Involvement of bone morphogenetic protein-4 and bone morphogenetic protein-7 in the differentiation of the adrenergic phenotype in developing sympathetic neurons

Neural crest origin of sympathetic neurons at the dawn of vertebrates

The neural crest is an embryonic stem cell population unique to vertebrates1 whose expansion and diversification are thought to have promoted vertebrate evolution by enabling emergence of new cell types and structures such as jaws and peripheral ganglia2. Although jawless vertebrates have sensory ganglia, convention has it that trunk sympathetic chain ganglia arose only in jawed vertebrates3-8. Here, by contrast, we report the presence of trunk sympathetic neurons in the sea lamprey, Petromyzon marinus, an extant jawless vertebrate. These neurons arise from sympathoblasts near the dorsal aorta that undergo noradrenergic specification through a transcriptional program homologous to that described in gnathostomes. Lamprey sympathoblasts populate the extracardiac space and extend along the length of the trunk in bilateral streams, expressing the catecholamine biosynthetic pathway enzymes tyrosine hydroxylase and dopamine β-hydroxylase. CM-DiI lineage tracing analysis further confirmed that these cells derive from the trunk neural crest. RNA sequencing of isolated ammocoete trunk sympathoblasts revealed gene profiles characteristic of sympathetic neuron function. Our findings challenge the prevailing dogma that posits that sympathetic ganglia are a gnathostome innovation, instead suggesting that a late-developing rudimentary sympathetic nervous system may have been characteristic of the earliest vertebrates.

Sympathetic innervation of the development, maturity, and aging of the gastrointestinal tract

The sympathetic nervous system inhibits gut motility, secretion, and blood flow in the gut microvasculature and can modulate gastrointestinal inflammation. Sympathetic neurons signal via catecholamines, neuropeptides, and gas mediators. In the current review, we summarize the current understanding of the mature sympathetic innervation of the gastrointestinal tract with a focus mainly on the prevertebral sympathetic ganglia as the main output to the gut. We also highlight recent work regarding the developmental processes of sympathetic innervation. The anatomy, neurochemistry, and connections of the sympathetic prevertebral ganglia with different parts of the gut are considered in adult organisms during prenatal and postnatal development and aging. The processes and mechanisms that control the development of sympathetic neurons, including their migratory pathways, neuronal differentiation, and aging, are reviewed.

Endothelial-derived angiocrine factors as instructors of embryonic development

Blood vessels are well-known to play roles in organ development and repair, primarily owing to their fundamental function in delivering oxygen and nutrients to tissues to promote their growth and homeostasis. Endothelial cells however are not merely passive conduits for carrying blood. There is now evidence that endothelial cells of the vasculature actively regulate tissue-specific development, morphogenesis and organ function, as well as playing roles in disease and cancer. Angiocrine factors are growth factors, cytokines, signaling molecules or other regulators produced directly from endothelial cells to instruct a diverse range of signaling outcomes in the cellular microenvironment, and are critical mediators of the vascular control of organ function. The roles of angiocrine signaling are only beginning to be uncovered in diverse fields such as homeostasis, regeneration, organogenesis, stem-cell maintenance, cell differentiation and tumour growth. While in some cases the specific angiocrine factor involved in these processes has been identified, in many cases the molecular identity of the angiocrine factor(s) remain to be discovered, even though the importance of angiocrine signaling has been implicated. In this review, we will specifically focus on roles for endothelial-derived angiocrine signaling in instructing tissue morphogenesis and organogenesis during embryonic and perinatal development.

Interplay: The Essential Role between INSM1 and N-Myc in Aggressive Neuroblastoma

Simple Summary

Neuroblastoma (NB) is a cancer that starts in certain very early forms of nerve cells of the sympathetic nervous system, most often found in an embryo or fetus. Symptoms may include bone pain, an abdominal mass, frequent urination, limping, anemia, spinal cord weakness, or bruising of the eye area. N-Myc is a key driver of high-risk NB. An elevated expression of N-Myc often predicts a poorer prognosis, in both time to tumor progression and overall survival rate. We discovered a transcription factor, insulinoma-associated-1 (INSM1), as the downstream target gene of N-Myc. INSM1 has emerged as a novel NB biomarker that plays a critical role in facilitating NB tumor cell development. Both N-Myc and INSM1 demonstrate high clinical relevance to NB. Therefore, further understanding the association of INSM1 and N-Myc functions in aggressive NB should be beneficial for future NB treatment.

Abstract

An aggressive form of neuroblastoma (NB), a malignant childhood cancer derived from granule neuron precursors and sympathoadrenal lineage, frequently comprises MYCN amplification/elevated N-Myc expression, which contributes to the development of neural crest-derived embryonal malignancy. N-Myc is an oncogenic driver in NB. Persistent N-Myc expression during the maturation of SA precursor cells can cause blockage of the apoptosis and induce abnormal proliferation, resulting in NB development. An insulinoma-associated-1 (INSM1) zinc-finger transcription factor has emerged as an NB biomarker that plays a critical role in facilitating tumor cell growth and transformation. INSM1 plays an essential role in sympathoadrenal cell differentiation. N-Myc activates endogenous INSM1 through an E2-box of the INSM1 proximal promoter, whereas INSM1 enhances N-Myc stability via RAC-α-serine/threonine protein kinase (AKT) phosphorylation in NB. The ectopic expression of INSM1 stimulates NB tumor growth in contrast to the knockdown of INSM1 that inhibits NB cell proliferation. The clinical pathological result and bioinformatics analysis show that INSM1 is a strong diagnostic and a prognostic biomarker for the evaluation of NB progression. The INSM1/N-Myc expression shows high clinical relevance in NB. Therefore, targeting the INSM1/N-Myc-associated signaling axis should be a feasible approach to identifying new drugs for the suppression of NB tumor growth.

Innervation in organogenesis

Proper innervation of peripheral organs helps to maintain physiological homeostasis and elicit responses to external stimuli. Disruptions to normal function can result in pathophysiological consequences. The establishment of connections and communication between the central nervous system and the peripheral organs is accomplished through the peripheral nervous system. Neuronal connections with target tissues arise from ganglia partitioned throughout the body. Organ innervation is initiated during development with stimuli being conducted through several types of neurons including sympathetic, parasympathetic, and sensory. While the physiological modulation of mature organs by these nerves is largely understood, their role in mammalian development is only beginning to be uncovered. Interactions with cells in target tissues can affect the development and eventual function of several organs, highlighting their significance. This chapter will cover the origin of peripheral neurons, factors mediating organ innervation, and the composition and function of organ-specific nerves during development. This emerging field aims to identify the functional contribution of innervation to development which will inform future investigations of normal and abnormal mammalian organogenesis, as well as contribute to regenerative and organ replacement efforts where nerve-derived signals may have significant implications for the advancement of such studies.

Cell Fate Decisions in the Neural Crest, from Pigment Cell to Neural Development

The neural crest shows an astonishing multipotency, generating multiple neural derivatives, but also pigment cells, skeletogenic and other cell types. The question of how this process is controlled has been the subject of an ongoing debate for more than 35 years. Based upon new observations of zebrafish pigment cell development, we have recently proposed a novel, dynamic model that we believe goes some way to resolving the controversy. Here, we will firstly summarize the traditional models and the conflicts between them, before outlining our novel model. We will also examine our recent dynamic modelling studies, looking at how these reveal behaviors compatible with the biology proposed. We will then outline some of the implications of our model, looking at how it might modify our views of the processes of fate specification, differentiation, and commitment.

