"Bioelectricity in Development, Regeneration, and Cancers" Cell Bio 2023: A Joint Meeting of the American Society of Cell Biology and European Molecular Biology Organization December 2-6, 2023, in Boston, MA, USA.

Cell Bio conferences-organized jointly by the American Society of Cell Biology (ASCB) and European Molecular Biology Organization (EMBO)-showcase a diverse global community of the brightest researchers in Cell Biology and in emerging interdisciplinary topics, including bioelectricity. In this report, we briefly overview the Cell Bio 2023 subgroup meeting "Bioelectricity in Development, Regeneration, and Cancers." This subgroup meeting featured 12 talks (7 Principal Investigators and 5 junior scientists) exploring the role of bioelectricity in endogenous and diseased states in model systems ranging from cells in culture to single-cell organisms such as yeast all the way to mammalian systems (including tools and technology developed for exploring bioelectricity and electrotaxis in cells and tissues).

Embryos assist morphogenesis of others through calcium and ATP signaling mechanisms in collective teratogen resistance.

Information for organismal patterning can come from a variety of sources. We investigate the possibility that instructive influences for normal embryonic development are provided not only at the level of cells within the embryo, but also via interactions between embryos. To explore this, we challenge groups of embryos with disruptors of normal development while varying group size.

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.

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.

HCN2 channel-induced rescue of brain, eye, heart and gut teratogenesis caused by nicotine, ethanol and aberrant notch signalling.

Organogenesis is a complex process that can be disrupted by embryonic exposure to teratogens or mutation-induced alterations in signalling 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 and 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 and eye) as well as non-CNS (heart and gut) organ defects induced by three different teratogenic conditions: nicotine exposure, ethanol exposure or aberrant Notch protein.

Preventing Ethanol-Induced Brain and Eye Morphology Defects Using Optogenetics.

Embryonic exposure to the teratogen ethanol leads to dysmorphias, including eye and brain morphology defects associated with fetal alcohol spectrum disorder (FASD). Exposure of embryos to ethanol leads to similar developmental defects, including brain and eye dysmorphism, confirming our work and the work of others showing Xenopus as a useful system for studies of the brain and eye birth defects associated with FASD. Several targets of ethanol action have been hypothesized, one being regulation of potassium channel.

HCN2 Channel-Induced Rescue of Brain Teratogenesis Local and Long-Range Bioelectric Repair.

Embryonic exposure to the teratogen nicotine results in brain defects, by disrupting endogenous spatial pre patterns necessary for normal brain size and patterning. Extending prior work in that showed that misexpression of ion channels can rescue morphogenesis, we demonstrate and characterize a novel aspect of developmental bioelectricity: channel-dependent repair signals propagate long-range across the embryo. We show that distal HCN2 channel misexpression and distal transplants of HCN2-expressing tissue, non-cell-autonomously reverse profound defects, rescuing brain anatomy, gene expression, and learning.

From non-excitable single-cell to multicellular bioelectrical states supported by ion channels and gap junction proteins: Electrical potentials as distributed controllers.

Endogenous bioelectric patterns within tissues are an important driver of morphogenesis and a tractable component of a number of disease states. Developing system-level understanding of the dynamics by which non-neural bioelectric circuits regulate complex downstream cascades is a key step towards both, an evolutionary understanding of ion channel genes, and novel strategies in regenerative medicine. An important capability gap is deriving rational modulation strategies targeting individual cells' bioelectric states to achieve global (tissue- or organ-level) outcomes.

HCN2 Rescues brain defects by enforcing endogenous voltage pre-patterns.

Endogenous bioelectrical signaling coordinates cell behaviors toward correct anatomical outcomes. Lack of a model explaining spatialized dynamics of bioelectric states has hindered the understanding of the etiology of some birth defects and the development of predictive interventions. Nicotine, a known neuroteratogen, induces serious defects in brain patterning and learning.

The brain is required for normal muscle and nerve patterning during early Xenopus development.

Possible roles of brain-derived signals in the regulation of embryogenesis are unknown. Here we use an amputation assay in Xenopus laevis to show that absence of brain alters subsequent muscle and peripheral nerve patterning during early development. The muscle phenotype can be rescued by an antagonist of muscarinic acetylcholine receptors.

HCN4 ion channel function is required for early events that regulate anatomical left-right patterning in a nodal and lefty asymmetric gene expression-independent manner.

Laterality is a basic characteristic of all life forms, from single cell organisms to complex plants and animals. For many metazoans, consistent left-right asymmetric patterning is essential for the correct anatomy of internal organs, such as the heart, gut, and brain; disruption of left-right asymmetry patterning leads to an important class of birth defects in human patients. Laterality functions across multiple scales, where early embryonic, subcellular and chiral cytoskeletal events are coupled with asymmetric amplification mechanisms and gene regulatory networks leading to asymmetric physical forces that ultimately result in distinct left and right anatomical organ patterning.

Coordinating heart morphogenesis: A novel role for hyperpolarization-activated cyclic nucleotide-gated (HCN) channels during cardiogenesis in .

Hyperpolarization-activated cyclic-nucleotide gated channel (HCN) proteins are important regulators of both neuronal and cardiac excitability. Among the 4 HCN isoforms, HCN4 is known as a pacemaker channel, because it helps control the periodicity of contractions in vertebrate hearts. Although the physiological role of HCN4 channel has been studied in adult mammalian hearts, an earlier role during embryogenesis has not been clearly established.

Genome-wide analysis reveals conserved transcriptional responses downstream of resting potential change in Xenopus embryos, axolotl regeneration, and human mesenchymal cell differentiation.

