Transmembrane potential of GlyCl-expressing instructor cells induces a neoplastic-like conversion of melanocytes via a serotonergic pathway

Aging as a loss of morphostatic information: A developmental bioelectricity perspective

Maintaining order at the tissue level is crucial throughout the lifespan, as failure can lead to cancer and an accumulation of molecular and cellular disorders. Perhaps, the most consistent and pervasive result of these failures is aging, which is characterized by the progressive loss of function and decline in the ability to maintain anatomical homeostasis and reproduce. This leads to organ malfunction, diseases, and ultimately death. The traditional understanding of aging is that it is caused by the accumulation of molecular and cellular damage. In this article, we propose a complementary view of aging from the perspective of endogenous bioelectricity which has not yet been integrated into aging research. We propose a view of aging as a morphostasis defect, a loss of biophysical prepattern information, encoding anatomical setpoints used for dynamic tissue and organ homeostasis. We hypothesize that this is specifically driven by abrogation of the endogenous bioelectric signaling that normally harnesses individual cell behaviors toward the creation and upkeep of complex multicellular structures in vivo. Herein, we first describe bioelectricity as the physiological software of life, and then identify and discuss the links between bioelectricity and life extension strategies and age-related diseases. We develop a bridge between aging and regeneration via bioelectric signaling that suggests a research program for healthful longevity via morphoceuticals. Finally, we discuss the broader implications of the homologies between development, aging, cancer and regeneration and how morphoceuticals can be developed for aging.

Collective intelligence: A unifying concept for integrating biology across scales and substrates

A defining feature of biology is the use of a multiscale architecture, ranging from molecular networks to cells, tissues, organs, whole bodies, and swarms. Crucially however, biology is not only nested structurally, but also functionally: each level is able to solve problems in distinct problem spaces, such as physiological, morphological, and behavioral state space. Percolating adaptive functionality from one level of competent subunits to a higher functional level of organization requires collective dynamics: multiple components must work together to achieve specific outcomes. Here we overview a number of biological examples at different scales which highlight the ability of cellular material to make decisions that implement cooperation toward specific homeodynamic endpoints, and implement collective intelligence by solving problems at the cell, tissue, and whole-organism levels. We explore the hypothesis that collective intelligence is not only the province of groups of animals, and that an important symmetry exists between the behavioral science of swarms and the competencies of cells and other biological systems at different scales. We then briefly outline the implications of this approach, and the possible impact of tools from the field of diverse intelligence for regenerative medicine and synthetic bioengineering.

Re-examining the evidence that ivermectin induces a melanoma-like state in Xenopus embryos

Modeling metastasis in animal systems has been an important focus for developing cancer therapeutics. Xenopus laevis is a well-established model, known for its use in identifying genetic mechanisms underlying diseases and disorders in humans. Prior literature has suggested that the drug, ivermectin, can be used in Xenopus to induce melanocytes to convert into a metastatic melanoma-like state, and thus could be ideal for testing possible melanoma therapies in vivo. However, there are notable inconsistencies between ivermectin studies in Xenopus and the application of ivermectin in mammalian systems, that are relevant to cancer and melanoma research. In this review, we examine the ivermectin-induced phenotypes in Xenopus, and we explore the current uses of ivermectin in human research. We conclude that while ivermectin may be a useful drug for many biomedical purposes, it is not ideal to induce a metastatic melanocyte phenotype in Xenopus for testing the effects of potential melanoma therapeutics.

Information integration during bioelectric regulation of morphogenesis of the embryonic frog brain

Spatiotemporal patterns of cellular resting potential regulate several aspects of development. One key aspect of the bioelectric code is that transcriptional and morphogenetic states are determined not by local, single-cell, voltage levels but by specific distributions of voltage across cell sheets. We constructed and analyzed a minimal dynamical model of collective gene expression in cells based on inputs of multicellular voltage patterns. Causal integration analysis revealed a higher-order mechanism by which information about the voltage pattern was spatiotemporally integrated into gene activity, as well as a division of labor among and between the bioelectric and genetic components. We tested and confirmed predictions of this model in a system in which bioelectric control of morphogenesis regulates gene expression and organogenesis: the embryonic brain of the frog Xenopus laevis. This study demonstrates that machine learning and computational integration approaches can advance our understanding of the information-processing underlying morphogenetic decision-making, with a potential for other applications in developmental biology and regenerative medicine.

Inter-organ communication during tissue regeneration

Tissue regeneration is not simply a local repair event occurring in isolation from the distant, uninjured parts of the body. Rather, evidence indicates that regeneration is a whole-animal process involving coordinated interactions between different organ systems. Here, we review recent studies that reveal how remote uninjured tissues and organ systems respond to and engage in regeneration. We also discuss the need for toolkits and technological advancements to uncover and dissect organ communication during regeneration.

Bioelectric networks: the cognitive glue enabling evolutionary scaling from physiology to mind

Each of us made the remarkable journey from mere matter to mind: starting life as a quiescent oocyte ("just chemistry and physics"), and slowly, gradually, becoming an adult human with complex metacognitive processes, hopes, and dreams. In addition, even though we feel ourselves to be a unified, single Self, distinct from the emergent dynamics of termite mounds and other swarms, the reality is that all intelligence is collective intelligence: each of us consists of a huge number of cells working together to generate a coherent cognitive being with goals, preferences, and memories that belong to the whole and not to its parts. Basal cognition is the quest to understand how Mind scales-how large numbers of competent subunits can work together to become intelligences that expand the scale of their possible goals. Crucially, the remarkable trick of turning homeostatic, cell-level physiological competencies into large-scale behavioral intelligences is not limited to the electrical dynamics of the brain. Evolution was using bioelectric signaling long before neurons and muscles appeared, to solve the problem of creating and repairing complex bodies. In this Perspective, I review the deep symmetry between the intelligence of developmental morphogenesis and that of classical behavior. I describe the highly conserved mechanisms that enable the collective intelligence of cells to implement regulative embryogenesis, regeneration, and cancer suppression. I sketch the story of an evolutionary pivot that repurposed the algorithms and cellular machinery that enable navigation of morphospace into the behavioral navigation of the 3D world which we so readily recognize as intelligence. Understanding the bioelectric dynamics that underlie construction of complex bodies and brains provides an essential path to understanding the natural evolution, and bioengineered design, of diverse intelligences within and beyond the phylogenetic history of Earth.

A Novel Perspective on Neuronal Control of Anatomical Patterning, Remodeling, and Maintenance

While the nervous system may be best known as the sensory communication center of an organism, recent research has revealed a myriad of multifaceted roles for both the CNS and PNS from early development to adult regeneration and remodeling. These systems work to orchestrate tissue pattern formation during embryonic development and continue shaping pattering through transitional periods such as metamorphosis and growth. During periods of injury or wounding, the nervous system has also been shown to influence remodeling and wound healing. The neuronal mechanisms responsible for these events are largely conserved across species, suggesting this evidence may be important in understanding and resolving many human defects and diseases. By unraveling these diverse roles, this paper highlights the necessity of broadening our perspective on the nervous system beyond its conventional functions. A comprehensive understanding of the complex interactions and contributions of the nervous system throughout development and adulthood has the potential to revolutionize therapeutic strategies and open new avenues for regenerative medicine and tissue engineering. This review highlights an important role for the nervous system during the patterning and maintenance of complex tissues and provides a potential avenue for advancing biomedical applications.

