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Self-organizing three-dimensional cellular models derived from human pluripotent stem cells or primary tissue have great potential to provide insights into how the human nervous system develops, what makes it unique and how disorders of the nervous system arise, progress and could be treated. Here, to facilitate progress and improve communication with the scientific community and the public, we clarify and provide a basic framework for the nomenclature of human multicellular models of nervous system development and disease, including organoids, assembloids and transplants., (© 2022. Springer Nature Limited.)

In most animals, the majority of the nervous system is generated and assembled into neuronal circuits during embryonic development 1 . However, during juvenile stages, nervous systems still undergo extensive anatomical and functional changes to eventually form a fully mature nervous system by the adult stage 2,3 . The molecular changes in post-mitotic neurons across post-embryonic development and the genetic programs that control these temporal transitions are not well understood 4,5 . Here, using the model system Caenorhabditis elegans, we comprehensively characterized the distinct functional states (locomotor behaviour) and the corresponding distinct molecular states (transcriptome) of the post-mitotic nervous system across temporal transitions during post-embryonic development. We observed pervasive, neuron-type-specific changes in gene expression, many of which are controlled by the developmental upregulation of the conserved heterochronic microRNA LIN-4 and the subsequent promotion of a mature neuronal transcriptional program through the repression of its target, the transcription factor lin-14. The functional relevance of these molecular transitions are exemplified by a temporally regulated target gene of the LIN-14 transcription factor, nlp-45, a neuropeptide-encoding gene, which we find is required for several distinct temporal transitions in exploratory activity during post-embryonic development. Our study provides insights into regulatory strategies that control neuron-type-specific gene batteries to modulate distinct behavioural states across temporal, sexual and environmental dimensions of post-embryonic development., (© 2021. The Author(s), under exclusive licence to Springer Nature Limited.)

The evolutionary origin of metazoan cell types such as neurons and muscles is not known. Using whole-body single-cell RNA sequencing in a sponge, an animal without nervous system and musculature, we identified 18 distinct cell types. These include nitric oxide–sensitive contractile pinacocytes, amoeboid phagocytes, and secretory neuroid cells that reside in close contact with digestive choanocytes that express scaffolding and receptor proteins. Visualizing neuroid cells by correlative x-ray and electron microscopy revealed secretory vesicles and cellular projections enwrapping choanocyte microvilli and cilia. Our data show a communication system that is organized around sponge digestive chambers, using conserved modules that became incorporated into the pre- and postsynapse in the nervous systems of other animals.

Trogocytosis is a general biological process that involves one cell physically taking small parts of the membrane and other components from another cell. In trogocytosis, one cell seems to take little "bites" from another cell resulting in multiple outcomes from these cell-cell interactions. Trogocytosis was first described in protozoan parasites, which by taking pieces of host cells, kill them and cause tissue damage. Now, it is known that this process is also performed by cells of the immune system with important consequences such as cell communication and activation, elimination of microbial pathogens, and even control of cancer cells. More recently, trogocytosis has also been reported to occur in cells of the central nervous system and in various cells during development. Some of the molecules involved in phagocytosis also participate in trogocytosis. However, the molecular mechanisms that regulate trogocytosis are still a mystery. Elucidating these mechanisms is becoming a research area of much interest. For example, why neutrophils can engage trogocytosis to kill Trichomonas vaginalis parasites, but neutrophils use phagocytosis to eliminate already death parasites? Thus, trogocytosis is a significant process in normal physiology that multiple cells from different organisms use in various scenarios of health and disease. In this review, we present the basic principles known on the process of trogocytosis and discuss the importance in this process to host-pathogen interactions and to normal functions in the immune and nervous systems., Competing Interests: The authors declare that there is no conflict of interest regarding the publication of this paper., (Copyright © 2021 Eileen Uribe-Querol and Carlos Rosales.)

Complex nervous systems have a modular architecture, whereby reiterative groups of neurons ("modules") that share certain structural and functional properties are integrated into large neural circuits. Neurons develop from proliferating progenitor cells that, based on their location and time of appearance, are defined by certain genetic programs. Given that genes expressed by a given progenitor play a fundamental role in determining the properties of its lineage (i.e., the neurons descended from that progenitor), one efficient developmental strategy would be to have lineages give rise to the structural modules of the mature nervous system. It is clear that this strategy plays an important role in neural development of many invertebrate animals, notably insects, where the availability of genetic techniques has made it possible to analyze the precise relationship between neuronal origin and differentiation since several decades. Similar techniques, developed more recently in the vertebrate field, reveal that functional modules of the mammalian cerebral cortex are also likely products of developmentally defined lineages. We will review studies that relate cell lineage to circuitry and function from a comparative developmental perspective, aiming at enhancing our understanding of neural progenitors and their lineages, and translating findings acquired in different model systems into a common conceptual framework., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Although the human brain would be an ideal model for studying human neuropathology, it is difficult to perform in vitro culture of human brain cells from genetically engineered healthy or diseased brain tissue. Therefore, a suitable model for studying the molecular mechanisms responsible for neurological diseases that can appropriately mimic the human brain is needed. Somatic cell nuclear transfer (SCNT) was performed using an established porcine Yucatan EGFP cell line and whole seeding was performed using SCNT blastocysts. Two Yucatan EGFP porcine embryonic stem-like cell (pESLC) lines were established. These pESLC lines were then used to establish an in vitro neuro-organoids. Aggregates were cultured in vitro until 61 or 102 days after neural induction, neural patterning, and neural expansion. The neuro-organoids were sampled at each step and the expression of the dopaminergic neuronal marker (TH) and mature neuronal marker (MAP2) was confirmed by reverse transcription-PCR. Expression of the neural stem cell marker (PAX6), neural precursor markers (S100 and SOX2), and early neural markers (MAP2 and Nestin) were confirmed by immunofluorescence staining. In conclusion, we successfully established neuro-organoids derived from pESLCs in vitro. This protocol can be used as a tool to develop in vitro models for drug development, patient-specific chemotherapy, and human central nervous system disease studies.

