Distribution of a reeler gene-related antigen in the developing cerebellum: an immunohistochemical study with an allogeneic antibody CR-50 on normal and reeler mice.

Molecular Neurobiology Laboratory, Tsukuba Life Science Center, Institute of Physical and Chemical Research (RIKEN), Ibaraki, Japan.

We have immunohistochemically investigated the expression of a reeler gene-related antigen in the mouse cerebellum by using a monoclonal antibody, CR-50. This antibody probes a distinct allelic antigen present in normal but not in reeler mutant mice, and this antigen is localized in the brain regions in which morphological abnormalities occur in reeler mice (Ogawa et al., Neuron 14: 899-912, 1995). The developing normal cerebellum showed transient immunoreactivity to CR-50 in a limited set of neurons and in the extracellular space near the pial surface. An early population of CR-50-labeled cells emerged on embryonic day (E) 13 along the dorsal cerebellar surface, comprising the nuclear transitory zone (NTZ). Bromodeoxyuridine labeling revealed the time of origin of these cells to be at E11-12. From E14 to E18, some CR-50-labeled cells were stacked in the inner border of the external granular layer (EGL), whereas others were scattered in deep areas, such as the cerebellar nuclei and the surrounding intermediate zone or white matter. In the first postnatal week, these subcortical structures became immunonegative. However, CR-50 antigen was continuously produced until the second postnatal week by another population of cells occupying i) the premigratory zone (PMZ), the inner half of the EGL, and ii) the internal granular layer (IGL). These later CR-50-positive cells were smaller than the earlier type and showed the morphology typical of granule neurons. Both types of CR-50-labeled cells were positive for a DNA-binding protein, zic. By treating living cerebellar slices with CR-50, the extracellular antigen was localized as a puncutate staining pattern in the NTZ, PMZ, and molecular layer (ML), but not in the subcortical regions and IGL. Purkinje cells were negative for CR-50 and aligned as a monolayer adjacent to the PMZ, though their dendritic trees were closely associated with the extracellular CR-50-antigen in the PMZ and ML. Staining of dissociated cells suggested that the extracellular antigen is initially present throughout the surfaces of the CR-50/anti-zic double positive neurons, and is then rearranged to concentrate on their processes contacting with Purkinje cells. The spatiotemporal expressions of the CR-50 antigen in the cerebellum are consistent with the possibility that this antigen is involved in cell-cell interactions related to the histogenetic assembly of Purkinje cells.

PMID: 8863127 [PubMed - indexed for MEDLINE]

Localization of gp130 in the developing and adult mouse cerebellum.

Department of Neuroscience, The Ohio State University, 4068 Graves Hall, 333 W. 10th Avenue, Columbus, OH 43210, USA.

Interleukin-6 (IL-6) type cytokines show functional redundancy in the immune, hematopoietic, and nervous system, which is believed to result from sharing of the signal transducing receptor gp130. IL-6 type cytokines and their binding receptors have been localized in the adult cerebellum. However, the cellular localization and developmental regulation of gp130 in the cerebellum have not been determined. In the present study the expression pattern of gp130 in the developing and adult mouse cerebellum was investigated. At embryonic day (E)15 and E17, gp130 immunoreactivity is present primarily in fiber bundles that course from the brainstem to the cerebellum. At postnatal day (P)0, gp130 immunoreactivity first appears in the Purkinje cell layer, external granule cell layer, and cerebellar nuclei. As Purkinje cells differentiate, gp130 immunoreactivity progressively extends from the cell body along their developing dendritic arbor. All Purkinje cells show intense gp130 immunoreactivity in their cell bodies by P7. In contrast the gp130 immunoreactivity detected in fiber bundles at E15 and E17 is downregulated postnatally, and cannot be detected after P7. Granule cells show gp130 immunoreactivity at P0 in the external granule cell layer and subsequently in the internal granule cell layer. Astrocytes in the white matter express gp130 at P0, and show intense gp130 immunoreactivity between P7 and P14. As the cerebellum matures gp130 immunoreactivity in the white matter decreases. The present description of the differential spatial and temporal distribution of gp130 provides an initial step in defining specific cellular populations that are potential targets of IL-6 type cytokines during cerebellar ontogeny.

PMID: 10989258 [PubMed - indexed for MEDLINE]

Expression of glial progenitor markers p75NTR and S100 protein in the developing mouse parathyroid gland.

