Role of the chemokine SDF-1 as the meningeal attractant for embryonic cerebellar neurons

Intracerebellar administration of the chemokine Cxcl3 reduces the volume of medulloblastoma lesions at an advanced stage by promoting the migration and differentiation of preneoplastic precursor cells

The prognosis for many pediatric brain tumors, including cerebellar medulloblastoma (MB), remains dismal but there is promise in new therapies. We have previously generated a mouse model developing spontaneous MB at high frequency, Ptch1+/-/Tis21-/-. In this model, reproducing human tumorigenesis, we identified the decline of the Cxcl3 chemokine in cerebellar granule cell precursors (GCPs) as responsible for a migration defect, which causes GCPs to stay longer in the proliferative area rather than differentiate and migrate internally, making them targets of transforming insults. We demonstrated that 4-week Cxcl3 infusion in cerebella of 1-month-old mice, at the initial stage of MB formation, forces preneoplastic GCPs (pGCPs) to leave lesions and differentiate, with a complete suppression of MB development. In this study, we sought to verify the effect of 4-week Cxcl3 treatment in 3-month-old Ptch1+/-/Tis21-/- mice, when MB lesions are at an advanced, irreversible stage. We found that Cxcl3 treatment reduces tumor volumes by sevenfold and stimulates the migration and differentiation of pGCPs from the lesion to the internal cerebellar layers. We also tested whether the pro-migratory action of Cxcl3 favors metastases formation, by xenografting DAOY human MB cells in the cerebellum of immunosuppressed mice. We showed that DAOY cells express the Cxcl3 receptor, Cxcr2, and that Cxcl3 triggers their migration. However, Cxcl3 did not significantly affect the frequency of metastases or the growth of DAOY-generated MBs. Finally, we mapped the expression of the Cxcr2 receptor in human MBs, by evaluating a well-characterized series of 52 human MBs belonging to different MB molecular subgroups. We found that Cxcr2 was variably expressed in all MB subgroups, suggesting that Cxcl3 could be used for therapy of different MBs.

CXCL12 promotes the crossing of retinal ganglion cell axons at the optic chiasm

Binocular vision requires the segregation of retinal ganglion cell (RGC) axons extending from the retina into the ipsilateral and contralateral optic tracts. RGC axon segregation occurs at the optic chiasm, which forms at the ventral diencephalon midline. Using expression analyses, retinal explants and genetically modified mice, we demonstrate that CXCL12 (SDF1) is required for axon segregation at the optic chiasm. CXCL12 is expressed by the meninges bordering the optic pathway, and CXCR4 by both ipsilaterally and contralaterally projecting RGCs. CXCL12 or ventral diencephalon meninges potently promoted axon outgrowth from both ipsilaterally and contralaterally projecting RGCs. Further, a higher proportion of axons projected ipsilaterally in mice lacking CXCL12 or its receptor CXCR4 compared with wild-type mice as a result of misrouting of presumptive contralaterally specified RGC axons. Although RGCs also expressed the alternative CXCL12 receptor ACKR3, the optic chiasm developed normally in mice lacking ACKR3. Our data support a model whereby meningeal-derived CXCL12 helps drive axon growth from CXCR4-expressing RGCs towards the diencephalon midline, enabling contralateral axon growth. These findings further our understanding of the molecular and cellular mechanisms controlling optic pathway development.

CXCL12-CXCR4/CXCR7 Axis in Cancer: from Mechanisms to Clinical Applications

Cancer is a multi-step disease caused by the accumulation of genetic mutations and/or epigenetic changes, and is the biggest challenge around the world. Cytokines, including chemokines, exhibit expression changes and disorders in all human cancers. These cytokine abnormalities can disrupt homeostasis and immune function, and make outstanding contributions to various stages of cancer development such as invasion, metastasis, and angiogenesis. Chemokines are a superfamily of small molecule chemoattractive cytokines that mediate a variety of cellular functions. Importantly, the interactions of chemokine members CXCL12 and its receptors CXCR4 and CXCR7 have a broad impact on tumor cell proliferation, survival, angiogenesis, metastasis, and tumor microenvironment, and thus participate in the onset and development of many cancers including leukemia, breast cancer, lung cancer, prostate cancer and multiple myeloma. Therefore, this review aims to summarize the latest research progress and future challenges regarding the role of CXCL12-CXCR4/CXCR7 signaling axis in cancer, and highlights the potential of CXCL12-CXCR4/CXCR7 as a biomarker or therapeutic target for cancer, providing essential strategies for the development of novel targeted cancer therapies.

The Regulatory Roles of Cerebellar Glycosphingolipid Microdomains/Lipid Rafts

Lipid rafts are dynamic assemblies of glycosphingolipids, sphingomyelin, cholesterol, and specific proteins which are stabilized into platforms involved in the regulation of vital cellular processes. Cerebellar lipid rafts are cell surface ganglioside microdomains for the attachment of GPI-anchored neural adhesion molecules and downstream signaling molecules such as Src-family kinases and heterotrimeric G proteins. In this review, we summarize our recent findings on signaling in ganglioside GD3 rafts of cerebellar granule cells and several findings by other groups on the roles of lipid rafts in the cerebellum. TAG-1, of the contactin group of immunoglobulin superfamily cell adhesion molecules, is a phosphacan receptor. Phosphacan regulates the radial migration signaling of cerebellar granule cells, via Src-family kinase Lyn, by binding to TAG-1 on ganglioside GD3 rafts. Chemokine SDF-1α, which induces the tangential migration of cerebellar granule cells, causes heterotrimeric G protein Goα translocation to GD3 rafts. Furthermore, the functional roles of cerebellar raft-binding proteins including cell adhesion molecule L1, heterotrimeric G protein Gsα, and L-type voltage-dependent calcium channels are discussed.

Parasagittal Fibroblastic Meningioma in Accompaniment with Scalp Basal Cell Carcinoma: Report of a Case

Introduction: Accompaniment of meningioma with other tumors especially cerebral tumors is quite rare. In some institutes, cases of simultaneous meningioma and glioma are seen and reported previously. Case Presentation: We reported a meningioma with the accompaniment of scalp basal cell carcinoma (BCC) with no signs and symptoms of Gorlin syndrome and no history of radiation. Conclusions: Expression of some adjacent cancerous lesions might have a local cancerous induction effect.

Early life adversity drives sex-specific anhedonia and meningeal immune gene expression through mast cell activation

Exposure to early life adversity (ELA) in the form of physical and/or psychological abuse or neglect increases the risk of developing psychiatric and inflammatory disorders later in life. It has been hypothesized that exposure to ELA results in persistent, low grade inflammation that leads to increased disease susceptibility by amplifying the crosstalk between stress-processing brain networks and the immune system, but the mechanisms remain largely unexplored. The meninges, a layer of three overlapping membranes that surround the central nervous system (CNS)- dura mater, arachnoid, and piamater - possess unique features that allow them to play a key role in coordinating immune trafficking between the brain and the peripheral immune system. These include a network of lymphatic vessels that carry cerebrospinal fluid from the brain to the deep cervical lymph nodes, fenestrated blood vessels that allow the passage of molecules from blood to the CNS, and a rich population of resident mast cells, master regulators of the immune system. Using a mouse model of ELA consisting of neonatal maternal separation plus early weaning (NMSEW), we sought to explore the effects of ELA on sucrose preference behavior, dura mater expression of inflammatory markers and mast cell histology in adult male and female C57Bl/6 mice. We found that NMSEW alone does not affect sucrose preference behavior in males or females, but it increases the dura mater expression of the genes coding for mast cell protease CMA1 (cma1) and the inflammatory cytokine TNF alpha (tnf alpha) in females. When NMSEW is combined with an adult mild stress (that does not affect behavior or gene expression in NH animals) females show reduced sucrose preference and even greater increases in meningeal cma1 levels. Interestingly, systemic administration of the mast cell stabilizer Ketotifen before exposure to adult stress prevents both, reduction in sucrose preference an increases in cma1 expression in NMSEW females, but facilitates stress-induced sucrose anhedonia in NMSEW males and NH females. Finally, histological analyses showed that, compared to males, females have increased baseline activation levels of mast cells located in the transverse sinus of the dura mater, where the meningeal lymphatics run along, and that, in males and females exposed to adult stress, NMSEW increases the number of mast cells in the interparietal region of the dura mater and the levels of mast cell activation in the sagittal sinus regions of the dura mater. Together, our results indicate that ELA induces long-term meningeal immune gene changes and heightened sensitivity to adult stress-induced behavioral and meningeal immune responses and that these effects could mediated via mast cells.