Understanding how an adult brain reaches an appropriate size and cell composition from a pool of progenitors that proliferates and differentiates is a key question in Developmental Neurobiology. Not only the control of final size but also, the proper arrangement of cells of different embryonic origins is fundamental in this process. Each neural progenitor has to produce a precise number of sibling cells that establish clones, and all these clones will come together to form the functional adult nervous system. Lineage cell tracing is a complex and challenging process that aims to reconstruct the offspring that arise from a single progenitor cell. This tracing can be achieved through strategies based on genetically modified organisms, using either genetic tracers, transfected viral vectors or DNA constructs, and even single-cell sequencing. Combining different reporter proteins and the use of transgenic mice revolutionized clonal analysis more than a decade ago and now, the availability of novel genome editing tools and single-cell sequencing techniques has vastly improved the capacity of lineage tracing to decipher progenitor potential. This review brings together the strategies used to study cell lineages in the brain and the role they have played in our understanding of the functional clonal relationships among neural cells. In addition, future perspectives regarding the study of cell heterogeneity and the ontogeny of different cell lineages will also be addressed.

Holothurians, or sea cucumbers, belong to the phylum Echinodermata. They show good regenerative abilities. The present review provides an analysis of available data on the molecular aspects of regeneration mechanisms in holothurians. The genes and signaling pathways activated during the asexual reproduction and the formation of the anterior and posterior parts of the body, as well as the molecular mechanisms that provide regeneration of the nervous and digestive systems, are considered here. Damage causes a strong stress response, the signs of which are recorded even at late regeneration stages. In holothurian tissues, the concentrations of reactive oxygen species and antioxidant enzymes increase. Furthermore, the cellular and humoral components of the immune system are activated. Extracellular matrix remodeling and Wnt signaling play a major role in the regeneration in holothurians. All available morphological and molecular data show that the dedifferentiation of specialized cells in the remnant of the organ and the epithelial morphogenesis constitute the basis of regeneration in holothurians. However, depending on the type of damage, the mechanisms of regeneration may differ significantly in the spatial organization of regeneration process, the involvement of different cell types, and the depth of reprogramming of their genome (dedifferentiation or transdifferentiation).

The orderly development of the nervous system is characterized by phases of cell proliferation and differentiation, neural migration, axonal outgrowth and synapse formation, and stabilization. Each of these processes is a result of the modulation of genetic programs by extracellular cues. In particular, chondroitin sulfate proteoglycans (CSPGs) have been found to be involved in almost every aspect of this well-orchestrated yet delicate process. The evidence of their involvement is complex, often contradictory, and lacking in mechanistic clarity; however, it remains obvious that CSPGs are key cogs in building a functional brain. This review focuses on current knowledge of the role of CSPGs in each of the major stages of neural development with emphasis on areas requiring further investigation.

How evolutionary novelties have arisen is one of the central questions in evolutionary biology. Preexisting gene regulatory networks or signaling pathways have been shown to be co-opted for building novel traits in several organisms. However, the structure of entire gene regulatory networks and evolutionary events of gene co-option for emergence of a novel trait are poorly understood. In this study, to explore the genetic and molecular bases of the novel wing pigmentation pattern of a polka-dotted fruit fly (Drosophila guttifera), we performed de novo genome sequencing and transcriptome analyses. As a result, we comprehensively identified the genes associated with the pigmentation pattern. Furthermore, we revealed that 151 of these associated genes were positively or negatively regulated by wingless, a master regulator of wing pigmentation. Genes for neural development, Wnt signaling, Dpp signaling, and effectors (such as enzymes) for melanin pigmentation were included among these 151 genes. None of the known regulatory genes that regulate pigmentation pattern formation in other fruit fly species were included. Our results suggest that the novel pigmentation pattern of a polka-dotted fruit fly might have emerged through multistep co-options of multiple gene regulatory networks, signaling pathways, and effector genes, rather than recruitment of one large gene circuit., (© 2020 Federation of European Biochemical Societies.)

Over 250 million people suffer from schistosomiasis, a tropical disease caused by parasitic flatworms known as schistosomes. Humans become infected by free-swimming, water-borne larvae, which penetrate the skin. The earliest intra-mammalian stage, called the schistosomulum, undergoes a series of developmental transitions. These changes are critical for the parasite to adapt to its new environment as it navigates through host tissues to reach its niche, where it will grow to reproductive maturity. Unravelling the mechanisms that drive intra-mammalian development requires knowledge of the spatial organisation and transcriptional dynamics of different cell types that comprise the schistomulum body. To fill these important knowledge gaps, we perform single-cell RNA sequencing on two-day old schistosomula of Schistosoma mansoni. We identify likely gene expression profiles for muscle, nervous system, tegument, oesophageal gland, parenchymal/primordial gut cells, and stem cells. In addition, we validate cell markers for all these clusters by in situ hybridisation in schistosomula and adult parasites. Taken together, this study provides a comprehensive cell-type atlas for the early intra-mammalian stage of this devastating metazoan parasite.

Dendrites, branched structures extending from neuronal cell soma, are specialized for processing information from other neurons. The morphogenesis of dendritic structures is spatiotemporally regulated by well-orchestrated signaling cascades. Dysregulation of these processes impacts the wiring of neuronal circuit and efficacy of neurotransmission, which contribute to the pathogeneses of neurological disorders. While Cdk5 (cyclin-dependent kinase 5) plays a critical role in neuronal dendritic development, its underlying molecular control is not fully understood. In this study, we show that p39, one of the two neuronal Cdk5 activators, is a key regulator of dendritic morphogenesis. Pyramidal neurons deficient in p39 exhibit aberrant dendritic morphology characterized by shorter length and reduced arborization, which is comparable to dendrites in Cdk5-deficient neurons. RNA sequencing analysis shows that the adaptor protein, WDFY1 (WD repeat and FYVE domain-containing 1), acts downstream of Cdk5/p39 to regulate dendritic morphogenesis. While WDFY1 is elevated in p39-deficient neurons, suppressing its expression rescues the impaired dendritic arborization. Further phosphoproteomic analysis suggests that Cdk5/p39 mediates dendritic morphogenesis by modulating various downstream signaling pathways, including PI3K/Akt-, cAMP-, or small GTPase-mediated signaling transduction pathways, thereby regulating cytoskeletal organization, protein synthesis, and protein trafficking.