The Yin and Yang of Breast Cancer: Ion Channels as Determinants of Left-Right Functional Differences

Breast cancer is a complex and heterogeneous disease that displays diverse molecular subtypes and clinical outcomes. Although it is known that the location of tumors can affect their biological behavior, the underlying mechanisms are not fully understood. In our previous study, we found a differential methylation profile and membrane potential between left (L)- and right (R)-sided breast tumors. In this current study, we aimed to identify the ion channels responsible for this phenomenon and determine any associated phenotypic features. To achieve this, experiments were conducted in mammary tumors in mice, human patient samples, and with data from public datasets. The results revealed that L-sided tumors have a more depolarized state than R-sided. We identified a 6-ion channel-gene signature (CACNA1C, CACNA2D2, CACNB2, KCNJ11, SCN3A, and SCN3B) associated with the side: L-tumors exhibit lower expression levels than R-tumors. Additionally, in silico analyses show that the signature correlates inversely with DNA methylation writers and with key biological processes involved in cancer progression, such as proliferation and stemness. The signature also correlates inversely with patient survival rates. In an in vivo mouse model, we confirmed that KI67 and CD44 markers were increased in L-sided tumors and a similar tendency for KI67 was found in patient L-tumors. Overall, this study provides new insights into the potential impact of anatomical location on breast cancer biology and highlights the need for further investigation into possible differential treatment options.

Cellular signaling pathways as plastic, proto-cognitive systems: Implications for biomedicine

Many aspects of health and disease are modeled using the abstraction of a "pathway"-a set of protein or other subcellular activities with specified functional linkages between them. This metaphor is a paradigmatic case of a deterministic, mechanistic framework that focuses biomedical intervention strategies on altering the members of this network or the up-/down-regulation links between them-rewiring the molecular hardware. However, protein pathways and transcriptional networks exhibit interesting and unexpected capabilities such as trainability (memory) and information processing in a context-sensitive manner. Specifically, they may be amenable to manipulation via their history of stimuli (equivalent to experiences in behavioral science). If true, this would enable a new class of biomedical interventions that target aspects of the dynamic physiological "software" implemented by pathways and gene-regulatory networks. Here, we briefly review clinical and laboratory data that show how high-level cognitive inputs and mechanistic pathway modulation interact to determine outcomes in vivo. Further, we propose an expanded view of pathways from the perspective of basal cognition and argue that a broader understanding of pathways and how they process contextual information across scales will catalyze progress in many areas of physiology and neurobiology. We argue that this fuller understanding of the functionality and tractability of pathways must go beyond a focus on the mechanistic details of protein and drug structure to encompass their physiological history as well as their embedding within higher levels of organization in the organism, with numerous implications for data science addressing health and disease. Exploiting tools and concepts from behavioral and cognitive sciences to explore a proto-cognitive metaphor for the pathways underlying health and disease is more than a philosophical stance on biochemical processes; at stake is a new roadmap for overcoming the limitations of today's pharmacological strategies and for inferring future therapeutic interventions for a wide range of disease states.

Darwin's agential materials: evolutionary implications of multiscale competency in developmental biology

A critical aspect of evolution is the layer of developmental physiology that operates between the genotype and the anatomical phenotype. While much work has addressed the evolution of developmental mechanisms and the evolvability of specific genetic architectures with emergent complexity, one aspect has not been sufficiently explored: the implications of morphogenetic problem-solving competencies for the evolutionary process itself. The cells that evolution works with are not passive components: rather, they have numerous capabilities for behavior because they derive from ancestral unicellular organisms with rich repertoires. In multicellular organisms, these capabilities must be tamed, and can be exploited, by the evolutionary process. Specifically, biological structures have a multiscale competency architecture where cells, tissues, and organs exhibit regulative plasticity-the ability to adjust to perturbations such as external injury or internal modifications and still accomplish specific adaptive tasks across metabolic, transcriptional, physiological, and anatomical problem spaces. Here, I review examples illustrating how physiological circuits guiding cellular collective behavior impart computational properties to the agential material that serves as substrate for the evolutionary process. I then explore the ways in which the collective intelligence of cells during morphogenesis affect evolution, providing a new perspective on the evolutionary search process. This key feature of the physiological software of life helps explain the remarkable speed and robustness of biological evolution, and sheds new light on the relationship between genomes and functional anatomical phenotypes.

Morphoceuticals: perspectives for discovery of drugs targeting anatomical control mechanisms in regenerative medicine, cancer and aging

Morphoceuticals are a new class of interventions that target the setpoints of anatomical homeostasis for efficient, modular control of growth and form. Here, we focus on a subclass: electroceuticals, which specifically target the cellular bioelectrical interface. Cellular collectives in all tissues form bioelectrical networks via ion channels and gap junctions that process morphogenetic information, controlling gene expression and allowing cell networks to adaptively and dynamically control growth and pattern formation. Recent progress in understanding this physiological control system, including predictive computational models, suggests that targeting bioelectrical interfaces can control embryogenesis and maintain shape against injury, senescence and tumorigenesis. We propose a roadmap for drug discovery focused on manipulating endogenous bioelectric signaling for regenerative medicine, cancer suppression and antiaging therapeutics. Teaser: By taking advantage of the native problem-solving competencies of cells and tissues, a new kind of top-down approach to biomedicine becomes possible. Bioelectricity offers an especially tractable interface for interventions targeting the software of life for regenerative medicine applications.

Information Theory as an Experimental Tool for Integrating Disparate Biophysical Signaling Modules

There is a growing appreciation in the fields of cell biology and developmental biology that cells collectively process information in time and space. While many powerful molecular tools exist to observe biophysical dynamics, biologists must find ways to quantitatively understand these phenomena at the systems level. Here, we present a guide for the application of well-established information theory metrics to biological datasets and explain these metrics using examples from cell, developmental and regenerative biology. We introduce a novel computational tool named after its intended purpose, calcium imaging, (CAIM) for simple, rigorous application of these metrics to time series datasets. Finally, we use CAIM to study calcium and cytoskeletal actin information flow patterns between Xenopus laevis embryonic animal cap stem cells. The tools that we present here should enable biologists to apply information theory to develop a systems-level understanding of information processing across a diverse array of experimental systems.