Neuronal Polarity Pathways as Central Integrators of Cell-Extrinsic Information During Interactions of Neural Progenitors With Germinal Niches

Germinal niche interactions and their effect on developing neurons have become the subject of intense investigation. Dissecting the complex interplay of cell-extrinsic and cell-intrinsic factors at the heart of these interactions reveals the critical basic mechanisms of neural development and how it goes awry in pediatric neurologic disorders. A full accounting of how developing neurons navigate their niches to mature and integrate into a developing neural circuit requires a combination of genetic characterization of and physical access to neurons and their supporting cell types plus transformative imaging to determine the cell biological and gene-regulatory responses to niche cues. The mouse cerebellar cortex is a prototypical experimental system meeting all of these criteria. The lessons learned therein have been scaled to other model systems and brain regions to stimulate discoveries of how developing neurons make many developmental decisions. This review focuses on how mouse cerebellar granule neuron progenitors interact with signals in their germinal niche and how that affects the neuronal differentiation and cell polarization programs that underpin lamination of the developing cerebellum. We show how modeling of these mechanisms in other systems has added to the growing evidence of how defective neuronal polarity contributes to developmental disease.

A Hydrogel as a Bespoke Delivery Platform for Stromal Cell-Derived Factor-1

The defined self-assembly of peptides (SAPs) into nanostructured bioactive hydrogels has great potential for repairing traumatic brain injuries, as they maintain a stable, homeostatic environment at an injury site, preventing further degeneration. They also present a bespoke platform to restore function via the naturalistic presentation of therapeutic proteins, such as stromal-cell-derived factor 1 (SDF-1), expressed by meningeal cells. A key challenge to the use of the SDF protein, however, is its rapid diffusion and degradation. Here, we engineered a homeostatic hydrogel produced by incorporating recombinant SDF-1 protein within a self-assembled peptide hydrogel to create a supportive milieu for transplanted cells. Our hydrogel can concomitantly deliver viable primary neural progenitor cells and sustained active SDF-1 to support the nascent graft, resulting in increased neuronal differentiation. Moreover, this homeostatic hydrogel can ensure a healthy and larger graft core without impeding neuronal fiber growth and innervation. These findings demonstrate the regenerative potential of these hydrogels to improve the integration of grafted cells to treat neural injuries and diseases.

Drebrin regulates cytoskeleton dynamics in migrating neurons through interaction with CXCR4

Stromal cell-derived factor-1 (SDF-1) and chemokine receptor type 4 (CXCR4) are regulators of neuronal migration (e.g., GnRH neurons, cortical neurons, and hippocampal granule cells). However, how SDF-1/CXCR4 alters cytoskeletal components remains unclear. Developmentally regulated brain protein (drebrin) stabilizes actin polymerization, interacts with microtubule plus ends, and has been proposed to directly interact with CXCR4 in T cells. The current study examined, in mice, whether CXCR4 under SDF-1 stimulation interacts with drebrin to facilitate neuronal migration. Bioinformatic prediction of protein-protein interaction highlighted binding sites between drebrin and crystallized CXCR4. In migrating GnRH neurons, drebrin, CXCR4, and the microtubule plus-end binding protein EB1 were localized close to the cell membrane. Coimmunoprecipitation (co-IP) confirmed a direct interaction between drebrin and CXCR4 using wild-type E14.5 whole head and a GnRH cell line. Analysis of drebrin knockout (DBN1 KO) mice showed delayed migration of GnRH cells into the brain. A decrease in hippocampal granule cells was also detected, and co-IP confirmed a direct interaction between drebrin and CXCR4 in PN4 hippocampi. Migration assays on primary neurons established that inhibiting drebrin (either pharmacologically or using cells from DBN1 KO mice) prevented the effects of SDF-1 on neuronal movement. Bioinformatic prediction then identified binding sites between drebrin and the microtubule plus end protein, EB1, and super-resolution microscopy revealed decreased EB1 and drebrin coexpression after drebrin inhibition. Together, these data show a mechanism by which a chemokine, via a membrane receptor, communicates with the intracellular cytoskeleton in migrating neurons during central nervous system development.

Single-Cell Transcriptomic Analyses of the Developing Meninges Reveal Meningeal Fibroblast Diversity and Function

The meninges are a multilayered structure composed of fibroblasts, blood and lymphatic vessels, and immune cells. Meningeal fibroblasts secrete a variety of factors that control CNS development, yet strikingly little is known about their heterogeneity or development. Using single-cell sequencing, we report distinct transcriptional signatures for fibroblasts in the embryonic dura, arachnoid, and pia. We define new markers for meningeal layers and show conservation in human meninges. We find that embryonic meningeal fibroblasts are transcriptionally distinct between brain regions and identify a regionally localized pial subpopulation marked by the expression of μ-crystallin. Developmental analysis reveals a progressive, ventral-to-dorsal maturation of telencephalic meninges. Our studies have generated an unparalleled view of meningeal fibroblasts, providing molecular profiles of embryonic meningeal fibroblasts by layer and yielding insights into the mechanisms of meninges development and function.

The Role of Immune Factors in Shaping Fetal Neurodevelopment

Fetal neurodevelopment in utero is profoundly shaped by both systemic maternal immunity and local processes at the maternal-fetal interface. Immune pathways are a critical participant in the normal physiology of pregnancy and perturbations of maternal immunity due to infections during this period have been increasingly linked to a diverse array of poor neurological outcomes, including diseases that manifest much later in postnatal life. While experimental models of maternal immune activation (MIA) have provided groundbreaking characterizations of the maternal pathways underlying pathogenesis, less commonly examined are the immune factors that serve pathogen-independent developmental functions in the embryo and fetus. In this review, we explore what is known about the in vivo role of immune factors in fetal neurodevelopment during normal pregnancy and provide an overview of how MIA perturbs the proper orchestration of this sequence of events. Finally, we discuss how the dysregulation of immune factors may contribute to the manifestation of a variety of neurological disorders.