Sensory and motor systems in insects with hemimetabolous development must be ready to mediate adaptive behavior directly on hatching from the egg. For the desert locust S. gregaria, cholinergic transmission from antennal sensillae to olfactory or mechanosensory centers in the brain requires that choline acetyltransferase (ChAT) and the vesicular acetylcholine transporter (vAChT) already be present in sensory cells in the first instar. In this study, we used immunolabeling to demonstrate that ChAT and vAChT are both expressed in sensory cells from identifiable sensilla types in the immature antennal nervous system. We observed ChAT expression in dendrites, neurites and somata of putative basiconic-type sensillae at the first instar stage. We also detected vAChT in the sensory axons of these sensillae in a major antennal nerve tract. We then examined whether evidence for cholinergic transmission is present during embryogenesis. Immunolabeling confirms that vAChT is expressed in somata typical of campaniform sensillae, as well as in small sensory cell clusters typically associated with either a large basiconic or coeloconic sensilla, at 99% of embryogenesis. The vAChT is also expressed in the somata of these sensilla types in multiple antennal regions at 90% of embryogenesis, but not at earlier (70%) embryonic stages. Neuromodulators are known to appear late in embryogenesis in neurons of the locust central complex, and the cholinergic system of the antenna may also only reach maturity shortly before hatching.

Several biocompatible materials have been applied for managing soft tissue lesions; cerium oxide nanoparticles (CNPs, or nanoceria) are among the most promising candidates due to their outstanding properties, including antioxidant, anti-inflammatory, antibacterial, and angiogenic activities. Much attention should be paid to the physical properties of nanoceria, since most of its biological characteristics are directly determined by some of these relevant parameters, including the particle size and shape. Nanoceria, either in bare or functionalized forms, showed the excellent capability of accelerating the healing process of both acute and chronic wounds. The skin, heart, nervous system, and ophthalmic tissues are the main targets of nanoceria-based therapies, and the other soft tissues may also be evaluated in upcoming experimental studies. For the repair and regeneration of soft tissue damage and defects, nanoceria-incorporated film, hydrogel, and nanofibrous scaffolds have been proven to be highly suitable replacements with satisfactory outcomes. Still, some concerns have remained regarding the long-term effects of nanoceria administration for human tissues and organs, such as its clearance from the vital organs. Moreover, looking at the future, it seems necessary to design and develop three-dimensional (3D) printed scaffolds containing nanoceria for possible use in the concepts of personalized medicine.

Biological sex in animals is often considered a fixed, individual-level characteristic. However, not all sex-specific features are static: for example, C. elegans males (XO) can sometimes exhibit hermaphrodite (XX)-like feeding behavior [1, 2]. (C. elegans hermaphrodites are somatic females that transiently produce self-sperm.) Essentially all somatic sex differences in C. elegans are governed by the master regulator tra-1, whose activity is controlled by chromosomal sex and is necessary and sufficient to specify the hermaphrodite state [3]. One aspect of this state is high expression of the chemoreceptor odr-10. In hermaphrodites, high odr-10 expression promotes feeding, but in males, low odr-10 expression facilitates exploration [4]. However, males suppress this sex difference in two contexts: juvenile males exhibit high odr-10 expression and food deprivation activates odr-10 in adult males [4-6]. Remarkably, we find that both of these phenomena require tra-1. In juvenile (L3) males, tra-1 is expressed in numerous neurons; this expression diminishes as individuals mature into adulthood, a process that requires conserved regulators of sexual maturation. tra-1 remains expressed in a small number of neurons in adult males, where it likely has a permissive role in odr-10 activation. Thus, the neuronal functions of tra-1 are not limited to hermaphrodites; rather, tra-1 also acts in the male nervous system to transiently suppress a sexual dimorphism, developmentally and in response to nutritional stress. Our results show that the molecular and functional representation of sexual state in C. elegans is neither static nor homogeneous, challenging traditional notions about the nature of biological sex., Competing Interests: Declaration of Interests The authors declare no competing interests., (Copyright © 2020 The Authors. Published by Elsevier Inc. All rights reserved.)

Following the spectacular success of molecular genetics in deciphering the genetic code in the 1960s, several of its leading practitioners felt sufficiently emboldened to use their newly acquired skills to move on and study that most enigmatic of biological organs - the brain. Sydney Brenner's approach was to focus on Caenorhabditis elegans , a nematode that is genetically tractable, has a nervous system that generates a rich repertoire of behaviours yet is small enough to allow anatomical reconstructions with ultrastructural precision. Through force of personality and some inspired pioneering studies, Brenner managed to ignite a bonfire of enthusiasm for this organism, which has resulted in its nervous system becoming the best understood of that in any organism. Initially, many were skeptical that this rather strange structure with just a few hundred neurons would yield insights that were relevant to vertebrate nervous systems. However, fifty years on we know that the basic repertoire of molecular components of worm and human nervous systems are remarkably similar. Furthermore, worms have a similar diversity of these components rather than a primitive sub-set. It appears that the fundamental difference in a vertebrate nervous system is a huge expansion of the neural units that comprise a basic brain such as that exemplified in C. elegans.