Department of Anatomy, Kitasato University School of Medicine, Sagamihara, Kanagawa 228-8555, Japan. kameda@med.kitasato-u.ac.jp

Drosophila glial cells missing (Drosophila Gcm) is a transcription factor that is required for the differentiation of glial cells. Gcm2, a mouse homologue of Drosophila Gcm, is a master regulatory gene of parathyroid development and is expressed in the parathyroid rudiment. We have found that the mouse parathyroid exhibits the glial progenitor markers, p75(NTR) and S100 protein, during fetal development. At embryonic day 11.5 (E11.5), a bulge of the parathyroid rudiment is formed in the cranial part of the third pharyngeal pouch. The rudiment exhibits immunoreactivity for p75(NTR) and S100 protein, in addition to secretory protein 1/chromogranin A. While the thymus rudiment, which arises from the caudal part of the third pharyngeal pouch, is moving downwards, the parathyroid is attached to the top of thymus. The parathyroid comes into contact with the thyroid lobe at E13.5 and then separates from the thymus. The parathyroid maintains intense immunoreactivity for p75(NTR) and S100 protein during the migration and development in the thyroid lobe. The co-localization of p75(NTR) and S100 in the developing parathyroid cells has been confirmed by confocal microscopy. Other glial markers, viz. glial fibrillary acidic protein, Sox10, vimentin and nestin, are not expressed in the parathyroid at any stage of development. The neural progenitor markers, neurofilament 160 and TuJ1, are also absent from the parathyroid. Taken together, we suggest that Gcm2 supplies only some glial progenitor characteristics to the parathyroid rudiment.

PMID: 17024414 [PubMed - indexed for MEDLINE]

Genetic background modifies intestinal pseudo-obstruction and the expression of a reporter gene in Hox11L1-/- mice.

Department of Pediatrics, University of Washington School of Medicine, Children's Hospital and Regional Medical Center, 4800 Sand Point Way NW, Seattle, WA 98105, USA.

BACKGROUND & AIMS: The transcription factor Hox11L1 is expressed by enteric neurons. Two groups mutated murine Hox11L1, and reported lethal intestinal pseudo-obstruction and colonic hyperganglionosis in many, but not all, homozygous null mutants. We investigated the regulation of Hox11L1 and factors that influence the penetrance of pseudo-obstruction in Hox11L1-null mice. METHODS: Expression of beta-galactosidase (lacZ), under control of putative Hox11L1 regulatory sequences, was assessed in transgenic mice wild-type, heterozygous, and null for native Hox11L1. Transgene expression and signs of pseudo-obstruction were compared in null mice with different genetic backgrounds. RESULTS: In enteric neurons and other parts of the nervous system, the transgene was expressed in a pattern consistent with native Hox11L1. Enteric beta-galactosidase activity initiated in the proximal small intestine and spread cranially and caudally in a subset of postmitotic enteric neurons. Hox11L1-lacZ transgene expression persisted in Hox11L1-null animals, suggesting that Hox11L1 is not required cell autonomously for neuronal survival. Genetic background dramatically affected the phenotypes of Hox11L1-null animals, with complete penetrance of severe proximal colonic distention on a predominantly C57BL/6J (B6) background and very low penetrance of dysmotility on a 129SvJ (129) background. Coincidently, Hox11L1-lacZ expression by most enteric neurons, but not CNS neurons, was lost on a 129 background. CONCLUSIONS: Cis-acting, 5' regulatory elements are sufficient to regulate site-specific expression of Hox11L1 in vivo. Expression of the transgene by enteric neurons and penetrance of pseudo-obstruction in Hox11L1-null animals are influenced by one or more modifier genes, counterparts of which may play a similar role in human disease.

PMID: 14598259 [PubMed - indexed for MEDLINE]

Expression, synaptic localization, and developmental regulation of Ack1/Pyk1, a cytoplasmic tyrosine kinase highly expressed in the developing and adult brain.