Chemokine receptor CXCR7 non-cell-autonomously controls pontine neuronal migration and nucleus formation

Long distance tangential migration transports neurons from their birth places to distant destinations to be incorporated into neuronal circuits. How neuronal migration is guided during these long journeys is still not fully understood. We address this issue by studying the migration of pontine nucleus (PN) neurons in the mouse hindbrain. PN neurons migrate from the lower rhombic lip first anteriorly and then turn ventrally near the trigeminal ganglion root towards the anterior ventral hindbrain. Previously we showed that in mouse depleted of chemokine receptor CXCR4 or its ligand CXCL12, PN neurons make their anterior-to-ventral turn at posteriorized positions. However, the mechanism that spatiotemporally controls the anterior-to-ventral turning is still unclear. Furthermore, the role of CXCR7, the atypical receptor of CXCL12, in pontine migration has yet to be examined. Here, we find that the PN is elongated in Cxcr7 knockout due to a broadened anterior-to-ventral turning positions. Cxcr7 is not expressed in migrating PN neurons en route to their destinations, but is strongly expressed in the pial meninges. Neuroepithelium-specific knockout of Cxcr7 does not recapitulate the PN phenotype in Cxcr7 knockout, suggesting that CXCR7 acts non-cell-autonomously possibly from the pial meninges. We show further that CXCR7 regulates pontine migration by modulating CXCL12 protein levels.

Role of FOXC1 in regulating APSCs self-renewal via STI-1/PrPC signaling

Forkhead box protein C1 (FOXC1) is known to regulate developmental processes in the skull and brain. Methods: The unique multipotent arachnoid-pia stem cells (APSCs) isolated from human and mouse arachnoid-pia membranes of meninges were grown as 3D spheres and displayed a capacity for self-renewal. Additionally, APSCs also expressed the surface antigens as mesenchymal stem cells. By applying the FOXC1 knockout mice and mouse brain explants, signaling cascade of FOXC1-STI-1-PrP^C was investigated to demonstrate the molecular regulatory pathway for APSCs self-renewal. Moreover, APSCs implantation in stroke model was also verified whether neurogenic property of APSCs could repair the ischemic insult of the stroke brain. Results: Activated FOXC1 regulated the proliferation of APSCs in a cell cycle-dependent manner, whereas FOXC1-mediated APSCs self-renewal was abolished in FOXC1 knockout mice (FOXC1^-/- mice). Moreover, upregulation of STI-1 regulated by FOXC1 enhanced cell survival and self-renewal of APSCs through autocrine signaling of cellular prion protein (PrP^C). Mouse brain explants STI-1 rescues the cortical phenotype in vitro and induces neurogenesis in the FOXC1 ^-/- mouse brain. Furthermore, administration of APSCs in ischemic brain restored the neuroglial microenvironment and improved neurological dysfunction. Conclusion: We identified a novel role for FOXC1 in the direct regulation of the STI-1-PrP^C signaling pathway to promote cell proliferation and self-renewal of APSCs.

Developmental biology of the meninges

The meninges are membranous layers surrounding the central nervous system. In the head, the meninges lie between the brain and the skull, and interact closely with both during development. The cranial meninges originate from a mesenchymal sheath on the surface of the developing brain, called primary meninx, and undergo differentiation into three layers with distinct histological characteristics: the dura mater, the arachnoid mater, and the pia mater. While genetic regulation of meningeal development is still poorly understood, mouse mutants and other models with meningeal defects have demonstrated the importance of the meninges to normal development of the calvaria and the brain. For the calvaria, the interactions with the meninges are necessary for the progression of calvarial osteogenesis during early development. In later stages, the meninges control the patterning of the skull and the fate of the sutures. For the brain, the meninges regulate diverse processes including cell survival, cell migration, generation of neurons from progenitors, and vascularization. Also, the meninges serve as a stem cell niche for the brain in the postnatal life. Given these important roles of the meninges, further investigation into the molecular mechanisms underlying meningeal development can provide novel insights into the coordinated development of the head.

Glioblastoma cancer stem cell biology: Potential theranostic targets

Glioblastoma multiforme (GBM) is among the most incurable cancers. GBMs survival rate has not markedly improved, despite new radical surgery protocols, the introduction of new anticancer drugs, new treatment protocols, and advances in radiation techniques. The low efficacy of therapy, and short interval between remission and recurrence, could be attributed to the resistance of a small fraction of tumorigenic cells to treatment. The existence and importance of cancer stem cells (CSCs) is perceived by some as controversial. Experimental evidences suggest that the presence of therapy-resistant glioblastoma stem cells (GSCs) could explain tumor recurrence and metastasis. Some scientists, including most of the authors of this review, believe that GSCs are the driving force behind GBM relapses, whereas others however, question the existence of GSCs. Evidence has accumulated indicating that non-tumorigenic cancer cells with high heterogeneity, could undergo reprogramming and become GSCs. Hence, targeting GSCs as the "root cells" initiating malignancy has been proposed to eradicate this devastating disease. Most standard treatments fail to completely eradicate GSCs, which can then cause the recurrence of the disease. To effectively target GSCs, a comprehensive understanding of the biology of GSCs as well as the mechanisms by which these cells survive during treatment and develop into new tumor, is urgently needed. Herein, we provide an overview of the molecular features of GSCs, and elaborate how to facilitate their detection and efficient targeting for therapeutic interventions. We also discuss GBM classifications based on the molecular stem cell subtypes with a focus on potential therapeutic approaches.

Nerve cells developmental processes and the dynamic role of cytokine signaling

The stunning diversity of neurons and glial cells makes possible the higher functions of the central nervous system (CNS), allowing the organism to sense, interpret and respond appropriately to the external environment. This cellular diversity derives from a single primary progenitor cell type initiating lineage leading to the formation of both differentiated neurons and glial cells. The processes governing the differentiation of the progenitor pool of cells into mature nerve cells will be here briefly reviewed. They involve morphological transformations, specialized modes of cell division, migration, and controlled cell death, and are regulated through cell-cell interactions and cues provided by the extracellular matrix, as well as by humoral factors from the cerebrospinal fluid and the blood system. In this respect, a quite large body of studies have been focused on cytokines, proteins representing the main signaling network that coordinates immune defense and the maintenance of homeostasis. At the same time, they are deeply involved in CNS development as regulatory factors. This dual role in the nervous system appears of particular relevance for CNS pathology, since cytokine dysregulation (occurring as a consequence of maternal infection, exposure to environmental factors or prenatal hypoxia) can profoundly impact on neurodevelopment and likely influence the response of the adult tissue during neuroinflammatory events.

CXCR4/SDF1 signalling promotes sensory neuron clustering in vitro

During the development of the peripheral nervous system, a subgroup of neural crest cells migrate away from the neural tube and coalesce into clusters of sensory neurons (ganglia). Mechanisms involved in the formation of the dorsal root ganglia (DRG) from neural crest cells are currently unclear. Mice carrying mutations in Cxcr4, which is known to control neural crest migration, exhibit malformed DRG. In order to investigate this phenomenon, we modelled sensory neuron differentiation in vitro by directing the differentiation of human induced pluripotent stem cells into sensory neurons under SDF1 (agonist), AMD3100 (antagonist) or control conditions. There we could show a marked effect on the clustering activity of the neurons in vitro, suggesting that CXCR4 signalling is involved in facilitating DRG condensation.

Summary: The signalling mechanisms directing sensory neuron gangliogenesis are not well understood. Here, we model this process through stem cell differentiation and show that CXCR4 signalling facilitates neural clustering.

Potential use of CXCL12/CXCR4 and sonic hedgehog pathways as therapeutic targets in medulloblastoma

Medulloblastoma (MB) is the most common malignant brain tumor occurring in children, and although high long-term survival rates have been reached with current therapeutic protocols, several neurological injuries are still observed among survivors. It has been shown that the development of MB is highly dependent on the microenvironment surrounding it and that the CXCL12 chemokine and its receptor, CXCR4 and the Sonic Hedgehog (SHH) pathway are crucial for cerebellar development, coordinating proliferation and migration of embryonic cells and malfunctions in these axes can lead to MB development. Indeed, the concomitant overactivation of these axes was suggested to define a new MB molecular subgroup. New molecules are being studied, aiming to inhibit either CXCR4 or the SHH pathways and have been tested in preclinical settings for the treatment of cancers. The use of these molecules could improve MB treatment and save patients from aggressive surgery, chemotherapy and radiotherapy regimens, which are responsible for severe neurological consequences. This review aims to summarize current data about the experimental inhibition of CXCR4 and SHH pathways in MB and its potential implications in treatment of this cancer.