The formation of the nervous system and its striking complexity is a remarkable feat of development. C. elegans served as a unique model to dissect the molecular events in neurodevelopment, from its early visionaries to the current booming neuroscience community. Soon after being introduced as a model, C. elegans was mapped at the level of genes, cells, and synapses, providing the first metazoan with a complete cell lineage, sequenced genome, and connectome. Here, I summarize mechanisms underlying C. elegans neurodevelopment, from the generation and diversification of neural components to their navigation and connectivity. I point out recent noteworthy findings in the fields of glia biology, sex dimorphism and plasticity in neurodevelopment, highlighting how current research connects back to the pioneering studies by Brenner, Sulston and colleagues. Multifaceted investigations in model organisms, connecting genes to cell function and behavior, expand our mechanistic understanding of neurodevelopment while allowing us to formulate emerging questions for future discoveries.

John Sulston changed the way we do science, not once, but three times - initially with the complete cell lineage of the nematode Caenorhabditis elegans , next with completion of the genome sequences of the worm and human genomes and finally with his strong and active advocacy for open data sharing. His contributions were widely recognized and in 2002 he received the Nobel Prize in Physiology and Medicine.

It is not known at present whether neuronal cell-type diversity-defined by cell-type-specific anatomical, biophysical, functional and molecular signatures-can be reduced to relatively simple molecular descriptors of neuronal identity 1 . Here we show, through examination of the expression of all of the conserved homeodomain proteins encoded by the Caenorhabditis elegans genome 2 , that the complete set of 118 neuron classes of C. elegans can be described individually by unique combinations of the expression of homeodomain proteins, thereby providing-to our knowledge-the simplest currently known descriptor of neuronal diversity. Computational and genetic loss-of-function analyses corroborate the notion that homeodomain proteins not only provide unique descriptors of neuron type, but also have a critical role in specifying neuronal identity. We speculate that the pervasive use of homeobox genes in defining unique neuronal identities reflects the evolutionary history of neuronal cell-type specification.

Regional brain morphology has a complex genetic architecture, consisting of many common polymorphisms with small individual effects. This has proven challenging for genome-wide association studies (GWAS). Due to the distributed nature of genetic signal across brain regions, multivariate analysis of regional measures may enhance discovery of genetic variants. Current multivariate approaches to GWAS are ill-suited for complex, large-scale data of this kind. Here, we introduce the Multivariate Omnibus Statistical Test (MOSTest), with an efficient computational design enabling rapid and reliable inference, and apply it to 171 regional brain morphology measures from 26,502 UK Biobank participants. At the conventional genome-wide significance threshold of α = 5 × 10 -8 , MOSTest identifies 347 genomic loci associated with regional brain morphology, more than any previous study, improving upon the discovery of established GWAS approaches more than threefold. Our findings implicate more than 5% of all protein-coding genes and provide evidence for gene sets involved in neuron development and differentiation.

One approach to understand the construction of complex systems is to investigate whether there are simple design principles that are commonly used in building such a system. In the context of nervous system development, one may ask whether the generation of its highly diverse sets of constituents, that is, distinct neuronal cell types, relies on genetic mechanisms that share specific common features. Specifically, are there common patterns in the function of regulatory genes across different neuron types and are those regulatory mechanisms not only used in different parts of one nervous system, but are they conserved across animal phylogeny? We address these questions here by focusing on one specific, highly conserved and well-studied regulatory factor, the POU homeodomain transcription factor UNC-86. Work over the last 30 years has revealed a common and paradigmatic theme of unc-86 function throughout most of the neuron types in which Caenorhabditis elegans unc-86 is expressed. Apart from its role in preventing lineage reiterations during development, UNC-86 operates in combination with distinct partner proteins to initiate and maintain terminal differentiation programs, by coregulating a vast array of functionally distinct identity determinants of specific neuron types. Mouse orthologs of unc-86, the Brn3 genes, have been shown to fulfill a similar function in initiating and maintaining neuronal identity in specific parts of the mouse brain and similar functions appear to be carried out by the sole Drosophila ortholog, Acj6. The terminal selector function of UNC-86 in many different neuron types provides a paradigm for neuronal identity regulation across phylogeny. This article is categorized under: Gene Expression and Transcriptional Hierarchies > Regulatory Mechanisms Invertebrate Organogenesis > Worms Nervous System Development > Vertebrates: Regional Development., (© 2020 Wiley Periodicals, Inc.)

The developing nervous system is remarkably sensitive to environmental signals, including disruptive toxins, such as polybrominated diphenyl ethers (PBDEs). PBDEs are an environmentally pervasive class of brominated flame retardants whose neurodevelopmental toxicity mechanisms remain largely unclear. Using dissociated cortical neurons from embryonic Rattus norvegicus , we found here that chronic exposure to 6-OH-BDE-47, one of the most prevalent hydroxylated PBDE metabolites, suppresses both spontaneous and evoked neuronal electrical activity. On the basis of our previous work on mitogen-activated protein kinase (MAPK)/extracellular signal-related kinase (ERK) (MEK) biology and our observation that 6-OH-BDE-47 is structurally similar to kinase inhibitors, we hypothesized that certain hydroxylated PBDEs mediate neurotoxicity, at least in part, by impairing the MEK-ERK axis of MAPK signal transduction. We tested this hypothesis on three experimental platforms: 1) in silico , where modeling ligand-protein docking suggested that 6-OH-BDE-47 is a promiscuous ATP-competitive kinase inhibitor; 2) in vitro in dissociated neurons, where 6-OH-BDE-47 and another specific hydroxylated BDE metabolite similarly impaired phosphorylation of MEK/ERK1/2 and activity-induced transcription of a neuronal immediate early gene; and 3) in vivo in Drosophila melanogaster , where developmental exposures to 6-OH-BDE-47 and a MAPK inhibitor resulted in offspring displaying similarly increased frequency of mushroom-body β-lobe midline crossing, a metric of axonal guidance. Taken together, our results support that certain ortho-hydroxylated PBDE metabolites are promiscuous kinase inhibitors and can cause disruptions of critical neurodevelopmental processes, including neuronal electrical activity, pre-synaptic functions, MEK-ERK signaling, and axonal guidance., (© 2020 Poston et al.)