Developmental Neurobiology and Regeneration Lab, Institute of Biomedical Research of Barcelona-Parc Científic de Barcelona, University of Barcelona, Josep Samitier 1-5, E08028 Barcelona, Spain. jurena@pcb.ub.es

Cytosolic tyrosine kinases play a critical role both in neural development and in adult brain function and plasticity. Here we isolated a cDNA with high homology to human Ack1 and mouse Tnk2. This cDNA directs the expression of a 125-kD protein that can be autophosphorylated in tyrosines. Initially, this clone was named Pyk1 for proline-rich tyrosine kinase (Lev et al., 1995); however, since it corresponds to the mouse homolog of Ack1, here we called it Ack1/Pyk1. In this study we show that Ack1/Pyk1 mRNA and protein is highly expressed in the developing and adult brain. The highest levels of Ack1/Pyk1 expression were detected in the hippocampus, neocortex, and cerebellum. Electron microscopy studies showed that Ack1/Pyk1 protein is expressed in these regions both at dendritic spines and presynaptic axon terminals, indicating a role in synaptic function. Furthermore, we demonstrate that Ack1/Pyk1 mRNA levels are strongly upregulated by increased neural activity, produced by intraperitoneal kainate injections. During development, Ack1/Pyk1 was also expressed in the proliferative ventricular zones and in postmitotic maturing neurons. In neuronal cultures, Ack1/Pyk1 was detected in developing dendrites and axons, including dendritic tips and growth cones. Moreover, Ack1/Pyk1 colocalized with Cdc42 GTPase in neuronal cultures and coimmunoprecipitated with Cdc42 in HEK 293T cells. Altogether, our findings indicate that Ack1/Pyk1 tyrosine kinase may be involved both in adult synaptic function and plasticity and in brain development. (c) 2005 Wiley-Liss, Inc.

PMID: 16052498 [PubMed - indexed for MEDLINE]

BMP mRNA and protein expression in the developing mouse olfactory system.

Department of Human and Animal Biology, University of Torino, 10123 Torino, Italy.

The bone morphogenetic proteins (BMPs) play fundamental roles during the organization of the central nervous system. The presence of these proteins has also been demonstrated in regions of the adult brain that are characterized by neural plasticity. In this study, we examined the expression of BMP4, 6, and 7 mRNAs and proteins in the murine olfactory system. The olfactory system is a useful model for studying cell proliferation and neural differentiation because both of these processes persist throughout life in the olfactory epithelium (OE) and olfactory bulb (OB). Our results demonstrate a differential expression of BMP4, 6, and 7 in the embryonic, postnatal, and adult olfactory system. In particular, BMP4 and BMP7 showed similar immunostaining patterns, being expressed in the olfactory region from the earliest stages studied (embryonic day 15.5) to adulthood. During development BMPs were expressed in the OE, olfactory bulb nerve layer, glomerular layer (GL), mitral cell layer (MCL), and subventricular zone. During the first postnatal week of life, BMP4 and 7 immunoreactivity (-ir) was particularly evident in the GL, MCL, and in the subependymal layer (SEL), which originates postnatally from the subventricular zone. In adults, BMP4 and 7 immunostaining was present in the GL and SEL. Within the SEL, BMP4 and 7 proteins were expressed primarily in association with the astrocytic glial compartment. BMP6-ir was always found in mature olfactory receptor neurons and their axonal projections to the OB. In summary, these data support the hypothesis that BMPs play a role in the morphogenesis of the olfactory system during development and in its plasticity during adulthood. Copyright 2002 Wiley-Liss, Inc.

PMID: 12210138 [PubMed - indexed for MEDLINE]

Radial glia development in the mouse olfactory bulb.

Department of Anatomy and Neurobiology, Program in Neuroscience, The University of Maryland, School of Medicine, Baltimore, Maryland 21201, USA. apuche@umaryland.edu

Radial glia are critical for cell migration and lamination of the cortex. In most developing cortical structures, radial glia, as their name suggests, extend processes from the ventricle to the pia in regular parallel arrangements. However, immunohistochemical labeling from several laboratories suggests that radial glia have a more branched morphology in the olfactory bulb. To investigate the morphology of radial glia in the mouse olfactory bulb we (1) labeled radial glia and olfactory receptor neuron axons at 24-hour intervals by immunohistochemistry; and (2) developed a novel method of generating and applying "nanocrystals" of 1,1'-dioctadecyl-3,3,3',3'- tetramethylindocarbocyanine perchlorate (DiI) to the ventricle surface such that the processes of single olfactory bulb radial glia are labeled in the embryonic olfactory bulb. We examined the structure and interactions of radial glia with ingrowing olfactory receptor neuron (ORN) axons in late embryonic olfactory bulb development. These results showed that olfactory bulb radial glia do not form straight parallel structures as do radial glia in the neocortex but rather have a convoluted trajectory from the ventricle to the bulb surface. Moreover, olfactory bulb radial glia consistently extend tangential branches at the level of the internal plexiform layer. Beginning at embryonic day 17.5, two types of radial glia can be distinguished: type I radial glia have a process that extends from the ventricle into the glomerular layer. These apical processes form highly restricted tufts, or "glial glomeruli" at the same time that ORN axons are forming "axonal glomeruli." In type II radial glia the apical process does not enter the glomerular layer but instead ramifies within the external plexiform layer. The tight spatiotemporal relationship between the glomerulization of radial glia processes and ORN axons during development suggest that radial glia processes could play a role in the formation and/or stabilization of mammalian glomeruli. Copyright 2001 Wiley-Liss, Inc.