Encapsulation of young donor age dopaminergic grafts in a GDNF-loaded collagen hydrogel further increases their survival, reinnervation, and functional efficacy after intrastriatal transplantation in hemi-Parkinsonian rats

Biomaterials have been shown to significantly improve the outcome of cellular reparative approaches for Parkinson's disease in experimental studies because of their ability to provide transplanted cells with a supportive microenvironment and shielding from the host immune system. However, given that the margin for improvement in such reparative therapies is considerable, further studies are required to fully investigate and harness the potential of biomaterials in this context. Given that several recent studies have demonstrated improved brain repair in Parkinsonian models when using dopaminergic grafts derived from younger foetal donors, we hypothesized that encapsulating these cells in a supportive biomaterial would further improve their reparative efficacy. Thus, this study aimed to determine the impact of a GDNF-loaded collagen hydrogel on the survival, reinnervation, and functional efficacy of dopaminergic neurons derived from young donors. To do so, hemi-Parkinsonian (6-hydroxydopamine-lesioned) rats received intrastriatal transplants of embryonic day 12 cells extracted from the rat ventral mesencephalon either alone, in a collagen hydrogel, with GDNF, or in a GDNF-loaded collagen hydrogel. Methamphetamine-induced rotational behaviour was assessed at three weekly intervals for a total of 12 weeks, after which rats were sacrificed for postmortem assessment of graft survival. We found that, following intrastriatal transplantation to the lesioned striatum, the GDNF-loaded collagen hydrogel significantly increased the survival (4-fold), reinnervation (5.4-fold), and functional efficacy of the embryonic day 12 dopaminergic neurons. In conclusion, this study further demonstrates the significant potential of biomaterial hydrogel scaffolds for cellular brain repair approaches in neurodegenerative diseases such as Parkinson's disease.

Multisystem multitasking by CXCL12 and its receptors CXCR4 and ACKR3

Chemokines are named and best known for their chemotactic cytokine activity in the hematopoietic system; however, their importance extends far beyond leukocytes, cell movement and immunoregulation. CXCL12, the most protean of chemokines, regulates development in multiple systems, including the hematopoietic, cardiovascular and nervous systems, and regulates diverse cell functions, including differentiation, distribution, activation, immune synapse formation, effector function, proliferation and survival in the immune system alone. The broad importance of CXCL12 is revealed by the complex lethal developmental phenotypes in mice lacking either Cxcl12 or either one of its two known 7-transmembrane domain receptors Cxcr4 and Ackr3, as well as by gain-of-function mutations in human CXCR4, which cause WHIM syndrome, a multisystem and combined immunodeficiency disease and the only Mendelian condition caused by a chemokine system mutation. In addition, wild type CXCR4 is important in the pathogenesis of HIV/AIDS and cancer. Thus, CXCL12 and its receptors CXCR4 and ACKR3 provide extraordinary examples of multisystem multitasking in the chemokine system in both health and disease.

Dextran-coated iron oxide nanoparticle-improved therapeutic effects of human mesenchymal stem cells in a mouse model of Parkinson's disease

Parkinson's disease (PD) is a prevalent neurodegenerative disease characterized by the loss of dopaminergic (DA) neurons. With their migration capacity toward the sites of diseased DA neurons in the PD brain, mesenchymal stem cells (MSCs) have the potential to differentiate to DA neurons for the replacement of damaged neurons and to secrete neurotrophic factors for the protection and regeneration of diseased DA neurons; therefore MSCs show promise for the treatment of PD. In this study, for the first time, we demonstrate that dextran-coated iron oxide nanoparticles (Dex-IO NPs) can improve the therapeutic efficacy of human MSCs (hMSCs) in a mouse model of PD induced by a local injection of 6-hydroxydopamine (6-OHDA). In situ examinations not only show that Dex-IO NPs can improve the rescue effect of hMSCs on the loss of host DA neurons but also demonstrate that Dex-IO NPs can promote the migration capacity of hMSCs toward lesioned DA neurons and induce the differentiation of hMSCs to DA-like neurons at the diseased sites. We prove that in vitro Dex-IO NPs can enhance the migration of hMSCs toward 6-OHDA-damaged SH-SY5Y-derived DA-like cells, induce hMSCs to differentiate to DA-like neurons in the conditioned media derived from 6-OHDA-damaged SH-SY5Y-derived DA-like cells and promote the protection/regeneration effects of hMSCs on 6-OHDA-damaged SH-SY5Y-derived DA-like cells. We confirm the potential of MSCs for cell-based therapy for PD. Dex-IO NPs can be used as a tool to accelerate and optimize MSC therapeutics for PD applicable clinically.

The RacGAP β-Chimaerin is essential for cerebellar granule cell migration

During mammalian cerebellar development, postnatal granule cell progenitors proliferate in the outer part of the External Granule Layer (EGL). Postmitotic granule progenitors migrate tangentially in the inner EGL before switching to migrate radially inward, past the Purkinje cell layer, to achieve their final position in the mature Granule Cell Layer (GCL). Here, we show that the RacGAP β-chimaerin is expressed by a small population of late-born, premigratory granule cells. β-chimaerin deficiency causes a subset of granule cells to become arrested in the EGL, where they differentiate and form ectopic neuronal clusters. These clusters of granule cells are able to recruit aberrantly projecting mossy fibers. Collectively, these data suggest a role for β-chimaerin as an intracellular mediator of Cerebellar Granule Cell radial migration.

Embryology

With the growing recognition of the extent and prevalence of human cerebellar disorders, an understanding of developmental programs that build the mature cerebellum is necessary. In this chapter we present an overview of the basic epochs and key molecular regulators of the developmental programs of cerebellar development. These include early patterning of the cerebellar territory, the genesis of cerebellar cells from multiple spatially distinct germinal zones, and the extensive migration and coordinated cellular rearrangements that result in the formation of the exquisitely foliated and laminated mature cerebellum. This knowledge base is founded on extensive analysis of animal models, particularly mice, due in large part to the ease of genetic manipulation of this important model organism. Since cerebellar structure and function are largely conserved across species, mouse cerebellar development is highly relevant to humans and has led to important insights into the developmental pathogenesis of human cerebellar disorders. Human fetal cerebellar development remains largely undescribed; however, several human-specific developmental features are known which are relevant to human disease and underline the importance of ongoing human fetal research.

Phenotypic outcomes in Mouse and Human Foxc1 dependent Dandy-Walker cerebellar malformation suggest shared mechanisms

FOXC1 loss contributes to Dandy-Walker malformation (DWM), a common human cerebellar malformation. Previously, we found that complete Foxc1 loss leads to aberrations in proliferation, neuronal differentiation and migration in the embryonic mouse cerebellum (Haldipur et al., 2014). We now demonstrate that hypomorphic Foxc1 mutant mice have granule and Purkinje cell abnormalities causing subsequent disruptions in postnatal cerebellar foliation and lamination. Particularly striking is the presence of a partially formed posterior lobule which echoes the posterior vermis DW 'tail sign' observed in human imaging studies. Lineage tracing experiments in Foxc1 mutant mouse cerebella indicate that aberrant migration of granule cell progenitors destined to form the posterior-most lobule causes this unique phenotype. Analyses of rare human del chr 6p25 fetal cerebella demonstrate extensive phenotypic overlap with our Foxc1 mutant mouse models, validating our DWM models and demonstrating that many key mechanisms controlling cerebellar development are likely conserved between mouse and human.

