The neural crest, a multifaceted structure of the vertebrates

Anisodamine affects the pigmentation, mineral density, craniofacial area, and eye development in zebrafish embryos

Anisodamine is one of the major components of the tropine alkaloid family and is widely used in the treatment of pain, motion sickness, pupil dilatation, and detoxification of organophosphorus poisoning. As a muscarinic receptor antagonist, the low toxicity and moderate drug effect of anisodamine often result in high doses for clinical use, making it important to fully investigate its toxicity. In this study, zebrafish embryos were exposed to 1.3-, 2.6-, and 5.2-mM anisodamine for 7 days to study the toxic effects of drug exposure on pigmentation, mineral density, craniofacial area, and eye development. The results showed that exposure to anisodamine at 1.3 mM resulted in cranial malformations and abnormal pigmentation in zebrafish embryos; 2.6- and 5.2-mM anisodamine resulted in significant eye development defects and reduced bone density in zebrafish embryos. The associated toxicities were correlated with functional development of neural crest cells through gene expression (col1a2, ddb1, dicer1, mab21l1, mab21l2, sox10, tyrp1b, and mitfa) in the dose of 5.2-mM exposed group. In conclusion, this study provides new evidence of the developmental toxicity of high doses of anisodamine in aqueous solutions to organisms and provides a warning for the safe use of this drug.

Conservation of Zebrafish MicroRNA-145 and Its Role during Neural Crest Cell Development

The neural crest is a multipotent cell population that develops from the dorsal neural fold of vertebrate embryos in order to migrate extensively and differentiate into a variety of tissues. A number of gene regulatory networks coordinating neural crest cell specification and differentiation have been extensively studied to date. Although several publications suggest a common role for microRNA-145 (miR-145) in molecular reprogramming for cell cycle regulation and/or cellular differentiation, little is known about its role during in vivo cranial neural crest development. By modifying miR-145 levels in zebrafish embryos, abnormal craniofacial development and aberrant pigmentation phenotypes were detected. By whole-mount in situ hybridization, changes in expression patterns of col2a1a and Sry-related HMG box (Sox) transcription factors sox9a and sox9b were observed in overexpressed miR-145 embryos. In agreement, zebrafish sox9b expression was downregulated by miR-145 overexpression. In silico and in vivo analysis of the sox9b 3′UTR revealed a conserved potential miR-145 binding site likely involved in its post-transcriptional regulation. Based on these findings, we speculate that miR-145 participates in the gene regulatory network governing zebrafish chondrocyte differentiation by controlling sox9b expression.

Development of the Autonomic Nervous System: Clinical Implications

Investigations of the cellular and molecular mechanisms that mediate the development of the autonomic nervous system have identified critical genes and signaling pathways that, when disrupted, cause disorders of the autonomic nervous system. This review summarizes our current understanding of how the autonomic nervous system emerges from the organized spatial and temporal patterning of precursor cell migration, proliferation, communication, and differentiation, and discusses potential clinical implications for developmental disorders of the autonomic nervous system, including familial dysautonomia, Hirschsprung disease, Rett syndrome, and congenital central hypoventilation syndrome.

Cardiac Neural Crest Cells: Their Rhombomeric Specification, Migration, and Association with Heart and Great Vessel Anomalies

Outflow tract abnormalities are the most frequent congenital heart defects. These are due to the absence or dysfunction of the two main cell types, i.e., neural crest cells and secondary heart field cells that migrate in opposite directions at the same stage of development. These cells directly govern aortic arch patterning and development, ascending aorta dilatation, semi-valvular and coronary artery development, aortopulmonary septation abnormalities, persistence of the ductus arteriosus, trunk and proximal pulmonary arteries, sub-valvular conal ventricular septal/rotational defects, and non-compaction of the left ventricle. In some cases, depending on the functional defects of these cells, additional malformations are found in the expected spatial migratory area of the cells, namely in the pharyngeal arch derivatives and cervico-facial structures. Associated non-cardiovascular anomalies are often underestimated, since the multipotency and functional alteration of these cells can result in the modification of multiple neural, epidermal, and cervical structures at different levels. In most cases, patients do not display the full phenotype of abnormalities, but congenital cardiac defects involving the ventricular outflow tract, ascending aorta, aortic arch and supra-aortic trunks should be considered as markers for possible impaired function of these cells. Neural crest cells should not be considered as a unique cell population but on the basis of their cervical rhombomere origins R3-R5 or R6-R7-R8 and specific migration patterns: R3-R4 towards arch II, R5-R6 arch III and R7-R8 arch IV and VI. A better understanding of their development may lead to the discovery of unknown associated abnormalities, thereby enabling potential improvements to be made to the therapeutic approach.

