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Development (Cambridge, England) Feb 2017Neural tube closure has been studied for many decades, across a range of vertebrates, as a paradigm of embryonic morphogenesis. Neurulation is of particular interest in... (Review)
Review
Neural tube closure has been studied for many decades, across a range of vertebrates, as a paradigm of embryonic morphogenesis. Neurulation is of particular interest in view of the severe congenital malformations - 'neural tube defects' - that result when closure fails. The process of neural tube closure is complex and involves cellular events such as convergent extension, apical constriction and interkinetic nuclear migration, as well as precise molecular control via the non-canonical Wnt/planar cell polarity pathway, Shh/BMP signalling, and the transcription factors Grhl2/3, Pax3, Cdx2 and Zic2. More recently, biomechanical inputs into neural tube morphogenesis have also been identified. Here, we review these cellular, molecular and biomechanical mechanisms involved in neural tube closure, based on studies of various vertebrate species, focusing on the most recent advances in the field.
Topics: Animals; Body Patterning; Cell Movement; Cell Polarity; Embryonic Development; Fibronectins; Humans; Laminin; Morphogenesis; Neural Tube; Neural Tube Defects; Neurulation; Proteoglycans; Risk Factors; Signal Transduction; Stress, Mechanical; Transcription Factors
PubMed: 28196803
DOI: 10.1242/dev.145904 -
Nature Nov 2021Understanding human organ formation is a scientific challenge with far-reaching medical implications. Three-dimensional stem-cell cultures have provided insights into...
Understanding human organ formation is a scientific challenge with far-reaching medical implications. Three-dimensional stem-cell cultures have provided insights into human cell differentiation. However, current approaches use scaffold-free stem-cell aggregates, which develop non-reproducible tissue shapes and variable cell-fate patterns. This limits their capacity to recapitulate organ formation. Here we present a chip-based culture system that enables self-organization of micropatterned stem cells into precise three-dimensional cell-fate patterns and organ shapes. We use this system to recreate neural tube folding from human stem cells in a dish. Upon neural induction, neural ectoderm folds into a millimetre-long neural tube covered with non-neural ectoderm. Folding occurs at 90% fidelity, and anatomically resembles the developing human neural tube. We find that neural and non-neural ectoderm are necessary and sufficient for folding morphogenesis. We identify two mechanisms drive folding: (1) apical contraction of neural ectoderm, and (2) basal adhesion mediated via extracellular matrix synthesis by non-neural ectoderm. Targeting these two mechanisms using drugs leads to morphological defects similar to neural tube defects. Finally, we show that neural tissue width determines neural tube shape, suggesting that morphology along the anterior-posterior axis depends on neural ectoderm geometry in addition to molecular gradients. Our approach provides a new route to the study of human organ morphogenesis in health and disease.
Topics: Ectoderm; Humans; Models, Biological; Morphogenesis; Neural Plate; Neural Tube; Neural Tube Defects; Organ Culture Techniques; Regeneration; Stem Cells
PubMed: 34707290
DOI: 10.1038/s41586-021-04026-9 -
Development (Cambridge, England) Aug 2021The spinal cord receives input from peripheral sensory neurons and controls motor output by regulating muscle innervating motor neurons. These functions are carried out...
The spinal cord receives input from peripheral sensory neurons and controls motor output by regulating muscle innervating motor neurons. These functions are carried out by neural circuits comprising molecularly distinct neuronal subtypes generated in a characteristic spatiotemporal arrangement from progenitors in the embryonic neural tube. To gain insight into the diversity and complexity of cells in the developing human neural tube, we used single-cell mRNA sequencing to profile cervical and thoracic regions in four human embryos of Carnegie stages (CS) CS12, CS14, CS17 and CS19 from gestational weeks 4-7. Analysis of progenitor and neuronal populations from the neural tube and dorsal root ganglia identified dozens of distinct cell types and facilitated the reconstruction of the differentiation pathways of specific neuronal subtypes. Comparison with mouse revealed overall similarity of mammalian neural tube development while highlighting some human-specific features. These data provide a catalogue of gene expression and cell type identity in the human neural tube that will support future studies of sensory and motor control systems. The data can be explored at https://shiny.crick.ac.uk/scviewer/neuraltube/.
Topics: Animals; Cell Differentiation; Embryo, Mammalian; Ganglia, Spinal; Gene Expression; Gene Expression Profiling; Humans; Mice; Motor Neurons; Neural Tube; Sensory Receptor Cells; Spinal Cord; Thorax; Transcriptome
PubMed: 34351410
DOI: 10.1242/dev.199711 -
Nature Dec 2022Our understanding of human early development is severely hampered by limited access to embryonic tissues. Due to their close evolutionary relationship with humans,...