DOI:http://dx.doi.org/10.7554/eLife.20898.001

Bivalent 14-mer peptide ligands of CXCR4 with polyproline linkers with anti-chemotactic activity against Jurkat cells

Interaction of CXCR4 with its endogenous ligand, stromal-cell derived factor-1 (SDF-1)/CXCL12, induces various physiological functions involving chemotaxis. Bivalent ligands with a polyproline helix bearing a cyclic pentapeptide, FC131, were previously shown to have higher binding affinities for CXCR4 than the corresponding monovalent ligands. Bivalent ligands based on a 14-mer peptide T140 derivative with polyproline linkers have been designed and synthesized. The activity of these peptides as well as the effect of bivalency of the ligand on CXCR4 binding has been assessed. The binding affinity of these series of bivalent ligands is increased as the linker length increases up to the 12-/15-mer proline linker. The inhibitory activity against chemotaxis on Jurkat cells also depends on the linker length. The T140-derived bivalent ligands with the 9- and 12-mer proline linkers showed the most effective inhibition against chemotaxis at 1000 nM, which is even higher than that of known CXCR4 antagonists in the monomer structure. The effective metastatic inhibition by bivalent T140 derivatives indicates the therapeutic potential. Copyright © 2017 European Peptide Society and John Wiley & Sons, Ltd.

Functional Genomics Identifies Tis21-Dependent Mechanisms and Putative Cancer Drug Targets Underlying Medulloblastoma Shh-Type Development

We have recently generated a novel medulloblastoma (MB) mouse model with activation of the Shh pathway and lacking the MB suppressor Tis21 (Patched1^+/-/Tis21^KO ). Its main phenotype is a defect of migration of the cerebellar granule precursor cells (GCPs). By genomic analysis of GCPs in vivo, we identified as drug target and major responsible of this defect the down-regulation of the promigratory chemokine Cxcl3. Consequently, the GCPs remain longer in the cerebellum proliferative area, and the MB frequency is enhanced. Here, we further analyzed the genes deregulated in a Tis21-dependent manner (Patched1^+/-/Tis21 wild-type vs. Ptch1^+/-/Tis21 knockout), among which are a number of down-regulated tumor inhibitors and up-regulated tumor facilitators, focusing on pathways potentially involved in the tumorigenesis and on putative new drug targets. The data analysis using bioinformatic tools revealed: (i) a link between the Shh signaling and the Tis21-dependent impairment of the GCPs migration, through a Shh-dependent deregulation of the clathrin-mediated chemotaxis operating in the primary cilium through the Cxcl3-Cxcr2 axis; (ii) a possible lineage shift of Shh-type GCPs toward retinal precursor phenotype, i.e., the neural cell type involved in group 3 MB; (iii) the identification of a subset of putative drug targets for MB, involved, among the others, in the regulation of Hippo signaling and centrosome assembly. Finally, our findings define also the role of Tis21 in the regulation of gene expression, through epigenetic and RNA processing mechanisms, influencing the fate of the GCPs.

Valproic Acid and Other HDAC Inhibitors Upregulate FGF21 Gene Expression and Promote Process Elongation in Glia by Inhibiting HDAC2 and 3

BACKGROUND

Fibroblast growth factor 21, a novel regulator of glucose and lipid metabolism, has robust protective properties in neurons. However, its expression and function in glia are unknown. Valproic acid, a mood stabilizer and anticonvulsant, is a histone deacetylase inhibitor and a dynamic gene regulator. We investigated whether histone deacetylase inhibition by valproic acid and other inhibitors upregulates fibroblast growth factor 21 expression and, if so, sought to identify the histone deacetylase isoform(s) involved and their role in altering glial cell morphology.

METHODS

C6 glioma or primary cortical glial cultures were treated with histone deacetylase inhibitors, and fibroblast growth factor 21 levels and length of cell processes were subsequently measured. Histone deacetylase 1, 2, or 3 was also knocked down to detect which isoform was involved in regulating fibroblast growth factor 21 mRNA levels. Finally, knockdown and overexpression of fibroblast growth factor 21 were performed to determine whether it played a role in regulating cell process length.

RESULTS

Treatment of C6 cells or primary glial cultures with valproic acid elevated fibroblast growth factor 21 mRNA levels, extended cell process length, and markedly increased acetylated histone-H3 levels. Other histone deacetylase inhibitors including pan- and class I-specific inhibitors, or selective knockdown of histone deacetylase 2 or 3 isoform produced similar effects. Knockdown or overexpression of fibroblast growth factor 21 significantly decreased or increased C6 cell process length, respectively.

CONCLUSIONS

In glial cell line and primary glia, using pharmacological inhibition and selective gene silencing of histone deacetylases to boost fibroblast growth factor 21 mRNA levels results in elongation of cell processes. Our study provides a new mechanism via which histone deacetylase 2 and 3 participate in upregulating fibroblast growth factor 21 transcription and extending process outgrowth in glia.

Ex Vivo Culture of Chick Cerebellar Slices and Spatially Targeted Electroporation of Granule Cell Precursors

The cerebellar external granule layer (EGL) is the site of the largest transit amplification in the developing brain, and an excellent model for studying neuronal proliferation and differentiation. In addition, evolutionary modifications of its proliferative capability have been responsible for the dramatic expansion of cerebellar size in the amniotes, making the cerebellum an excellent model for evo-devo studies of the vertebrate brain. The constituent cells of the EGL, cerebellar granule progenitors, also represent a significant cell of origin for medulloblastoma, the most prevalent paediatric neuronal tumour. Following transit amplification, granule precursors migrate radially into the internal granular layer of the cerebellum where they represent the largest neuronal population in the mature mammalian brain. In chick, the peak of EGL proliferation occurs towards the end of the second week of gestation. In order to target genetic modification to this layer at the peak of proliferation, we have developed a method for genetic manipulation through ex vivo electroporation of cerebellum slices from embryonic Day 14 chick embryos. This method recapitulates several important aspects of in vivo granule neuron development and will be useful in generating a thorough understanding of cerebellar granule cell proliferation and differentiation, and thus of cerebellum development, evolution and disease.

Tangential migration of glutamatergic neurons and cortical patterning during development: Lessons from Cajal-Retzius cells

Tangential migration is a mode of cell movement, which in the developing cerebral cortex, is defined by displacement parallel to the ventricular surface and orthogonal to the radial glial fibers. This mode of long-range migration is a strategy by which distinct neuronal classes generated from spatially and molecularly distinct origins can integrate to form appropriate neural circuits within the cortical plate. While it was previously believed that only GABAergic cortical interneurons migrate tangentially from their origins in the subpallial ganglionic eminences to integrate in the cortical plate, it is now known that transient populations of glutamatergic neurons also adopt this mode of migration. These include Cajal-Retzius cells (CRs), subplate neurons (SPs), and cortical plate transient neurons (CPTs), which have crucial roles in orchestrating the radial and tangential development of the embryonic cerebral cortex in a noncell-autonomous manner. While CRs have been extensively studied, it is only in the last decade that the molecular mechanisms governing their tangential migration have begun to be elucidated. To date, the mechanisms of SPs and CPTs tangential migration remain unknown. We therefore review the known signaling pathways, which regulate parameters of CRs migration including their motility, contact-redistribution and adhesion to the pial surface, and discuss this in the context of how CR migration may regulate their signaling activity in a spatial and temporal manner. © 2015 Wiley Periodicals, Inc. Develop Neurobiol 76: 847-881, 2016.

