Ependymal Cell Differentiation Research Articles

Heterozygous FOXJ1 Mutations Cause Incomplete Ependymal Cell Differentiation and Communicating Hydrocephalus

Heterozygous mutations affecting FOXJ1, a transcription factor governing multiciliated cell development, have been associated with obstructive hydrocephalus in humans. However, factors that disrupt multiciliated ependymal cell function often cause communicating hydrocephalus, raising questions about whether FOXJ1 mutations cause hydrocephalus primarily by blocking cerebrospinal fluid (CSF) flow or by different mechanisms. Here, we show that heterozygous FOXJ1 mutations are also associated with communicating hydrocephalus in humans and cause communicating hydrocephalus in mice. Disruption of one Foxj1 allele in mice leads to incomplete ependymal cell differentiation and communicating hydrocephalus. Mature ependymal cell number and motile cilia number are decreased, and 12% of motile cilia display abnormal axonemes. We observed decreased microtubule attachment to basal bodies, random localization and orientation of basal body patches, loss of planar cell polarity, and a disruption of unidirectional CSF flow. Thus, heterozygous FOXJ1 mutations impair ventricular multiciliated cell differentiation, thereby causing communicating hydrocephalus. CSF flow obstruction may develop secondarily in some patients harboring FOXJ1 mutations.Graphical Heterozygous FOXJ1 mutations impair motile cilia structure and basal body alignment, thereby disrupting CSF flow dynamics and causing communicating hydrocephalus.

Ependyma in Neurodegenerative Diseases, Radiation-Induced Brain Injury and as a Therapeutic Target for Neurotrophic Factors.

The neuron loss caused by the progressive damage to the nervous system is proposed to be the main pathogenesis of neurodegenerative diseases. Ependyma is a layer of ciliated ependymal cells that participates in the formation of the brain-cerebrospinal fluid barrier (BCB). It functions to promotes the circulation of cerebrospinal fluid (CSF) and the material exchange between CSF and brain interstitial fluid. Radiation-induced brain injury (RIBI) shows obvious impairments of the blood-brain barrier (BBB). In the neuroinflammatory processes after acute brain injury, a large amount of complement proteins and infiltrated immune cells are circulated in the CSF to resist brain damage and promote substance exchange through the BCB. However, as the protective barrier lining the brain ventricles, the ependyma is extremely vulnerable to cytotoxic and cytolytic immune responses. When the ependyma is damaged, the integrity of BCB is destroyed, and the CSF flow and material exchange is affected, leading to brain microenvironment imbalance, which plays a vital role in the pathogenesis of neurodegenerative diseases. Epidermal growth factor (EGF) and other neurotrophic factors promote the differentiation and maturation of ependymal cells to maintain the integrity of the ependyma and the activity of ependymal cilia, and may have therapeutic potential in restoring the homeostasis of the brain microenvironment after RIBI or during the pathogenesis of neurodegenerative diseases.

P53/p21 pathway activation contributes to the ependymal fate decision downstream of GemC1

Multiciliated ependymal cells and adult neural stem cells are components of the adult neurogenic niche, essential for brain homeostasis. These cells share a common glial cell lineage regulated by the Geminin family members Geminin and GemC1/Mcidas. Ependymal precursors require GemC1/Mcidas expression to massively amplify centrioles and become multiciliated cells. Here, we show that GemC1-dependent differentiation is initiated in actively cycling radial glial cells, in which a DNA damage response, including DNA replication-associated damage and dysfunctional telomeres, is induced, without affecting cell survival. Genotoxic stress is not sufficient by itself to induce ependymal cell differentiation, although the absence of p53 or p21 in progenitors hinders differentiation by maintaining cell division. Activation of the p53-p21 pathway downstream of GemC1 leads to cell-cycle slowdown/arrest, which permits timely onset of ependymal cell differentiation in progenitor cells.

Loss of RNA-Binding Protein HuR Leads to Defective Ependymal Cells and Hydrocephalus.