Our understanding of human early development is severely hampered by limited access to embryonic tissues. Due to their close evolutionary relationship with humans, nonhuman primates are often used as surrogates to understand human development but currently suffer from a lack of in vivo datasets, especially from gastrulation to early organogenesis during which the major embryonic cell types are dynamically specified. To fill this gap, we collected six Carnegie stage 8-11 cynomolgus monkey (Macaca fascicularis) embryos and performed in-depth transcriptomic analyses of 56,636 single cells. Our analyses show transcriptomic features of major perigastrulation cell types, which help shed light on morphogenetic events including primitive streak development, somitogenesis, gut tube formation, neural tube patterning and neural crest differentiation in primates. In addition, comparative analyses with mouse embryos and human embryoids uncovered conserved and divergent features of perigastrulation development across species-for example, species-specific dependency on Hippo signalling during presomitic mesoderm differentiation-and provide an initial assessment of relevant stem cell models of human early organogenesis. This comprehensive single-cell transcriptome atlas not only fills the knowledge gap in the nonhuman primate research field but also serves as an invaluable resource for understanding human embryogenesis and developmental disorders.
Topics: Animals; Humans; Mice; Gastrulation; Macaca fascicularis; Organogenesis; Single-Cell Analysis; Embryoid Bodies; Gene Expression Profiling; Primitive Streak; Neural Tube; Neural Crest; Hippo Signaling Pathway; Mesoderm; Stem Cells
PubMed: 36517595
DOI: 10.1038/s41586-022-05526-y -
Development (Cambridge, England) Mar 2019The coordinated spatial and temporal regulation of gene expression in the vertebrate neural tube determines the identity of neural progenitors and the function and...
The coordinated spatial and temporal regulation of gene expression in the vertebrate neural tube determines the identity of neural progenitors and the function and physiology of the neurons they generate. Progress has been made deciphering the gene regulatory programmes that are responsible for this process; however, the complexity of the tissue has hampered the systematic analysis of the network and the underlying mechanisms. To address this, we used single cell mRNA sequencing to profile cervical and thoracic regions of the developing mouse neural tube between embryonic days 9.5-13.5. We confirmed that the data accurately recapitulates neural tube development, allowing us to identify new markers for specific progenitor and neuronal populations. In addition, the analysis highlighted a previously underappreciated temporal component to the mechanisms that generate neuronal diversity, and revealed common features in the sequence of transcriptional events that lead to the differentiation of specific neuronal subtypes. Together, the data offer insight into the mechanisms that are responsible for neuronal specification and provide a compendium of gene expression for classifying spinal cord cell types that will support future studies of neural tube development, function and disease.
Topics: Animals; Cell Differentiation; Cluster Analysis; Female; Gene Expression Profiling; Gene Expression Regulation, Developmental; Gene Regulatory Networks; Interneurons; Male; Mice; Neural Tube; Neurons; Organogenesis; RNA, Messenger; Single-Cell Analysis; Spinal Cord; Time Factors; Transcription Factors; Transcriptome
PubMed: 30846445
DOI: 10.1242/dev.173807 -
Developmental Cell Jan 2023In many developing tissues, the patterns of gene expression that assign cell fate are organized by graded secreted signals. Cis-regulatory elements (CREs) interpret...
In many developing tissues, the patterns of gene expression that assign cell fate are organized by graded secreted signals. Cis-regulatory elements (CREs) interpret these signals to control gene expression, but how this is accomplished remains poorly understood. In the neural tube, a gradient of the morphogen sonic hedgehog (Shh) patterns neural progenitors. We identify two distinct ways in which CREs translate graded Shh into differential gene expression in mouse neural progenitors. In most progenitors, a common set of CREs control gene activity by integrating cell-type-specific inputs. By contrast, the most ventral progenitors use a unique set of CREs, established by the pioneer factor FOXA2. This parallels the role of FOXA2 in endoderm, where FOXA2 binds some of the same sites. Together, the data identify distinct cis-regulatory strategies for the interpretation of morphogen signaling and raise the possibility of an evolutionarily conserved role for FOXA2 across tissues.
Topics: Animals; Mice; Neural Tube; Hedgehog Proteins; Cell Differentiation; Nervous System; Signal Transduction; Gene Expression Regulation, Developmental
PubMed: 36516856
DOI: 10.1016/j.devcel.2022.11.016 -
Cell Jan 2024During development, morphogens pattern tissues by instructing cell fate across long distances. Directly visualizing morphogen transport in situ has been inaccessible, so...
During development, morphogens pattern tissues by instructing cell fate across long distances. Directly visualizing morphogen transport in situ has been inaccessible, so the molecular mechanisms ensuring successful morphogen delivery remain unclear. To tackle this longstanding problem, we developed a mouse model for compromised sonic hedgehog (SHH) morphogen delivery and discovered that endocytic recycling promotes SHH loading into signaling filopodia called cytonemes. We optimized methods to preserve in vivo cytonemes for advanced microscopy and show endogenous SHH localized to cytonemes in developing mouse neural tubes. Depletion of SHH from neural tube cytonemes alters neuronal cell fates and compromises neurodevelopment. Mutation of the filopodial motor myosin 10 (MYO10) reduces cytoneme length and density, which corrupts neuronal signaling activity of both SHH and WNT. Combined, these results demonstrate that cytoneme-based signal transport provides essential contributions to morphogen dispersion during mammalian tissue development and suggest MYO10 is a key regulator of cytoneme function.