The sympathies of the body: functional organization and neuronal differentiation in the peripheral sympathetic nervous system

During the last 30 years, our understanding of the development and diversification of postganglionic sympathetic neurons has dramatically increased. In parallel, the list of target structures has been critically extended from the cardiovascular system and selected glandular structures to metabolically relevant tissues such as white and brown adipose tissue, lymphoid tissues, bone, and bone marrow. A critical question now emerges for the integration of the diverse sympathetic neuron classes into neural circuits specific for these different target tissues to achieve the homeostatic regulation of the physiological ends affected.

Adrenal medulla development and medullary-cortical interactions

The mammalian adrenal gland is composed of two distinct tissue types in a bidirectional connection, the catecholamine-producing medulla derived from the neural crest and the mesoderm-derived cortex producing steroids. The medulla mainly consists of chromaffin cells derived from multipotent nerve-associated descendants of Schwann cell precursors. Already during adrenal organogenesis, close interactions between cortex and medulla are necessary for proper differentiation and morphogenesis of the gland. Moreover, communication between the cortex and the medulla ensures a regular function of the adult adrenal. In tumor development, interfaces between the two parts are also common. Here, we summarize the development of the mammalian adrenal medulla and the current understanding of the cortical-medullary interactions under development and in health and disease.

Stem cells, evolutionary aspects and pathology of the adrenal medulla: A new developmental paradigm

The mammalian adrenal gland is composed of two main components; the catecholaminergic neural crest-derived medulla, found in the center of the gland, and the mesoderm-derived cortex producing steroidogenic hormones. The medulla is composed of neuroendocrine chromaffin cells with oxygen-sensing properties and is dependent on tissue interactions with the overlying cortex, both during development and in adulthood. Other relevant organs include the Zuckerkandl organ containing extra-adrenal chromaffin cells, and carotid oxygen-sensing bodies containing glomus cells. Chromaffin and glomus cells reveal a number of important similarities and are derived from the multipotent nerve-associated descendants of the neural crest, or Schwann cell precursors. Abnormalities in complex developmental processes during differentiation of nerve-associated and other progenitors into chromaffin and oxygen-sensing populations may result in different subtypes of paraganglioma, neuroblastoma and pheochromocytoma. Here, we summarize recent findings explaining the development of chromaffin and oxygen-sensing cells, as well as the potential mechanisms driving neuroendocrine tumor initiation.

The diversity of neuronal phenotypes in rodent and human autonomic ganglia

Selective sympathetic and parasympathetic pathways that act on target organs represent the terminal actors in the neurobiology of homeostasis and often become compromised during a range of neurodegenerative and traumatic disorders. Here, we delineate several neurotransmitter and neuromodulator phenotypes found in diverse parasympathetic and sympathetic ganglia in humans and rodent species. The comparative approach reveals evolutionarily conserved and non-conserved phenotypic marker constellations. A developmental analysis examining the acquisition of selected neurotransmitter properties has provided a detailed, but still incomplete, understanding of the origins of a set of noradrenergic and cholinergic sympathetic neuron populations, found in the cervical and trunk region. A corresponding analysis examining cholinergic and nitrergic parasympathetic neurons in the head, and a range of pelvic neuron populations, with noradrenergic, cholinergic, nitrergic, and mixed transmitter phenotypes, remains open. Of particular interest are the molecular mechanisms and nuclear processes that are responsible for the correlated expression of the various genes required to achieve the noradrenergic phenotype, the segregation of cholinergic locus gene expression, and the regulation of genes that are necessary to generate a nitrergic phenotype. Unraveling the neuron population-specific expression of adhesion molecules, which are involved in axonal outgrowth, pathway selection, and synaptic organization, will advance the study of target-selective autonomic pathway generation.

Neurovascular Interactions in the Nervous System

Molecular cross talk between the nervous and vascular systems is necessary to maintain the correct coupling of organ structure and function. Molecular pathways shared by both systems are emerging as major players in the communication of the neuronal compartment with the endothelium. Here we review different aspects of this cross talk and how vessels influence the development and homeostasis of the nervous system. Beyond the classical role of the vasculature as a conduit to deliver oxygen and metabolites needed for the energy-demanding neuronal compartment, vessels emerge as powerful signaling systems that control and instruct a variety of cellular processes during the development of neurons and glia, such as migration, differentiation, and structural connectivity. Moreover, a broad spectrum of mild to severe vascular dysfunctions occur in various pathologies of the nervous system, suggesting that mild structural and functional changes at the neurovascular interface may underlie cognitive decline in many of these pathological conditions.

Ager-CreERT2: A New Genetic Tool for Studying Lung Alveolar Development, Homeostasis, and Repair

The alveolar region of the lung is composed of two major epithelial cell types: cuboidal alveolar type 2 cells (AT2 cells), which produce surfactant proteins, and large, thin, alveolar type 1 cells (AT1 cells), specialized for efficient gas exchange. AT1 cells cover more than 95% of the alveolar surface and constitute a major barrier to the entry of pathogenic agents. Relatively few genetic tools are available for studying the development of AT1 cells, the function of genes expressed in them, and the effect of specifically killing them in vivo in the adult lung. One distinguishing feature of AT1 cells is the high level of expression of the gene Ager, encoding the advanced glycation endproduct-specific receptor, a member of the immunoglobulin superfamily of cell surface receptors. In this paper, we report the generation of a novel Ager-CreER^T2 allele in which Cre recombinase is inserted into the first coding exon of the endogenous gene. After treatment with tamoxifen the allele enables Ager⁺ progenitor cells to be efficiently lineage labeled during late embryonic development and AT1 cells to be killed in the adult lung using a Rosa26-diphtheria toxin A allele. Significantly, adult mice in which approximately 50% of the AT1 cells are killed survive the loss; repair is associated with increased proliferation of SFTPC⁺ (surfactant protein C-positive) AT2 cells and the upregulation of Ager expression. The Ager-CreER^T2 allele thus expands the repertoire of genetic tools for studying AT1 turnover, physiology, and repair.

Endothelin receptor Aa regulates proliferation and differentiation of Erb-dependent pigment progenitors in zebrafish

Skin pigment patterns are important, being under strong selection for multiple roles including camouflage and UV protection. Pigment cells underlying these patterns form from adult pigment stem cells (APSCs). In zebrafish, APSCs derive from embryonic neural crest cells, but sit dormant until activated to produce pigment cells during metamorphosis. The APSCs are set-aside in an ErbB signaling dependent manner, but the mechanism maintaining quiescence until metamorphosis remains unknown. Mutants for a pigment pattern gene, parade, exhibit ectopic pigment cells localised to the ventral trunk, but also supernumerary cells restricted to the Ventral Stripe. Contrary to expectations, these melanocytes and iridophores are discrete cells, but closely apposed. We show that parade encodes Endothelin receptor Aa, expressed in the blood vessels, most prominently in the medial blood vessels, consistent with the ventral trunk phenotype. We provide evidence that neuronal fates are not affected in parade mutants, arguing against transdifferentiation of sympathetic neurons to pigment cells. We show that inhibition of BMP signaling prevents specification of sympathetic neurons, indicating conservation of this molecular mechanism with chick and mouse. However, inhibition of sympathetic neuron differentiation does not enhance the parade phenotype. Instead, we pinpoint ventral trunk-restricted proliferation of neural crest cells as an early feature of the parade phenotype. Importantly, using a chemical genetic screen for rescue of the ectopic pigment cell phenotype of parade mutants (whilst leaving the embryonic pattern untouched), we identify ErbB inhibitors as a key hit. The time-window of sensitivity to these inhibitors mirrors precisely the window defined previously as crucial for the setting aside of APSCs in the embryo, strongly implicating adult pigment stem cells as the source of the ectopic pigment cells. We propose that a novel population of APSCs exists in association with medial blood vessels, and that their quiescence is dependent upon Endothelin-dependent factors expressed by the blood vessels.