Screening Biophysical Sensors and Neurite Outgrowth Actuators in Human Induced-Pluripotent-Stem-Cell-Derived Neurons

All living cells maintain a charge distribution across their cell membrane (membrane potential) by carefully controlled ion fluxes. These bioelectric signals regulate cell behavior (such as migration, proliferation, differentiation) as well as higher-level tissue and organ patterning. Thus, voltage gradients represent an important parameter for diagnostics as well as a promising target for therapeutic interventions in birth defects, injury, and cancer. However, despite much progress in cell and molecular biology, little is known about bioelectric states in human stem cells. Here, we present simple methods to simultaneously track ion dynamics, membrane voltage, cell morphology, and cell activity (pH and ROS), using fluorescent reporter dyes in living human neurons derived from induced neural stem cells (hiNSC). We developed and tested functional protocols for manipulating ion fluxes, membrane potential, and cell activity, and tracking neural responses to injury and reinnervation in vitro. Finally, using morphology sensor, we tested and quantified the ability of physiological actuators (neurotransmitters and pH) to manipulate nerve repair and reinnervation. These methods are not specific to a particular cell type and should be broadly applicable to the study of bioelectrical controls across a wide range of combinations of models and endpoints.

HCN2 Channel-induced Rescue of Brain, Eye, Heart, and Gut Teratogenesis Caused by Nicotine, Ethanol, and Aberrant Notch Signaling

Organogenesis is a complex process that can be disrupted by embryonic exposure to teratogens or mutation-induced alterations in signaling pathways, both of which result in organ mispatterning. Building on prior work in Xenopus laevis that showed that increased HCN2 ion channel activity rescues nicotine-induced brain & eye morphogenesis, we demonstrate much broader HCN2-based rescue of organ patterning defects. Induced HCN2 expression in both local or distant tissues can rescue CNS (brain & eye) as well as non-CNS (heart, & gut) organ defects induced by three different teratogenic conditions: nicotine exposure, ethanol exposure, or aberrant Notch protein. Rescue can also be induced by small-molecule HCN2 channel activators, even with delayed treatment initiation. Our results suggest that HCN2 (likely mediated by bioelectric signals) can be an effective regulator of organogenesis from all three germ layers (ectoderm, mesoderm, and endoderm) and reveal non-cell-autonomous influences on organ formation that work at considerable distance during embryonic development. These results suggest molecular bioelectric strategies for repair that could be explored in the future for regenerative medicine. This article is protected by copyright. All rights reserved.

Technological Approach to Mind Everywhere: An Experimentally-Grounded Framework for Understanding Diverse Bodies and Minds

Synthetic biology and bioengineering provide the opportunity to create novel embodied cognitive systems (otherwise known as minds) in a very wide variety of chimeric architectures combining evolved and designed material and software. These advances are disrupting familiar concepts in the philosophy of mind, and require new ways of thinking about and comparing truly diverse intelligences, whose composition and origin are not like any of the available natural model species. In this Perspective, I introduce TAME-Technological Approach to Mind Everywhere-a framework for understanding and manipulating cognition in unconventional substrates. TAME formalizes a non-binary (continuous), empirically-based approach to strongly embodied agency. TAME provides a natural way to think about animal sentience as an instance of collective intelligence of cell groups, arising from dynamics that manifest in similar ways in numerous other substrates. When applied to regenerating/developmental systems, TAME suggests a perspective on morphogenesis as an example of basal cognition. The deep symmetry between problem-solving in anatomical, physiological, transcriptional, and 3D (traditional behavioral) spaces drives specific hypotheses by which cognitive capacities can increase during evolution. An important medium exploited by evolution for joining active subunits into greater agents is developmental bioelectricity, implemented by pre-neural use of ion channels and gap junctions to scale up cell-level feedback loops into anatomical homeostasis. This architecture of multi-scale competency of biological systems has important implications for plasticity of bodies and minds, greatly potentiating evolvability. Considering classical and recent data from the perspectives of computational science, evolutionary biology, and basal cognition, reveals a rich research program with many implications for cognitive science, evolutionary biology, regenerative medicine, and artificial intelligence.

Bioelectric Dysregulation in Cancer Initiation, Promotion, and Progression

Cancer is primarily a disease of dysregulation – both at the genetic level and at the tissue organization level. One way that tissue organization is dysregulated is by changes in the bioelectric regulation of cell signaling pathways. At the basis of bioelectricity lies the cellular membrane potential or V_mem, an intrinsic property associated with any cell. The bioelectric state of cancer cells is different from that of healthy cells, causing a disruption in the cellular signaling pathways. This disruption or dysregulation affects all three processes of carcinogenesis – initiation, promotion, and progression. Another mechanism that facilitates the homeostasis of cell signaling pathways is the production of extracellular vesicles (EVs) by cells. EVs also play a role in carcinogenesis by mediating cellular communication within the tumor microenvironment (TME). Furthermore, the production and release of EVs is altered in cancer. To this end, the change in cell electrical state and in EV production are responsible for the bioelectric dysregulation which occurs during cancer. This paper reviews the bioelectric dysregulation associated with carcinogenesis, including the TME and metastasis. We also look at the major ion channels associated with cancer and current technologies and tools used to detect and manipulate bioelectric properties of cells.

Beyond Neurons: Long Distance Communication in Development and Cancer

Cellular communication is important in all aspects of tissue and organism functioning, from the level of single cells, two discreet populations, and distant tissues of the body. Long distance communication networks integrate individual cells into tissues to maintain a complex organism during development, but when communication between cells goes awry, disease states such as cancer emerge. Herein we discuss the growing body of evidence suggesting that communication methods known to be employed by neurons, also exist in other cell types. We identify three major areas of long-distance communication: bioelectric signaling, tunneling nanotubes (TNTs), and macrophage modulation of networks, and draw comparisons about how these systems operate in the context of development and cancer. Bioelectric signaling occurs between cells through exchange of ions and tissue-level electric fields, leading to changes in biochemical gradients and molecular signaling pathways to control normal development and tumor growth and invasion in cancer. TNTs transport key morphogens and other cargo long distances, mediating electrical coupling, tissue patterning, and malignancy of cancer cells. Lastly macrophages maintain long distance signaling networks through trafficking of vesicles during development, providing communication relays and priming favorable microenvironments for cancer metastasis. By drawing comparisons between non-neural long distance signaling in the context of development and cancer we aim to encourage crosstalk between the two fields to cultivate new hypotheses and potential therapeutic strategies.

Understanding Lung Carcinogenesis from a Morphostatic Perspective: Prevention and Therapeutic Potential of Phytochemicals for Targeting Cancer Stem Cells

Lung cancer is still one of the deadliest cancers, with over two million incidences annually. Prevention is regarded as the most efficient way to reduce both the incidence and death figures. Nevertheless, treatment should still be improved, particularly in addressing therapeutic resistance due to cancer stem cells—the assumed drivers of tumor initiation and progression. Phytochemicals in plant-based diets are thought to contribute substantially to lung cancer prevention and may be efficacious for targeting lung cancer stem cells. In this review, we collect recent literature on lung homeostasis, carcinogenesis, and phytochemicals studied in lung cancers. We provide a comprehensive overview of how normal lung tissue operates and relate it with lung carcinogenesis to redefine better targets for lung cancer stem cells. Nine well-studied phytochemical compounds, namely curcumin, resveratrol, quercetin, epigallocatechin-3-gallate, luteolin, sulforaphane, berberine, genistein, and capsaicin, are discussed in terms of their chemopreventive and anticancer mechanisms in lung cancer and potential use in the clinic. How the use of phytochemicals can be improved by structural manipulations, targeted delivery, concentration adjustments, and combinatorial treatments is also highlighted. We propose that lung carcinomas should be treated differently based on their respective cellular origins. Targeting quiescence-inducing, inflammation-dampening, or reactive oxygen species-balancing pathways appears particularly interesting.