Mammals differ in their regeneration potential after traumatic injury, which might be caused by species-specific regeneration programs. Here, we compared murine and human Schwann cell (SC) response to injury and developed an ex vivo injury model employing surgery-derived human sural nerves. Transcriptomic and lipid metabolism analysis of murine SCs following injury of sural nerves revealed down-regulation of lipogenic genes and regulator of lipid metabolism, including Pparg (peroxisome proliferator-activated receptor gamma) and S1P (sphingosine-1-phosphate). Human SCs failed to induce similar adaptations following ex vivo nerve injury. Pharmacological PPARg and S1P stimulation in mice resulted in up-regulation of lipid gene expression, suggesting a role in SCs switching towards a myelinating state. Altogether, our results suggest that murine SC switching towards a repair state is accompanied by transcriptome and lipidome adaptations, which are reduced in humans.

Signaling molecules that regulate neurodevelopmental processes in the early postnatal subventricular zone (SVZ) are critical for proper brain development yet remain poorly characterized. Here, we report that Endothelin-1 (ET-1), a molecular component of the postnatal SVZ, promotes radial glial cell maintenance and proliferation in an autocrine manner via Notch signaling. Loss of ET-1 signaling increases neurogenesis and reduces oligodendrocyte progenitor cell proliferation (OPC) in the developing SVZ, thereby altering cellular output of the stem cell niche. We also show that ET-1 is required for increased neural stem cell and OPC proliferation in the adult mouse SVZ following demyelination. Lastly, high levels of ET-1 in the SVZ of patients with Cathepsin A-related arteriopathy with strokes and leukoencephalopathy correlate with an increased number of SVZ OPCs, suggesting ET-1's role as a regulator of glial progenitor proliferation may be conserved in humans. ET-1 signaling therefore presents a potential new therapeutic target for promoting SVZ-mediated cellular repair.

Homeodomain-interacting protein kinases (Hipks) have been previously associated with cell proliferation and cancer, however, their effects in the nervous system are less well understood. We have used Drosophila melanogaster to evaluate the effects of altered Hipk expression on the nervous system and muscle. Using genetic manipulation of Hipk expression we demonstrate that knockdown and over-expression of Hipk produces early adult lethality, possibly due to the effects on the nervous system and muscle involvement. We find that optimal levels of Hipk are critical for the function of dopaminergic neurons and glial cells in the nervous system, as well as muscle. Furthermore, manipulation of Hipk affects the structure of the larval neuromuscular junction (NMJ) by promoting its growth. Hipk regulates the phosphorylation of the synapse-associated cytoskeletal protein Hu-li tai shao (Hts; adducin in mammals) and modulates the expression of two important protein kinases, Calcium-calmodulin protein kinase II (CaMKII) and Partitioning-defective 1 (PAR-1), all of which may alter neuromuscular structure/function and influence lethality. Hipk also modifies the levels of an important nuclear protein, TBPH, the fly orthologue of TAR DNA-binding protein 43 (TDP-43), which may have relevance for understanding motor neuron diseases., Competing Interests: The authors have declared that no competing interests exist.

The ability of the nervous system to sense environmental stimuli and to relay these signals to immune cells via neurotransmitters and neuropeptides is indispensable for effective immunity and tissue homeostasis. Depending on the tissue microenvironment and distinct drivers of a certain immune response, the same neuronal populations and neuro-mediators can exert opposing effects, promoting or inhibiting tissue immunity. Here, we review the current understanding of the mechanisms that underlie the complex interactions between the immune and the nervous systems in different tissues and contexts. We outline current gaps in knowledge and argue for the importance of considering infectious and inflammatory disease within a conceptual framework that integrates neuro-immune circuits both local and systemic, so as to better understand effective immunity to develop improved approaches to treat inflammation and disease., Competing Interests: Declaration of Interests D.A. has contributed to scientific advisory boards at FARE, Genentech, KRF, Pfizer, and Takeda in the last twelve months. I.M.C. receives sponsored research support from GSK and Allergan Pharmaceuticals and is a member of scientific advisory boards for GSK and Kintai pharmaceuticals., (Copyright © 2020 Elsevier Inc. All rights reserved.)

The Citron protein was originally identified for its capability to specifically bind the active form of RhoA small GTPase, leading to the simplistic hypothesis that it may work as a RhoA downstream effector in actin remodeling. More than two decades later, a much more complex picture has emerged. In particular, it has become clear that in animals, and especially in mammals, the functions of the Citron gene ( CIT ) are intimately linked to many aspects of central nervous system (CNS) development and function, although the gene is broadly expressed. More specifically, CIT encodes two main isoforms, Citron-kinase (CIT-K) and Citron-N (CIT-N), characterized by complementary expression pattern and different functions. Moreover, in many of their activities, CIT proteins act more as upstream regulators than as downstream effectors of RhoA. Finally it has been found that, besides working through actin, CIT proteins have many crucial functional interactions with the microtubule cytoskeleton and may directly affect genome stability. In this review, we will summarize these advances and illustrate their actual or potential relevance for CNS diseases, including microcephaly and psychiatric disorders.

State-of-the-art tissue-clearing methods provide subcellular-level optical access to intact tissues from individual organs and even to some entire mammals. When combined with light-sheet microscopy and automated approaches to image analysis, existing tissue-clearing methods can speed up and may reduce the cost of conventional histology by several orders of magnitude. In addition, tissue-clearing chemistry allows whole-organ antibody labelling, which can be applied even to thick human tissues. By combining the most powerful labelling, clearing, imaging and data-analysis tools, scientists are extracting structural and functional cellular and subcellular information on complex mammalian bodies and large human specimens at an accelerated pace. The rapid generation of terabyte-scale imaging data furthermore creates a high demand for efficient computational approaches that tackle challenges in large-scale data analysis and management. In this Review, we discuss how tissue-clearing methods could provide an unbiased, system-level view of mammalian bodies and human specimens and discuss future opportunities for the use of these methods in human neuroscience.