Neuroblastoma-A Neural Crest Derived Embryonal Malignancy

Neuroblastoma is a neural crest derived malignancy of the peripheral nervous system and is the most common and deadliest tumor of infancy. It is characterized by clinical heterogeneity with a disease spectrum ranging from spontaneous regression without any medical intervention to treatment resistant tumors with metastatic spread and poor patient survival. The events that lead to the development of neuroblastoma from the neural crest have not been fully elucidated. Here we discuss factors and processes within the neural crest that when dysregulated have the potential to be initiators or drivers of neuroblastoma development. A more precise biological understanding of neuroblastoma causes and cell of origin is highly warranted. This will give valuable information for the development of medicines that specifically target molecules within neuroblastoma cells and also give hint about the mechanisms behind treatment resistance that is frequently seen in neuroblastoma.

Adipocyte-secreted BMP8b mediates adrenergic-induced remodeling of the neuro-vascular network in adipose tissue

Activation of brown adipose tissue-mediated thermogenesis is a strategy for tackling obesity and promoting metabolic health. BMP8b is secreted by brown/beige adipocytes and enhances energy dissipation. Here we show that adipocyte-secreted BMP8b contributes to adrenergic-induced remodeling of the neuro-vascular network in adipose tissue (AT). Overexpression of bmp8b in AT enhances browning of the subcutaneous depot and maximal thermogenic capacity. Moreover, BMP8b-induced browning, increased sympathetic innervation and vascularization of AT were maintained at 28 °C, a condition of low adrenergic output. This reinforces the local trophic effect of BMP8b. Innervation and vascular remodeling effects required BMP8b signaling through the adipocytes to 1) secrete neuregulin-4 (NRG4), which promotes sympathetic axon growth and branching in vitro, and 2) induce a pro-angiogenic transcriptional and secretory profile that promotes vascular sprouting. Thus, BMP8b and NRG4 can be considered as interconnected regulators of neuro-vascular remodeling in AT and are potential therapeutic targets in obesity.

Enhancing thermogenesis is a promising therapeutic strategy for promoting metabolic health. Here the authors show that adipocyte-secreted BMP8b contributes to optimizing the thermogenic response by remodeling of the neuro-vascular networks in brown and white adipose tissue.

Differentiation of Human Embryonic Stem Cells to Sympathetic Neurons: A Potential Model for Understanding Neuroblastoma Pathogenesis

Background and Aims

Previous studies modelling human neural crest differentiation from stem cells have resulted in a low yield of sympathetic neurons. Our aim was to optimise a method for the differentiation of human embryonic stem cells (hESCs) to sympathetic neuron-like cells (SN) to model normal human SNS development.

Results

Using stromal-derived inducing activity (SDIA) of PA6 cells plus BMP4 and B27 supplements, the H9 hESC line was differentiated to neural crest stem-like cells and SN-like cells. After 7 days of PA6 cell coculture, mRNA expression of SNAIL and SOX-9 neural crest specifier genes and the neural marker peripherin (PRPH) increased. Expression of the pluripotency marker OCT 4 decreased, whereas TP53 and LIN28B expression remained high at levels similar to SHSY5Y and IMR32 neuroblastoma cell lines. A 5-fold increase in the expression of the catecholaminergic marker tyrosine hydroxylase (TH) and the noradrenergic marker dopamine betahydroxylase (DBH) was observed by day 7 of differentiation. Fluorescence-activated cell sorting for the neural crest marker p75, enriched for cells expressing p75, DBH, TH, and PRPH, was more specific than p75 neural crest stem cell (NCSC) microbeads. On day 28 post p75 sorting, dual immunofluorescence identified sympathetic neurons by PRPH and TH copositivity cells in 20% of the cell population. Noradrenergic sympathetic neurons, identified by copositivity for both PHOX2B and DBH, were present in 9.4% ± 5.5% of cells.

Conclusions

We have optimised a method for noradrenergic SNS development using the H9 hESC line to improve our understanding of normal human SNS development and, in a future work, the pathogenesis of neuroblastoma.

The morphogenesis of the renal plexus: Renal artery and sympathetic fibers

To examine the origin and development of the renal plexus and its relationship to the renal vessels in embryos and early human fetuses. Serial sections of 34 human embryos (stages 16 to 23 of Carnegie, 4 or 5-8 weeks) and 38 fetuses (9-19 weeks) were analyzed. Throughout the embryonic period, the kidney was not innervated by the renal plexus. Those nerves appeared at the beginning of the early fetal period (9 weeks) as branches given off by the immature autonomic abdominal plexus. The renal nerves started to approach to the kidney during the early fetal period at 9-10 weeks of development. They were distributed in close proximity to the renal arteries and their branches. They were observed first with the settlement of the renal veins. The renal artery is present as a branch of the abdominal aorta at stage 19 (between 6 and 7 weeks) prior to development of the renal plexus. The renal veins were not present during the embryonic period but appeared at the start of the fetal period, along with the renal nerves that emerged from segmented sympathetic para-aortic bodies (SPBs). Clin. Anat. 32:272-276, 2019. © 2018 Wiley Periodicals, Inc.

Regulation of neuronal and photoreceptor cell differentiation by Wnt signaling from iris-derived stem/progenitor cells of the chick in flat vs. Matrigel-embedding cultures

Previously we developed a simple culture method of the iris tissues and reported novel properties of neural stem/progenitor-like cells in the iris tissues of the chick and pig. When the iris epithelium or connective tissue (stroma) was treated with dispase, embedded in Matrigel, and cultured, neuronal cells extended from the explants within 24 h of culture, and cells positively stained for photoreceptor cell markers were also observed within a few days of culturing. In ordinary flat tissue culture conditions, explants had the same differentiation properties to those in tissue environments. Previously, we suggested that iris neural stem/progenitor cells are simply suppressed from neuronal differentiation within tissue, and that separation from the tissue releases the cells from this suppression mechanism. Here, we examined whether Wnt signaling suppressed neuronal differentiation of iris tissue cells in tissue environments because the lens, which has direct contact with the iris, is a rich source of Wnt proteins. When the Wnt signaling activator 6-bromoindirubin-3'-oxime (BIO) was administered to Matrigel culture, neuronal differentiation was markedly suppressed, but cell proliferation was not affected. When Wnt signaling inhibitors, such as DKK-1 and IWR-1, were applied to the same culture, they did not have any effect on cell differentiation and proliferation. However, when the inhibitors were applied to flat tissue culture, cells with neural properties emerged. These results indicate that the interaction of iris tissue with neighboring tissues and the environment regulates the stemness nature of iris tissue cells, and that Wnt signaling is a major factor.

Sympathetic tales: subdivisons of the autonomic nervous system and the impact of developmental studies

Remarkable progress in a range of biomedical disciplines has promoted the understanding of the cellular components of the autonomic nervous system and their differentiation during development to a critical level. Characterization of the gene expression fingerprints of individual neurons and identification of the key regulators of autonomic neuron differentiation enables us to comprehend the development of different sets of autonomic neurons. Their individual functional properties emerge as a consequence of differential gene expression initiated by the action of specific developmental regulators. In this review, we delineate the anatomical and physiological observations that led to the subdivision into sympathetic and parasympathetic domains and analyze how the recent molecular insights melt into and challenge the classical description of the autonomic nervous system.