Endogenous bioelectric signaling via changes in cellular resting potential (V mem) is a key regulator of patterning during regeneration and embryogenesis in numerous model systems. Depolarization of V mem has been functionally implicated in dedifferentiation, tumorigenesis, anatomical re-specification, and appendage regeneration. However, no unbiased analyses have been performed to understand genome-wide transcriptional responses to V mem change in vivo.

Local and long-range endogenous resting potential gradients antagonistically regulate apoptosis and proliferation in the embryonic CNS.

Bioelectric signals, particularly transmembrane voltage potentials (Vmem), play an important role in large-scale patterning during embryonic development. Endogenous bioelectric gradients across tissues function as instructive factors during eye, brain, and other morphogenetic processes. An important and still poorly-understood aspect is the control of cell behaviors by the voltage states of distant cell groups.

Endogenous gradients of resting potential instructively pattern embryonic neural tissue via Notch signaling and regulation of proliferation.

Biophysical forces play important roles throughout embryogenesis, but the roles of spatial differences in cellular resting potentials during large-scale brain morphogenesis remain unknown. Here, we implicate endogenous bioelectricity as an instructive factor during brain patterning in Xenopus laevis. Early frog embryos exhibit a characteristic hyperpolarization of cells lining the neural tube; disruption of this spatial gradient of the transmembrane potential (Vmem) diminishes or eliminates the expression of early brain markers, and causes anatomical mispatterning of the brain, including absent or malformed regions.

The type 7 serotonin receptor, 5-HT 7 , is essential in the mammary gland for regulation of mammary epithelial structure and function.

Autocrine-paracrine activity of serotonin (5-hydroxytryptamine, 5-HT) is a crucial homeostatic parameter in mammary gland development during lactation and involution. Published studies suggested that the 5-HT7 receptor type was important for mediating several effects of 5-HT in the mammary epithelium. Here, using 5-HT7 receptor-null (HT7KO) mice we attempt to understand the role of this receptor in mediating 5-HT actions within the mammary gland.

Shaping the Future of Research: a perspective from junior scientists.

The landscape of scientific research and funding is in flux as a result of tight budgets, evolving models of both publishing and evaluation, and questions about training and workforce stability. As future leaders, junior scientists are uniquely poised to shape the culture and practice of science in response to these challenges. A group of postdocs in the Boston area who are invested in improving the scientific endeavor, planned a symposium held on October 2 (nd) and 3 (rd), 2014, as a way to join the discussion about the future of US biomedical research.

Neurally Derived Tissues in Xenopus laevis Embryos Exhibit a Consistent Bioelectrical Left-Right Asymmetry.

Consistent left-right asymmetry in organ morphogenesis is a fascinating aspect of bilaterian development. Although embryonic patterning of asymmetric viscera, heart, and brain is beginning to be understood, less is known about possible subtle asymmetries present in anatomically identical paired structures. We investigated two important developmental events: physiological controls of eye development and specification of neural crest derivatives, in Xenopus laevis embryos.

Transmembrane voltage potential controls embryonic eye patterning in Xenopus laevis.

Uncovering the molecular mechanisms of eye development is crucial for understanding the embryonic morphogenesis of complex structures, as well as for the establishment of novel biomedical approaches to address birth defects and injuries of the visual system. Here, we characterize change in transmembrane voltage potential (V(mem)) as a novel biophysical signal for eye induction in Xenopus laevis. During normal embryogenesis, a striking hyperpolarization demarcates a specific cluster of cells in the anterior neural field.

Intraluminal volume homeostasis: A common sertonergic mechanism among diverse epithelia.

Volume homeostasis is a common physiological phenomenon for fluid secreting organs, such as exocrine and endocrine glands. It is a manifestation of a finite intraluminal space and an ever changing demand for secretory fluids. Volume homeostasis addresses issues of fluid secretion, storage and clearance for efficient functioning.

Multiple cellular responses to serotonin contribute to epithelial homeostasis.

Epithelial homeostasis incorporates the paradoxical concept of internal change (epithelial turnover) enabling the maintenance of anatomical status quo. Epithelial cell differentiation and cell loss (cell shedding and apoptosis) form important components of epithelial turnover. Although the mechanisms of cell loss are being uncovered the crucial triggers that modulate epithelial turnover through regulation of cell loss remain undetermined.

Altered serotonin physiology in human breast cancers favors paradoxical growth and cell survival.

Introduction: The breast microenvironment can either retard or accelerate the events associated with progression of latent cancers. However, the actions of local physiological mediators in the context of breast cancers are poorly understood. Serotonin (5-HT) is a critical local regulator of epithelial homeostasis in the breast and other organs.

In vitro multipotent differentiation and barrier function of a human mammary epithelium.

As demonstrated by a variety of animal studies, barrier function in the mammary epithelium is essential for a fully functioning and differentiated gland. However, there is a paucity of information on barrier function in human mammary epithelium. Here, we have established characteristics of a polarizing differentiating model of human mammary epithelial cells capable of forming a high-resistance/low-conductance barrier in a predictable manner, viz.

Biphasic regulation of mammary epithelial resistance by serotonin through activation of multiple pathways.

Mammary gland homeostasis and the lactation-to-involution switch are regulated by serotonin (5-hydroxytryptamine (5-HT)). Mammary epithelial tight junctions are physiological targets of 5-HT, and their disruption marks an early stage of mammary gland involution. In these studies, we have identified signal transduction mechanism employed by 5-HT during regulation of mammary gland transepithelial resistance.