Innate and Adaptive Immunity Linked to Recognition of Antigens Shared by Neural Crest-Derived Tumors

In the adult, many embryologic processes can be co-opted by during cancer progression. The mechanisms of divisions, migration, and the ability to escape immunity recognition linked to specific embryo antigens are also expressed by malignant cells. In particular, cells derived from neural crests (NC) contribute to the development of multiple cell types including melanocytes, craniofacial cartilage, glia, neurons, peripheral and enteric nervous systems, and the adrenal medulla. This plastic performance is due to an accurate program of gene expression orchestrated with cellular/extracellular signals finalized to regulate long-distance migration, proliferation, differentiation, apoptosis, and survival. During neurulation, prior to initiating their migration, NC cells must undergo an epithelial–mesenchymal transition (EMT) in which they alter their actin cytoskeleton, lose their cell–cell junctions, apicobasal polarity, and acquire a motile phenotype. Similarly, during the development of the tumors derived from neural crests, comprising a heterogeneous group of neoplasms (Neural crest-derived tumors (NCDTs)), a group of genes responsible for the EMT pathway is activated. Here, retracing the molecular pathways performed by pluripotent cells at the boundary between neural and non-neural ectoderm in relation to the natural history of NCDT, points of contact or interposition are highlighted to better explain the intricate interplay between cancer cells and the innate and adaptive immune response.

Acetaminophen affects the survivor, pigmentation and development of craniofacial structures in zebrafish (Danio rerio) embryos

In spite of its toxic effects, N-acetyl-p-aminophenol (APAP), also commonly known as acetaminophen or paracetamol, is one of the most widely used analgesic and antipyretic agents. It can be obtained without a medical prescription. To test the effect over the zebrafish embryonic development, a Fish Embryo acute Toxicity (FET) test was carried out with acetaminophen to establish the range of concentrations that cause a harmful effect on the zebrafish development. Diminished pigmentation (in embryos treated from 0 h post-fertilization) and blockage of melanin synthesis (in larvae treated from 72 h post-fertilization) were detected, suggesting the involvement of this compound in the development of black pigment cells as described recently for human epidermal melanocytes. Morphological abnormalities such as aberrant craniofacial structures, pericardial edemas, and blood accumulation were also found. All these effects could be due to higher levels of apoptotic cells detected in treated embryos. Therefore, teratogenic effects of acetaminophen cannot be ruled out, and its wide use should be taken with caution.

Dicer1 is required for pigment cell and craniofacial development in zebrafish

The multidomain RNase III endoribonuclease DICER is required for the generation of most functional microRNAs (miRNAs). Loss of Dicer affects developmental processes at different levels. Here, we characterized the zebrafish Dicer1 mutant, dicer1^sa9205, which has a single point mutation induced by N-ethyl-N-nitrosourea mutagenesis. Heterozygous dicer1^sa9205 developed normally, being phenotypically indistinguishable from wild-type siblings. Homozygous dicer1^sa9205 mutants display smaller eyes, abnormal craniofacial development and aberrant pigmentation. Reduced numbers of both iridophores and melanocytes were observed in the head and ventral trunk of dicer1^sa9205 homozygotes; the effect on melanocytes was stronger and detectable earlier in development. The expression of microphthalmia-associated transcription factor a (mitfa), the master gene for melanocytes differentiation, was enhanced in dicer1-depleted fish. Similarly, the expression of SRY-box containing gene 10 (sox10), required for mitfa activation, was higher in mutants than in wild types. In silico and in vivo analyses of either sox10 or mitfa 3'UTRs revealed conserved potential miRNA binding sites likely involved in the post-transcriptional regulation of both genes. Based on these findings, we propose that dicer1 participates in the gene regulatory network governing zebrafish melanocyte differentiation by controlling the expression of mitfa and sox10.