Cell-Type Identification in the Autonomic Nervous System

The autonomic nervous system controls various internal organs and executes crucial functions through sophisticated neural connectivity and circuits. Its dysfunction causes an imbalance of homeostasis and numerous human disorders. In the past decades, great efforts have been made to study the structure and functions of this system, but so far, our understanding of the classification of autonomic neuronal subpopulations remains limited and a precise map of their connectivity has not been achieved. One of the major challenges that hinder rapid progress in these areas is the complexity and heterogeneity of autonomic neurons. To facilitate the identification of neuronal subgroups in the autonomic nervous system, here we review the well-established and cutting-edge technologies that are frequently used in peripheral neuronal tracing and profiling, and discuss their operating mechanisms, advantages, and targeted applications.

Neuroblastoma Origin and Therapeutic Targets for Immunotherapy

Neuroblastoma is a pediatric solid cancer of heterogeneous clinical behavior. The unique features of this type of cancer frequently hamper the process of determining clinical presentation and predicting therapy effectiveness. The tumor can spontaneously regress without treatment or actively develop and give rise to metastases despite aggressive multimodal therapy. In recent years, immunotherapy has become one of the most promising approaches to the treatment of neuroblastoma. Still, only one drug for targeted immunotherapy of neuroblastoma, chimeric monoclonal GD2-specific antibodies, is used in the clinic today, and its application has significant limitations. In this regard, the development of effective and safe GD2-targeted immunotherapies and analysis of other potential molecular targets for the treatment of neuroblastoma represents an important and topical task. The review summarizes biological characteristics of the origin and development of neuroblastoma and outlines molecular markers of neuroblastoma and modern immunotherapy approaches directed towards these markers.

Generation of Adrenal Chromaffin-like Cells from Human Pluripotent Stem Cells

Adrenomedullary chromaffin cells are catecholamine (CA)-producing cells originating from trunk neural crest (NC) via sympathoadrenal progenitors (SAPs). We generated NC and SAPs from human embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) in vitro via BMP2/FGF2 exposure, ascertained by qPCR and immunoexpression of SOX10, ASCL1, TFAP2α, and PHOX2B, and by fluorescence-activated cell sorting selection for p75NTR and GD2, and confirmed their trunk-like HOX gene expression. We showed that continuing BMP4 and curtailing FGF2 in vitro, augmented with corticosteroid mimetic, induced these cells to upregulate the chromaffin cell-specific marker PNMT and other CA synthesis and storage markers, and we demonstrated noradrenaline and adrenaline by Faglu and high-performance liquid chromatography. We showed these human cells' SAP-like property of migration and differentiation into cells expressing chromaffin cell markers by implanting them into avian embryos in vivo and in chorio-allantoic membrane grafts. These cells have the potential for investigating differentiation of human chromaffin cells and for modeling diseases involving this cell type.

Neuroblastoma pathogenesis: deregulation of embryonic neural crest development

Neuroblastoma (NB) is an aggressive pediatric cancer that originates from neural crest tissues of the sympathetic nervous system. NB is highly heterogeneous both from a clinical and a molecular perspective. Clinically, this cancer represents a wide range of phenotypes ranging from spontaneous regression of 4S disease to unremitting treatment-refractory progression and death of high-risk metastatic disease. At a cellular level, the heterogeneous behavior of NB likely arises from an arrest and deregulation of normal neural crest development. In the present review, we summarize our current knowledge of neural crest development as it relates to pathways promoting 'stemness' and how deregulation may contribute to the development of tumor-initiating CSCs. There is an emerging consensus that such tumor subpopulations contribute to the evolution of drug resistance, metastasis and relapse in other equally aggressive malignancies. As relapsed, refractory disease remains the primary cause of death for neuroblastoma, the identification and targeting of CSCs or other primary drivers of tumor progression remains a critical, clinically significant goal for neuroblastoma. We will critically review recent and past evidence in the literature supporting the concept of CSCs as drivers of neuroblastoma pathogenesis.

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.

Coordinate expression of pan-neuronal and functional signature genes in sympathetic neurons

Neuron subtypes of the mature nervous system differ in the expression of characteristic marker genes while they share the expression of generic neuronal genes. The regulatory logic that maintains subtype-specific and pan-neuronal genes is not well understood. To begin to address this issue, we analyze RNA sequencing results from whole sympathetic ganglia and single sympathetic neurons in the mouse. We focus on gene products involved in the neuronal cytoskeleton, neurotransmitter synthesis and storage, transmitter release and reception and electrical information processing. We find a particular high correlation in the expression of stathmin 2 and several members of the tubulin beta family, classical pan-neuronal markers. Noradrenergic transmitter-synthesizing enzymes and transporters are also well correlated in their cellular transcript levels. In addition, noradrenergic marker transcript levels correlate well with selected pan-neuronal markers. Such a correlation in transcript levels is also seen between a number of selected ion channel, receptor and synaptic protein genes. These results provide the foundation for the analyses of the coordinated expression of downstream target genes in nerve cells.

BMP-induced reprogramming of the neural retina into retinal pigment epithelium requires Wnt signalling

In vertebrates, the retinal pigment epithelium (RPE) and photoreceptors of the neural retina (NR) comprise a functional unit required for vision. During vertebrate eye development, a conversion of the RPE into NR can be induced by growth factors in vivo at optic cup stages, but the reverse process, the conversion of NR tissue into RPE, has not been reported. Here, we show that bone morphogenetic protein (BMP) signalling can reprogram the NR into RPE at optic cup stages in chick. Shortly after BMP application, expression of Microphthalmia-associated transcription factor (Mitf) is induced in the NR and selective cell death on the basal side of the NR induces an RPE-like morphology. The newly induced RPE differentiates and expresses Melanosomalmatrix protein 115 (Mmp115) and RPE65. BMP-induced Wnt2b expression is observed in regions of the NR that become pigmented. Loss of function studies show that conversion of the NR into RPE requires both BMP and Wnt signalling. Simultaneous to the appearance of ectopic RPE tissue, BMP application reprogrammed the proximal RPE into multi-layered retinal tissue. The newly induced NR expresses visual segment homeobox-containing gene (Vsx2), and the ganglion and photoreceptor cell markers Brn3α and Visinin are detected. Our results show that high BMP concentrations are required to induce the conversion of NR into RPE, while low BMP concentrations can still induce transdifferentiation of the RPE into NR. This knowledge may contribute to the development of efficient standardized protocols for RPE and NR generation for cell replacement therapies.

Endochondral Ossification Is Accelerated in Cholinesterase-Deficient Mice and in Avian Mesenchymal Micromass Cultures

Most components of the cholinergic system are detected in skeletogenic cell types in vitro, yet the function of this system in skeletogenesis remains unclear. Here, we analyzed endochondral ossification in mutant murine fetuses, in which genes of the rate-limiting cholinergic enzymes acetyl- (AChE), or butyrylcholinesterase (BChE), or both were deleted (called here A-B+, A+B-, A-B-, respectively). In all mutant embryos bone growth and cartilage remodeling into mineralizing bone were accelerated, as revealed by Alcian blue (A-blu) and Alizarin red (A-red) staining. In A+B- and A-B- onset of mineralization was observed before E13.5, about 2 days earlier than in wild type and A-B+ mice. In all mutants between E18.5 to birth A-blu staining disappeared from epiphyses prematurely. Instead, A-blu+ cells were dislocated into diaphyses, most pronounced so in A-B- mutants, indicating additive effects of both missing ChEs in A-B- mutant mice. The remodeling effects were supported by in situ hybridization (ISH) experiments performed on cryosections from A-B- mice, in which Ihh, Runx2, MMP-13, ALP, Col-II and Col-X were considerably decreased, or had disappeared between E18.5 and P0. With a second approach, we applied an improved in vitro micromass model from chicken limb buds that allowed histological distinction between areas of cartilage, apoptosis and mineralization. When treated with the AChE inhibitor BW284c51, or with nicotine, there was decrease in cartilage and accelerated mineralization, suggesting that these effects were mediated through nicotinic receptors (α7-nAChR). We conclude that due to absence of either one or both cholinesterases in KO mice, or inhibition of AChE in chicken micromass cultures, there is increase in cholinergic signalling, which leads to increased chondroblast production and premature mineralization, at the expense of incomplete chondrogenic differentiation. This emphasizes the importance of cholinergic signalling in cartilage and bone formation.