The chemokine receptor CXCR7 influences prognosis in human glioma in an IDH1-dependent manner

Aims

The chemokine receptor CXCR7 is found on glioma cells and glioma-associated vessels and dependent upon its localisation on tumour or endothelial cells the CXCR7 receptor can mediate glioma cell invasion and tumour angiogenesis. Its expression predicts survival in several types of cancers.

Methods

We immunohistochemically studied the expression of CXCR7 and its ligand SDF1α in a cohort of 354 human patients with glioma. In an in vivo glioma model, we studied the effect of selective CXCR7 inhibition on mean vascular density.

Results

Here we show that expression of either mutant isocitrate dehydrogenase (IDH) 1 or podoplanin (PDPN), two proteins present in basically non-overlapping glioma populations, predicts the prognostic significance of CXCR7. Specifically, expression of CXCR7 on endothelial cells in IDH1 mutant cases predicted poor outcome. Surprisingly, in PDPN expressing gliomas, one of the marker genes for the recently identified mesenchymal subgroup, expression of CXCR7 predicts diminished prognosis on tumour cells and better prognosis on endothelial cells.

Conclusions

Since CXCR7 is expressed on migrating cells our data suggest that, although ubiquitously present, angiogenesis and invasion are outcome-relevant events in specific glioma subgroups, providing a potentially important tool for targeted therapy assignment.

Directed migration of embryonic stem cell-derived neural cells in an applied electric field

Spinal cord injury or diseases, such as amyotrophic lateral sclerosis, can cause the loss of motor neurons and therefore results in the paralysis of muscles. Stem cells may improve functional recovery by promoting endogenous regeneration, or by directly replacing neurons. Effective directional migration of grafted neural cells to reconstruct functional connections is crucial in the process. Steady direct current electric fields (EFs) play an important role in the development of the central nervous system. A strong biological effect of EFs is the induction of directional cell migration. In this study, we investigated the guided migration of embryonic stem cell (ESC) derived presumptive motor neurons in an applied EF. The dissociated mouse ESC derived presumptive motor neurons or embryoid bodies were subjected to EFs stimulation and the cell migration was studied. We found that the migration of neural precursors from embryoid bodies was toward cathode pole of applied EFs. Single motor neurons migrated to the cathode of the EFs and reversal of EFs poles reversed their migration direction. The directedness and displacement of cathodal migration became more significant when the field strength was increased from 50 mV/mm to 100 mV/mm. EFs stimulation did not influence the cell migration velocity. Our work suggests that EFs may serve as a guidance cue to direct grafted cell migration in vivo.

Self-organization of polarized cerebellar tissue in 3D culture of human pluripotent stem cells

During cerebellar development, the main portion of the cerebellar plate neuroepithelium gives birth to Purkinje cells and interneurons, whereas the rhombic lip, the germinal zone at its dorsal edge, generates granule cells and cerebellar nuclei neurons. However, it remains elusive how these components cooperate to form the intricate cerebellar structure. Here, we found that a polarized cerebellar structure self-organizes in 3D human embryonic stem cell (ESC) culture. The self-organized neuroepithelium differentiates into electrophysiologically functional Purkinje cells. The addition of fibroblast growth factor 19 (FGF19) promotes spontaneous generation of dorsoventrally polarized neural-tube-like structures at the level of the cerebellum. Furthermore, addition of SDF1 and FGF19 promotes the generation of a continuous cerebellar plate neuroepithelium with rhombic-lip-like structure at one end and a three-layer cytoarchitecture similar to the embryonic cerebellum. Thus, human-ESC-derived cerebellar progenitors exhibit substantial self-organizing potential for generating a polarized structure reminiscent of the early human cerebellum at the first trimester.

Development of the cerebellum: simple steps to make a 'little brain'

The cerebellum is a pre-eminent model for the study of neurogenesis and circuit assembly. Increasing interest in the cerebellum as a participant in higher cognitive processes and as a locus for a range of disorders and diseases make this simple yet elusive structure an important model in a number of fields. In recent years, our understanding of some of the more familiar aspects of cerebellar growth, such as its territorial allocation and the origin of its various cell types, has undergone major recalibration. Furthermore, owing to its stereotyped circuitry across a range of species, insights from a variety of species have contributed to an increasingly rich picture of how this system develops. Here, we review these recent advances and explore three distinct aspects of cerebellar development - allocation of the cerebellar anlage, the significance of transit amplification and the generation of neuronal diversity - each defined by distinct regulatory mechanisms and each with special significance for health and disease.

Foxc1 dependent mesenchymal signalling drives embryonic cerebellar growth

Loss of Foxc1 is associated with Dandy-Walker malformation, the most common human cerebellar malformation characterized by cerebellar hypoplasia and an enlarged posterior fossa and fourth ventricle. Although expressed in the mouse posterior fossa mesenchyme, loss of Foxc1 non-autonomously induces a rapid and devastating decrease in embryonic cerebellar ventricular zone radial glial proliferation and concurrent increase in cerebellar neuronal differentiation. Subsequent migration of cerebellar neurons is disrupted, associated with disordered radial glial morphology. In vitro, SDF1α, a direct Foxc1 target also expressed in the head mesenchyme, acts as a cerebellar radial glial mitogen and a chemoattractant for nascent Purkinje cells. Its receptor, Cxcr4, is expressed in cerebellar radial glial cells and conditional Cxcr4 ablation with Nes-Cre mimics the Foxc1-/- cerebellar phenotype. SDF1α also rescues the Foxc1-/- phenotype. Our data emphasizes that the head mesenchyme exerts a considerable influence on early embryonic brain development and its disruption contributes to neurodevelopmental disorders in humans.

Role of CXCL12 and CXCR4 in normal cerebellar development and medulloblastoma

Chemokines and its receptors have significant impact on physiological and pathological processes and studies concerning their association with tumor biology are subject of great interest in scientific community. CXCL12/CXCR4 axis has been widely studied due to its significant role in tumor microenvironment, but it is also important to development and maintenance of tissues and organs, for example, in the brain and cerebellum. Studies have demonstrated that CXCL12 and CXCR4 are required for normal cerebellar development and that dysfunction in this pathway may be involved with medulloblastoma pathogenesis. In this context, a new molecular subgroup has been suggested based on the importance of the association between CXCR4 overexpression and sonic hedgehog subgroup. Treatment using CXCR4 antagonists showed significant results, evidencing the important role and possible therapeutic capacity of CXCR4 in MB. This review summarizes studies on MB cell biology, focusing on a chemokine-receptor axis, CXCL12/CXCR4, that may have implications for treatment strategies once it can improve life expectancy and reduce neurocognitive sequelae of patients with this neoplasia.

Chemokine signaling in development and disease

Chemokines are a group of small, secreted molecules that signal through G protein-coupled receptors to promote cell survival and proliferation and to provide directional guidance to migrating cells. CXCL12 is one of the most evolutionary conserved chemokines and signals through the chemokine receptor CXCR4 to guide cell migration during embryogenesis, immune cell trafficking and cancer metastasis. Here and in the accompanying poster, we provide an overview of chemokine signaling, focusing on CXCL12, and we highlight some of the different chemokine-dependent strategies used to guide migrating cells.