Multiciliated ependymal cells line the ventricle wall and generate CSF flow through ciliary beating. Defects in ependymal cells cause hydrocephalus; however, there are still significant gaps in our understanding the molecular, cellular and developmental mechanisms involved in the pathogenesis of hydrocephalus. Here, we demonstrate that specific deletion of RNA-binding protein (RBP) Hu antigen R (HuR) in the mouse brain results in hydrocephalus and causes postnatal death. HuR deficiency leads to impaired ependymal cell development with defective motile ciliogenesis in both female and male mice. Transcriptome-wide analysis reveals that HuR binds to mRNA transcripts related to ciliogenesis, including cilia and flagella associated protein 52 (Cfap52), the effector gene of Foxj-1 and Rfx transcriptional factors. HuR deficiency accelerates the degradation of Cfap52 mRNA, while overexpression of Cfap52 is able to promote the development of HuR-deficient ependymal cells. Taken together, our results unravel the important role of HuR in posttranscriptional regulation of ependymal cell development by stabilizing Cfap52 mRNA.SIGNIFICANCE STATEMENT This study identifies Hu antigen R (HuR) as a genetic factor involved in the pathogenesis of hydrocephalus. Mechanistically, HuR regulates ependymal cell differentiation and ciliogenesis through stabilizing Cfap52 mRNA, the effector gene of Foxj-1 and Rfx transcriptional factors.

IIIG9 inhibition in adult ependymal cells changes adherens junctions structure and induces cellular detachment

Ependymal cells have multiple apical cilia that line the ventricular surfaces and the central canal of spinal cord. In cancer, the loss of ependymal cell polarity promotes the formation of different types of tumors, such as supratentorial anaplastic ependymomas, which are highly aggressive in children. IIIG9 (PPP1R32) is a protein restricted to adult ependymal cells located in cilia and in the apical cytoplasm and has unknown function. In this work, we studied the expression and localization of IIIG9 in the adherens junctions (cadherin/β-catenin-positive junctions) of adult brain ependymal cells using confocal and transmission electron microscopy. Through in vivo loss-of-function studies, ependymal denudation (single-dose injection experiments of inhibitory adenovirus) was observed, inducing the formation of ependymal cells with a “balloon-like” morphology. These cells had reduced cadherin expression (and/or delocalization) and cleavage of the cell death marker caspase-3, with “cilia rigidity” morphology (probably vibrational beating activity) and ventriculomegaly occurring prior to these events. Finally, after performing continuous infusions of adenovirus for 14 days, we observed total cell denudation and reactive parenchymal astrogliosis. Our data confirmed that IIIG9 is essential for the maintenance of adherens junctions of polarized ependymal cells. Eventually, altered levels of this protein in ependymal cell differentiation may increase ventricular pathologies, such as hydrocephalus or neoplastic transformation.

High mobility group box 1 promotes the differentiation of spinal ependymal cells into astrocytes rather than neurons.

Spinal ependymal cells are involved in proliferation, differentiation and migration after spinal cord injury (SCI) and represent an endogenous source of repair cells for treating SCI. However, 95% of activated ependymal cells eventually differentiate into astrocytes after SCI and ultimately contribute more than half of the new astrocytes that form glial scars in vivo. The factors that regulate the fate of ependymal cells after SCI remain unclear. High mobility group box 1 (HMGB1) is regarded as an important proinflammatory factor in nerve injury, and recent studies have shown that HMGB1 can regulate the fate of stem cells after injury. In this study, we investigated whether HMGB1 released from reactive astrocytes after SCI regulates the proliferation and differentiation of ependymal cells in vitro. Ependymal cells extracted and cultured from the spinal cord of mice were separately treated with astrocyte culture medium (ACM), IL-1β, ACM (IL-1β) and the HMGB1 protein, and the proliferation and differentiation of ependymal cells were detected. Additionally, an HMGB1-neutralizing antibody (anti-HMGB1) was added to further verify the regulatory effect of HMGB1 on ependymal cells. The results showed that HMGB1 released from reactive astrocytes promoted ependymal cell differentiation into astrocytes and inhibited ependymal cell differentiation into neurons in vitro; however, the effect disappeared after the addition of anti-HMGB1. HMGB1 had no significant effect on ependymal cell proliferation. Our findings demonstrate that HMGB1 can regulate the differentiation of ependymal cells after SCI. These results provide a new strategy for the treatment of SCI.

