Notch signaling maintains neural rosette polarity

Stable and efficient generation of functional iPSC-derived neural progenitor cell rosettes through regulation of collective cell-cell behavior

Although the potential of stem cells to differentiate into several cell types has shown promise in regenerative medicine, low differentiation efficiency and poor reproducibility significantly limit their practical application. We developed an effective and robust differentiation strategy for the efficient and robust generation of neural progenitor cell rosettes from induced pluripotent stem cells (iPSCs) incorporating botulinum hemagglutinin (HA). Treatment with HA suppressed the spontaneous differentiation of iPSCs cultured under undirected differentiation conditions, resulting in the preservation of their pluripotency. Moreover, treatment with HA during neural progenitor differentiation combined with dual SMAD inhibition generated a highly homogeneous population of PAX6-and SOX1-expressing neural progenitor cells with 8.4-fold higher yields of neural progenitor cells than untreated control cultures. These neural progenitor cells formed radially organized rosettes surrounding the central lumen. This differentiation method enhanced the generation of functional iPSC-derived neural progenitor cell rosettes throughout the culture vessel, suggesting that the regulation of collective cell-cell behavior using HA plays a morphogenetically important role in rosette formation and maturation. These findings show the significance of HA in the suppression of spontaneous differentiation through spatial homogeneity. The study proposes a novel methodology for the efficient derivation of functional iPSC-derived neural progenitor cell rosettes.

A quest for genetic causes underlying signaling pathways associated with neural tube defects

Neural tube defects (NTDs) are serious congenital deformities of the nervous system that occur owing to the failure of normal neural tube closures. Genetic and non-genetic factors contribute to the etiology of neural tube defects in humans, indicating the role of gene-gene and gene-environment interaction in the occurrence and recurrence risk of neural tube defects. Several lines of genetic studies on humans and animals demonstrated the role of aberrant genes in the developmental risk of neural tube defects and also provided an understanding of the cellular and morphological programs that occur during embryonic development. Other studies observed the effects of folate and supplementation of folic acid on neural tube defects. Hence, here we review what is known to date regarding altered genes associated with specific signaling pathways resulting in NTDs, as well as highlight the role of various genetic, and non-genetic factors and their interactions that contribute to NTDs. Additionally, we also shine a light on the role of folate and cell adhesion molecules (CAMs) in neural tube defects.

Familial Alzheimer's Disease Mutations in PSEN1 Lead to Premature Human Stem Cell Neurogenesis

Mutations in presenilin 1 (PSEN1) or presenilin 2 (PSEN2), the catalytic subunit of γ-secretase, cause familial Alzheimer's disease (fAD). We hypothesized that mutations in PSEN1 reduce Notch signaling and alter neurogenesis. Expression data from developmental and adult neurogenesis show relative enrichment of Notch and γ-secretase expression in stem cells, whereas expression of APP and β-secretase is enriched in neurons. We observe premature neurogenesis in fAD iPSCs harboring PSEN1 mutations using two orthogonal systems: cortical differentiation in 2D and cerebral organoid generation in 3D. This is partly driven by reduced Notch signaling. We extend these studies to adult hippocampal neurogenesis in mutation-confirmed postmortem tissue. fAD cases show mutation-specific effects and a trend toward reduced abundance of newborn neurons, supporting a premature aging phenotype. Altogether, these results support altered neurogenesis as a result of fAD mutations and suggest that neural stem cell biology is affected in aging and disease.

Epidermoid cyst in a patient with Alagille syndrome: Coincidence or connection?

Background:

Alagille syndrome is a rare genetic syndrome, which arises due to defects in the Notch signaling pathway, resulting in liver, cardiopulmonary, renal, skeletal, and ophthalmologic problems, among others. Epidermoid cysts are rare congenital benign lesions that develop from ectopic ectodermal cell rests formed during neurulation.

Case Description:

A 24-year-old Alagille syndrome patient presented with hearing loss and was found to have a sizable posterior fossa mass. He underwent craniotomy for uneventful resection of the lesion, which was found to be an epidermoid cyst.

