-1,6-bisphosphate (G1,6P2) synthetase. Based upon these observations, we conclude that 3PG-PP72 is G1,6P2 synthetase and that it is phosphorylated directly by 1,3BPG, which is formed from 3PG and ATP by 3PG kinase present in a crude 3PG-PP72 preparation.

and to require a heat-labile cytosolic macromolecule factor for maximum activity. Maximal release occurred at 5/zM free Ca 2+ and within 5 min. Of the other divalent cations tested, only barium stimulated release of vesicular glutamate. The release was inhibited by N-ethylmaleimide. results are characteristic of exocytotic release of monoamines and peptides observed in endocrine systems, and constitute direct evidence for the notion that calcium-dependent release of glutamate originates from the vesicular pool. Amassed evidence indicates that glutamate serves as a major excitatory neurotransmitter in the vertebrate central nervous system (for review, see ref. 4). Despite the increased recognition of the neurotransmitter role of glutamate, the mechanism by which glutamate is released from the nerve terminal remains in large part to be elucidated. Substantial evidence now has been accumulated that glutamate is specifically taken up into highly purified isolated synaptic vesicles in an ATP-dependent manner [6, 8, 12, 15-18, 22], suggesting that glutamate could be accumulated and stored in synaptic vesicles in vivo. This is in accord with immunocytochemical evidence provided by Storm-Mathisen et al. [21] suggesting that glutamate is concentrated in certain synaptic vesicles distinct from ~,-aminobutyric acid (GABA)-containing vesicles. Recent evidence has indicated that glutamate released in a calcium-dependent manner originates from a non-cytoplasmic pool [20]. These lines of evidence argue for the involvement of synaptic vesicles in synaptic release of glutamate. In this study, we have investigated the calcium-dependent release of glutamate from the synaptic vesicles in a more direct manner, using a permeabilized synaptosome preparation. Evidence is presented that glutamate is indeed released directly from the synaptic vesicle in a calcium-dependent manner, in the presence of a cytosolic factor.

We have demonstrated previously that L-glutamate is taken up into isolated synaptic vesicles in an ATP-dependent manner, supporting the neurotransmitter role of this acidic amino acid. We now report that a nerve terminal cytosolic factor inhibits the ATP-dependent vesicular uptake of glutamate in a dose-dependent manner. This factor appears to be a protein with a molecular weight greater than 100,000, as estimated by size exclusion chromatography, and is precipitated by ammonium sulfate (40% saturation). The inhibitory factor is inactivated by heating to 100 degrees C. Proteolytic digestion of the ammonium sulfate fraction by trypsin or chymotrypsin did not reduce, but rather increased slightly, the inhibition of glutamate uptake. Unlike the native factor, the digest retained inhibitory activity after heating, suggesting that proteolytic digestion may generate active fragments. The inhibition of ATP-dependent vesicular glutamate uptake is not species-specific, as the factor obtained from both rat and bovine brains produced an equal degree of inhibition of glutamate uptake into vesicles of each species. These observations raise the possibility that vesicular uptake of glutamate may be regulated by an endogenous factor in vivo.

The ATP-dependent uptake of l-glutamate into synaptic vesicles has been well characterized, implicating a key role for synaptic vesicles in glutamatergic neurotransmission. In the present study, we provide evidence that vesicular glutamate uptake is selectively inhibited by the pep-tide-containing halogenated ergot bromocriptine. It is the most potent inhibitor of the agents tested; the IC5o was de-termined to be 22 μM. The uptake was also inhibited by other ergopeptines such as ergotamine and ergocristine, but with less potency. Ergots devoid of the peptide moiety, however, such as ergonovine, lergotrile, and methysergide, had little or no effect. Although bromocriptine is known to elicit dopaminergic and serotonergic effects, its inhibitory effect on vesicular glutamate uptake was not mimicked by agents known to interact with dopamine and serotonin receptors. Kinetic data suggest that bromocriptine competes with glutamate for the glutamate binding site on the glutamate trans-locator. It is proposed that this inhibitor could be useful as a prototype probe in identifying and characterizing the vesicular glutamate translocator, as well as in developing a more specific inhibitor of the transport system.

Although gamma-aminobutyric acid (GABA) and glycine are recognized as major amino acid inhibitory neurotransmitters in the central nervous system, their storage is poorly understood. In this study we have characterized vesicular GABA and glycine uptakes in the cerebrum and spinal cord, respectively. We present evidence that GABA and glycine are each taken up into isolated synaptic vesicles in an ATP-dependent manner and that the uptake is driven by an electrochemical proton gradient. Uptake for both amino acids exhibited kinetics with low affinity (Km in the millimolar range) similar to vesicular glutamate uptake. The ATP-dependent GABA uptake was not inhibited by the putative amino acid neurotransmitters glycine, taurine, glutamate, or aspartate or by GABA analogs, agonists, and antagonists. Similarly, ATP-dependent glycine uptake was hardly affected by GABA, taurine, glutamate, or aspartate or by glycine analogs or antagonists. The GABA uptake was not affected by chloride, which is in contrast to the uptake of the excitatory neurotransmitter glutamate, whereas the glycine uptake was slightly stimulated by low concentrations of chloride. Tissue distribution studies indicate that the vesicular uptake systems for GABA, glycine, and glutamate are distributed in different proportions in the cerebrum and spinal cord. These results suggest that the vesicular uptake systems for GABA, glycine, and glutamate are distinct from each other.

The ATP-dependent glutamate uptake system in synaptic vesicles prepared from mouse cerebellum was characterized, and the levels of glutamate uptake were investigated in the cerebellar mutant mice, staggerer and weaver, whose main defect is the loss of cerebellar granule cells, and the nervous mutant, whose main defect is the loss of Purkinje cells. The ATP-dependent glutamate uptake is stimulated by low concentrations of chloride, is insensitive to aspartate, and is inhibited by agents known to dissipate the electrochemical proton gradient. These properties are similar to those of the glutamate uptake system observed in the highly purified synaptic vesicles prepared from bovine cortex. The ATP-dependent glutamate uptake system is reduced by 68% in the staggerer and 57–67% in the weaver mutant; these reductions parallel the substantial loss of granule cells in those mutants. In contrast, the cerebellar levels of glutamate uptake are not altered significantly in the nervous mutant, which has lost Purkinje cells, but not granule cells. In view of evidence that granule cells are glutamatergic neurons and Purkinje cells are GABAergic neurons, these observations support the notion that the ATP-dependent glutamate uptake system is present in synaptic vesicles of glutamatergic neurons.

Publisher Summary This chapter discusses the glutamate accumulation into synaptic vesicles. A critical, but rate-limiting step, in the study of glutamate transport into synaptic vesicles is the preparation of synaptic vesicles that are free of contamination yet retain functional capability. However, this requires rather large quantities of affinity-purified antibodies to a synaptic vesicle protein, synapsin I, and, despite this requirement, the yield of such a vesicle preparation is too low to permit the analysis of vesicular glutamate uptake in small tissues. The chapter describes the assay and properties of the glutamate transport system in the synaptic vesicle in three preparations: (1) bovine brain synaptic vesicles highly purified by the use of antisynapsin I immunoglobulin G (IgG), (2) a bovine brain synaptic vesicle fraction purified by sucrose density gradient centrifugation, and (3) a rat brain crude synaptic vesicle fraction. Beyond the characterization of the properties of glutamate uptake into synaptic vesicles, little research has investigated in vivo changes in vesicular uptake.