BMP signaling suppresses Gemc1 expression and ependymal differentiation of mouse telencephalic progenitors

The lateral ventricles of the adult mammalian brain are lined by a single layer of multiciliated ependymal cells, which generate a flow of cerebrospinal fluid through directional beating of their cilia as well as regulate neurogenesis through interaction with adult neural stem cells. Ependymal cells are derived from a subset of embryonic neural stem-progenitor cells (NPCs, also known as radial glial cells) that becomes postmitotic during the late embryonic stage of development. Members of the Geminin family of transcriptional regulators including GemC1 and Mcidas play key roles in the differentiation of ependymal cells, but it remains largely unclear what extracellular signals regulate these factors and ependymal differentiation during embryonic and early-postnatal development. We now show that the levels of Smad1/5/8 phosphorylation and Id1/4 protein expression—both of which are downstream events of bone morphogenetic protein (BMP) signaling—decline in cells of the ventricular-subventricular zone in the mouse lateral ganglionic eminence in association with ependymal differentiation. Exposure of postnatal NPC cultures to BMP ligands or to a BMP receptor inhibitor suppressed and promoted the emergence of multiciliated ependymal cells, respectively. Moreover, treatment of embryonic NPC cultures with BMP ligands reduced the expression level of the ependymal marker Foxj1 and suppressed the emergence of ependymal-like cells. Finally, BMP ligands reduced the expression levels of Gemc1 and Mcidas in postnatal NPC cultures, whereas the BMP receptor inhibitor increased them. Our results thus implicate BMP signaling in suppression of ependymal differentiation from NPCs through regulation of Gemc1 and Mcidas expression during embryonic and early-postnatal stages of mouse telencephalic development.

Alternatively Polarized Macrophages Regulate the Growth and Differentiation of Ependymal Stem Cells through the SIRT2 Pathway.

Ependymal stem cells (EpSCs) are dormant stem cells in the adult spinal cord that proliferate rapidly and migrate to the site of injury after spinal cord injury (SCI). Although they can differentiate into neurons under appropriate conditions in vitro, EpSCs mainly differentiate into astrocytes in vivo. Our previous study confirmed that alternatively polarized macrophages (M2) facilitate the differentiation of EpSCs towards neurons, but the detailed mechanism remains elusive. In the present study, we found that M2 conditioned medium could upregulate the expression of Sirtuin 2 (SIRT2) in EpSCs in vitro through the BDNF/TrkB-MEK/ERK signaling pathway. As an important deacetylase, SIRT2 deacetylated stable Ac-α-tubulin (Acetyl alpha Tubulin) in microtubules and thus promoted EpSC differentiation into neurons. The present study provides a theoretical basis and a new way to improve neural recovery, such as regulating the growth and differentiation of EpSCs by increasing the proportion of M2 cells in the local microenvironment or upregulating the expression of SIRT2 in EpSCs.

Ependymal Vps35 Promotes Ependymal Cell Differentiation and Survival, Suppresses Microglial Activation, and Prevents Neonatal Hydrocephalus.