Conclusion:

While our case may represent a coincidental occurrence of two pathologies presenting together, given that epidermoid cysts arise from aberrant neurulation, and in light of the crucial role of the Notch signaling pathway both in normal neurogenesis and in the pathogenesis of Alagille syndrome, we hypothesize a possible association between these entities.

Novel JAG1 Deletion Variant in Patient with Atypical Alagille Syndrome

Alagille syndrome (AGS) is an autosomal-dominant disorder characterized by various degrees of abnormalities in the liver, heart, eyes, vertebrae, kidneys, face, vasculature, skeleton, and pancreas. This case report describes a newborn child exhibiting a congenital neural tube defect and peculiar craniofacial appearance characterized by a prominent forehead, deep-set eyes, bulbous nasal tip, and subtle upper lip. Just a few hours after birth, congenital heart disease was suspected for cyanosis and confirmed by heart evaluation. In particular, echocardiography indicated pulmonary atresia with ventricular septal defect with severe hypoplasia of the pulmonary branches (1.5 mm), large patent ductus arteriosus and several major aortopulmonary collateral arteries. Due to the association of peculiar craniofacial appearance and congenital heart disease, a form of Alagille syndrome was suspected. In addition, on the fifth day after birth, the patient developed jaundice, had acholic stools, and high levels of conjugated bilirubin and gamma-glutamyltransferase (GGT) were detected in the blood. Genetic testing revealed the novel variant c.802del in a single copy of the JAG1 gene. No variants in the NOTCH2 gene were detected. To the best of our knowledge, this is the first clinical description of a congenital neural tube defect in a molecularly confirmed Alagille patient. This work demonstrates a novel pathogenic heterozygous JAG1 mutation is associated with an atypical form of Alagille syndrome, suggesting an increased risk for neural tube defects compared to other Alagille patients.

A Polarizing Issue: Diversity in the Mechanisms Underlying Apico-Basolateral Polarization In Vivo

Polarization along an apico-basolateral axis is a hallmark of epithelial cells and is essential for their selective barrier and transporter functions, as well as for their ability to provide mechanical resiliency to organs. Loss of polarity along this axis perturbs development and is associated with a wide number of diseases. We describe three steps involved in polarization: symmetry breaking, polarity establishment, and polarity maintenance. While the proteins involved in these processes are highly conserved among epithelial tissues and species, the execution of these steps varies widely and is context dependent. We review both theoretical principles underlying these steps and recent work demonstrating how apico-basolateral polarity is established in vivo in different tissues, highlighting how developmental and physiological contexts play major roles in the execution of the epithelial polarity program.

Notch-mediated inhibition of neurogenesis is required for zebrafish spinal cord morphogenesis

The morphogenesis of the nervous system requires coordinating the specification and differentiation of neural precursor cells, the establishment of neuroepithelial tissue architecture and the execution of specific cellular movements. How these aspects of neural development are linked is incompletely understood. Here we inactivate a major regulator of embryonic neurogenesis - the Delta/Notch pathway - and analyze the effect on zebrafish central nervous system morphogenesis. While some parts of the nervous system can establish neuroepithelial tissue architecture independently of Notch, Notch signaling is essential for spinal cord morphogenesis. In this tissue, Notch signaling is required to repress neuronal differentiation and allow thereby the emergence of neuroepithelial apico-basal polarity. Notch-mediated suppression of neurogenesis is also essential for the execution of specific morphogenetic movements of zebrafish spinal cord precursor cells. In the wild-type neural tube, cells divide at the organ midline to contribute one daughter cell to each organ half. Notch signaling deficient animals fail to display this behavior and therefore form a misproportioned spinal cord. Taken together, our findings show that Notch-mediated suppression of neurogenesis is required to allow the execution of morphogenetic programs that shape the zebrafish spinal cord.

Epsins Regulate Mouse Embryonic Stem Cell Exit from Pluripotency and Neural Commitment by Controlling Notch Activation

Epsins are part of the internalization machinery pivotal to control clathrin-mediated endocytosis. Here, we report that epsin family members are expressed in mouse embryonic stem cells (mESCs) and that epsin1/2 knockdown alters both mESC exits from pluripotency and their differentiation. Furthermore, we show that epsin1/2 knockdown compromises the correct polarization and division of mESC-derived neural progenitors and their conversion into expandable radial glia-like neural stem cells. Finally, we provide evidence that Notch signaling is impaired following epsin1/2 knockdown and that experimental restoration of Notch signaling rescues the epsin-mediated phenotypes. We conclude that epsins contribute to control mESC exit from pluripotency and allow their neural differentiation by appropriate modulation of Notch signaling.