The study of acoel morphologies has been recently stimulated by the knowledge that this group of animals represents an early offshoot of the Bilateria. Understanding how organ systems and tissues develop and the molecular underpinnings of the processes involved has become an area of new research. The microscopic anatomy of these organisms is best understood through the systematic use of immunochemistry and in situ hybridization procedures. These methods allow us to map, in precise detail, the expression patterns of genes and proteins, in space and time. With the additional use of genomic resources, they provide us with insights on how a group of "early" bilaterians have diversified over time. As these animals are new to the world of molecular studies, the protocols have involved a lot of new and specific adaptations to their specific anatomical-histological characteristics. Here we explain some of these protocols in detail, with the aim that should prove useful in our much-needed understanding of the origins of bilaterian animals. An anatomical sketch is provided at the beginning as a necessary guide for those not familiar with the Acoela.

During early embryogenesis, the ectoderm is rapidly subdivided into neural, neural crest and sensory progenitors. How the onset of lineage determinants and the loss of pluripotency markers are temporally and spatially coordinated in vivo is still debated. Here, we identify a crucial role for the transcription factor PRDM1 in the orderly transition from epiblast to defined neural lineages in chick. PRDM1 is initially expressed broadly in the entire epiblast, but becomes gradually restricted as cell fates are specified. We find that PRDM1 is required for the loss of some pluripotency markers and the onset of neural, neural crest and sensory progenitor specifier genes. PRDM1 directly activates their expression by binding to their promoter regions and recruiting the histone demethylase Kdm4a to remove repressive histone marks. However, once neural lineage determinants become expressed, they in turn repress PRDM1 , whereas prolonged PRDM1 expression inhibits neural, neural crest and sensory progenitor genes, suggesting that its downregulation is necessary for cells to maintain their identity. Therefore, PRDM1 plays multiple roles during ectodermal cell fate allocation., Competing Interests: Competing interestsThe authors declare no competing or financial interests., (© 2019. Published by The Company of Biologists Ltd.)

Cell membrane nanotubes, variously referred to as tunneling nanotubes and cytonemes, are currently the focus of much interest. They are of ancient origin, as indicated by their opportunistic use for cell invasion by pathogens, including bacteria and virus, and by their employment in bacterial networking. They play a significant role in cancer invasion and in the explanation of glioblastoma resistance to treatment. Their structure and properties have been investigated with optical tweezers. They have been detected in vivo. Their role in the immune system was early verified. Very recently, it was shown that they share many properties with nerve synapses, including the roles of glutamate and Ca ions. Similar features have also been observed in primitive plants. These results support the conjecture that, besides their roles in immunology, developmental biology and cancer, cell membrane nanotubes are the ancestors of the nervous system.

Background: The annelid anterior central nervous system is often described to consist of a dorsal prostomial brain, consisting of several commissures and connected to the ventral ganglionic nerve cord via circumesophageal connectives. In the light of current molecular phylogenies, our assumptions on the primary design of the nervous system in Annelida has to be reconsidered. For that purpose we provide a detailed investigation of the adult nervous system of Magelonidae - a putatively basally branching annelid family - and studied early stages of the development of the latter., Results: Our comparative investigation using an integrative morphological approach shows that the nervous system of Magelonidae is located inside the epidermis. The brain is composed of an anterior compact neuropil and posteriorly encircles the prostomial coelomic cavities. From the brain two lateral medullary cords branch off which fuse caudally. Prominent brain structures such as nuchal organs, ganglia or mushroom bodies are absent and the entire nervous system is medullary. Our investigations also contradict previous investigations and present an updated view on established assumptions and descriptions., Conclusion: The comprehensive dataset presented herein enables a detailed investigation of the magelonid anterior central nervous system for the first time. The data reveal that early in annelid evolution complexity of brains and anterior sensory structures rises. Polymorphic neurons in clusters and distinct brain parts, as well as lateral organs - all of which are not present in outgroup taxa and in the putative magelonid sister group Oweniidae - already evolved in Magelonidae. Commissures inside the brain, ganglia and nuchal organs, however, most likely evolved in the stem lineage of Amphinomidae + Sipuncula and Pleistoannelida (Errantia+ Sedentaria). The investigation demonstrates the necessity to continuously question established descriptions and interpretations of earlier publications and the need for transparent datasets. Our results also hint towards a stronger inclusion of larval morphology and developmental investigations in order to understand adult morphological features, not only in Annelida.

We developed a complex in vitro model of ischemic damage. Analysis of hippocampal cell viability in primary cultures after modeling of various stress factors revealed the features of action of the main pathological factors of ischemia. Neurotrophic factors BDNF and GDNF produced pronounced neuroprotective effect during modeling both the complex ischemic damage and its individual pathophysiological components. Neurotrophic factor GDNF produced the most pronounced protective effect.

The localisation and distribution of the serotoninergic nerve elements was studied for the first time in the flatworm Chimaericola leptogaster (Leuckart, 1830) using immunocytochemical methodology and confocal laser scanning microscopy. The musculature was investigated by histochemical staining of actin filaments; scanning electron microscopy was used to identify the sensory structures on the worm's surface. Uniciliated, bi-ciliated and multiciliated sensory endings have been described on the worm's surface. The morphological data demonstrate the presence of circular, longitudinal and diagonal muscles that comprise the musculature of C. leptogaster in the anterior, median and posterior body regions. Well-developed radial and circular muscle fibres were also observed surrounding the genital pore, two vaginae and in clumps of the haptor. The study revealed the presence of biogenic amine, serotonin, in the central and peripheral nervous systems of C. leptogaster: in the neurons and fibres of the cephalic ganglia and ventral nerve cord, in the innervation of reproductive system compartments. The localised sites of the serotoninergic elements point to important roles of serotonin in monogenean reproductive processes and, possibly, in the regulation of muscle function.