Hydrocephalus is a pathologic condition associated with various brain diseases, including Alzheimer's disease (AD). Dysfunctional ependymal cells (EpCs) are believed to contribute to the development of hydrocephalus. It is thus of interest to investigate EpCs' development and function. Here, we report that vacuolar protein sorting-associated protein 35 (VPS35) is critical for EpC differentiation, ciliogenesis, and survival, and thus preventing neonatal hydrocephalus. VPS35 is abundantly expressed in EpCs. Mice with conditional knock-out (cKO) of Vps35 in embryonic (Vps35GFAP-Cre and Vps35Emx1-Cre) or postnatal (Vps35Foxj1-CreER) EpC progenitors exhibit enlarged lateral ventricles (LVs) and hydrocephalus-like pathology. Further studies reveal marked reductions in EpCs and their cilia in both Vps35GFAP-Cre and Vps35Foxj1-CreER mutant mice. The reduced EpCs appear to be due to impairments in EpC differentiation and survival. Additionally, both Vps35GFAP-Cre and Vps35Foxj1-CreER neonatal pups exhibit increased cell proliferation and death largely in a region close to LV-EpCs. Many microglia close to the mutant LV-EpC region become activated. Depletion of the microglia by PLX3397, an antagonist of colony-stimulating factor 1 receptor (CSF1R), restores LV-EpCs and diminishes the pathology of neonatal hydrocephalus in Vps35Foxj1-CreER mice. Taken together, these observations suggest unrecognized functions of Vps35 in EpC differentiation, ciliogenesis, and survival in neonatal LV, and reveal pathologic roles of locally activated microglia in EpC homeostasis and hydrocephalus development.SIGNIFICANCE STATEMENT This study reports critical functions of vacuolar protein sorting-associated protein 35 (VPS35) not only in promoting ependymal cell (EpC) differentiation, ciliogenesis, and survival, but also in preventing local microglial activation. The dysfunctional EpCs and activated microglia are likely to induce hydrocephalus.

Bone Morphogenetic Proteins Inhibit Ciliogenesis of Ependymal Cells in Vitro.

Ependymal cells have an essential role in regulating the dynamics of the cerebrospinal fluid flow by the movement of their multiple cilia. Impaired generation or function of cilia could cause hydrocephalus due to the disordered dynamics of the cerebrospinal fluid flow. However, molecular bases regulating differentiation of the ependymal cells and their ciliogenesis have not been fully elucidated. We report here that bone morphogenetic proteins (BMPs), growth factors orchestrating tissue architecture throughout the body, inhibit ciliogenesis during ependymal cell differentiation in primary cell culture. Previous in vitro study has reported that ectopic expression of Smad6 and Smad7 promotes differentiation of embryonic stem cells into multi-ciliated ependymal-like cells. Since Smad6 and Smad7 have been known as the intracellular inhibitory factors of the BMP signaling pathway, the activation of the pathway could cause a deficit in ciliogenesis of ependymal cells. To examine whether activation of the pathway affects ciliogenesis, we investigated the effects of two BMPs, BMP2 and BMP4, on the ependymal differentiation of the primary cultured cells prepared from the neonatal mouse brain. Supplementation of BMP2 or BMP4 in culture media significantly reduced the number of cells with multiple cilia among the total cells, while most of the cells expressed FoxJ1, a master regulator of ciliogenesis. Activation of the pathway was confirmed by the phosphorylation of intracellular Smad1/5/8, downstream factors of the BMP receptors. These in vitro results suggest that inhibition of the BMP signaling pathway might be essential for ciliogenesis during the ependymal cell differentiation in vivo.

GemC1 is a critical switch for neural stem cell generation in the postnatal brain.

The subventricular zone (SVZ) is one of two main niches where neurogenesis persists during adulthood, as it retains neural stem cells (NSCs) with self-renewal capacity and multi-lineage potency. Another critical cellular component of the niche is the population of postmitotic multiciliated ependymal cells. Both cell types are derived from radial glial cells that become specified to each lineage during embryogenesis. We show here that GemC1, encoding Geminin coiled-coil domain-containing protein 1, is associated with congenital hydrocephalus in humans and mice. Our results show that GemC1 deficiency drives cells toward a NSC phenotype, at the expense of multiciliated ependymal cell generation. The increased number of NSCs is accompanied by increased levels of proliferation and neurogenesis in the postnatal SVZ. Finally, GemC1-knockout cells display altered chromatin organization at multiple loci, further supporting a NSC identity. Together, these findings suggest that GemC1 regulates the balance between NSC generation and ependymal cell differentiation, with implications for the pathogenesis of human congenital hydrocephalus.