The effect of folic acid deficiency on FGF pathway via Brachyury regulation in neural tube defects

Folate deficiency in early development leads to disturbance in multiple processes, including neurogenesis during which fibroblast growth factor (FGF) pathway is one of the crucial pathways. Whether folic acid (FA) directly affects FGF pathways to influence neurodevelopment and the possible mechanism remains unclear. In this study, we presented evidence that in human FA-insufficient encephalocele, the FGF pathway was interfered. Furthermore, in Brachyury knockout mice devoid of such T-box transcription factors regulating embryonic neuromesodermal bipotency and a key component of FGF pathway, change in expression of Brachyury downstream targets, activator Fgf8 and suppressor dual specificity phosphatase 6 was detected, along with the reduction in expression of other key FGF pathway genes. By using a FA-deficient cell model, we further demonstrated that decrease in Brachyury expression was through alteration in hypermethylation at the Brachyury promoter region under FA deficiency conditions, and suppression of Brachyury promoted the inactivation of the FGF pathway. Correspondingly, FA supplementation partially reverses the effects seen in FA-deficient embryoid bodies. Lastly, in mice with maternal folate-deficient diets, aberrant FGF pathway activity was found in fetal brain dysplasia. Taken together, our findings highlight the effect of FA on FGF pathways during neurogenesis, and the mechanism may be due to the low expression of Brachyury gene via hypermethylation under FA-insufficient conditions.-Chang, S., Lu, X., Wang, S., Wang, Z., Huo, J., Huang, J., Shangguan, S., Li, S., Zou, J., Bao, Y., Guo, J., Wang, F., Niu, B., Zhang, T., Qiu, Z., Wu, J., Wang, L. The effect of folic acid deficiency on FGF pathway via Brachyury regulation in neural tube defects.

PCDH19 regulation of neural progenitor cell differentiation suggests asynchrony of neurogenesis as a mechanism contributing to PCDH19 Girls Clustering Epilepsy

PCDH19-Girls Clustering Epilepsy (PCDH19-GCE) is a childhood epileptic encephalopathy characterised by a spectrum of neurodevelopmental problems. PCDH19-GCE is caused by heterozygous loss-of-function mutations in the X-chromosome gene, Protocadherin 19 (PCDH19) encoding a cell-cell adhesion molecule. Intriguingly, hemizygous males are generally unaffected. As PCDH19 is subjected to random X-inactivation, heterozygous females are comprised of a mosaic of cells expressing either the normal or mutant allele, which is thought to drive pathology. Despite being the second most prevalent monogeneic cause of epilepsy, little is known about the role of PCDH19 in brain development. In this study we show that PCDH19 is highly expressed in human neural stem and progenitor cells (NSPCs) and investigate its function in vitro in these cells of both mouse and human origin. Transcriptomic analysis of mouse NSPCs lacking Pcdh19 revealed changes to genes involved in regulation of neuronal differentiation, and we subsequently show that loss of Pcdh19 causes increased NSPC neurogenesis. We reprogramed human fibroblast cells harbouring a pathogenic PCDH19 mutation into human induced pluripotent stem cells (hiPSC) and employed neural differentiation of these to extend our studies into human NSPCs. As in mouse, loss of PCDH19 function caused increased neurogenesis, and furthermore, we show this is associated with a loss of human NSPC polarity. Overall our data suggests a conserved role for PCDH19 in regulating mammalian cortical neurogenesis and has implications for the pathogenesis of PCDH19-GCE. We propose that the difference in timing or "heterochrony" of neuronal cell production originating from PCDH19 wildtype and mutant NSPCs within the same individual may lead to downstream asynchronies and abnormalities in neuronal network formation, which in-part predispose the individual to network dysfunction and epileptic activity.

