- Neuroembryology. [Review]
- WIWiley Interdiscip Rev Dev Biol 2016 Dec 01
- How is it that some cells become neurons? And how is it that neurons become organized in the spinal cord and brain to allow us to walk and talk, to see, recall events in our lives, feel pain, keep ou...
How is it that some cells become neurons? And how is it that neurons become organized in the spinal cord and brain to allow us to walk and talk, to see, recall events in our lives, feel pain, keep our balance, and think? The cells that are specified to form the brain and spinal cord are originally located on the outside surface of the embryo. They loop inward to form the neural tube in a process called neurulation. Structures that are nearby send signals to the posterior neural tube to form and pattern the spinal cord so that the dorsal side receives sensory input and the ventral side sends motor signals from neurons to muscles. In the brain, stem cells near the center of the neural tube migrate out to form a mantel zone, and a set of dividing cells from the mantle zone migrate further to produce a second set of neurons at the outer surface of the brain. These neurons will form the cerebral cortex, which contains six discrete layers. Each layer has different connections and different functions. For further resources related to this article, please visit the WIREs website.
- Sensory evolution in blind cavefish is driven by early embryonic events during gastrulation and neurulation. [Journal Article]
- DDevelopment 2016 Dec 01; 143(23):4521-4532
- Natural variations in sensory systems constitute adaptive responses to the environment. Here, we compared sensory placode development in the blind cave-adapted morph and the eyed river-dwelling morph...
Natural variations in sensory systems constitute adaptive responses to the environment. Here, we compared sensory placode development in the blind cave-adapted morph and the eyed river-dwelling morph of Astyanax mexicanus Focusing on the lens and olfactory placodes, we found a trade-off between these two sensory components in the two morphs: from neural plate stage onwards, cavefish have larger olfactory placodes and smaller lens placodes. In a search for developmental mechanisms underlying cavefish sensory evolution, we analyzed the roles of Shh, Fgf8 and Bmp4 signaling, which are known to be fundamental in patterning the vertebrate head and are subtly modulated in space and time during cavefish embryogenesis. Modulating these signaling systems at the end of gastrulation shifted the balance toward a larger olfactory derivative. Olfactory tests to assess potential behavioral outcomes of such developmental evolution revealed that Astyanax cavefish are able to respond to a 10(5)-fold lower concentration of amino acids than their surface-dwelling counterparts. We suggest that similar evolutionary developmental mechanisms may be used throughout vertebrates to drive adaptive sensory specializations according to lifestyle and habitat.
- Unjoined primary and secondary neural tubes: junctional neural tube defect, a new form of spinal dysraphism caused by disturbance of junctional neurulation. [Journal Article]
- CNChilds Nerv Syst 2016 Oct 29
- CONCLUSIONS: The developmental error of this peculiar malformation probably occurs during the critical transition between the end of primary and the beginning of secondary neurulation, in a stage aptly called junctional neurulation. We describe the current knowledge concerning junctional neurulation and speculate on the embryogenesis of this new class of spinal dysraphism, which we call junctional neural tube defect.
- Localization and distribution of superoxide dismutase-1 in the neural tube morphogenesis of chick embryo. [Journal Article]
- IJInt J Dev Neurosci 2016 Oct 22; 56:1-9
- Superoxide dismutase 1 (SOD- 1) is an antioxidant enzyme that regulates the levels of Reactive oxygen species (ROS) by catalyzing the conversion of superoxide radical into hydrogen peroxide (H2O2) an...
Superoxide dismutase 1 (SOD- 1) is an antioxidant enzyme that regulates the levels of Reactive oxygen species (ROS) by catalyzing the conversion of superoxide radical into hydrogen peroxide (H2O2) and oxygen. ROS are known to play a significant role in various cellular processes, via redox modification of a variety of molecules that participate in signaling pathways involved in this processes. As the levels of ROS in cells are controlled by the levels of antioxidant enzymes, thus SOD-1 may be indirectly involved in regulating different cellular processes by maintaining the required levels of H2O2. Therefore, in the present study we have investigated the possible involvement of SOD- 1 in the neurulation during the development of chick embryo. During gastrulation, SOD- 1 immunoreactivity was observed throughout the ectoderm and cauda mesoderm areas, however, its presence during neurulation was restricted to certain areas of neural tube particularly in the dorsal neural tube where neural tube closure takes place. Assaying enzyme activity revealed a significant increase in the SOD activity during neurulation. Further, inhibition of SOD- 1 by Diethyldithiocarbamate (DDC) induced abnormalities in the development of the neural tube. SOD- 1 inhibition specifically affected the closure of neural tube in the anterior region. Thus, here we report the presence of SOD- 1 mainly in the ectoderm and tissues of ectodermal origin during gastrulation to neurulation which suggests that it may be involved in the regulating the cellular processes during neural tube morphogenesis.
- Rho GTPases in mammalian spinal neural tube closure. [Journal Article]
- SGSmall GTPases 2016 Oct 21; :1-7
- Neural tube closure is an important morphogenetic event that involves dramatic reshaping of both neural and non-neural tissues. Rho GTPases are key cytoskeletal regulators involved in cell motility a...
Neural tube closure is an important morphogenetic event that involves dramatic reshaping of both neural and non-neural tissues. Rho GTPases are key cytoskeletal regulators involved in cell motility and in several developmental processes, and are thus expected to play pivotal roles in neurulation. Here, we discuss 2 recent studies that shed light on the roles of distinct Rho GTPases in different tissues during neurulation. RhoA plays an essential role in regulating actomyosin dynamics in the neural epithelium of the elevating neural folds, while Rac1 is required for the formation of cell protrusions in the non-neural surface ectoderm during neural fold fusion.