Ascidian embryos highlight the importance of cell lineages in animal development. As simple proto-vertebrates, they also provide insights into the evolutionary origins of cell types such as cranial placodes and neural crest cells. Here we have determined single-cell transcriptomes for more than 90,000 cells that span the entirety of development-from the onset of gastrulation to swimming tadpoles-in Ciona intestinalis. Owing to the small numbers of cells in ascidian embryos, this represents an average of over 12-fold coverage for every cell at every stage of development. We used single-cell transcriptome trajectories to construct virtual cell-lineage maps and provisional gene networks for 41 neural subtypes that comprise the larval nervous system. We summarize several applications of these datasets, including annotating the synaptome of swimming tadpoles and tracing the evolutionary origin of cell types such as the vertebrate telencephalon.

In this study, we used neural stem cells (NSCs) as a toxicology tool to assess the potential developmental neurotoxicity of drinking water from Taihu Lake. We found that the condensed drinking water could inhibit the proliferation and differentiation of NSCs, especially the tap water. Inductively coupled plasma mass spectrometry and high-performance liquid chromatography analysis showed that nickel was detected in the tap water with a high concentration. Our study revealed that nickel could inhibit NSCs proliferation and differentiation, which is induced not only by the intracellular reactive oxygen species generation, but also by the protein levels upregulation of p-c-Raf, p-MEK1/2 and p-Erk1/2 through the axon guidance signal pathways. These findings will provide a new way of research insight for investigation of nickel-induced neurotoxicity. Meanwhile, our test method confirmed the feasibility and reliability of stem cell assays for developmental neurotoxicity testing.

Knowledge of connectivity in the nervous system is essential to understanding its function. Here we describe connectomes for both adult sexes of the nematode Caenorhabditis elegans, an important model organism for neuroscience research. We present quantitative connectivity matrices that encompass all connections from sensory input to end-organ output across the entire animal, information that is necessary to model behaviour. Serial electron microscopy reconstructions that are based on the analysis of both new and previously published electron micrographs update previous results and include data on the male head. The nervous system differs between sexes at multiple levels. Several sex-shared neurons that function in circuits for sexual behaviour are sexually dimorphic in structure and connectivity. Inputs from sex-specific circuitry to central circuitry reveal points at which sexual and non-sexual pathways converge. In sex-shared central pathways, a substantial number of connections differ in strength between the sexes. Quantitative connectomes that include all connections serve as the basis for understanding how complex, adaptive behavior is generated.

Mathematical and computational modeling enables biologists to integrate data from observations and experiments into a theoretical framework. In this review, we describe how developmental processes associated with stem-cell-driven growth of tissue in both the embryonic and adult nervous system can be modeled using cellular automata (CA). A cellular automaton is defined by its discrete nature in time, space, and state. The discrete space is represented by a uniform grid or lattice containing agents that interact with other agents within their local neighborhood. This possibility of local interactions of agents makes the cellular automata approach particularly well suited for studying through modeling how complex patterns at the tissue level emerge from fundamental developmental processes (such as proliferation, migration, differentiation, and death) at the single-cell level. As part of this review, we provide a primer for how to define biologically inspired rules governing these processes so that they can be implemented into a CA model. We then demonstrate the power of the CA approach by presenting simulations (in the form of figures and movies) based on building models of three developmental systems: the formation of the enteric nervous system through invasion by neural crest cells; the growth of normal and tumorous neurospheres induced by proliferation of adult neural stem/progenitor cells; and the neural fate specification through lateral inhibition of embryonic stem cells in the neurogenic region of Drosophila., (© 2019 Wiley Periodicals, Inc.)

The kinetochore is a complex of proteins, broadly conserved from yeast to man, that resides at the centromere and is essential for chromosome segregation in dividing cells. There are no known functions of the core complex outside of the centromere. We now show that the proteins of the kinetochore have an essential post-mitotic function in neurodevelopment. At the embryonic neuromuscular junction of Drosophila melanogaster, mutation or knockdown of many kinetochore components cause neurites to overgrow and prevent formation of normal synaptic boutons. Kinetochore proteins were detected in synapses and axons in Drosophila. In post-mitotic cultured hippocampal neurons, knockdown of mis12 increased the filopodia-like protrusions in this region. We conclude that the proteins of the kinetochore are repurposed to sculpt developing synapses and dendrites and thereby contribute to the correct development of neuronal circuits in both invertebrates and mammals., (Copyright © 2019 Elsevier Inc. All rights reserved.)

MicroRNAs (miRNAs) control various biological processes by inducing translational repression and transcript degradation of the target genes. In mammalian development, knowledge of the timing and expression pattern of each miRNA is important to determine and predict its function in vivo So far, no systematic analyses of the spatiotemporal expression pattern of miRNAs during mammalian neurodevelopment have been performed. Here, we isolated total RNAs from the embryonic dorsal forebrain of mice at different developmental stages and subjected these RNAs to microarray analyses. We selected 279 miRNAs that exhibited high signal intensities or ascending or descending expression dynamics. To ascertain the expression patterns of these miRNAs, we used locked nucleic acid (LNA)-modified miRNA probes in in situ hybridization experiments. Multiple miRNAs exhibited spatially restricted/enriched expression in anatomically distinct regions or in specific neuron subtypes in the embryonic brain and spinal cord, such as in the ventricular area, the striatum (and other basal ganglia), hypothalamus, choroid plexus, and the peripheral nervous system. These findings provide new insights into the expression and function of miRNAs during the development of the nervous system and could be used as a resource to facilitate studies in neurodevelopment., (© 2019 Shu et al.)

