Search for: All records

IntroductionIn the developing brain, neurons extend an axonal process through a complex and changing environment to form synaptic connections with the correct targets in response to extracellular cues. Microtubule and actin filaments provide mechanical support and drive axon growth in the correct direction. The axonal cytoskeleton responds to extracellular guidance cues. Netrin-1 is a multifunctional guidance cue that can induce alternate responses based on the bound receptor. The mechanism by which actin responds to Netrin-1 is well described. However, how Netrin-1 influences the microtubule cytoskeleton is less understood. Appropriate microtubule function is required for axon pathfinding, as mutations in tubulin phenocopy axon crossing defects of Netrin-1 and DCC mutants. Microtubule stabilization is required for attractive guidance cue response. The C-terminal tails of microtubules can be post-translationally modified. Post-translational modifications (PTMs) help control the microtubule cytoskeleton. MethodsWe measured polyglutamylation in cultured primary mouse cortical neurons before and after Netrin-1 stimulation. We used immunohistochemistry to measure how Netrin-1 stimulation alters microtubule-associated protein localization. Next, we manipulated TTLL1 to determine if Netrin-1-induced axon growth and MAP localization depend on polyglutamylation levels. ResultsIn this study, we investigated if Netrin-1 signaling alters microtubule PTMs in the axon. We found that microtubule polyglutamylation increases after Netrin-1 stimulation. This change in polyglutamylation is necessary for Netrin-1-induced axonal growth rate increases. We next determined that MAP1B and DCX localization changes in response to Netrin-1. These proteins can both stabilize the microtubule cytoskeleton and may be responsible for Netrin-1-induced growth response in neurons. The changes in DCX and MAP1B depend on TTLL1, a protein responsible for microtubule polyglutamylation. 

Abstract Thousands of people suffer from nausea with pregnancy each year. Nausea can be alleviated with cannabidiol (CBD), a primary component of cannabis that is widely available. However, it is unknown how fetal CBD exposure affects embryonic development and postnatal outcomes. CBD binds and activates receptors that are expressed in the fetal brain and are important for brain development, including serotonin receptors (5HT_1A), voltage-gated potassium (Kv)7 receptors, and the transient potential vanilloid 1 receptor (TRPV1). Excessive activation of each of these receptors can disrupt neurodevelopment. Here, we test the hypothesis that fetal CBD exposure in mice alters offspring neurodevelopment and postnatal behavior. We administered 50 mg/kg CBD in sunflower oil or sunflower oil alone to pregnant mice from embryonic day 5 through birth. We show that fetal CBD exposure sensitizes adult male offspring to thermal pain through TRPV1. We show that fetal CBD exposure decreases problem-solving behaviors in female CBD-exposed offspring. We demonstrate that fetal CBD exposure increases the minimum current required to elicit action potentials and decreases the number of action potentials in female offspring layer 2/3 prefrontal cortex (PFC) pyramidal neurons. Fetal CBD exposure reduces the amplitude of glutamate uncaging-evoked excitatory post-synaptic currents, consistent with CBD-exposed female problem-solving behavior deficits. Combined, these data show that fetal CBD exposure disrupts neurodevelopment and postnatal behavior in a sex specific manner. 

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). The subgroup meeting concluded with a discussion on the current challenges and opportunities for the field of bioelectricity. 

People use cannabidiol (CBD), the primary non-psychoactive cannabinoid of cannabis, as a treatment for symptoms that are commonly associated with pregnancy including nausea, pain, and anxiety. Many people believe CBD is safe to take during pregnancy. However, CBD crosses the placenta and affects the activity of protein targets that are expressed in the fetal brain. Cannabidiol alters the activity of ion channels including voltage- gated sodium, potassium, and calcium channels that control the electrical activity of neurons. Abnormal electrical activity could disrupt brain function via changes in axon growth and synapse structure and function. Furthermore, CBD alters the activity of G- protein coupled receptors that are expressed in the fetal brain and are important for axon growth and guidance suggesting that fetal exposure could prevent axons from reaching their correct targets. Indeed, cannabidiol exposure reduces axon growth in vitro and in vivo. This raises the possibility that CBD consumption during pregnancy could disrupt fetal brain development. Recent studies show that oral cannabidiol consumption during pregnancy alters the excitability of the pyramidal neurons of the prefrontal cortex and affects postnatal cognitive function in mouse offspring. Furthermore, fetal CBD exposure increases thermal pain sensitivity in offspring. Gestational cannabidiol exposure affects compulsivity and memory in a different rodent model. Here, we discuss how CBD affects various ion channels and G-protein coupled receptors, the roles of these proteins in neurodevelopment, and evidence that CBD affects brain development. 