- Genetic backgrounds and modifier genes of NTD mouse models: An opportunity for greater understanding of the multifactorial etiology of neural tube defects. [Review]
- BDBirth Defects Res A Clin Mol Teratol 2016 Oct 21
- Neurulation, the early embryonic process of forming the presumptive brain and spinal cord, is highly complex and involves hundreds of genes in multiple genetic pathways. Mice have long served as a ge...
Neurulation, the early embryonic process of forming the presumptive brain and spinal cord, is highly complex and involves hundreds of genes in multiple genetic pathways. Mice have long served as a genetic model for studying human neurulation, and the resulting neural tube defects (NTDs) that arise when neurulation is disrupted. Because mice appear to show mostly single gene inheritance for NTDs and humans show multifactorial inheritance, mice sometimes have been characterized as a simpler model for the identification and study of NTD genes. But are they a simple model? When viewed on different genetic backgrounds, many genes show significant variation in the penetrance and expressivity of NTD phenotypes, suggesting the presence of modifier loci that interact with the target gene to affect the phenotypic expression. Looking at mutations on different genetic backgrounds provides us with an opportunity to explore these complex genetic interactions, which are likely to better emulate similar processes in human neurulation. Here, we review NTD genes known to show strain-specific phenotypic variation. We focus particularly on the gene Cecr2, which is studied using both a hypomorphic and a presumptive null mutation on two different backgrounds: one susceptible (BALB/c) and one resistant (FVB/N) to NTDs. This strain difference has led to a search for genetic modifiers within a region on murine chromosome 19. Understanding how genetic variants alter the phenotypic outcome in NTD mouse models will help to direct future studies in humans, particularly now that more genome wide sequencing approaches are being used. Birth Defects Research (Part A), 2016. © 2016 Wiley Periodicals, Inc.
- Methylome analysis for spina bifida shows SOX18 hypomethylation as a risk factor with evidence for a complex (epi)genetic interplay to affect neural tube development. [Journal Article]
- CEClin Epigenetics 2016; 8:108
- CONCLUSIONS: This is the first genome-wide methylation study in leukocytes for patients with NTDs. We report SOX18 as a novel MMC risk gene but our findings also suggest that SOX18 hypomethylation must interplay with environmental and (epi)genetic factors to cause NTDs. Further studies are needed that combine methylome data with next-generation sequencing approaches to unravel NTD etiology.
- EphA7 modulates apical constriction of hindbrain neuroepithelium during neurulation in Xenopus. [Journal Article]
- BBBiochem Biophys Res Commun 2016 Oct 28; 479(4):759-765
- Eph receptor tyrosine kinases (RTKs) and their ephrin ligands play multiple roles in the developing nervous system, including cell segregation, axon guidance and synaptic plasticity. Here we report t...
Eph receptor tyrosine kinases (RTKs) and their ephrin ligands play multiple roles in the developing nervous system, including cell segregation, axon guidance and synaptic plasticity. Here we report the expression and function of EphA7 in Xenopus hindbrain development. EphA7 is specifically expressed in the hindbrain throughout neurulation in Xenopus embryos. Knockdown of EphA7 by specific morpholino oligonucleotide (MO) disrupted cranial neural tube closure and disturbed apical constriction of hindbrain neuroepithelial cells, indicating weakened cell surface tension. In neural plate explants, EphA7 knockdown inhibited apical filamentous actin (F-actin) accumulation. We further showed that EphA7 is involved in the phosphorylation and activation of focal adhesion kinase (FAK) in vivo and in vitro, a key regulator of actin assembly. Our findings reveal that EphA7 functions as a critical regulator of apical constriction of hindbrain neuroepithelial cells.
- Mechanics of neurulation: From classical to current perspectives on the physical mechanics that shape, fold, and form the neural tube. [Review]
- BDBirth Defects Res A Clin Mol Teratol 2016 Sep 13
- Neural tube defects arise from mechanical failures in the process of neurulation. At the most fundamental level, formation of the neural tube relies on coordinated, complex tissue movements that mech...
Neural tube defects arise from mechanical failures in the process of neurulation. At the most fundamental level, formation of the neural tube relies on coordinated, complex tissue movements that mechanically transform the flat neural epithelium into a lumenized epithelial tube (Davidson, 2012). The nature of this mechanical transformation has mystified embryologists, geneticists, and clinicians for more than 100 years. Early embryologists pondered the physical mechanisms that guide this transformation. Detailed observations of cell and tissue movements as well as experimental embryological manipulations allowed researchers to generate and test elementary hypotheses of the intrinsic and extrinsic forces acting on the neural tissue. Current research has turned toward understanding the molecular mechanisms underlying neurulation. Genetic and molecular perturbation have identified a multitude of subcellular components that correlate with cell behaviors and tissue movements during neural tube formation. In this review, we focus on methods and conceptual frameworks that have been applied to the study of amphibian neurulation that can be used to determine how molecular and physical mechanisms are integrated and responsible for neurulation. We will describe how qualitative descriptions and quantitative measurements of strain, force generation, and tissue material properties as well as simulations can be used to understand how embryos use morphogenetic programs to drive neurulation. Birth Defects Research (Part A), 2016. © 2016 Wiley Periodicals, Inc.
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- Limited dorsal myeloschisis associated with dermoid elements. [Journal Article]
- CNChilds Nerv Syst 2016 Aug 19
- CONCLUSIONS: We present our series of LDMs associated with dermoid elements and recommend excising the entire length of the intradural LDM stalk from its dural entry point to its merge point with the spinal cord during the initial treatment to avoid secondary deterioration and additional surgery.