Cancer as a form of life: Musings of the cancer and evolution symposium

Advanced cancer is one of the major problems in oncology as currently, despite the recent technological and scientific advancements, the mortality of metastatic disease remains very high at 70-90%. The field of oncology is in urgent need of novel ideas in order to improve quality of life and prognostic of cancer patients. The Cancer and Evolution Symposium organized online October 14-16, 2020 brought together a group of specialists from different fields that presented innovative strategies for better understanding, preventing, diagnosing, and treating cancer. Today still, the main reasons behind the high incidence and mortality of advanced cancer are, on one hand, the paucity of funding and effort directed to cancer prevention and early detection, and, on the other hand, the lack of understanding of the cancer process itself. I argue that besides being a disease, cancer is also a form of life, and, this frame of reference may provide a fresh look on this complex process. Here, I provide a different angle to several contemporary cancer theories discussing them from the perspective of "cancer-forms of life" (i.e. bionts) point of view. The perspectives and the several "bionts" introduced here, by no means exclusive or comprehensive, are just a shorthand that will hopefully encourage the readers, to further explore the contemporary oncology theoretical landscape.

Bioelectrical approaches to cancer as a problem of the scaling of the cellular self

One lens with which to understand the complex phenomenon of cancer is that of developmental biology. Cancer is the inevitable consequence of a breakdown of the communication that enables individual cells to join into computational networks that work towards large-scale, morphogenetic goals instead of more primitive, unicellular objectives. This perspective suggests that cancer may be a physiological disorder, not necessarily due to problems with the genetically-specified protein hardware. One aspect of morphogenetic coordination is bioelectric signaling, and indeed an abnormal bioelectric signature non-invasively reveals the site of incipient tumors in amphibian models. Functionally, a disruption of resting potential states triggers metastatic melanoma phenotypes in embryos with no genetic defects or carcinogen exposure. Conversely, optogenetic or molecular-biological modulation of bioelectric states can override powerful oncogenic mutations and prevent or normalize tumors. The bioelectrically-mediated information flows that harness cells toward body-level anatomical outcomes represent a very attractive and tractable endogenous control system, which is being targeted by emerging approaches to cancer.

Connexin 43 gap junctional intercellular communication inhibits evx1 expression and joint formation in regenerating fins

The gap junction protein Connexin 43 (Cx43) contributes to cell fate decisions that determine the location of fin ray joints during regeneration. Here, we provide insights into how Cx43, expressed medially, influences changes in gene expression in lateral skeletal precursor cells. Using the Gap27 peptide inhibitor specific to Cx43, we show that Cx43-gap junctional intercellular communication (GJIC) influences Cx43-dependent skeletal phenotypes, including segment length. We also demonstrate that Cx43-GJIC influences the expression of the Smp/β-catenin pathway in the lateral skeletal precursor cells, and does not influence the Sema3d pathway. Moreover, we show that the cx43^lh10 allele, which has increased Cx43 protein levels, exhibits increased regenerate length and segment length. These phenotypes are rescued by Gap27, suggesting that increased Cx43 is responsible for the observed Cx43 phenotypes. Finally, our findings suggest that inhibition of Cx43 hemichannel activity does not influence Cx43-dependent skeletal phenotypes. These data provide evidence that Cx43-GJIC is responsible for regulating cell fate decisions associated with appropriate joint formation in the regenerating fin.

Sertraline induces DNA damage and cellular toxicity in Drosophila that can be ameliorated by antioxidants

Sertraline hydrochloride is a commonly prescribed antidepressant medication that acts by amplifying serotonin signaling. Numerous studies have suggested that children of women  taking sertraline during pregnancy have an increased risk of developmental defects. Resolving the degree of risk for human fetuses requires comprehensive knowledge of the pathways affected by this drug. We utilized a Drosophila melanogaster model system to assess the effects of sertraline throughout development. Ingestion of sertraline by females did not affect their fecundity or embryogenesis in their progeny. However, larvae that consumed sertraline experienced delayed developmental progression and reduced survival at all stages of development. Genetic experiments showed that these effects were mostly independent of aberrant extracellular serotonin levels. Using an ex vivo imaginal disc culture system, we showed that mitotically active sertraline-treated tissues accumulate DNA double-strand breaks and undergo apoptosis at increased frequencies. Remarkably, the sertraline-induced genotoxicity was partially rescued by co-incubation with ascorbic acid, suggesting that sertraline induces oxidative DNA damage. These findings may have implications for the biomedicine of sertraline-induced birth defects.

Post-SSRI Sexual Dysfunction: A Bioelectric Mechanism?

Selective serotonin reuptake inhibitor (SSRI) drugs, targeting serotonin transport, are widely used. A puzzling and biomedically important phenomenon concerns the persistent sexual dysfunction following SSRI use seen in some patients. What could be the mechanism of a persistent physiological state brought on by a transient exposure to serotonin transport blockers? In this study, we briefly review the clinical facts concerning this side effect of serotonin reuptake inhibitors and suggest a possible mechanism. Bioelectric circuits (among neural or non-neural cells) could persistently maintain alterations of bioelectric cell properties (resting potential), resulting in long-term changes in electrophysiology and signaling. We present new data revealing this phenomenon in planarian flatworms, in which brief SSRI exposures induce long-lasting changes in resting potential profile. We also briefly review recent data linking neurotransmitter signaling to developmental bioelectrics. Further study of tissue bioelectric memory could enable the design of ionoceutical interventions to counteract side effects of SSRIs and similar drugs.

How much are microplastics harmful to the health of amphibians? A study with pristine polyethylene microplastics and Physalaemus cuvieri

Microplastics (MPs) are critical emerging pollutants found in the environment worldwide; however, its toxicity in aquatic in amphibians, is poorly known. Thus, the aim of the present study is to assess the toxicological potential of polyethylene microplastics (PE MPs) in Physalaemus cuvieri tadpoles. According to the results, tadpoles' exposure to MP PE at concentration 60 mg/L for 7 days led to mutagenic effects, which were evidenced by the increased number of abnormalities observed in nuclear erythrocytes. The small size of erythrocytes and their nuclei area, perimeter, width, length, and radius, as well as the lower nucleus/cytoplasm ratio observed in tadpoles exposed to PE MPs confirmed its cytotoxicity. External morphological changes observed in the animal models included reduced ratio between total length and mouth-cloaca distance, caudal length, ocular area, mouth area, among others. PE MPs increased the number of melanophores in the skin and pigmentation rate in the assessed areas. Finally, PE MPs were found in gills, gastrointestinal tract, liver, muscle tissues of the tail and in the blood, a fact that confirmed MP accumulation by tadpoles. Therefore, the present study pioneering evidenced how MPs can affect the health of amphibians.