The convergent roles of CD271/p75 in neural crest-derived melanoma plasticity

The embryonic microenvironment is an important source of signals that promote multipotent cells to adopt a specific fate and direct cells along distinct migratory pathways. Yet, the ability of the embryonic microenvironment to retain multipotent progenitors or reprogram de-differentiated cells is less clear. Mistakes in cell differentiation or migration often result in developmental defects and tumorigenesis, including aggressive cancers that share many characteristics with embryonic progenitor cells. This is a striking feature of the vertebrate neural crest, a multipotent and highly migratory cell population first identified by His (1868) with the potential to metamorphose into aggressive melanoma cancer. In this perspective, we address the roles of CD271/p75 in tumor initiation, phenotype switching and reprogramming of metastatic melanoma and discuss the convergence of these roles in melanoma plasticity.

Derivation and characterization of putative craniofacial mesenchymal progenitor cells from human induced pluripotent stem cells

The introduction and widespread adoption of induced pluripotent stem cell (iPSC) technology has opened new avenues for craniofacial regenerative medicine. Neural crest cells (NCCs) are the precursor population to many craniofacial structures, including dental and periodontal structures, and iPSC-derived NCCs may, in the near future, offer an unlimited supply of patient-specific cells for craniofacial repair interventions. Here, we used an established protocol involving simultaneous Wnt signaling activation and TGF-β signaling inhibition to differentiate three human iPSC lines to cranial NCCs. We then derived a mesenchymal progenitor cell (NCC-MPCs) population with chondrogenic and osteogenic potential from cranial NCCs and investigated their similarity to widely studied human postnatal dental or periodontal stem/progenitor cells. NCC-MPCs were quite distinct from both their precursor cells (NCCs) and bone-marrow mesenchymal stromal cells, a stromal population of mesodermal origin. Despite their similarity with dental stem/progenitor cells, NCC-MPCs were clearly differentiated by a core set of 43 genes, including ACKR3 (CXCR7), whose expression (both at transcript and protein level) appear to be specific to NCC-MPCs. Altogether, our data demonstrate the feasibility of craniofacial mesenchymal progenitor derivation from human iPSCs through a neural crest-intermediate and set the foundation for future studies regarding their full differentiation repertoire and their in vivo existence.

Tyrosinase and nestin immunohistochemical expression in melanocytic nevi as a histopathologic pattern to trace melanocyte differentiation and nevogenesis

While histological analysis represents a powerful tool for the classification of melanocytic lesions as benign or malignant, a clear-cut distinction between a nevus and a melanoma is sometimes a challenging step of the diagnostic process. The immunohistochemical detection of tyrosinase, cardinal melanogenic enzyme during melanocytic maturation, has often been helpful in formulating a differential diagnosis due to the peculiar staining pattern in nevocytes compared with melanoma cells. Tyrosinase distribution in nevi appears to overlap with the cytoarchitectural changes observable within these lesions, that result in epidermal or superficial dermal nevocytes being larger and strongly expressing melanocytic differentiation antigens, such as tyrosinase, compared with deeper dermal nevus cells. Our study aimed to evaluate the immunohistochemical expression pattern of tyrosinase in different histological types of acquired dysplastic melanocytic nevi, including junctional, compound, and intradermal nevi. Moreover, to estimate whether in nevocytes the expression of tyrosinase was associated with their differentiation state, we investigated the expression of two recognized markers of pluripotency, CD34 and nestin. In all examined nevi, our analysis revealed a remarkable immunoreactivity for tyrosinase in junctional and superficial dermal nevocytes and a decreasing gradient of staining in dermal nevocytes, up to become negative in deeper dermis. Meanwhile, junctional and dermal nevocytes were lacking in CD34 protein. Furthermore, nestin immunostaining showed an opposite distribution compared with tyrosinase, leading us to look into the tyrosinase/nestin expression pattern in melanocytic nevus as a tool to better understand the final stages of differentiation of melanocyte precursors toward their ultimate anatomical site into the epidermis.