Mouse Model of Alagille Syndrome and Mechanisms of Jagged1 Missense Mutations

BACKGROUND & AIMS

Alagille syndrome is a genetic disorder characterized by cholestasis, ocular abnormalities, characteristic facial features, heart defects, and vertebral malformations. Most cases are associated with mutations in JAGGED1 (JAG1), which encodes a Notch ligand, although it is not clear how these contribute to disease development. We aimed to develop a mouse model of Alagille syndrome to elucidate these mechanisms.

METHODS

Mice with a missense mutation (H268Q) in Jag1 (Jag1^+/Ndr mice) were outbred to a C3H/C57bl6 background to generate a mouse model for Alagille syndrome (Jag1^Ndr/Ndr mice). Liver tissues were collected at different timepoints during development, analyzed by histology, and liver organoids were cultured and analyzed. We performed transcriptome analysis of Jag1^Ndr/Ndr livers and livers from patients with Alagille syndrome, cross-referenced to the Human Protein Atlas, to identify commonly dysregulated pathways and biliary markers. We used species-specific transcriptome separation and ligand-receptor interaction assays to measure Notch signaling and the ability of JAG1^Ndr to bind or activate Notch receptors. We studied signaling of JAG1 and JAG1^Ndr via NOTCH 1, NOTCH2, and NOTCH3 and resulting gene expression patterns in parental and NOTCH1-expressing C2C12 cell lines.

RESULTS

Jag1^Ndr/Ndr mice had many features of Alagille syndrome, including eye, heart, and liver defects. Bile duct differentiation, morphogenesis, and function were dysregulated in newborn Jag1^Ndr/Ndr mice, with aberrations in cholangiocyte polarity, but these defects improved in adult mice. Jag1^Ndr/Ndr liver organoids collapsed in culture, indicating structural instability. Whole-transcriptome sequence analyses of liver tissues from mice and patients with Alagille syndrome identified dysregulated genes encoding proteins enriched at the apical side of cholangiocytes, including CFTR and SLC5A1, as well as reduced expression of IGF1. Exposure of Notch-expressing cells to JAG1^Ndr, compared with JAG1, led to hypomorphic Notch signaling, based on transcriptome analysis. JAG1-expressing cells, but not JAG1^Ndr-expressing cells, bound soluble Notch1 extracellular domain, quantified by flow cytometry. However, JAG1 and JAG1^Ndr cells each bound NOTCH2, and signaling from NOTCH2 signaling was reduced but not completely inhibited, in response to JAG1^Ndr compared with JAG1.

CONCLUSIONS

In mice, expression of a missense mutant of Jag1 (Jag1^Ndr) disrupts bile duct development and recapitulates Alagille syndrome phenotypes in heart, eye, and craniofacial dysmorphology. JAG1^Ndr does not bind NOTCH1, but binds NOTCH2, and elicits hypomorphic signaling. This mouse model can be used to study other features of Alagille syndrome and organ development.

Five steps to form neural rosettes: structure and function

Neural rosette formation is a critical morphogenetic process during neural development, whereby neural stem cells are enclosed in rosette niches to equipoise proliferation and differentiation. How neural rosettes form and provide a regulatory micro-environment remains to be elucidated. We employed the human embryonic stem cell-based neural rosette system to investigate the structural development and function of neural rosettes. Our study shows that neural rosette formation consists of 5 types of cell movements: intercalation, constriction, polarization, elongation, and lumen formation. Ca2+ signaling plays a pivotal role in the five steps by regulating the actions of the cytoskeletal complexes, ACTIN, MYOSIN II, and TUBULIN during intercalation, constriction, and elongation. These in turn control the polarizing elements, ZO-1, PARD3, and β-CATENIN during polarization and lumen formation in neural rosette formation. We further demonstrated that the dismantlement of neural rosettes, mediated by the destruction of cytoskeletal elements, promoted neurogenesis and astrogenesis prematurely, indicating that an intact rosette structure is essential for orderly neural development.