Part and Parcel of the Cardiac Autonomic Nerve System: Unravelling Its Cellular Building Blocks during Development

The autonomic nervous system (cANS) is essential for proper heart function, and complications such as heart failure, arrhythmias and even sudden cardiac death are associated with an altered cANS function. A changed innervation state may underlie (part of) the atrial and ventricular arrhythmias observed after myocardial infarction. In other cardiac diseases, such as congenital heart disease, autonomic dysfunction may be related to disease outcome. This is also the case after heart transplantation, when the heart is denervated. Interest in the origin of the autonomic nerve system has renewed since the role of autonomic function in disease progression was recognized, and some plasticity in autonomic regeneration is evident. As with many pathological processes, autonomic dysfunction based on pathological innervation may be a partial recapitulation of the early development of innervation. As such, insight into the development of cardiac innervation and an understanding of the cellular background contributing to cardiac innervation during different phases of development is required. This review describes the development of the cANS and focuses on the cellular contributions, either directly by delivering cells or indirectly by secretion of necessary factors or cell-derivatives.

Acetylcholinesterase Regulates Skeletal In Ovo Development of Chicken Limbs by ACh-Dependent and -Independent Mechanisms

Formation of the vertebrate limb presents an excellent model to analyze a non-neuronal cholinergic system (NNCS). Here, we first analyzed the expression of acetylcholinesterase (AChE) by IHC and of choline acetyltransferase (ChAT) by ISH in developing embryonic chicken limbs (stages HH17-37). AChE outlined formation of bones, being strongest at their distal tips, and later also marked areas of cell death. At onset, AChE and ChAT were elevated in two organizing centers of the limb anlage, the apical ectodermal ridge (AER) and zone of polarizing activity (ZPA), respectively. Thereby ChAT was expressed shortly after AChE, thus strongly supporting a leading role of AChE in limb formation. Then, we conducted loss-of-function studies via unilateral implantation of beads into chicken limb anlagen, which were soaked in cholinergic components. After varying periods, the formation of cartilage matrix and of mineralizing bones was followed by Alcian blue (AB) and Alizarin red (AR) stainings, respectively. Both acetylcholine (ACh)- and ChAT-soaked beads accelerated bone formation in ovo. Notably, inhibition of AChE by BW284c51, or by the monoclonal antibody MAB304 delayed cartilage formation. Since bead inhibition of BChE was mostly ineffective, an ACh-independent action during BW284c51 and MAB304 inhibition was indicated, which possibly could be due to an enzymatic side activity of AChE. In conclusion, skeletogenesis in chick is regulated by an ACh-dependent cholinergic system, but to some extent also by an ACh-independent aspect of the AChE protein.

Transfection of arginine decarboxylase gene increases the neuronal differentiation of neural progenitor cells

Growing evidence suggests that the clinical use of neural progenitor cells (NPCs) is hampered by heterogeneity, poor neuronal yield and low survival rate. Recently, we reported that retrovirus-delivered human arginine decarboxylase (hADC) genes improve cell survival against oxidative insult in murine NPCs in vitro. This study investigates whether the induced expression of hADC gene in mNPCs induces any significant change in the cell fate commitment. The evaluation of induced hADC gene function was assessed by knockdown of hADC gene using specific siRNA. The hADC gene delivery triggered higher expression of N-CAM, cell adhesion molecule and MAP-2, neuronal marker. However, the hADC gene knockdown showed downregulation of N-CAM and MAP-2 expression suggesting that hADC gene delivery favors cell fate commitment of mNPCs towards neuronal lineage. Neurite outgrowth was significantly longer in the hADC infected cells. The neurotrophic signal, BDNF aided in the neuronal commitment, differentiation, and maturation of hADC-mNPCs through PI3K and ERK1/2 activation. The induction of neuron-like differentiation is believed to be regulated by the expression of GSK-3β and Wnt/β-catenin signaling pathways. Our findings suggest that hADC gene delivery favors cell fate commitment of mNPCs towards neuronal lineage, bring new advances in the field of neurogenesis and cell therapy.

CD114: A New Member of the Neural Crest-Derived Cancer Stem Cell Marker Family

The neural crest is a population of cells in the vertebrate embryo that gives rise to a wide range of tissues and cell types, including components of the peripheral nervous system and the craniofacial skeleton as well as melanocytes and the adrenal medulla. Aberrations in neural crest development can lead to numerous diseases, including cancers such as melanoma and neuroblastoma. Cancer stem cells (CSCs) have been identified in these neural crest-derived tumors, and these CSCs demonstrate resistance to treatment and are likely key contributors to disease relapse. Patients with neural crest-derived tumors often have poor outcomes due to frequent relapses, likely due to the continued presence of residual treatment-resistant CSCs, and therapies directed against these CSCs are likely to improve patient outcomes. CSCs share many of the same genetic and biologic features of primordial neural crest cells, and therefore a better understanding of neural crest development will likely lead to the development of effective therapies directed against these CSCs. Signaling through STAT3 has been shown to be required for neural crest development, and granulocyte colony stimulating factor (GCSF)-mediated activation of STAT3 has been shown to play a role in the pathogenesis of neural crest-derived tumors. Expression of the cell surface marker CD114 (the receptor for GCSF) has been identified as a potential marker for CSCs in neural crest-derived tumors, suggesting that CD114 expression and function may contribute to disease relapse and poor patient outcomes. Here we review the processes of neural crest development and tumorigenesis and we discuss the previously identified markers for CSC subpopulations identified in neural crest tumors and their role in neural crest tumor biology. We also discuss the potential for CD114 and downstream intracellular signaling pathways as potential targets for CSC-directed therapy. J. Cell. Biochem. 118: 221-231, 2017. © 2016 Wiley Periodicals, Inc.

In vivo time-lapse imaging reveals extensive neural crest and endothelial cell interactions during neural crest migration and formation of the dorsal root and sympathetic ganglia

During amniote embryogenesis the nervous and vascular systems interact in a process that significantly affects the respective morphogenesis of each network by forming a "neurovascular" link. The importance of neurovascular cross-talk in the central nervous system has recently come into focus with the growing awareness that these two systems interact extensively both during development, in the stem-cell niche, and in neurodegenerative conditions such as Alzheimer's Disease and Amyotrophic Lateral Sclerosis. With respect to the peripheral nervous system, however, there have been no live, real-time investigations of the potential relationship between these two developing systems. To address this deficit, we used multispectral 4D time-lapse imaging in a transgenic quail model in which endothelial cells (ECs) express a yellow fluorescent marker, while neural crest cells (NCCs) express an electroporated red fluorescent marker. We monitored EC and NCC migration in real-time during formation of the peripheral nervous system. Our time-lapse recordings indicate that NCCs and ECs are physically juxtaposed and dynamically interact at multiple locations along their trajectories. These interactions are stereotypical and occur at precise anatomical locations along the NCC migratory pathway. NCCs migrate alongside the posterior surface of developing intersomitic vessels, but fail to cross these continuous streams of motile ECs. NCCs change their morphology and migration trajectory when they encounter gaps in the developing vasculature. Within the nascent dorsal root ganglion, proximity to ECs causes filopodial retraction which curtails forward persistence of NCC motility. Overall, our time-lapse recordings support the conclusion that primary vascular networks substantially influence the distribution and migratory behavior of NCCs and the patterned formation of dorsal root and sympathetic ganglia.