MicroRNAs and the neural crest: From induction to differentiation

MicroRNAs are small noncoding RNAs that can control gene expression by base pairing to partially complementary mRNAs. Regulation by microRNAs plays essential roles in diverse biological processes such as neural crest formation during embryonic development. The neural crest is a multipotent cell population that develops from the dorsal neural fold of vertebrate embryos in order to migrate extensively and differentiate into a variety of tissues. Gene regulatory networks that coordinate neural crest cell specification and differentiation have been considerably studied so far. Although it is known that microRNAs play important roles in neural crest development, posttranscriptional regulation by microRNAs has not been deeply characterized yet. This review is focused on the microRNAs identified so far in order to regulate gene expression of neural crest cells during vertebrate development.

The Biological Role of Nestin(+)-Cells in Physiological and Pathological Cardiovascular Remodeling

The intermediate filament protein nestin was identified in diverse populations of cells implicated in cardiovascular remodeling. Cardiac resident neural progenitor/stem cells constitutively express nestin and following an ischemic insult migrate to the infarct region and participate in angiogenesis and neurogenesis. A modest number of normal adult ventricular fibroblasts express nestin and the intermediate filament protein is upregulated during the progression of reparative and reactive fibrosis. Nestin depletion attenuates cell cycle re-entry suggesting that increased expression of the intermediate filament protein in ventricular fibroblasts may represent an activated phenotype accelerating the biological impact during fibrosis. Nestin immunoreactivity is absent in normal adult rodent ventricular cardiomyocytes. Following ischemic damage, the intermediate filament protein is induced in a modest population of pre-existing adult ventricular cardiomyocytes bordering the peri-infarct/infarct region and nestin⁽⁺⁾-ventricular cardiomyocytes were identified in the infarcted human heart. The appearance of nestin⁽⁺⁾-ventricular cardiomyocytes post-myocardial infarction (MI) recapitulates an embryonic phenotype and depletion of the intermediate filament protein inhibits cell cycle re-entry. Recruitment of the serine/threonine kinase p38 MAPK secondary to an overt inflammatory response after an ischemic insult may represent a seminal event limiting the appearance of nestin⁽⁺⁾-ventricular cardiomyocytes and concomitantly suppressing cell cycle re-entry. Endothelial and vascular smooth muscle cells (VSMCs) express nestin and upregulation of the intermediate filament protein may directly contribute to vascular remodeling. This review will highlight the biological role of nestin⁽⁺⁾-cells during physiological and pathological remodeling of the heart and vasculature and discuss the phenotypic advantage attributed to the intermediate filament protein.

The avian embryo as a model for fetal alcohol spectrum disorder

Prenatal alcohol exposure (PAE) remains a leading preventable cause of structural birth defects and permanent neurodevelopmental disability. The chicken (Gallus gallus domesticus) is a powerful embryological research model, and was possibly the first in which the teratogenicity of alcohol was demonstrated. Pharmacologically relevant exposure to alcohol in the range of 20-70 mmol/L (20-80 mg/egg) disrupt the growth of chicken embryos, morphogenesis, and behavior, and the resulting phenotypes strongly parallel those of mammalian models. The avian embryo's direct accessibility has enabled novel insights into the teratogenic mechanisms of alcohol. These include the contribution of IGF1 signaling to growth suppression, the altered flow dynamics that reshape valvuloseptal morphogenesis and mediate its cardiac teratogenicity, and the suppression of Wnt and Shh signals thereby disrupting the migration, expansion, and survival of the neural crest, and underlie its characteristic craniofacial deficits. The genetic diversity within commercial avian strains has enabled the identification of unique loci, such as ribosome biogenesis, that modify vulnerability to alcohol. This venerable research model is equally relevant for the future, as the application of technological advances including CRISPR, optogenetics, and biophotonics to the embryo's ready accessibility creates a unique model in which investigators can manipulate and monitor the embryo in real-time to investigate the effect of alcohol on cell fate.

From proliferation to target innervation: signaling molecules that direct sympathetic nervous system development

The sympathetic division of the autonomic nervous system includes a variety of cells including neurons, endocrine cells and glial cells. A recent study (Furlan et al. 2017) has revised thinking about the developmental origin of these cells. It now appears that sympathetic neurons and chromaffin cells of the adrenal medulla do not have an immediate common ancestor in the form a "sympathoadrenal cell", as has been long believed. Instead, chromaffin cells arise from Schwann cell precursors. This review integrates the new findings with the expanding body of knowledge on the signalling pathways and transcription factors that regulate the origin of cells of the sympathetic division of the autonomic nervous system.