Quick, Single-Frequency Dielectric Characterization of Blood Samples of Pediatric Cancer Patients by a Cylindrical Capacitor: Pilot Study

In this paper, as an application in biometrics, the electrical capacitance of normal and cancerous blood samples is experimentally determined in order to test the null hypothesis that the electrical capacitance of the two samples differs. The samples taken from healthy donors and patients diagnosed with different types of hematologic cancer are examined by a cylindrical capacitor with blood as its dielectric. The capacitance of these samples is measured at room temperature and a single frequency of 120 Hz, well below the frequency where β -dispersion starts, using a simple LCR meter device. The measurements indicate that the capacitance of the blood increases under applied electric field for a short period of time and asymptotically reaches its steady-state value. The measured values for the healthy group agreed with previous data in the literature. By the use of the unpaired two-tailed T-test, it is found that cancerous blood has higher values of capacitance when compared to normal samples ( p < 0.05 ). The reasons that might lead to such alterations are discussed from a biological perspective. Moreover, based on correlation calculations, a strong negative association is observed between blood capacitance and red blood cell (RBC) count in each group. Furthermore, sensitivity (SE) and specificity (SP) analysis demonstrates that for a threshold value between 15 and 17 for the capacitance value, both SE and SP are 100%. These preliminary findings on capacitance values may pave the way for the development of inexpensive and easy-to-use diagnosis tools for hematologic cancers at medical facilities and for in-home use, especially for children.

Endogenous Bioelectrics in Development, Cancer, and Regeneration: Drugs and Bioelectronic Devices as Electroceuticals for Regenerative Medicine

A major frontier in the post-genomic era is the investigation of the control of coordinated growth and three-dimensional form. Dynamic remodeling of complex organs in regulative embryogenesis, regeneration, and cancer reveals that cells and tissues make decisions that implement complex anatomical outcomes. It is now essential to understand not only the genetics that specifies cellular hardware but also the physiological software that implements tissue-level plasticity and robust morphogenesis. Here, we review recent discoveries about the endogenous mechanisms of bioelectrical communication among non-neural cells that enables them to cooperate in vivo. We discuss important advances in bioelectronics, as well as computational and pharmacological tools that are enabling the taming of biophysical controls toward applications in regenerative medicine and synthetic bioengineering.

Toward Decoding Bioelectric Events in Xenopus Embryogenesis: New Methodology for Tracking Interplay Between Calcium and Resting Potentials In Vivo

Although chemical signaling during embryogenesis is readily addressed by a plethora of available techniques, the developmental functions of ionic signaling are still poorly understood. It is increasingly realized that bioelectric events in nonneural cells are critical for pattern regulation, but their study has been hampered by difficulties in monitoring and manipulating them in vivo. Recent developments in visualizing electrical signaling dynamics in the field of neuroscience have facilitated functional experiments that reveal instructive developmental bioelectric signals. However, there is a pressing need for additional tools to explore time-dependent ionic signaling to understand complex endogenous dynamics. Here, we present methodological advances, including 4D imaging and data analysis, for improved tracking of calcium flux in the Xenopus laevis embryo, lowering the barrier for in vivo physiology work in this important model system. Using these techniques, we investigated the relationship between bioelectric ion channel activity and calcium, finding that cell hyperpolarization and depolarization both induce persistent static elevation of cytoplasmic calcium levels that fade over developmental time. These calcium changes correlate with increased cell mobility in early embryos and abnormal craniofacial morphology in later embryos. We thus highlight membrane potential modulation as a tractable tool for modulation of signaling cascades that rely on calcium as a transduction mechanism. The methods we describe facilitate the study of important novel aspects of developmental physiology, are extendable to numerous classes of existing and forthcoming fluorescent physiological reporters, and establish highly accessible, inexpensive protocols for their investigation.

Maintenance of Melanocyte Stem Cell Quiescence by GABA-A Signaling in Larval Zebrafish

In larval zebrafish, melanocyte stem cells (MSCs) are quiescent, but can be recruited to regenerate the larval pigment pattern following melanocyte ablation. Through pharmacological experiments, we found that inhibition of γ-aminobutyric acid (GABA)-A receptor function, specifically the GABA-A ρ subtype, induces excessive melanocyte production in larval zebrafish. Conversely, pharmacological activation of GABA-A inhibited melanocyte regeneration. We used clustered regularly interspaced short palindromic repeats/Cas9 to generate two mutant alleles of gabrr1, a subtype of GABA-A receptors. Both alleles exhibited robust melanocyte overproduction, while conditional overexpression of gabrr1 inhibited larval melanocyte regeneration. Our data suggest that gabrr1 signaling is necessary to maintain MSC quiescence and sufficient to reduce, but not eliminate, melanocyte regeneration in larval zebrafish.

Bioelectric Control of Metastasis in Solid Tumors

As the leading cause of death in cancer, there is an urgent need to develop treatments to target the dissemination of primary tumor cells to secondary organs, known as metastasis. Bioelectric signaling has emerged in the last century as an important controller of cell growth, and with the development of current molecular tools we are now beginning to identify its role in driving cell migration and metastasis in a variety of cancer types. This review summarizes the currently available research for bioelectric signaling in solid tumor metastasis. We review the steps of metastasis and discuss how these can be controlled by bioelectric cues at the level of a cell, a population of cells, and the tissue. The role of ion channel, pump, and exchanger activity and ion flux is discussed, along with the importance of the membrane potential and the relationship between ion flux and membrane potential. We also provide an overview of the evidence for control of metastasis by external electric fields (EFs) and draw from examples in embryogenesis and regeneration to discuss the implications for endogenous EFs. By increasing our understanding of the dynamic properties of bioelectric signaling, we can develop new strategies that target metastasis to be translated into the clinic.

Hierarchical pattern formation during amphibian limb regeneration

In 1901 T.H. Morgan proposed in "Regeneration" that pattern formation in amphibian limb regeneration is a stepwise process. Since, biologist have continued to piece together the molecular components of this process to better understand the "patterning code" responsible for regenerate formation. Within this context, several different models have been proposed; however, all are based on one of two underlying hypotheses. The first is the "morphogen hypothesis" that dictates that pattern emerges from localized expression of signaling molecules, which produce differing position-specific cellular responses in receptive cells depending on the intensity of the signal. The second hypothesis is that cells in the remaining tissues retain memory of their patterning information, and use this information to generate new cells with the missing positional identities. A growing body of evidence supports the possibility that these two mechanisms are not mutually exclusive. Here, we propose our theory of hierarchical pattern formation, which consists of 4 basic steps. The first is the existence of cells with positional memory. The second is the communication of positional information through cell-cell interactions in a regeneration-permissive environment. The third step is the induction of molecular signaling centers. And the last step is the interpretation of these signals by specialized cell types to ultimately restore the limb in its entirety. Biological codes are intertwined throughout this model, and we will discuss their multiple roles and mechanisms.