PMID: 11329125 [PubMed - indexed for MEDLINE]

Common origin and developmental dependence on c-ret of subsets of enteric and sympathetic neuroblasts.

Division of Developmental Neurobiology, National Institute for Medical Research, Mill Hill, London, UK.

c-ret encodes a tyrosine kinase receptor that is necessary for normal development of the mammalian enteric nervous system. Germline mutations in c-ret lead to congenital megacolon in humans, while a loss-of-function allele (ret.k-) causes intestinal aganglionosis in mice. Here we examine in detail the function of c-ret during neurogenesis, as well as the lineage relationships among cell populations in the enteric nervous system and the sympathetic nervous system that are dependent on c-ret function. We report that, while the intestine of newborn ret.k- mice is devoid of enteric ganglia, the esophagus and stomach are only partially affected; furthermore, the superior cervical ganglion is absent, while more posterior sympathetic ganglia and the adrenal medulla are unaffected. Analysis of mutant embryos shows that the superior cervical ganglion anlage is present at E10.5, but absent by E12.5, suggesting that c-ret is required for the survival or proliferation of sympathetic neuroblasts. In situ hybridization studies, as well as direct labelling of cells with DiI, indicate that a common pool of neural crest cells derived from the postotic hindbrain normally gives rise to most of the enteric nervous system and the superior cervical ganglion, and is uniquely dependent on c-ret function for normal development. We term this the sympathoenteric lineage. In contrast, a distinct sympathoadrenal lineage derived from trunk neural crest forms the more posterior sympathetic ganglia, and also contributes to the foregut enteric nervous system. Overall, our studies reveal previously unknown complexities of cell lineage and genetic control mechanisms in the developing mammalian peripheral nervous system.

PMID: 8565847 [PubMed - indexed for MEDLINE]

Mash1 is required for glomus cell formation in the mouse carotid body.

Department of Anatomy, Kitasato University School of Medicine, Sagamihara, Kanagawa 228-8555, Japan. kameda@med.kitasato-u.ac.jp

The carotid body consists of chemoreceptive glomus cells, sustentacular cells and nerve endings. The murine carotid body, located at the carotid bifurcation, is always joined to the superior cervical ganglion of the sympathetic trunk. Glomus cells and sympathetic neurons are immunoreactive for the TuJ1, PGP9.5, tyrosine hydroxylase (TH) and neuropeptide Y (NPY) markers. Glomus cells are also immunoreactive for serotonin (5-HT). A targeted mutation of Mash1, a mouse homolog of the Drosophila achaete-scute complex, results in the elimination of sympathetic ganglia. In Mash1 null mutant mice, the carotid body primordium forms normally in the wall of the third arch artery at embryonic day (E) 13.0 and continues to develop, although the superior cervical ganglion is completely absent. However, no cells in the mutant carotid body display the TuJ1, PGP 9.5, TH, NPY and 5-HT markers throughout development. The absence of glomus cells was also confirmed by electron microscopy. The carotid body of newborn null mutants is composed of mesenchymal-like cells and nerve fibers. Many cells immunoreactive for the S-100 protein, a sustentacular cell marker, appear in the mutant carotid body during fetal development. The Mash1 gene is thus required for the genesis of glomus cells but not for sustentacular cells.

PMID: 15878769 [PubMed - indexed for MEDLINE]

Astrocyte heterogeneity revealed by expression of a GFAP-LacZ transgene.

Department of Neurobiology and Civitan International Research Center, University of Alabama at Birmingham, Birmingham, AL 35294-0021, USA.