Effect of Differently Polarized Macrophages on Proliferation and Differentiation of Ependymal Cells from Adult Spinal Cord.

Ependymal cells (EpCs) are a kind of multi-potent stem cells in the central canal of adult spinal cord, which proliferate following spinal cord injury (SCI). Although they can differentiate into functional neurons in vitro, EpC progeny differentiate mainly into astrocytes after SCI, and the mechanism remains unclear. The present study aimed to explore whether neuroinflammation induced by classically activated macrophages (M1) or alternatively activated macrophages (M2) had an effect on EpC proliferation and/or differentiation. EpCs were isolated from intact spinal cord of adult mice and co-cultured with M1 or M2, respectively, in vitro. EpC proliferation was detected using a Cell Counting Kit-8 (CCK8) assay and Ki67 staining. Expression of Sox2 (SRY-box 2) in EpCs derived from different groups was detected by immunofluorescence and western blotting. Also explored was whether the mitogen activated protein kinase (MAPK) signaling pathway was involved in EpC proliferation. Immunofluorescence staining of βIII-tubulin and MAP2 were performed to assess the differentiation direction of EpCs in different culture conditions. Immunofluorescence and western blotting assays showed much more Sox2-positive EpCs in the group EpCs-M1 than the group EpCs-M2 in vitro (p < 0.01). The percentage of EpCs with positive Sox2 staining was decreased after tumor necrosis factor α (TNFα) antibody was added into the medium of EpCs-M1. Correspondingly, fewer Sox2-positive staining cells were observed in the central canal of TNFα-deficient mice with SCI. M1 co-culture promoted EpC proliferation significantly, which could be downregulated by Sox2 gene silencing (p < 0.01). Interestingly, M1 regulated the expression of Sox2 through the MAPK signaling pathway, especially the activation of ERK and p38 kinase. Co-culture in M2 conditioned medium obviously increased the proportion of βIII-tubulin-positive cells (p < 0.01). Small amounts of MAP2-positive neurons could be detected on day 7 in the M2 group and the control group. M1 conditioned medium could promote EpC proliferation in response to SCI through the TNFα-MAPK-Sox2 signaling pathway; M2 conditioned medium favors EpCs differentiating toward neurons.

The mouse Jhy gene regulates ependymal cell differentiation and ciliogenesis.

During the first postnatal week of mouse development, radial glial cells lining the ventricles of the brain differentiate into ependymal cells, undergoing a morphological change from pseudostratified cuboidal cells to a flattened monolayer. Concomitant with this change, multiple motile cilia are generated and aligned on each nascent ependymal cell. Proper ependymal cell development is crucial to forming the brain tissue:CSF barrier, and to the establishment of ciliary CSF flow, but the mechanisms that regulate this differentiation event are poorly understood. The JhylacZ mouse line carries an insertional mutation in the Jhy gene (formerly 4931429I11Rik), and homozygous JhylacZ/lacZ mice develop a rapidly progressive juvenile hydrocephalus, with defects in ependymal cilia morphology and ultrastructure. Here we show that beyond just defective motile cilia, JhylacZ/lacZ mice display abnormal ependymal cell differentiation. Ventricular ependyma in JhylacZ/lacZ mice retain an unorganized and multi-layered morphology, representative of undifferentiated ependymal (radial glial) cells, and they show altered expression of differentiation markers. Most JhylacZ/lacZ ependymal cells do eventually acquire some differentiated ependymal characteristics, suggesting a delay, rather than a block, in the differentiation process, but ciliogenesis remains perturbed. JhylacZ/lacZ ependymal cells also manifest disruptions in adherens junction formation, with altered N-cadherin localization, and have defects in the polarized organization of the apical motile cilia that do form. Functional studies showed that cilia of JhylacZ/lacZ mice have severely reduced motility, a potential cause for the development of hydrocephalus. This work shows that JHY does not only control ciliogenesis, but is a crucial component of the ependymal differentiation process, with ciliary defects likely a consequence of altered ependymal differentiation.