Notch Signaling in Development, Tissue Homeostasis, and Disease

Notch signaling is an evolutionarily highly conserved signaling mechanism, but in contrast to signaling pathways such as Wnt, Sonic Hedgehog, and BMP/TGF-β, Notch signaling occurs via cell-cell communication, where transmembrane ligands on one cell activate transmembrane receptors on a juxtaposed cell. Originally discovered through mutations in Drosophila more than 100 yr ago, and with the first Notch gene cloned more than 30 yr ago, we are still gaining new insights into the broad effects of Notch signaling in organisms across the metazoan spectrum and its requirement for normal development of most organs in the body. In this review, we provide an overview of the Notch signaling mechanism at the molecular level and discuss how the pathway, which is architecturally quite simple, is able to engage in the control of cell fates in a broad variety of cell types. We discuss the current understanding of how Notch signaling can become derailed, either by direct mutations or by aberrant regulation, and the expanding spectrum of diseases and cancers that is a consequence of Notch dysregulation. Finally, we explore the emerging field of Notch in the control of tissue homeostasis, with examples from skin, liver, lung, intestine, and the vasculature.

Complement C5aR1 Signaling Promotes Polarization and Proliferation of Embryonic Neural Progenitor Cells through PKCζ

The complement system, typically associated with innate immunity, is emerging as a key controller of nonimmune systems including in development, with recent studies linking complement mutations with neurodevelopmental disease. A key effector of the complement response is the activation fragment C5a, which, through its receptor C5aR1, is a potent driver of inflammation. Surprisingly, C5aR1 is also expressed during early mammalian embryogenesis; however, no clearly defined function is ascribed to C5aR1 in development. Here we demonstrate polarized expression of C5aR1 on the apical surface of mouse embryonic neural progenitor cells in vivo and on human embryonic stem cell-derived neural progenitors. We also show that signaling of endogenous C5a during mouse embryogenesis drives proliferation of neural progenitor cells within the ventricular zone and is required for normal brain histogenesis. C5aR1 signaling in neural progenitors was dependent on atypical protein kinase C ζ, a mediator of stem cell polarity, with C5aR1 inhibition reducing proliferation and symmetric division of apical neural progenitors in human and mouse models. C5aR1 signaling was shown to promote the maintenance of cell polarity, with exogenous C5a increasing the retention of polarized rosette architecture in human neural progenitors after physical or chemical disruption. Transient inhibition of C5aR1 during neurogenesis in developing mice led to behavioral abnormalities in both sexes and MRI-detected brain microstructural alterations, in studied males, demonstrating a requirement of C5aR1 signaling for appropriate brain development. This study thus identifies a functional role for C5a-C5aR1 signaling in mammalian neurogenesis and provides mechanistic insight into recently identified complement gene mutations and brain disorders.SIGNIFICANCE STATEMENT The complement system, traditionally known as a controller of innate immunity, now stands as a multifaceted signaling family with a broad range of physiological actions. These include roles in the brain, where complement activation is associated with diseases, including epilepsy and schizophrenia. This study has explored complement regulation of neurogenesis, identifying a novel relationship between the complement activation peptide C5a and the neural progenitor proliferation underpinning formation of the mammalian brain. C5a was identified as a regulator of cell polarity, with inhibition of C5a receptors during embryogenesis leading to abnormal brain development and behavioral deficits. This work demonstrates mechanisms through which dysregulation of complement causes developmental disease and highlights the potential risk of complement inhibition for therapeutic purposes in pregnancy.

The Cellular Prion Protein Controls Notch Signaling in Neural Stem/Progenitor Cells

The prion protein is infamous for its involvement in a group of neurodegenerative diseases known as Transmissible Spongiform Encephalopathies. In the longstanding quest to decipher the physiological function of its cellular isoform, PrP^C , the discovery of its participation to the self-renewal of hematopoietic and neural stem cells has cast a new spotlight on its potential role in stem cell biology. However, still little is known on the cellular and molecular mechanisms at play. Here, by combining in vitro and in vivo murine models of PrP^C depletion, we establish that PrP^C deficiency severely affects the Notch pathway, which plays a major role in neural stem cell maintenance. We document that the absence of PrP^C in a neuroepithelial cell line or in primary neurospheres is associated with drastically reduced expression of Notch ligands and receptors, resulting in decreased levels of Notch target genes. Similar alterations of the Notch pathway are recovered in the neuroepithelium of Prnp^-/- embryos during a developmental window encompassing neural tube closure. In addition, in line with Notch defects, our data show that the absence of PrP^C results in altered expression of Nestin and Olig2 as well as N-cadherin distribution. We further provide evidence that PrP^C controls the expression of the epidermal growth factor receptor (EGFR) downstream from Notch. Finally, we unveil a negative feedback action of EGFR on both Notch and PrP^C . As a whole, our study delineates a molecular scenario through which PrP^C takes part to the self-renewal of neural stem and progenitor cells. Stem Cells 2017;35:754-765.