The Order of Cancer: A Theory of Malignant Progression by Inverse Morphogenesis

Local spread patterns of malignant tumors follow permissive tissue territories, i.e., cancer fields, as shown for cervical and vulvar carcinoma. The cancer fields are associated in reverse order to the mature derivatives of the morphogenetic fields instrumental in the stepwise development of the tissue from which the tumor arose. This suggests that cancer progression may be linked to morphogenesis by inversion of the cellular bauplan sequence. Successive attractor transitions caused by proliferation-associated constraints of topobiological information processing are proposed for both morphogenesis and cancer. In morphogenesis these transitions sequentially activate bauplans with increasing complexity at decreasing plasticity restricting the permissive territories of the progenitor cell populations. Somatic mutations leading to cell proliferation in domains normally reserved for differentiation trigger the inverse cascade of bauplan changes that increase topobiological plasticity at decreased complexity and stepwise enlarge the permissive territory of neoplastic cells consistent with the clinical manifestations of cancer. The order provided by the sequence of attractor transitions and the defined topography of the permissive territories can be exploited for more accurate tumor staging and for locoregional tumor treatment either by surgery or radiotherapy with higher curative potential.

Ion Channel and Neurotransmitter Modulators as Electroceutical Approaches to the Control of Cancer

The activities of individual cells must be tightly coordinated in order to build and maintain complex 3-dimensional body structures during embryogenesis and regeneration. Thus, one way to view cancer is within systems biology as a network disorder affecting the ability of cells to properly interact with a morphodynamic field of instructive signals that keeps proliferation and migration orchestrated toward the anatomical needs of the host or-ganism. One layer of this set of instructive microenvironmental cues is bioelectrical. Voltage gradients among all somatic cells (not just excitable nerve and muscle) control cell behavior, and the ionic coupling of cells into networks via electrochemical synapses allows them to implement tissue-level patterning decisions. These gradients have been increasingly impli-cated in the induction and suppression of tumorigenesis and metastasis, in the emerging links between developmental bioelectricity to the cancer problem. Consistent with the well-known role of neurotransmitter molecules in transducing electrical activity to downstream cascades in the brain, serotonergic signaling has likewise been implicated in cancer. Here, we review these recent data and propose new approaches for manipulating bioelectric and neurotransmitter pathways in cancer biology based on a bioelectric view of cancer. To sup-port this methodology, we present new data on the effects of the SSRI Prozac and its analog (ZINC ID = ZINC06811610) on survival of both cancer (MCF7) and normal (MCF10A) breast cells exposed to these compounds. We found an IC50 concentration (25 μM for Pro-zac and 100 μM for the Prozac analog) at which these compounds inhibited tumor cell sur-vival and proliferation. Additionally, at these concentrations, we did not observe alterations in a non-tumoral cell line. This constitutes a proof-of-concept demonstration for our hy-pothesis that the use of both existing and novel drugs as electroceuticals could serve as an alternative to highly toxic chemotherapy strategies replacing or augmenting them with less toxic alternatives. We believe this new approach forms an exciting roadmap for future bio-medical advances.

Planarian regeneration as a model of anatomical homeostasis: Recent progress in biophysical and computational approaches

Planarian behavior, physiology, and pattern control offer profound lessons for regenerative medicine, evolutionary biology, morphogenetic engineering, robotics, and unconventional computation. Despite recent advances in the molecular genetics of stem cell differentiation, this model organism's remarkable anatomical homeostasis provokes us with truly fundamental puzzles about the origin of large-scale shape and its relationship to the genome. In this review article, we first highlight several deep mysteries about planarian regeneration in the context of the current paradigm in this field. We then review recent progress in understanding of the physiological control of an endogenous, bioelectric pattern memory that guides regeneration, and how modulating this memory can permanently alter the flatworm's target morphology. Finally, we focus on computational approaches that complement reductive pathway analysis with synthetic, systems-level understanding of morphological decision-making. We analyze existing models of planarian pattern control and highlight recent successes and remaining knowledge gaps in this interdisciplinary frontier field.

Selective Serotonin Reuptake Inhibitor Use During Pregnancy and Major Malformations: The Importance of Serotonin for Embryonic Development and the Effect of Serotonin Inhibition on the Occurrence of Malformations

Bioelectric signaling is transduced by neurotransmitter pathways in many cell types. One of the key mediators of bioelectric control mechanisms is serotonin, and its transporter SERT, which is targeted by a broad class of blocker drugs (selective serotonin reuptake inhibitors [SSRIs]). Studies showing an increased risk of multiple malformations associated with gestational use of SSRI have been accumulating but debate remains on whether SSRI as a class has the potential to generate these malformations. This review highlights the importance of serotonin for embryonic development; the effect of serotonin inhibition during early pregnancy on the occurrence of multiple diverse malformations that have been shown to occur in human pregnancies; that the risks outweigh the benefits of SSRI use during gestation in populations of mild to moderately depressed pregnant women, which encompass the majority of pregnant depressed women; and that the malformations seen in human pregnancies constitute a pattern of malformations consistent with the known mechanisms of action of SSRIs. We present at least three mechanisms by which SSRI can affect development. These studies highlight the relevance of basic bioelectric and neurotransmitter mechanism for biomedicine.

Anti-cancer drugs in aquatic environment can cause cancer: Insight about mutagenicity in tadpoles

Cyclophosphamide (Cyc) and 5-fluorouracil (5-FU) are two of the most used antineoplastic drugs (AD) in the world. However, their discharge in the environment became a yet-unknown environmental issue that has impact on some groups of animals, such as amphibians. We assessed tadpoles (Lithobates catesbeianus) exposed to environmental concentrations (EC) of Cyc and 5-FU to evaluate whether they can cause morphological and mutagenic changes in them. We defined the following groups: control, positive control (50 mg/L of Cyc), EC-Cyc-I (0.2 μg/L), EC-Cyc-II (0.5 μg/L), EF-Cyc (2.0 μg/L), EC-5-FU-I (13.0 μg/L), EC-5-FU-II (30.4 μg/L) and EF-5-FU (123.5 μg/L). EC groups presented predictive AD concentrations in 10% and 25% hospital-effluent dilutions in water. EF groups met gross hospital-effluent concentrations. Based on our data, ADs caused intestinal changes and influenced the interocular distance in tadpoles after 30-day exposure. We also observed the aneugenic and clastogenic effect of ADs due to the higher frequency of micronucleated and binucleated erythrocytes, and blebbed, multilobulated, notched and kidney-shaped nuclei in animals exposed to them. Based on such changes, we assume that Cyc and 5-FU can trigger malignant cell transformation processes, and cancer, in animals exposed to them, even at low concentrations. Our study is the first to describe that Cyc and 5-FU, spread in the environment, cause damages in non-target organisms opposite to their original end.