Prdm16 is required for the maintenance of neural stem cells in the postnatal forebrain and their differentiation into ependymal cells.

We and others showed previously that PR domain-containing 16 (Prdm16) is a transcriptional regulator required for stem cell function in multiple fetal and neonatal tissues, including the nervous system. However, Prdm16 germline knockout mice died neonatally, preventing us from testing whether Prdm16 is also required for adult stem cell function. Here we demonstrate that Prdm16 is required for neural stem cell maintenance and neurogenesis in the adult lateral ventricle subventricular zone and dentate gyrus. We also discovered that Prdm16 is required for the formation of ciliated ependymal cells in the lateral ventricle. Conditional Prdm16 deletion during fetal development using Nestin-Cre prevented the formation of ependymal cells, disrupting cerebrospinal fluid flow and causing hydrocephalus. Postnatal Prdm16 deletion using Nestin-CreERT2 did not cause hydrocephalus or prevent the formation of ciliated ependymal cells but caused defects in their differentiation. Prdm16 was required in neural stem/progenitor cells for the expression of Foxj1, a transcription factor that promotes ependymal cell differentiation. These studies show that Prdm16 is required for adult neural stem cell maintenance and neurogenesis as well as the formation of ependymal cells.

Expression of a Novel Ciliary Protein, IIIG9, During the Differentiation and Maturation of Ependymal Cells.

IIIG9 is the regulatory subunit 32 of protein phosphatase 1 (PPP1R32), a key phosphatase in the regulation of ciliary movement. IIIG9 localization is restricted to cilia in the trachea, fallopian tube, and testicle, suggesting its involvement in the polarization of ciliary epithelium. In the adult brain, IIIG9 mRNA has only been detected in ciliated ependymal cells that cover the ventricular walls. In this work, we prepared a polyclonal antibody against rat IIIG9 and used this antibody to show for the first time the ciliary localization of this protein in adult ependymal cells. We demonstrated IIIG9 localization at the apical border of the ventricular wall of 17-day-old embryonic (E17) and 1-day-old postnatal (PN1) brains and at the level of ependymal cilia at 10- and 20-day-old postnatal (PN10-20) using temporospatial distribution analysis and comparing the localization with a ciliary marker. Spectral confocal and super-resolution Structured Illumination Microscopy (SIM) analysis allowed us to demonstrate that IIIG9 shows a punctate pattern that is preferentially located at the borders of ependymal cilia in situ and in cultures of ependymocytes obtained from adult rat brains. Finally, by immunogold ultrastructural analysis, we showed that IIIG9 is preferentially located between the axoneme and the ciliary membrane. Taken together, our data allow us to conclude that IIIG9 is localized in the cilia of adult ependymal cells and that its expression is correlated with the process of ependymal differentiation and with the maturation of radial glia. Similarly, its particular localization within ependymal cilia suggests a role of this protein in the regulation of ciliary movement.

How a radial glial cell decides to become a multiciliated ependymal cell.

The V-SVZ adult neurogenic niche is located in the wall of the lateral ventricles and contains neural stem cells, with self-renewing and differentiating ability and postmitotic multiciliated ependymal cells, an important structural and trophic component of the niche. The niche is established at postnatal stages from a subpopulation of radial glial cells, determined during embryogenesis. Radial glial cells constitute a heterogeneous population, which give rise, in addition to niche cellular components, to neurons and glial cells. The mechanisms that direct their fate commitment towards V-SVZ niche cells are largely unknown. In the present review, we discuss recent findings on the signaling networks governing fate commitment decisions of radial glial cells towards multiciliated ependymal cells. We highlight the role of two novel factors: McIdas and GemC1/Lynkeas and the molecular pathways which they activate in order to promote ependymal cell differentiation. Finally, we discuss a possible crosstalk of known signaling pathways, such as Notch, STAT3, and BMPs, for the specification of ependymal versus adult neural stem cells in the V-SVZ niche. GLIA 2017;65:1032-1042.