Intermittent high oxygen influences the formation of neural retinal tissue from human embryonic stem cells

The vertebrate retina is a highly multilayered nervous tissue with a large diversity of cellular components. With the development of stem cell technologies, human retinas can be generated in three-dimensional (3-D) culture in vitro. However, understanding the factors modulating key productive processes and the way that they influence development are far from clear. Oxygen, as the most essential element participating in metabolism, is a critical factor regulating organic development. In this study, using 3-D culture of human stem cells, we examined the effect of intermittent high oxygen treatment (40% O₂) on the formation and cellular behavior of neural retinas (NR) in the embryonic body (EB). The volume of EB and number of proliferating cells increased significantly under 40% O₂ on day 38, 50, and 62. Additionally, the ratio of PAX6+ cells within NR was significantly increased. The neural rosettes could only develop with correct apical-basal polarity under 40% O₂. In addition, the generation, migration and maturation of retinal ganglion cells were enhanced under 40% O₂. All of these results illustrated that 40% O₂ strengthened the formation of NR in EB with characteristics similar to the in vivo state, suggesting that the hyperoxic state facilitated the retinal development in vitro.

Self-Organization of Spatial Patterning in Human Embryonic Stem Cells

The developing embryo is a remarkable example of self-organization, where functional units are created in a complex spatiotemporal choreography. Recently, human embryonic stem cells (ESCs) have been used to recapitulate in vitro the self-organization programs that are executed in the embryo in vivo. This represents an unique opportunity to address self-organization in humans that is otherwise not addressable with current technologies. In this chapter, we review the recent literature on self-organization of human ESCs, with a particular focus on two examples: formation of embryonic germ layers and neural rosettes. Intriguingly, both activation and elimination of TGFβ signaling can initiate self-organization, albeit with different molecular underpinnings. We discuss the mechanisms underlying the formation of these structures in vitro and explore future challenges in the field.

Neural differentiation from embryonic stem cells in vitro: An overview of the signaling pathways

Neurons derived from embryonic stem cells (ESCs) have gained great merit in both basic research and regenerative medicine. Here we review and summarize the signaling pathways that have been reported to be involved in the neuronal differentiation of ESCs, particularly those associated with in vitro differentiation. The inducers and pathways explored include retinoic acid, Wnt/β-catenin, transforming growth factor/bone morphogenetic protein, Notch, fibroblast growth factor, cytokine, Hedgehog, c-Jun N-terminal kinase/mitogen-activated protein kinase and others. Some other miscellaneous molecular factors that have been reported in the literature are also summarized and discussed. These include calcium, calcium receptor, calcineurin, estrogen receptor, Hox protein, ceramide, glycosaminioglycan, ginsenoside Rg1, opioids, two pore channel 2, nitric oxide, chemically defined medium, cell-cell interactions, and physical stimuli. The interaction or crosstalk between these signaling pathways and factors will be explored. Elucidating these signals in detail should make a significant contribution to future progress in stem cell biology and allow, for example, better comparisons to be made between differentiation in vivo and in vitro. Of equal importance, a comprehensive understanding of the pathways that are involved in the development of neurons from ESCs in vitro will also accelerate their application as part of translational medicine.