EDEn-Electroceutical Design Environment: Ion Channel Tissue Expression Database with Small Molecule Modulators

The emerging field of bioelectricity has revealed numerous new roles for ion channels beyond the nervous system, which can be exploited for applications in regenerative medicine. Developing such biomedical interventions for birth defects, cancer, traumatic injury, and bioengineering first requires knowledge of ion channel targets expressed in tissues of interest. This information can then be used to select combinations of small molecule inhibitors and/or activators that manipulate the bioelectric state. Here, we provide an overview of electroceutical design environment (EDEn), the first bioinformatic platform that facilitates the design of such therapeutic strategies. This database includes information on ion channels and ion pumps, linked to known chemical modulators and their properties. The database also provides information about the expression levels of the ion channels in over 100 tissue types. The graphical interface allows the user to readily identify chemical entities that can alter the electrical properties of target cells and tissues.

Effects of Ivermectin Exposure on Regeneration of D. dorotocephala Planaria: Exploiting Human-Approved Ion Channel Drugs as Morphoceuticals

Transformative applications in regenerative medicine await increased control of processes implementing repair and remodeling of complex living structures. Recent work reveals ion channel drugs as a powerful toolkit for modulating endogenous bioelectric circuits that control growth and form in vivo and in vitro. It is therefore especially important to develop assays in model systems that will enable the testing of these "morphoceuticals"-compounds with predictable effects on anatomical structure. The regenerative planaria are an ideal model system for this purpose. Several studies have shown a role for bioelectric signaling in planarian regeneration, but these have focused on Dugesia japonica and Schmidtea mediterranea. It is not known how the alterations of ion channel activity would affect regeneration in other species of planaria-an important aspect of building robust computational models of bioelectric circuits. Here, the effect of ivermectin (IVM), a chloride channel opener drug commonly used to combat heartworm is tested, on regeneration in a new species of planaria: Dugesia dorotocephala. Exposure to IVM during regeneration results in patterning abnormalities, such as bifurcated tails with partial heads, as well as delayed regeneration. These data extend our understanding of the effects of human-approved ion channel drugs on regenerative processes.

Xenopus Models of Cancer: Expanding the Oncologist's Toolbox

The use of the Xenopus model system has provided diverse contributions to cancer research, not least because of the striking parallels between tumour pathogenesis and early embryo development. Cell cycle regulation, signalling pathways, and cell behaviours such as migration are frequently perturbed in cancers; all have been investigated using Xenopus, and these developmental events can additionally act as an assay for drug development studies. In this mini-review, we focus our discussion primarily on whole embryo Xenopus models informing cancer biology; the contributions to date and future potential. Insights into tumour immunity, oncogene function, and visualisation of vascular responses during tumour formation have all been achieved with naturally occurring tumours and induced-tumour-like-structures in Xenopus. Finally, as we are now entering the era of genetically modified Xenopus models, we can harness genome editing techniques to recapitulate human disease through creating embryos with analogous genetic abnormalities. With the speed, versatility and accessibility that epitomise the Xenopus system, this new range of pre-clinical Xenopus models has great potential to advance our mechanistic understanding of oncogenesis and provide an early in vivo model for chemotherapeutic development.

Emerging Roles of the Membrane Potential: Action Beyond the Action Potential

Whilst the phenomenon of an electrical resting membrane potential (RMP) is a central tenet of biology, it is nearly always discussed as a phenomenon that facilitates the propagation of action potentials in excitable tissue, muscle, and nerve. However, as ion channel research shifts beyond these tissues, it became clear that the RMP is a feature of virtually all cells studied. The RMP is maintained by the cell’s compliment of ion channels. Transcriptome sequencing is increasingly revealing that equally rich compliments of ion channels exist in both excitable and non-excitable tissue. In this review, we discuss a range of critical roles that the RMP has in a variety of cell types beyond the action potential. Whereas most biologists would perceive that the RMP is primarily about excitability, the data show that in fact excitability is only a small part of it. Emerging evidence show that a dynamic membrane potential is critical for many other processes including cell cycle, cell-volume control, proliferation, muscle contraction (even in the absence of an action potential), and wound healing. Modulation of the RMP is therefore a potential target for many new drugs targeting a range of diseases and biological functions from cancer through to wound healing and is likely to be key to the development of successful stem cell therapies.

Involvement of AMP-activated Protein Kinase (AMPK) in Regulation of Cell Membrane Potential in a Gastric Cancer Cell Line

Membrane potential (V_mem) is a key bioelectric property of non-excitable cells that plays important roles in regulating cell proliferation. However, the regulation of V_mem itself remains largely unexplored. We found that, under nutrient starvation, during which cell division is inhibited, MKN45 gastric cancer cells were in a hyperpolarized state associated with a high intracellular chloride concentration. AMP-activated protein kinase (AMPK) activity increased, and expression of cystic fibrosis transmembrane conductance regulator (CFTR) decreased, in nutrient-starved cells. Furthermore, the increase in intracellular chloride concentration level and V_mem hyperpolarization in nutrient-starved cells was suppressed by inhibition of AMPK activity. Intracellular chloride concentrations and hyperpolarization increased after over-activation of AMPK using the specific activator AICAR or suppression of CFTR activity using specific inhibitor GlyH-101. Under these conditions, proliferation of MKN45 cells was inhibited. These results reveal that AMPK controls the dynamic change in V_mem by regulating CFTR and influencing the intracellular chloride concentration, which in turn influences cell-cycle progression. These findings offer new insights into the mechanisms underlying cell-cycle arrest regulated by AMPK and CFTR.

The bioelectric code: An ancient computational medium for dynamic control of growth and form

What determines large-scale anatomy? DNA does not directly specify geometrical arrangements of tissues and organs, and a process of encoding and decoding for morphogenesis is required. Moreover, many species can regenerate and remodel their structure despite drastic injury. The ability to obtain the correct target morphology from a diversity of initial conditions reveals that the morphogenetic code implements a rich system of pattern-homeostatic processes. Here, we describe an important mechanism by which cellular networks implement pattern regulation and plasticity: bioelectricity. All cells, not only nerves and muscles, produce and sense electrical signals; in vivo, these processes form bioelectric circuits that harness individual cell behaviors toward specific anatomical endpoints. We review emerging progress in reading and re-writing anatomical information encoded in bioelectrical states, and discuss the approaches to this problem from the perspectives of information theory, dynamical systems, and computational neuroscience. Cracking the bioelectric code will enable much-improved control over biological patterning, advancing basic evolutionary developmental biology as well as enabling numerous applications in regenerative medicine and synthetic bioengineering.