PHOX2B Is Associated with Neuroblastoma Cell Differentiation

Neuroblastoma is a common pediatric malignancy that accounts for ∼15% of tumor-related deaths in children. The tumor is generally believed to originate from neural crest cells during early sympathetic neurogenesis. As the degree of neuroblastoma differentiation has been correlated with clinical outcome, clarifying the molecular mechanisms that drive neuroblastoma progression and differentiation is important for increasing the survival of these patients. In a previous study, the authors identified paired-like homeobox 2b (PHOX2B) as a key mediator of neuroblastoma pathogenesis in a TH-MYCN mouse model. In the present study, they aimed to define whether PHOX2B is also associated with proliferation and differentiation of human neuroblastoma cells. PHOX2B expression in neuroblastoma cells was evaluated by immunoblot analyses, and the effects of PHOX2B on the proliferation of neuroblastoma cells in vitro were determined using clonogenic and sphere formation assays. Xenograft experiments in NOD/SCID mice were used to examine the in vivo response to PHOX2B knockdown. Their data demonstrated that PHOX2B acts as a prognostic marker in neuroblastoma and that retinoic acid-induced neuronal differentiation downregulates PHOX2B expression, thereby suppressing the self-renewal capacity of neuroblastoma cells and inhibiting tumorigenicity. These findings confirmed that PHOX2B is a key regulator of neuroblastoma differentiation and stemness maintenance and indicated that PHOX2B might serve as a potential therapeutic target in neuroblastoma patients.

Distinct roles of hand2 in developing and adult autonomic neurons

The bHLH transcription factor Hand2 is essential for the acquisition and maintenance of noradrenergic properties of embryonic sympathetic neurons and controls neuroblast proliferation. Hand2 is also expressed in embryonic and postnatal parasympathetic ganglia and remains expressed in sympathetic neurons up to the adult stage. Here, we address its function in developing parasympathetic and adult sympathetic neurons. We conditionally deleted Hand2 in the parasympathetic sphenopalatine ganglion by crossing a line of floxed Hand2 mice with DbhiCre transgenic mice, taking advantage of the transient Dbh expression in parasympathetic ganglia. Hand2 elimination does not affect Dbh expression and sphenopalatine ganglion size at E12.5 and E16.5, in contrast to sympathetic ganglia. These findings demonstrate different functions for Hand2 in the parasympathetic and sympathetic lineage. Our previous Hand2 knockdown in postmitotic, differentiated chick sympathetic neurons resulted in decreased expression of noradrenergic marker genes but it was unclear whether Hand2 is required for maintaining noradrenergic neuron identity in adult animals. We now show that Hand2 elimination in adult Dbh-expressing sympathetic neurons does not decrease the expression of Th and Dbh, in contrast to the situation during development. However, gene expression profiling of adult sympathetic neurons identified 75 Hand2-dependent target genes. Interestingly, a notable proportion of down-regulated genes (15%) encode for proteins with synaptic and neurotransmission functions. These results demonstrate a change in Hand2 target genes during maturation of sympathetic neurons. Whereas Hand2 controls genes regulating noradrenergic differentiation during development, Hand2 seems to be involved in the regulation of genes controlling neurotransmission in adult sympathetic neurons. © 2016 Wiley Periodicals, Inc. Develop Neurobiol 76: 1111-1124, 2016.

Generating trunk neural crest from human pluripotent stem cells

Neural crest cells (NCC) are stem cells that generate different lineages, including neuroendocrine, melanocytic, cartilage, and bone. The differentiation potential of NCC varies according to the level from which cells emerge along the neural tube. For example, only anterior “cranial” NCC form craniofacial bone, whereas solely posterior “trunk” NCC contribute to sympathoadrenal cells. Importantly, the isolation of human fetal NCC carries ethical and scientific challenges, as NCC induction typically occur before pregnancy is detectable. As a result, current knowledge of NCC biology derives primarily from non-human organisms. Important differences between human and non-human NCC, such as expression of HNK1 in human but not mouse NCC, suggest a need to study human NCC directly. Here, we demonstrate that current protocols to differentiate human pluripotent stem cells (PSC) to NCC are biased toward cranial NCC. Addition of retinoic acid drove trunk-related markers and HOX genes characteristic of a posterior identity. Subsequent treatment with bone morphogenetic proteins (BMPs) enhanced differentiation to sympathoadrenal cells. Our approach provides methodology for detailed studies of human NCC, and clarifies roles for retinoids and BMPs in the differentiation of human PSC to trunk NCC and to sympathoadrenal lineages.

Putting together the clues of the everlasting neuro-cardiac liaison

Starting from the late embryonic development, the sympathetic nervous system extensively innervates the heart and modulates its activity during the entire lifespan. The distribution of myocardial sympathetic processes is finely regulated by the secretion of limiting amounts of pro-survival neurotrophic factors by cardiac cells. Norepinephrine release by the neurons rapidly modulates myocardial electrophysiology, and increases the rate and force of cardiomyocyte contractions. Sympathetic processes establish direct interaction with cardiomyocytes, characterized by the presence of neurotransmitter vesicles and reduced cell-cell distance. Whether such contacts have a functional role in both neurotrophin- and catecholamine-dependent communication between the two cell types, is poorly understood. In this review we will address the effects of the sympathetic neuron activity on the myocardium and the hypothesis that the direct neuro-cardiac contact might have a key role both in norepinephrine and neurotrophin mediated signaling. This article is part of a Special Issue entitled: Cardiomyocyte Biology: Integration of Developmental and Environmental Cues in the Heart edited by Marcus Schaub and Hughes Abriel.

Neuroblastoma and Its Zebrafish Model

Neuroblastoma, an important developmental tumor arising in the peripheral sympathetic nervous system (PSNS), accounts for approximately 10 % of all cancer-related deaths in children. Recent genomic analyses have identified a spectrum of genetic alterations in this tumor. Amplification of the MYCN oncogene is found in 20 % of cases and is often accompanied by mutational activation of the ALK (anaplastic lymphoma kinase) gene, suggesting their cooperation in tumor initiation and spread. Understanding how complex genetic changes function together in oncogenesis has been a continuing and daunting task in cancer research. This challenge was addressed in neuroblastoma by generating a transgenic zebrafish model that overexpresses human MYCN and activated ALK in the PSNS, leading to tumors that closely resemble human neuroblastoma and new opportunities to probe the mechanisms that underlie the pathogenesis of this tumor. For example, coexpression of activated ALK with MYCN in this model triples the penetrance of neuroblastoma and markedly accelerates tumor onset, demonstrating the interaction of these modified genes in tumor development. Further, MYCN overexpression induces adrenal sympathetic neuroblast hyperplasia, blocks chromaffin cell differentiation, and ultimately triggers a developmentally-timed apoptotic response in the hyperplastic sympathoadrenal cells. In the context of MYCN overexpression, activated ALK provides prosurvival signals that block this apoptotic response, allowing continued expansion and oncogenic transformation of hyperplastic neuroblasts, thus promoting progression to neuroblastoma. This application of the zebrafish model illustrates its value in rational assessment of the multigenic changes that define neuroblastoma pathogenesis and points the way to future studies to identify novel targets for therapeutic intervention.