Cell polarity and neurogenesis in embryonic stem cell-derived neural rosettes

Embryonic stem cells (ESCs) undergoing neural differentiation form radial arrays of neural stem cells, termed neural rosettes. These structures manifest many of the properties associated with embryonic and adult neurogenesis, including cell polarization, interkinetic nuclear migration (INM), and a gradient of neuronal differentiation. We now identify novel rosette structural features that serve to localize key regulators of neurogenesis. Cells within neural rosettes have specialized basal as well as apical surfaces, based on localization of the extracellular matrix receptor β1 integrin. Apical processes of cells in mature rosettes terminate at the lumen, where adherens junctions are apparent. Primary cilia are randomly distributed in immature rosettes and tightly associated with the neural stem cell's apical domain as rosettes mature. Components of two signaling pathways known to regulate neurogenesis in vivo and in rosettes, Hedgehog and Notch, are apically localized, with the Hedgehog effector Smoothened (Smo) associated with primary cilia and the Notch pathway γ-secretase subunit Presenilin 2 associated with the adherens junction. Increased neuron production upon treatment with the Notch inhibitor DAPT suggests a major role for Notch signaling in maintaining the neural stem cell state, as previously described. A less robust outcome was observed with manipulation of Hedgehog levels, though consistent with a role in neural stem cell survival or proliferation. Inhibition of both pathways resulted in an additive effect. These data support a model by which cells extending a process to the rosette lumen maintain neural stem cell identity whereas release from this association, either through asymmetric cell division or apical abscission, promotes neuronal differentiation.

Cell surface antigen profiling using a novel type of antibody array immobilised to plasma ion-implanted polycarbonate

To identify and sort out subpopulations of cells from more complex and heterogeneous assemblies of cells is important for many biomedical applications, and the development of cost- and labour-efficient techniques to accomplish this is warranted. In this report, we have developed a novel array-based platform to discriminate cellular populations based on differences in cell surface antigen expressions. These cell capture microarrays were produced through covalent immobilisation of CD antibodies to plasma ion immersion implantation-treated polycarbonate (PIII-PC), which offers the advantage of a transparent matrix, allowing direct light microscopy visualisation of captured cells. The functionality of the PIII-PC array was validated using several cell types, resulting in unique surface antigen expression profiles. PIII-PC results were compatible with flow cytometry, nitrocellulose cell capture arrays and immunofluorescent staining, indicating that the technique is robust. We report on the use of this PIII-PC cluster of differentiation (CD) antibody array to gain new insights into neural differentiation of mouse embryonic stem (ES) cells and into the consequences of genetic targeting of the Notch signalling pathway, a key signalling mechanism for most cellular differentiation processes. Specifically, we identify CD98 as a novel marker for neural precursors and polarised expression of CD9 in the apical domain of ES cell-derived neural rosettes. We further identify expression of CD9 in hitherto uncharacterised non-neural cells and enrichment of CD49e- and CD117-positive cells in Notch signalling-deficient ES cell differentiations. In conclusion, this work demonstrates that covalent immobilisation of antibody arrays to the PIII-PC surface provides faithful cell surface antigen data in a cost- and labour-efficient manner. This may be used to facilitate high throughput identification and standardisation of more precise marker profiles during stem cell differentiation and in various genetic and disease contexts.

Inhibition of Notch signaling facilitates the differentiation of human-induced pluripotent stem cells into neural stem cells

Neural stem cells (NSCs) derived from induced pluripotent stem cells (iPSCs) are becoming an appealing source of cell-based therapies of brain diseases. As such, it is important to understand the molecular mechanisms that regulate the differentiation of iPSCs toward NSCs. It is well known that Notch signaling governs the retention of stem cell features and drives stem cells fate. However, further studies are required to investigate the role of Notch signaling in the NSCs differentiation of iPSCs. In this study, we successfully generated NSCs from human iPSCs using serum-free medium supplemented with retinoic acid (RA) in vitro. We then assessed changes in the expression of Notch signaling-related molecules and some miRNAs (9, 34a, 200b), which exert their regulation by targeting Notch signaling. Moreover, we used a γ-secretase inhibitor (DAPT) to disturb Notch signaling. Data revealed that the levels of the Notch signaling-related molecules decreased, whereas those miRNAs increased, during this differentiation process. Inhibition of Notch signaling accelerated the formation of the neural rosette structures and the expression of NSC and mature neurocyte marker genes. This suggests that Notch signaling negatively regulated the neuralization of human iPSCs, and that this process may be regulated by some miRNAs.