A role for human brain pericytes in neuroinflammation

BACKGROUND

Brain inflammation plays a key role in neurological disease. Although much research has been conducted investigating inflammatory events in animal models, potential differences in human brain versus rodent models makes it imperative that we also study these phenomena in human cells and tissue.

METHODS

Primary human brain cell cultures were generated from biopsy tissue of patients undergoing surgery for drug-resistant epilepsy. Cells were treated with pro-inflammatory compounds IFNγ, TNFα, IL-1β, and LPS, and chemokines IP-10 and MCP-1 were measured by immunocytochemistry, western blot, and qRT-PCR. Microarray analysis was also performed on late passage cultures treated with vehicle or IFNγ and IL-1β.

RESULTS

Early passage human brain cell cultures were a mixture of microglia, astrocytes, fibroblasts and pericytes. Later passage cultures contained proliferating fibroblasts and pericytes only. Under basal culture conditions all cell types showed cytoplasmic NFκB indicating that they were in a non-activated state. Expression of IP-10 and MCP-1 were significantly increased in response to pro-inflammatory stimuli. The two chemokines were expressed in mixed cultures as well as cultures of fibroblasts and pericytes only. The expression of IP-10 and MCP-1 were regulated at the mRNA and protein level, and both were secreted into cell culture media. NFκB nuclear translocation was also detected in response to pro-inflammatory cues (except IFNγ) in all cell types. Microarray analysis of brain pericytes also revealed widespread changes in gene expression in response to the combination of IFNγ and IL-1β treatment including interleukins, chemokines, cellular adhesion molecules and much more.

CONCLUSIONS

Adult human brain cells are sensitive to cytokine challenge. As expected 'classical' brain immune cells, such as microglia and astrocytes, responded to cytokine challenge but of even more interest, brain pericytes also responded to such challenge with a rich repertoire of gene expression. Immune activation of brain pericytes may play an important role in communicating inflammatory signals to and within the brain interior and may also be involved in blood brain barrier (BBB) disruption . Targeting brain pericytes, as well as microglia and astrocytes, may provide novel opportunities for reducing brain inflammation and maintaining BBB function and brain homeostasis in human brain disease.

Characterization and expression of the CXCR1 and CXCR4 in miiuy croaker and evolutionary analysis shows the strong positive selection pressures imposed in mammal CXCR1

The innate immune system can recognize non-self, danger signals, and pathogen associated molecular patterns and provides a first line of antimicrobial host defense. Therefore, it plays an instructive role and is pretty important in vertebrates. In innate immune responses, CXCRs act as the main receptors of CXC chemokines and play a vital role in host defense and inflammation. In present study, we cloned two cDNA molecules of CXCR1 and CXCR4 in Miichthys miiuy (miiuy croaker). In these two genes, we found the most highly conserved DRY motif in the second intracellular loop adjacent to the third transmembrane domain. The expressions of CXCR1 and CXCR4 showed that they were ubiquitously expressed in ten normal tissues. After infection with Vibrio anguillarum and Vibrio harveyi, the expressions of CXCRs in the immune tissues were significantly regulated in most of tissues except that of CXCR1 in the kidney after V. harveyi injection. Evolutionary analysis showed that only the ancestral lineages of CXCR4 in amphibians underwent positive selection, indicating that the ancestors of amphibians boarded the land and had to further evolve to adapt to terrestrial environments. Multiple ML methods were implemented to detect the robust positively selected candidates for sites. In total, we detected 12 and 3 positively selected sites in the subsets of current mammal and fish CXCR1 genes, and only one site under positive selection was found in mammalian CXCR4 subsets. These positively selected sites were mainly located in the extracellular domains of CXCRs. The sliding window analysis and evolution test tended to favor positive selection acting on the N-terminal domain of CXCR1, which was the critical region for ligand/receptor signaling for neutrophils and receptor-ligand interaction, indicating that the N-terminal of CXCR1 in mammals underwent more positive selection than that of fish.

Ectopic cerebellar cell migration causes maldevelopment of Purkinje cells and abnormal motor behaviour in Cxcr4 null mice

SDF-1/CXCR4 signalling plays an important role in neuronal cell migration and brain development. However, the impact of CXCR4 deficiency in the postnatal mouse brain is still poorly understood. Here, we demonstrate the importance of CXCR4 on cerebellar development and motor behaviour by conditional inactivation of Cxcr4 in the central nervous system. We found CXCR4 plays a key role in cerebellar development. Its loss leads to defects in Purkinje cell dentritogenesis and axonal projection in vivo but not in cell culture. Transcriptome analysis revealed the most significantly affected pathways in the Cxcr4 deficient developing cerebellum are involved in extra cellular matrix receptor interactions and focal adhesion. Consistent with functional impairment of the cerebellum, Cxcr4 knockout mice have poor coordination and balance performance in skilled motor tests. Together, these results suggest ectopic the migration of granule cells impairs development of Purkinje cells, causes gross cerebellar anatomical disruption and leads to behavioural motor defects in Cxcr4 null mice.

Biomarkers in autism

Autism spectrum disorders (ASDs) are complex, heterogeneous disorders caused by an interaction between genetic vulnerability and environmental factors. In an effort to better target the underlying roots of ASD for diagnosis and treatment, efforts to identify reliable biomarkers in genetics, neuroimaging, gene expression, and measures of the body's metabolism are growing. For this article, we review the published studies of potential biomarkers in autism and conclude that while there is increasing promise of finding biomarkers that can help us target treatment, there are none with enough evidence to support routine clinical use unless medical illness is suspected. Promising biomarkers include those for mitochondrial function, oxidative stress, and immune function. Genetic clusters are also suggesting the potential for useful biomarkers.

Cxcl12/Cxcr4 signaling controls the migration and process orientation of A9-A10 dopaminergic neurons

CXCL12/CXCR4 signaling has been reported to regulate three essential processes for the establishment of neural networks in different neuronal systems: neuronal migration, cell positioning and axon wiring. However, it is not known whether it regulates the development of A9-A10 tyrosine hydroxylase positive (TH(+)) midbrain dopaminergic (mDA) neurons. We report here that Cxcl12 is expressed in the meninges surrounding the ventral midbrain (VM), whereas CXCR4 is present in NURR1(+) mDA precursors and mDA neurons from E10.5 to E14.5. CXCR4 is activated in NURR1(+) cells as they migrate towards the meninges. Accordingly, VM meninges and CXCL12 promoted migration and neuritogenesis of TH(+) cells in VM explants in a CXCR4-dependent manner. Moreover, in vivo electroporation of Cxcl12 at E12.5 in the basal plate resulted in lateral migration, whereas expression in the midline resulted in retention of TH(+) cells in the IZ close to the midline. Analysis of Cxcr4(-/-) mice revealed the presence of VM TH(+) cells with disoriented processes in the intermediate zone (IZ) at E11.5 and marginal zone (MZ) at E14. Consistently, pharmacological blockade of CXCR4 or genetic deletion of Cxcr4 resulted in an accumulation of TH(+) cells in the lateral aspect of the IZ at E14, indicating that CXCR4 is required for the radial migration of mDA neurons in vivo. Altogether, our findings demonstrate that CXCL12/CXCR4 regulates the migration and orientation of processes in A9-A10 mDA neurons.