Sympatho-adrenal morphogenesis regulated by the dorsal aorta

The autonomic nervous system, composed of sympathetic- and para-sympathetic neurons, plays essential roles in a variety of physiological functions including homeostasis and responses to external stimuli. We here present an overview of recent findings concerning how the sympathetic nervous system is formed during the early development, paying particular attention to the morphogenesis of those tissues derived from migrating neural crest cells. Neural crest cells, originally multipotent, are progressively specified to sympathetic ganglia neurons and adrenomedullary cells during their migration through the body. Importantly, the dorsal aorta, the first-forming blood vessel, acts as a signaling center for their migration and differentiation. BMP signals emanating from the dorsal aorta are essential for establishing environmental cues that directly act on the migrating cells. The mechanisms underlying these early neuro-vascular interactions provide insights into understanding diseases caused by malfunctions and malformations of the autonomic nervous system.

Vascular Mural Cells Promote Noradrenergic Differentiation of Embryonic Sympathetic Neurons

The sympathetic nervous system controls smooth muscle tone and heart rate in the cardiovascular system. Postganglionic sympathetic neurons (SNs) develop in close proximity to the dorsal aorta (DA) and innervate visceral smooth muscle targets. Here, we use the zebrafish embryo to ask whether the DA is required for SN development. We show that noradrenergic (NA) differentiation of SN precursors temporally coincides with vascular mural cell (VMC) recruitment to the DA and vascular maturation. Blocking vascular maturation inhibits VMC recruitment and blocks NA differentiation of SN precursors. Inhibition of platelet-derived growth factor receptor (PDGFR) signaling prevents VMC differentiation and also blocks NA differentiation of SN precursors. NA differentiation is normal in cloche mutants that are devoid of endothelial cells but have VMCs. Thus, PDGFR-mediated mural cell recruitment mediates neurovascular interactions between the aorta and sympathetic precursors and promotes their noradrenergic differentiation.

Phox2B correlates with MYCN and is a prognostic marker for neuroblastoma development

Neuroblastoma is the one of the most common extracranial childhood malignancies, accounting for ∼15% of tumor-associated deaths in children. It is generally considered that neuroblastoma originates from neural crest cells in the paravertebral sympathetic ganglia and the adrenal medulla. However, the mechanism by which neuroblastoma arises during sympathetic neurogenesis and the cellular mechanism that drives neuroblastoma development remains unclear. The present study investigated the cell components during neuroblastoma development in the tyrosine hydroxylase-v-myc avian myelocytomatosis viral oncogene neuroblastoma derived homolog (TH-MYCN) mouse model, a transgenic mouse model of human neuroblastoma. The present study demonstrates that paired-like homeobox 2b (Phox2B)⁺ neuronal progenitors are the major cellular population in hyperplastic lesions and primary tumors. In addition, Phox2B⁺ neuronal progenitors in hyperplastic lesions or primary tumors were observed to be in an actively proliferative and undifferentiated state. The current study also demonstrated that high expression levels of Phox2B promotes neuroblastoma cell proliferation and xenograft tumor growth. These findings indicate that the proliferation of undifferentiated Phox2B⁺ neuronal progenitors is a cellular mechanism that promotes neuroblastoma development and indicates that Phox2B is a critical regulator in neuroblastoma pathogenesis.

Molecular control of the neural crest and peripheral nervous system development

A transient and unique population of multipotent stem cells, known as neural crest cells (NCCs), generate a bewildering array of cell types during vertebrate development. An attractive model among developmental biologists, the study of NCC biology has provided a wealth of knowledge regarding the cellular and molecular mechanisms important for embryogenesis. Studies in numerous species have defined how distinct phases of NCC specification, proliferation, migration, and survival contribute to the formation of multiple functionally distinct organ systems. NCC contributions to the peripheral nervous system (PNS) are well known. Critical developmental processes have been defined that provide outstanding models for understanding how extracellular stimuli, cell-cell interactions, and transcriptional networks cooperate to direct cellular diversification and PNS morphogenesis. Dissecting the complex extracellular and intracellular mechanisms that mediate the formation of the PNS from NCCs may have important therapeutic implications for neurocristopathies, neuropathies, and certain forms of cancer.

Segregation of neuronal and neuroendocrine differentiation in the sympathoadrenal lineage

Neuronal and neuroendocrine cells possess the capacity for Ca(2+)-regulated discharge of messenger molecules, which they release into synapses or the blood stream, respectively. The neural-crest-derived sympathoadrenal lineage gives rise to the sympathetic neurons of the autonomic nervous system and the neuroendocrine chromaffin cells of the adrenal medulla. These cells provide an excellent model system for studying common and distinct developmental mechanisms underlying the acquisition of neuroendocrine and neuronal properties. As catecholaminergic cells, they possess common markers related to noradrenaline synthesis, storage and release, but they also display diverging gene expression patterns and are morphologically and functionally different. The precise mechanisms that underlie the diversification of sympathoadrenal cells into neurons and neuroendocrine cells are not fully understood. However, in the past we could show that the establishment of a chromaffin phenotype does not depend on signals from the adrenal cortex and that chromaffin cells and sympathetic neurons apparently differ from the onset of their catecholaminergic differentiation. Nevertheless, the cues that specifically induce neuroendocrine features remain elusive. The early development of the progenitors of chromaffin cells and sympathetic neurons depends on a common set of transcription factors with overlapping but distinct influences on their development. In addition to the well-defined role of transcription factors as developmental regulators, our understanding of post-transcriptional gene regulation by microRNAs has substantially increased within the last few decades. This review highlights the major similarities and differences between chromaffin cells and sympathetic neurons, summarizes our current knowledge of the roles of selected transcription factors, microRNAs and environmental signals for the neuroendocrine differentiation of sympathoadrenal cells, and draws comparisons with the development of other endocrine and neuronal cells.

Signaling molecules and transcription factors involved in the development of the sympathetic nervous system, with special emphasis on the superior cervical ganglion

The cells that constitute the sympathetic nervous system originate from the neural crest. This review addresses the current understanding of sympathetic ganglion development viewed from molecular and morphological perspectives. Development of the sympathetic nervous system is categorized into three main steps, as follows: (1) differentiation and migration of cells in the neural crest lineage for formation of the primary sympathetic chain, (2) differentiation of sympathetic progenitors, and (3) growth and survival of sympathetic ganglia. The signaling molecules and transcription factors involved in each of these developmental stages are elaborated mostly on the basis of the results of targeted mutation of respective genes. Analyses in mutant mice revealed differences between the superior cervical ganglion (SCG) and the other posterior sympathetic ganglia. This review provides a summary of the similarities and differences in the development of the SCG and other posterior sympathetic ganglia. Relevant to the development of sympathetic ganglia is the demonstration that neuroendocrine cells, such as adrenal chromaffin cells and carotid body glomus cells, share a common origin with the sympathetic ganglia. Neural crest cells at the trunk level give rise to common sympathoadrenal progenitors of sympathetic neurons and chromaffin cells, while progenitors segregated from the SCG give rise to glomus cells. After separation from the sympathetic primordium, the progenitors of both chromaffin cells and glomus cells colonize the anlage of the adrenal gland and carotid body, respectively. This review highlights the biological properties of chromaffin cells and glomus cells, because, although both cell types are derivatives of sympathetic primordium, they are distinct in many respects.

The prenatal origins of cancer

The concept that some childhood malignancies arise from postnatally persistent embryonal cells has a long history. Recent research has strengthened the links between driver mutations and embryonal and early postnatal development. This evidence, coupled with much greater detail on the cell of origin and the initial steps in embryonal cancer initiation, has identified important therapeutic targets and provided renewed interest in strategies for the early detection and prevention of childhood cancer.