Amphioxus is the living chordate closest to the ancestral form of vertebrates, and in a key position to reveal essential aspects of the evolution of the brain Bauplan of vertebrates. The dorsal neural cord of this species at the larval stage is characterized by a small cerebral vesicle at its anterior end and a large posterior region. The latter is comparable in some aspects to the hindbrain and spinal cord regions of vertebrates. The rostral end of the cerebral vesicle contains a median pigment spot and associated rows of photoreceptor and other nerve cells; this complex is known as "the frontal eye." However, this is not a complete eye in the sense that it has neither eye muscles nor lens (only a primitive retina-like tissue). Cranial nerves III, IV, and VI take part in the motor control of eye muscles in all vertebrates. Using a recent model that postulates distinct molecularly characterized hypothalamo-prethalamic and mesodiencephalic domains in the early cerebral vesicle of amphioxus, we analyze here possible scenarios for the origin from the common ancestor of cephalochordates and vertebrates of the cranial nerves related with extrinsic eye muscle innervations. Anat Rec, 302:452-462, 2019. © 2018 Wiley Periodicals, Inc., (© 2018 Wiley Periodicals, Inc.)

The dynamic interaction between neurons and glia is a fundamental aspect of developmental neurobiology. Astrocytic processes are extremely complex and can physically surround neuronal synapses where they are involved in regulating neuronal activity and synaptic plasticity. This review describes important roles glial cells play in synapse maturation and stabilization in the developing central nervous system. We highlight recent evidence showing that the motility of astrocytic and radial glial processes is modulated by neuronal signals and is important for normal synapse maturation and function. Examples of glia-derived molecules that influence synapse maturation and stabilization are presented. We close by touching on recent and future trends in neuron-glia research., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

During development, both cells and tissues must acquire the correct shape to allow their proper function. This is especially relevant in the nervous system, where the shape of individual cell processes, such as the axons and dendrites, and the shape of entire tissues, such as the folding of the neocortex, are highly specialized. While many aspects of neural development have been uncovered, there are still several open questions concerning the mechanisms governing cell and tissue shape. In this review, we discuss the role of the extracellular matrix (ECM) in these processes. In particular, we consider how the ECM regulates cell shape, proliferation, differentiation and migration, and more recent work highlighting a key role of ECM in the morphogenesis of neural tissues.

Dendritic arbors are crucial for nervous system assembly, but the intracellular mechanisms that govern their assembly remain incompletely understood. Here, we show that the dendrites of PVD neurons in Caenorhabditis elegans are patterned by distinct pathways downstream of the DMA-1 leucine-rich transmembrane (LRR-TM) receptor. DMA-1/LRR-TM interacts through a PDZ ligand motif with the guanine nucleotide exchange factor TIAM-1/GEF in a complex with act-4/Actin to pattern higher order 4° dendrite branches by localizing F-actin to the distal ends of developing dendrites. Surprisingly, TIAM-1/GEF appears to function independently of Rac1 guanine nucleotide exchange factor activity. A partially redundant pathway, dependent on HPO-30/Claudin, regulates formation of 2° and 3° branches, possibly by regulating membrane localization and trafficking of DMA-1/LRR-TM. Collectively, our experiments suggest that HPO-30/Claudin localizes the DMA-1/LRR-TM receptor on PVD dendrites, which in turn can control dendrite patterning by directly modulating F-actin dynamics through TIAM-1/GEF., Competing Interests: LT, CD, MR, NR, YS, ML, HB No competing interests declared, (© 2019, Tang et al.)

Weaning is a critical period for the growth and development of mammals, in which various physiological and biochemical indicators of the body have undergone great changes. The development, differentiation, and maturation of the nervous system are regulated by many proteins. Changes in related proteins affect the physiological functions of the nervous system. However, the regulation of selfrenewal and differentiation of the nervous system at this stage is still poorly understood. The mechanism of differentiation and regulation of the major proteins in the nervous system during this special period of weaning remains to be investigated. Therefore, this paper aims to summarize the alteration of the nervous system during weaning and provide the basis for subsequent research., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)

The last common ancestor of Bilateria and Cnidaria is considered to develop a nervous system over 500 million years ago. Despite the long course of evolution, many of the neuron-related genes, which are active in Bilateria, are also found in the cnidarian Hydra. Thus, Hydra is a good model to study the putative primitive nervous system in the last common ancestor that had the great potential to evolve to a more advanced one. Regionalization of the nervous system is one of the advanced features of bilaterian nervous system. Although a regionalized nervous system is already known to be present in Hydra, its developmental mechanisms are poorly understood. In this study we show how it is formed and maintained, focusing on the neuropeptide Hym-176 gene and its paralogs. First, we demonstrate that four axially localized neuron subsets that express different combination of the neuropeptide Hym-176 gene and its paralogs cover almost an entire body, forming a regionalized nervous system in Hydra. Second, we show that positional information governed by the Wnt signaling pathway plays a key role in determining the regional specificity of the neuron subsets as is the case in bilaterians. Finally, we demonstrated two basic mechanisms, regionally restricted new differentiation and phenotypic conversion, both of which are in part conserved in bilaterians, are involved in maintaining boundaries between the neuron subsets. Therefore, this study is the first comprehensive analysis of the anatomy and developmental regulation of the divergently evolved and axially regionalized peptidergic nervous system in Hydra, implicating an ancestral origin of neural regionalization., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Mouse embryonic stem cells (mESCs) are pluripotent cells capable of differentiating in vitro to form the ~200 types of cells of the developing embryo and adult, including cells of the nervous system. This makes mESCs a useful tool for studying the molecular mechanisms of mammalian embryonic development. Many protocols involving the use of growth factors and small molecules to differentiate mESCs into neural progenitors and neurons currently exist. However, there is a paucity of protocols available that recapitulate the developmental process. Our laboratory has developed a protocol to recapitulate mammalian neural lineage development by differentiating mESCs to mature neurons via intermediate cell populations observed during in vivo embryo development. This protocol uses the amino acid L-proline to direct the differentiation of mESCs, grown as embryoid bodies, into Sox1 + neurectoderm, followed by differentiation to form Nestin + , BLBP + , and NeuN + neural cell types.