The temporal dynamics of morphogen presentation impacts transcriptional responses and tissue patterning (1). However, the mechanisms controlling morphogen release are far from clear. We found that inwardly rectifying potassium (Irk) channels regulate endogenous transient increases in intracellular calcium and Bone Morphogenetic Protein (BMP/Dpp) release for Drosophila wing development (2). Inhibition of Irk channels reduces BMP/Dpp signaling, and ultimately disrupts wing morphology (2, 3). Ion channels impact development of several tissues and organisms in which BMP signaling is essential (2-15). In neurons and pancreatic beta cells, Irk channels modulate membrane potential to affect intracellular Ca++ to control secretion of neurotransmitters and insulin (15-21). Based on Irk activity in neurons, we hypothesized that electrical activity controls endoplasmic reticulum Ca++ release into the cytoplasm to regulate the release of BMP. To test this hypothesis, we reduced expression of proteins that control endoplasmic reticulum calcium (Stim, Orai, SERCA, SK, and Best2) and documented wing phenotypes. We found that reduced Stim and SERCA function decreases amplitude and frequency of endogenous calcium transients in the wing disc and reduced Dpp/BMP release in the wing disc. Together, our results suggest control of endoplasmic reticulum is required for Dpp/BMP release. 

Smoking cigarettes during pregnancy is associated with adverse effects on infants including low birth weight, defective lung development, and skeletal abnormalities. Pregnant women are increasingly turning to vaping [use of electronic (e)-cigarettes] as a perceived safer alternative to cigarettes. However, nicotine disrupts fetal development, suggesting that like cigarette smoking, nicotine vaping may be detrimental to the fetus. To test the impact of maternal vaping on fetal lung and skeletal development in mice, pregnant dams were exposed to e-cigarette vapor throughout gestation. At embryonic day (E)18.5, vape exposed litter sizes were reduced and some embryos exhibited growth restriction compared to air exposed controls. Fetal lungs were collected for histology and whole transcriptome sequencing. Maternally nicotine vaped embryos exhibited histological and transcriptional changes consistent with impaired distal lung development. Embryonic lung gene expression changes mimicked transcriptional changes observed in adult mouse lungs exposed to cigarette smoke, suggesting that the developmental defects may be due to direct nicotine exposure. Fetal skeletons were analyzed for craniofacial and long bone lengths. Nicotine directly binds and inhibits the Kcnj2 potassium channel which is important for bone development. The length of the maxilla, palatal shelves, humerus, and femur were reduced in vaped embryos, which was further exacerbated by loss of one copy of the Kcnj2 gene. Nicotine vapor exposed Kcnj2KO/+ embryos also had significantly lower birth weights than unexposed animals of either genotype. Kcnj2 mutants had severely defective lungs with and without vape exposure, suggesting that potassium channels may be broadly involved in mediating the detrimental developmental effects of nicotine vaping. These data indicate that intrauterine nicotine exposure disrupts fetal lung and skeletal development likely through inhibition of Kcnj2. 

To execute the intricate process of development, cells coordinate across tissues and organs to determine where each cell divides and differentiates. This coordination requires complex communication between cells. Growing evidence suggests that bioelectrical signals controlled via ion channels contribute to cell communication during development. Ion channels collectively regulate the transmembrane potential of cells, and their function plays a conserved role in the development of organisms from flies to humans. Spontaneous calcium oscillations can be found in nearly every cell type and tissue, and disruption of these oscillations leads to defects in development. However, the mechanism by which bioelectricity regulates development is still unclear. Ion channels play essential roles in the processes of cell death, proliferation, migration, and in each of the major canonical developmental signaling pathways. Previous reviews focus on evidence for one potential mechanism by which bioelectricity affects morphogenesis, but there is evidence that supports multiple different mechanisms which are not mutually exclusive. Evidence supports bioelectricity contributing to development through multiple different mechanisms. Here, we review evidence for the importance of bioelectricity in morphogenesis and provide a comprehensive review of the evidence for several potential mechanisms by which ion channels may act in developmental processes. 

The role of ion channels in neurons and muscles has been well characterized. However, recent work has demonstrated both the presence and necessity of ion channels in diverse cell types for morphological development. For example, mutations that disrupt ion channels give rise to abnormal structural development in species of flies, frogs, fish, mice, and humans. Furthermore, medications and recreational drugs that target ion channels are associated with higher incidence of birth defects in humans. In this review we establish the effects of several teratogens on development including epilepsy treatment drugs (topiramate, valproate, ethosuximide, phenobarbital, phenytoin, and carbamazepine), nicotine, heat, and cannabinoids. We then propose potential links between these teratogenic agents and ion channels with mechanistic insights from model organisms. Finally, we talk about the role of a particular ion channel, Kir2.1, in the formation and development of bone as an example of how ion channels can be used to uncover important processes in morphogenesis. Because ion channels are common targets of many currently used medications, understanding how ion channels impact morphological development will be important for prevention of birth defects. It is becoming increasingly clear that ion channels have functional roles outside of tissues that have been classically considered excitable.