Nerve injury and recovery after lateral lumbar interbody fusion with and without bone morphogenetic protein-2 augmentation: a cohort-controlled study

BACKGROUND CONTEXT

Despite common use of intraoperative electrophysiologic neuromonitoring, injuries to the lumbar plexus during lateral lumbar interbody fusion (LLIF) have been reported. Emerging data suggest that recombinant human bone morphogenetic protein-2 (rhBMP-2) use during an anterior or transforaminal lumbar interbody fusion may be associated with an increased risk of neurological deficit. Clinical data on the sequelae of rhBMP-2 implantation in close proximity to the lumbosacral plexus during LLIF remains to be understood.

PURPOSE

The purpose of this study was to compare the incidence of neurologic deficits and pain in patients undergoing LLIF with and without rhBMP-2.

STUDY DESIGN/SETTING

Retrospective outcome analysis in controlled cohorts undergoing the lateral exposure technique for LLIF with and without rhBMP-2.

METHODS

The electronic medical records of patients undergoing LLIF with and without supplemental posterior fusion for degenerative spinal conditions were retrospectively reviewed over a 6-year period. Patients with previous lumbar spine surgery or follow-up of less than 6 months were excluded. Patients were divided into 2 groups, Group 1 (rhBMP-2 use; n=72) and Group 2 (autograft/allograft use; n=72), and were matched according to the age at the time of surgery, gender, weight, body mass index, side of approach, total number of treated spinal segments, use of supplemental posterior fusion, and length of follow-up.

RESULTS

Immediately after surgery, a sensory deficit was recorded in 33 patients in Group 1 and 35 patients in Group 2 (odds ratio [OR] 0.895; 90% confidence interval [CI] 0.516-1.550; p=.739). At last follow-up, a persistent sensory deficit was identified in 29 patients whose LLIF procedure was supplemented by rhBMP-2 and 20 patients in whom autograft/allograft was used (OR 1.754; 90% CI 0.976-3.151; p=.115). A motor deficit was recorded in 37 patients immediately after the rhBMP-2 procedure and 28 patients treated with autograft/allograft (OR 1.661; 90% CI 0.953-2.895; p=.133). A persistent motor deficit was recorded in 35 and 17 patients in Groups 1 and 2, respectively, at last follow-up (OR 3.060; 90% CI 1.681-5.571; p=.002). During the first postoperative examination, 37 patients in Group 1 and 25 patients in Group 2 complained of anterior thigh or groin pain (OR 1.987; 90% CI 1.133-3.488; p=.045). At last follow-up, there was a significantly higher number of patients in Group 1 who complained of persistent anterior thigh or groin pain than Group 2 (8 vs. 0 patients) (OR 16.470; 90% CI 1.477-183.700; p=.006).

CONCLUSIONS

Our results provide evidence of an increased rate of postoperative neurologic deficit and anterior thigh/groin pain after LLIF using rhBMP-2, when compared with matched controls without rhBMP-2 exposure. This study suggests a potential direct deleterious effect of rhBMP-2 on the lumbosacral plexus.

Down-regulation of RE-1 silencing transcription factor (REST) in advanced prostate cancer by hypoxia-induced miR-106b~25

Clinically aggressive prostate cancer (PCa) is linked to androgen resistance, metastasis, and expression of neuroendocrine markers. To understand mechanism(s) of neuroendocrine differentiation (NED) of PCa epithelia, we compared neuronal differentiation occurring during embryogenesis, in primary cultures of neural crest (NC) cells, and NED in PCa cell lines (LNCaP and PC3). We demonstrate, hypoxia promotes neuronal and neuroendocrine differentiation of NC cells and PCa cells, respectively, by inducing the miR-106 b~25 cluster. In turn, miR-106b~25 comprised of miR-106b, miR-93 and miR-25, down-regulates the transcriptional repressor REST, which represses neuron-specific protein-coding and miRNA genes. In prostate tumors of high Gleason score (≥ 8), an inverse trend was observed between REST and miR-106b~25 induction. Employing miRNA PCR arrays, we identified miRNAs up-regulated by hypoxia in LNCaP cells and REST-knockdown in NC cells. Significantly, a subset of miRNAs (miR-9, miR-25, miR-30d and miR302b) is up-regulated in high Gleason score (≥ 8) PCa, suggesting a mechanism by which NED contributes to PCa malignancy. We propose that loss of REST and induction of this set of microRNAs can serve as potential novel clinical markers of advanced PCa.

Synaptic protein and pan-neuronal gene expression and their regulation by Dicer-dependent mechanisms differ between neurons and neuroendocrine cells

BACKGROUND

Neurons in sympathetic ganglia and neuroendocrine cells in the adrenal medulla share not only their embryonic origin from sympathoadrenal precursors in the neural crest but also a range of functional features. These include the capacity for noradrenaline biosynthesis, vesicular storage and regulated release. Yet the regulation of neuronal properties in early neuroendocrine differentiation is a matter of debate and the developmental expression of the vesicle fusion machinery, which includes components found in both neurons and neuroendocrine cells, is not resolved.

RESULTS

Analysis of synaptic protein and pan-neuronal marker mRNA expression during mouse development uncovers profound differences between sympathetic neurons and adrenal chromaffin cells, which result in qualitatively similar but quantitatively divergent transcript profiles. In sympathetic neurons embryonic upregulation of synaptic protein mRNA follows early and persistent induction of pan-neuronal marker transcripts. In adrenal chromaffin cells pan-neuronal marker expression occurs only transiently and synaptic protein messages remain at distinctly low levels throughout embryogenesis. Embryonic induction of synaptotagmin I (Syt1) in sympathetic ganglia and postnatal upregulation of synaptotagmin VII (Syt7) in adrenal medulla results in a cell type-specific difference in isoform prevalence. Dicer 1 inactivation in catecholaminergic cells reduces high neuronal synaptic protein mRNA levels but not their neuroendocrine low level expression. Pan-neuronal marker mRNAs are induced in chromaffin cells to yield a more neuron-like transcript pattern, while ultrastructure is not altered.

CONCLUSIONS

Our study demonstrates that remarkably different gene regulatory programs govern the expression of synaptic proteins in the neuronal and neuroendocrine branch of the sympathoadrenal system. They result in overlapping but quantitatively divergent transcript profiles. Dicer 1-dependent regulation is required to establish high neuronal mRNA levels for synaptic proteins and to maintain repression of neurofilament messages in neuroendocrine cells.

BMP-Smad 1/5/8 signalling in the development of the nervous system

The transcription factors, Smad1, Smad5 and Smad8, are the pivotal intracellular effectors of the bone morphogenetic protein (BMP) family of proteins. BMPs and their receptors are expressed in the nervous system (NS) throughout its development. This review focuses on the actions of Smad 1/5/8 in the developing NS. The mechanisms by which these Smad proteins regulate the induction of the neuroectoderm, the central nervous system (CNS) primordium, and finally the neural crest, which gives rise to the peripheral nervous system (PNS), are reviewed herein. We describe how, following neural tube closure, the most dorsal aspect of the tube becomes a signalling centre for BMPs, which directs the pattern of the development of the dorsal spinal cord (SC), through the action of Smad1, Smad5 and Smad8. The direct effects of Smad 1/5/8 signalling on the development of neuronal and non-neuronal cells from various neural progenitor cell populations are then described. Finally, this review discusses the neurodevelopmental abnormalities associated with the knockdown of Smad 1/5/8.