title: Endogenous gradients of resting potential instructively pattern embryonic neural tissue via Notch signaling and regulation of proliferation.
abstract: 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. This effect is mediated by voltage-gated calcium signaling and gap-junctional communication. In addition to cell-autonomous effects, we show that hyperpolarization of transmembrane potential (Vmem) in ventral cells outside the brain induces upregulation of neural cell proliferation at long range. Misexpression of the constitutively active form of Notch, a suppressor of neural induction, impairs the normal hyperpolarization pattern and neural patterning; forced hyperpolarization by misexpression of specific ion channels rescues brain defects induced by activated Notch signaling. Strikingly, hyperpolarizing posterior or ventral cells induces the production of ectopic neural tissue considerably outside the neural field. The hyperpolarization signal also synergizes with canonical reprogramming factors (POU and HB4), directing undifferentiated cells toward neural fate in vivo. These data identify a new functional role for bioelectric signaling in brain patterning, reveal interactions between Vmem and key biochemical pathways (Notch and Ca(2+) signaling) as the molecular mechanism by which spatial differences of Vmem regulate organogenesis of the vertebrate brain, and suggest voltage modulation as a tractable strategy for intervention in certain classes of birth defects.
authors.affiliation: Biology Department, Center for Regenerative and Developmental Biology, Tufts University, Medford, Massachusetts 02155-4243 and.
authors.forename: Vaibhav P
authors.initials: VP
authors.lastname: Pai
authors.affiliation: Biology Department, Center for Regenerative and Developmental Biology, Tufts University, Medford, Massachusetts 02155-4243 and.
authors.forename: Joan M
authors.identifier: http://orcid.org/0000-0002-1972-053X
authors.initials: JM
authors.lastname: Lemire
authors.affiliation: Biology Department, Center for Regenerative and Developmental Biology, Tufts University, Medford, Massachusetts 02155-4243 and.
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Paré
authors.affiliation: Stem Cell Institute, University of Minnesota, Minneapolis, Minnesota 55455.
authors.forename: Gufa
authors.initials: G
authors.lastname: Lin
authors.affiliation: Stem Cell Institute, University of Minnesota, Minneapolis, Minnesota 55455.
authors.forename: Ying
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Biology Department, Center for Regenerative and Developmental Biology, Tufts University, Medford, Massachusetts 02155-4243 and michael.levin@tufts.edu.
authors.forename: Michael
authors.initials: M
authors.lastname: Levin
mesh_terms: D000367:Age Factors; D000818:Animals; D019521:Body Patterning / Q000235:genetics / Q000502:physiology*; D002118:Calcium / Q000378:metabolism; D049109:Cell Proliferation / Q000502:physiology*; D004625:Embryo, Nonmammalian; D005456:Fluorescent Dyes / Q000378:metabolism; D017629:Gap Junctions / Q000187:drug effects / Q000502:physiology; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects / Q000502:physiology; D007473:Ion Channels / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D008564:Membrane Potentials / Q000235:genetics / Q000502:physiology*; D008845:Microinjections; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism; D054259:Neural Tube / Q000166:cytology / Q000196:embryology; D009474:Neurons / Q000502:physiology*; D051880:Receptors, Notch / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014161:Transduction, Genetic; D014982:Xenopus laevis
chemical_list: D005456:Fluorescent Dyes; D007473:Ion Channels; C549535:NOTCH1 protein, Xenopus; D009419:Nerve Tissue Proteins; D051880:Receptors, Notch; D014157:Transcription Factors; D002118:Calcium
keywords: bioelectricity; brain morphogenesis; long range; proliferation; resting potential