Topics: Animals; Mice; Biological Transport; Cell Membrane Structures; Hedgehog Proteins; Myosins; Pseudopodia; Signal Transduction; Neural Tube
PubMed: 38171360
DOI: 10.1016/j.cell.2023.12.003 -
Journal of Anatomy Jul 2016Microtubules (MTs) are key cellular components, long known to participate in morphogenetic events that shape the developing embryo. However, the links between the... (Review)
Review
Microtubules (MTs) are key cellular components, long known to participate in morphogenetic events that shape the developing embryo. However, the links between the cellular functions of MTs, their effects on cell shape and polarity, and their role in large-scale morphogenesis remain poorly understood. Here, these relationships were examined with respect to two strategies for generating the vertebrate neural tube: bending and closure of the mammalian neural plate; and cavitation of the teleost neural rod. The latter process has been compared with 'secondary' neurulation that generates the caudal spinal cord in mammals. MTs align along the apico-basal axis of the mammalian neuroepithelium early in neural tube closure, participating functionally in interkinetic nuclear migration, which indirectly impacts on cell shape. Whether MTs play other functional roles in mammalian neurulation remains unclear. In the zebrafish, MTs are important for defining the neural rod midline prior to its cavitation, both by localizing apical proteins at the tissue midline and by orienting cell division through a mirror-symmetric MT apparatus that helps to further define the medial localization of apical polarity proteins. Par proteins have been implicated in centrosome positioning in neuroepithelia as well as in the control of polarized morphogenetic movements in the neural rod. Understanding of MT functions during early nervous system development has so far been limited, partly by techniques that fail to distinguish 'cause' from 'effect'. Future developments will likely rely on novel ways to selectively impair MT function in order to investigate the roles they play.
Topics: Animals; Cell Polarity; Cell Shape; Humans; Microtubules; Neural Tube; Neuroepithelial Cells; Neurulation
PubMed: 27025884
DOI: 10.1111/joa.12468 -
Birth Defects Research Jan 2017Susceptibility to neural tube defects (NTDs), such as anencephaly and spina bifida is influenced by genetic and environmental factors including maternal nutrition.... (Review)
Review
Susceptibility to neural tube defects (NTDs), such as anencephaly and spina bifida is influenced by genetic and environmental factors including maternal nutrition. Maternal periconceptional supplementation with folic acid significantly reduces the risk of an NTD-affected pregnancy, but does not prevent all NTDs, and "folic acid non-responsive" NTDs continue to occur. Similarly, among mouse models of NTDs, some are responsive to folic acid but others are not. Among nutritional factors, inositol deficiency causes cranial NTDs in mice while supplemental inositol prevents spinal and cranial NTDs in the curly tail (Grhl3 hypomorph) mouse, rodent models of hyperglycemia or induced diabetes, and in a folate-deficiency induced NTD model. NTDs also occur in mice lacking expression of certain inositol kinases. Inositol-containing phospholipids (phosphoinositides) and soluble inositol phosphates mediate a range of functions, including intracellular signaling, interaction with cytoskeletal proteins, and regulation of membrane identity in trafficking and cell division. Myo-inositol has been trialed in humans for a range of conditions and appears safe for use in human pregnancy. In pilot studies in Italy and the United Kingdom, women took inositol together with folic acid preconceptionally, after one or more previous NTD-affected pregnancies. In nonrandomized cohorts and a randomized double-blind study in the United Kingdom, no recurrent NTDs were observed among 52 pregnancies reported to date. Larger-scale fully powered trials are needed to determine whether supplementation with inositol and folic acid would more effectively prevent NTDs than folic acid alone. Birth Defects Research 109:68-80, 2017. © 2016 The Authors Birth Defects Research Published by Wiley Periodicals, Inc.
Topics: Animals; Clinical Trials as Topic; Dietary Supplements; Disease Models, Animal; Female; Folic Acid; Folic Acid Deficiency; Humans; Inositol; Inositol Phosphates; Maternal Nutritional Physiological Phenomena; Mice; Neural Tube; Neural Tube Defects; Phosphatidylinositols; Pregnancy
PubMed: 27324558
DOI: 10.1002/bdra.23533 -
Neuroscience Bulletin Nov 2022It is clear that organoids are useful for studying the structure as well as the functions of organs and tissues; they are able to simulate cell-to-cell interactions,... (Review)
Review
It is clear that organoids are useful for studying the structure as well as the functions of organs and tissues; they are able to simulate cell-to-cell interactions, symmetrical and asymmetric division, proliferation, and migration of different cell groups. Some progress has been made using brain organoids to elucidate the genetic basis of certain neurodevelopmental disorders. Such as Parkinson's disease and Alzheimer's disease. However, research on organoids in early neural development has received insufficient attention, especially that focusing on neural tube precursors. In this review, we focus on the recent research progress on neural tube organoids and discuss both their challenges and potential solutions.
Topics: Humans; Organoids; Neural Tube; Neurodevelopmental Disorders; Brain; Alzheimer Disease
PubMed: 35753025
DOI: 10.1007/s12264-022-00896-9