SNX27 Deletion Causes Hydrocephalus by Impairing Ependymal Cell Differentiation and Ciliogenesis.

Down's syndrome (DS) in humans and mouse models has been shown previously to confer a high risk for the development of pathological hydrocephalus. Because we have previously described SNX27 as a component that is consistently downregulated in DS, we present here a robust Snx27-deleted mouse model that produces hydrocephalus and associated ciliary defects with complete penetrance. In addition, we find that γ-secretase/Notch modulation may be a candidate drug target in SNX27-associated hydrocephalus such as that observed in DS. Based on these findings, we anticipate that future study will determine whether modulation of a SNX27/Notch/γ-secretase pathway can also be of therapeutic interest to congenital hydrocephalus.

Endogenous neurogenesis in adult mammals after spinal cord injury.

During the whole life cycle of mammals, new neurons are constantly regenerated in the subgranular zone of the dentate gyrus and in the subventricular zone of the lateral ventricles. Thanks to emerging methodologies, great progress has been made in the characterization of spinal cord endogenous neural stem cells (ependymal cells) and identification of their role in adult spinal cord development. As recently evidenced, both the intrinsic and extrinsic molecular mechanisms of ependymal cells control the sequential steps of the adult spinal cord neurogenesis. This review introduces the concept of adult endogenous neurogenesis, the reaction of ependymal cells after adult spinal cord injury (SCI), the heterogeneity and markers of ependymal cells, the factors that regulate ependymal cells, and the niches that impact the activation or differentiation of ependymal cells.

Dystroglycan Suppresses Notch to Regulate Stem Cell Niche Structure and Function in the Developing Postnatal Subventricular Zone

While the extracellular matrix (ECM) is known to regulate neural stem cell quiescence in the adult subventricular zone (SVZ), the function of ECM in the developing SVZ remains unknown. Here, we report that the ECM receptor dystroglycan regulates a unique developmental restructuring of ECM in the early postnatal SVZ. Dystroglycan is furthermore required for ependymal cell differentiation and assembly of niche pinwheel structures, at least in part by suppressing Notch activation in radial glial cells, which leads to the increased expression of MCI, Myb, and FoxJ1, transcriptional regulators necessary for acquisition of the multiciliated phenotype. Dystroglycan also regulates perinatal radial glial cell proliferation and transition into intermediate gliogenic progenitors, such that either acute or constitutive loss of function in dystroglycan results in increased oligodendrogenesis. These findings reveal a role for dystroglycan in orchestrating both the assembly and function of the SVZ neural stem cell niche.

In Vivo Expression of the PTB-deleted Odin Mutant Results in Hydrocephalus.

Odin has been implicated in the downstream signaling pathway of receptor tyrosine kinases, such as the epidermal growth factor and Eph receptors. However, the physiologically relevant function of Odin needs to be further determined. In this study, we used Odin heterozygous mice to analyze the Odin expression pattern; the targeted allele contained a β-geo gene trap vector inserted into the 14th intron of the Odin gene. Interestingly, we found that Odin was exclusively expressed in ependymal cells along the brain ventricles. In particular, Odin was highly expressed in the subcommissural organ, a small ependymal glandular tissue. However, we did not observe any morphological abnormalities in the brain ventricles or ependymal cells of Odin null-mutant mice. We also generated BAC transgenic mice that expressed the PTB-deleted Odin (dPTB) after a floxed GFP-STOP cassette was excised by tissue-specific Cre expression. Strikingly, Odin-dPTB expression played a causative role in the development of the hydrocephalic phenotype, primarily in the midbrain. In addition, Odin-dPTB expression disrupted proper development of the subcommissural organ and interfered with ependymal cell maturation in the cerebral aqueduct. Taken together, our findings strongly suggest that Odin plays a role in the differentiation of ependymal cells during early postnatal brain development.