Autism spectrum disorder in children born preterm-role of exposure to perinatal inflammation

Autism Spectrum Disorder (ASD) is the collective term for neurodevelopmental disorders characterized by qualitative impairments in social interaction, communication, and a restricted range of activities and interests. Many countries, including Australia, have reported a dramatic increase in the number of diagnoses over the past three decades, with current prevalence of ASD at 1 in every 110 individuals (~1%). The potential role for an immune-mediated mechanism in ASD has been implicated by several studies, and some evidence suggests a potential link between prenatal infection-driven inflammation and subsequent development of ASD. Furthermore, a modest number of contemporary studies have reported a markedly increased prevalence of ASD in children born preterm, who are at highest risk of exposure to perinatal inflammation. However, the mechanisms that underpin the susceptibility to infection-driven inflammation during pregnancy and risk of preterm birth, and how these intersect with the subsequent development of ASD in the offspring, is not understood. This review aims to summarize and discuss the potential mechanisms and evidence for the role of prenatal infection on the central nervous system, and how it may increase the susceptibility for ASD pathogenesis in children born preterm.

CXCR4 signaling regulates radial glial morphology and cell fate during embryonic spinal cord development

Embryonic meninges secrete the chemokine SDF-1/CXCL12 as a chemotactic guide for migrating neural stem cells, but SDF-1 is not known to directly regulate the functions of radial glia. Recently, the developing meninges have been shown to regulate radial glial function, yet the mechanisms and signals responsible for this phenomenon remain unclear. Moreover, as a nonmigratory cell type, radial glia do not conform to traditional models associated with chemokine signaling in the central nervous system. Using fluorescent transgenes, in vivo genetic manipulations and pharmacological techniques, we demonstrate that SDF-1 derived from the meninges exerts a CXCR4-dependent effect on radial glia. Deletion of CXCR4 expression by radial glia influences their morphology, mitosis, and progression through both oligodendroglial and astroglial lineages. Additionally, disruption of CXCR4 signaling in radial glia has a transient effect on the migration of oligodendrocyte progenitors. These data indicate that a specific chemokine signal derived from the meninges has multiple regulatory effects on radial glia.

hebp3, a novel member of the heme-binding protein gene family, is expressed in the medaka meninges with higher abundance in females due to a direct stimulating action of ovarian estrogens

The brains of teleost fish exhibit remarkable sexual plasticity throughout their life span. To dissect the molecular basis for the development and reversal of sex differences in the teleost brain, we screened for genes differentially expressed between sexes in the brain of medaka (Oryzias latipes). One of the genes identified in the screen as being preferentially expressed in females was found to be a new member of the heme-binding protein gene family that includes hebp1 and hebp2 and was designated here as hebp3. The medaka hebp3 is expressed in the meninges with higher abundance in females, whereas there is no expression within the brain parenchyma. This female-biased expression of hebp3 is not attributable to the direct action of sex chromosome genes but results from the transient and reversible action of estrogens derived from the ovary. Moreover, estrogens directly activate the transcription of hebp3 via a palindromic estrogen-responsive element in the hebp3 promoter. Taken together, our findings demonstrate that hebp3 is a novel transcriptional target of estrogens, with female-biased expression in the meninges. The definite but reversible sexual dimorphism of the meningeal hebp3 expression may contribute to the development and reversal of sex differences in the teleost brain.

Increased susceptibility to severe chronic liver damage in CXCR4 conditional knock-out mice

BACKGROUND

The chemokine SDF-1 and its receptor CXCR4 are essential for the proper functioning of multiple organs. In the liver, cholangiocytes and hepatic progenitor cells (HPCs) are the main cells that produce SDF-1, and SDF-1 is thought to be essential for HPC-stimulated liver regeneration.

AIMS

In this study, CXCR4 conditionally targeted mice were used to analyze the role of SDF-1 in chronically damaged liver.

METHODS

Chronic liver damage was induced in MxCre CXCR4(f/null) mice and the control MxCre CXCR4(f/wt) mice by CCl(4). Serum markers were analyzed to assess liver function and damage, the number of cytokeratin-positive cells as a measure of HPCs, and the extent of liver fibrosis. Additional parameters relating to liver damage, such as markers of HPCs, liver function, MMPs, and TIMPs were measured by real-time PCR.

RESULTS

Serum ALT was significantly higher in MxCre CXCR4(f/null) mice than MxCre CXCR4(f/wt) mice. The number of cytokeratin-positive cells and the area of fibrosis were also increased in the MxCre CXCR4(f/null) mice. The expression of mRNAs for several markers related to hepatic damage and regeneration was also increased in the liver of MxCre CXCR4(f/null) mice, including primitive HPC marker prominin-1, MMP9, TNF-α, and α-SMA.

CONCLUSIONS

MxCre CXCR4(f/null) mice were susceptible to severe chronic liver damage, suggesting that SDF-1-CXCR4 signals are important for liver regeneration and preventing the progression of liver disease. Modulation of SDF-1 may therefore be a promising treatment strategy for patients with chronic liver disease.

CXCR7 mediates SDF1-induced melanocyte migration

Melanoblasts are derived from the neural crest and migrate to the dermal/epidermal border of skin and hair bulges. Although melanoblast migration during embryogenesis has been well investigated, there are only a few reports regarding the migration of mature melanocytes. Here, we demonstrate that a chemokine, stromal-derived factor-1 (SDF1, also known as CXCL12), and one of its receptor CXCR7 regulate normal human epidermal melanocyte (NHEM) migration. We found that SDF1 induces the directional migration of NHEMs. Interestingly, although both CXCR4 and CXCR7 are expressed in NHEMs, blockade of CXCR4 using a CXCR4-specific neutralizing antibody did not exert any influence on the SDF1-induced migration of NHEMs, whereas blockade of CXCR7 using a CXCR7-specific neutralizing antibody did influence migration. Furthermore, SDF1-induced NHEMs migration exhibited the early hallmark events of CXCR7 signaling associated with MAP kinase activation. It is known that the phosphorylation of ERK through CXCR7 signaling is mediated by β-arrestins. The treatment of NHEMs with SDF1 resulted in the phosphorylation of ERK in a β-arrestin 2-dependent manner. These results suggest that melanocytes may have a unique mechanism of migration via SDF1/CXCR7 signaling that is different from that of other cell types.

Chemokine CXCL12 and its receptors in the developing central nervous system: emerging themes and future perspectives

Homeostatic chemokine CXCL12 (also known as SDF-1) and its receptor CXCR4 are indispensable for the normal development of the nervous system. This chemokine system plays a plethora of functions in numerous neural developmental processes, from which the underlying molecular and cellular mechanisms are beginning to be unravelled. Recent identification of CXCR7 as a second receptor for CXCL12 provides opportunities to gain deeper insights into how CXCL12 operates in the nervous system. Here, we review the diverse roles of CXCL12 in the developing central nervous system, summarize the recent progress in uncovering CXCR7 functions, and discuss the emerging common themes from these works and future perspectives.

The immune system and developmental programming of brain and behavior

The brain, endocrine, and immune systems are inextricably linked. Immune molecules have a powerful impact on neuroendocrine function, including hormone-behavior interactions, during health as well as sickness. Similarly, alterations in hormones, such as during stress, can powerfully impact immune function or reactivity. These functional shifts are evolved, adaptive responses that organize changes in behavior and mobilize immune resources, but can also lead to pathology or exacerbate disease if prolonged or exaggerated. The developing brain in particular is exquisitely sensitive to both endogenous and exogenous signals, and increasing evidence suggests the immune system has a critical role in brain development and associated behavioral outcomes for the life of the individual. Indeed, there are associations between many neuropsychiatric disorders and immune dysfunction, with a distinct etiology in neurodevelopment. The goal of this review is to describe the important role of the immune system during brain development, and to discuss some of the many ways in which immune activation during early brain development can affect the later-life outcomes of neural function, immune function, mood and cognition.