Bioelectric signaling in regeneration: Mechanisms of ionic controls of growth and form

The ability to control pattern formation is critical for the both the embryonic development of complex structures as well as for the regeneration/repair of damaged or missing tissues and organs. In addition to chemical gradients and gene regulatory networks, endogenous ion flows are key regulators of cell behavior. Not only do bioelectric cues provide information needed for the initial development of structures, they also enable the robust restoration of normal pattern after injury. In order to expand our basic understanding of morphogenetic processes responsible for the repair of complex anatomy, we need to identify the roles of endogenous voltage gradients, ion flows, and electric fields. In complement to the current focus on molecular genetics, decoding the information transduced by bioelectric cues enhances our knowledge of the dynamic control of growth and pattern formation. Recent advances in science and technology place us in an exciting time to elucidate the interplay between molecular-genetic inputs and important biophysical cues that direct the creation of tissues and organs. Moving forward, these new insights enable additional approaches to direct cell behavior and may result in profound advances in augmentation of regenerative capacity.

Cross-limb communication during Xenopus hind-limb regenerative response: non-local bioelectric injury signals

Regeneration of damaged body-parts requires coordination of size, shape, location, and orientation of tissue with the rest of the body. It is not currently known how far injury sites communicate with the remaining soma during repair, or what information may emanate from the injury site to other regions. We examined the bioelectric properties (resting potential gradients in the epidermis) of Xenopus froglets undergoing hind-limb amputation and observed that the contralateral (un-damaged) limb exhibits apparent depolarization signals immediately after the opposite hind-limb is amputated. The pattern of depolarization matches that of the amputated limb and is correlated to the position and type of injury, revealing that information about damage is available to remote body tissues and is detectable non-invasively in vivo by monitoring of the bioelectric state. These data extend knowledge about the electrophysiology of regenerative response, identify a novel communication process via long-range spread of injury signaling, a phenomenon which we call bioelectric injury mirroring (BIM), and suggests revisions to regenerative medicine and diagnostic strategies focused entirely on the wound site and to the use of contralateral limbs as controls.

Use of genetically encoded, light-gated ion translocators to control tumorigenesis

It has long been known that the resting potential of tumor cells is depolarized relative to their normal counterparts. More recent work has provided evidence that resting potential is not just a readout of cell state: it regulates cell behavior as well. Thus, the ability to control resting potential in vivo would provide a powerful new tool for the study and treatment of tumors, a tool capable of revealing living-state physiological information impossible to obtain using molecular tools applied to isolated cell components. Here we describe the first use of optogenetics to manipulate ion-flux mediated regulation of membrane potential specifically to prevent and cause regression of oncogene-induced tumors. Injection of mutant-KRAS mRNA induces tumor-like structures with many documented similarities to tumors, in Xenopus tadpoles. We show that expression and activation of either ChR2^D156A, a blue-light activated cation channel, or Arch, a green-light activated proton pump, both of which hyperpolarize cells, significantly lowers the incidence of KRAS tumor formation. Excitingly, we also demonstrate that activation of co-expressed light-activated ion translocators after tumor formation significantly increases the frequency with which the tumors regress in a process called normalization. These data demonstrate an optogenetic approach to dissect the biophysics of cancer. Moreover, they provide proof-of-principle for a novel class of interventions, directed at regulating cell state by targeting physiological regulators that can over-ride the presence of mutations.

Bioelectric gene and reaction networks: computational modelling of genetic, biochemical and bioelectrical dynamics in pattern regulation

Gene regulatory networks (GRNs) describe interactions between gene products and transcription factors that control gene expression. In combination with reaction-diffusion models, GRNs have enhanced comprehension of biological pattern formation. However, although it is well known that biological systems exploit an interplay of genetic and physical mechanisms, instructive factors such as transmembrane potential (Vmem) have not been integrated into full GRN models. Here we extend regulatory networks to include bioelectric signalling, developing a novel synthesis: the bioelectricity-integrated gene and reaction (BIGR) network. Using in silico simulations, we highlight the capacity for Vmem to alter steady-state concentrations of key signalling molecules inside and out of cells. We characterize fundamental feedbacks where Vmem both controls, and is in turn regulated by, biochemical signals and thereby demonstrate Vmem homeostatic control, Vmem memory and Vmem controlled state switching. BIGR networks demonstrating hysteresis are identified as a mechanisms through which more complex patterns of stable Vmem spots and stripes, along with correlated concentration patterns, can spontaneously emerge. As further proof of principle, we present and analyse a BIGR network model that mechanistically explains key aspects of the remarkable regenerative powers of creatures such as planarian flatworms. The functional properties of BIGR networks generate the first testable, quantitative hypotheses for biophysical mechanisms underlying the stability and adaptive regulation of anatomical bioelectric pattern.

Endogenous Bioelectric Signaling Networks: Exploiting Voltage Gradients for Control of Growth and Form

Living systems exhibit remarkable abilities to self-assemble, regenerate, and remodel complex shapes. How cellular networks construct and repair specific anatomical outcomes is an open question at the heart of the next-generation science of bioengineering. Developmental bioelectricity is an exciting emerging discipline that exploits endogenous bioelectric signaling among many cell types to regulate pattern formation. We provide a brief overview of this field, review recent data in which bioelectricity is used to control patterning in a range of model systems, and describe the molecular tools being used to probe the role of bioelectrics in the dynamic control of complex anatomy. We suggest that quantitative strategies recently developed to infer semantic content and information processing from ionic activity in the brain might provide important clues to cracking the bioelectric code. Gaining control of the mechanisms by which large-scale shape is regulated in vivo will drive transformative advances in bioengineering, regenerative medicine, and synthetic morphology, and could be used to therapeutically address birth defects, traumatic injury, and cancer.

Bioelectric regulation of innate immune system function in regenerating and intact Xenopus laevis

Two key inputs that regulate regeneration are the function of the immune system, and spatial gradients of transmembrane potential (Vmem). Endogenous bioelectric signaling in somatic tissues during regenerative patterning is beginning to be understood, but its role in the context of immune response has never been investigated. Here, we show that Vmem levels modulate innate immunity activity in Xenopus laevis embryos. We developed an assay in which X. laevis embryos are infected with a uropathogenic microorganism, in the presence or absence of reagents that modify Vmem, prior to the ontogenesis of the adaptive immune system. General depolarization of the organism's Vmem by pharmacological or molecular genetic (ion channel misexpression) methods increased resistance to infection, while hyperpolarization made the embryos more susceptible to death by infection. Hyperpolarized specimens harbored a higher load of infectious microorganisms when compared to controls. We identified two mechanisms by which Vmem mediates immune function: serotonergic signaling involving melanocytes and an increase in the number of primitive myeloid cells. Bioinformatics analysis of genes whose transcription is altered by depolarization revealed a number of immune system targets consistent with mammalian data. Remarkably, amputation of the tail bud potentiates systemic resistance to infection by increasing the number of peripheral myeloid cells, revealing an interplay of regenerative response, innate immunity, and bioelectric regulation. Our study identifies bioelectricity as a new mechanism by which innate immune response can be regulated in the context of infection or regeneration. Vmem modulation using drugs already approved for human use could be exploited to improve resistance to infections in clinical settings.