Neural crest derived progenitor cells contribute to tumor stroma and aggressiveness in stage 4/M neuroblastoma

Pediatric tumors arise upon oncogenic transformation of stem/progenitor cells during embryonic development. Given this scenario, the existence of non-tumorigenic stem cells included within the aberrant tumoral niche, with a potential role in tumor biology, is an intriguing and unstudied possibility. Here, we describe the presence and function of non-tumorigenic neural crest-derived progenitor cells in aggressive neuroblastoma (NB) tumors. These cells differentiate into neural crest typical mesectodermal derivatives, giving rise to tumor stroma and promoting proliferation and tumor aggressiveness. Furthermore, an analysis of gene expression profiles in stage 4/M NB revealed a neural crest stem cell (NCSC) gene signature that was associated to stromal phenotype and high probability of relapse. Thus, this NCSC gene expression signature could be used in prognosis to improve stratification of stage 4/M NB tumors. Our results might facilitate the design of new therapies by targeting NCSCs and their contribution to tumor stroma.

Chlorpyrifos exposure affects fgf8, sox9, and bmp4 expression required for cranial neural crest morphogenesis and chondrogenesis in Xenopus laevis embryos

Chlorpyrifos (CPF) is an organophosphate insecticide used primarily to control foliage and soil-borne insect pests on a variety of food and feed crops. In mammals, maternal exposure to CPF has been reported to induce dose-related abnormalities such as slower brain growth and cerebral cortex thinning. In lower vertebrates, for example, fish and amphibians, teratogenic activity of this compound is correlated with several anatomical alterations. Little is known about the effects of CPF on mRNA expression of genes involved in early development of the anatomical structures appearing abnormal in embryos. This study investigated the effects of exposure to different CPF concentrations (10, 15 and 20 mg/L) on Xenopus laevis embryos from stage 4/8 to stage 46. Some of the morphological changes we detected in CPF-exposed embryos included cranial neural crest cell (NCC)-derived structures. For this reason, we analyzed the expression of select genes involved in hindbrain patterning (egr2), cranial neural crest chondrogenesis, and craniofacial development (fgf8, bmp4, sox9, hoxa2 and hoxb2). We found that CPF exposure induced a reduction in transcription of all the genes involved in NCC-dependent chondrogenesis, with largest reductions in fgf8 and sox9; whereas, in hindbrain, we did not find any alterations in egr2 expression. Changes in the expression of fgf8, bmp4, and sox9, which are master regulators of several developmental pathways, have important implications. If these changes are confirmed to belong to a general pattern of alterations in vertebrates prenatally exposed to OP, they might be useful to assess damage during vertebrate embryo development. Environ. Mol. Mutagen. 57:589-604, 2016. © 2016 Wiley Periodicals, Inc.

The Pluripotency of Neural Crest Cells and Their Role in Brain Development

The neural crest (NC) is, in the Chordate phylum, an innovation of vertebrates, which exhibits several original characteristics: its component cells are pluripotent and give rise to both ectodermal and mesodermal cell types. Moreover, during the early stages of neurogenesis, the NC cells exert a paracrine stimulating effect on the development of the preotic brain.

Tendon development and diseases

Tendon is a uniaxial connective tissue component of the musculoskeletal system. Tendon is involved in force transmission between muscle and bone. Tendon injury is very common and debilitating but tendon repair remains a clinical challenge for orthopedic medicine. In vertebrates, tendon is mainly composed of type I collagen fibrils, displaying a parallel organization along the tendon axis. The tendon-specific spatial organization of type I collagen provides the mechanical properties for tendon function. In contrast to other components of the musculoskeletal system, tendon biology is poorly understood. An important goal in tendon biology is to understand the mechanisms involved in the production and assembly of type I collagen fibrils during development, postnatal formation, and healing processes in order to design new therapies for tendon repair. In this review we highlight the current understanding of the molecular and mechanical signals known to be involved in tenogenesis during development, and how development provides insights into tendon healing processes. WIREs Dev Biol 2016, 5:5-23. doi: 10.1002/wdev.201 For further resources related to this article, please visit the WIREs website.