Glial fibrillary acidic protein (GFAP) is an intermediate filament protein present primarily in astrocytes. The gene is first expressed as astrocytes mature, and in the adult is strongly upregulated in response to CNS damage. Thus, in addition to its astrocyte specificity, transcriptional regulation of the GFAP gene is of interest as a reporter of CNS signaling during development and injury. Several laboratories have shown that approximately 2 kb of 5'-flanking DNA of the human or mouse GFAP gene is sufficient to direct transgene expression to astrocytes and to confer developmental and injury-induced regulation. Enhancer regions have been identified adjacent to the basal promoter and about 1500 bp upstream of the RNA start site. Juxtaposition of these two segments yielded a 447 bp promoter, gfa28, which strongly drove reporter activity in transfected glioma cells. We report here that in mice a gfa28-lacZ transgene expresses in only certain brain regions, revealing an unexpected heterogeneity among astrocytes. The restricted pattern of expression is present early in development, is not altered by injury, and is preserved in cultured astrocytes. However, astrocytes cultured from an inactive region strongly express a transiently transfected gfa28-lacZ construct, and activity of the embedded gfa28-lacZ transgene is partially restored by treatment with a histone deacetylase inhibitor. These results indicate that the absence of gfa28-lacZ expression in specific brain regions results from a developmental failure to remodel GFAP chromatin to an open structure. Thus, expression of the gfa28-lacZ transgene appears to serendipitously mark a distinct set of astrocyte precursors. Copyright 2006 Wiley-Liss, Inc.

PMID: 16482522 [PubMed - indexed for MEDLINE]

Patterned neuropathologic events occurring in hyh congenital hydrocephalic mutant mice.

Departamento de Biología Celular, Genética y Fisiología, Facultad de Ciencias, Universidad de Málaga, Málaga, Spain.

Hyh mutant mice develop long-lasting hydrocephalus and represent a good model for investigating neuropathologic events associated with hydrocephalus. The study of their brains by use of lectin binding, bromodeoxyuridine labeling, immunochemistry, and scanning electron microscopy revealed that certain events related to hydrocephalus followed a well-defined pattern. A program of neuroepithelium/ependyma denudation was initiated at embryonic day 12 and terminated at the end of the second postnatal week. After the third postnatal week the denuded areas remained permanently devoid of ependyma. In contrast, a selective group of ependymal areas resisted denudation throughout the lifespan. Ependymal denudation triggered neighboring astrocytes to proliferate. These astrocytes expressed particular glial markers and formed a superficial cell layer replacing the lost ependyma. The loss of the neuroepithelium/ependyma layer at specific regions of the ventricular walls and at specific stages of brain development would explain the fact that only certain brain structures had abnormal development. Therefore, commissural axons forming the corpus callosum and the hippocampal commissure displayed abnormalities, whereas those forming the anterior and posterior commissures did not; and the brain cortex was not homogenously affected, with the cingular and frontal cortices being the most altered regions. All of these telencephalic alterations developed at stages when hydrocephalus was not yet patent at the lateral ventricles, indicating that abnormal neural development and hydrocephalus are linked at the etiologic level, rather than the former being a consequence of the latter. All evidence collected on hydrocephalic hyh mutant mice indicates that a primary alteration in the neuroepithelium/ependyma cell lineage triggers both hydrocephalus and abnormalities in telencephalic development.

PMID: 18090917 [PubMed - indexed for MEDLINE]

GFAP-expressing cells in the postnatal subventricular zone display a unique glial phenotype intermediate between radial glia and astrocytes.

Department of Neurosurgery, Yale University School of Medicine, New Haven, Connecticut 06520-8082, USA.

Neural stem cells in the adult subventricular zone (SVZ) derive from radial glia and express the astroglial marker glial fibrillary acidic protein (GFAP). Thus, they have been termed astrocytes. However, it remains unknown whether these GFAP-expressing cells express the functional features common to astrocytes. Using immunostaining and patch clamp recordings in acute slices from transgenic mice expressing green fluorescent protein (GFP) driven by the promoter of human GFAP, we show that GFAP-expressing cells in the postnatal SVZ display typical glial properties shared by astrocytes and prenatal radial glia such as lack of action potentials, hyperpolarized resting potentials, gap junction coupling, connexin 43 expression, hemichannels, a passive current profile, and functional glutamate transporters. GFAP-expressing cells express both GLAST and GLT-1 glutamate transporters but lack AMPA-type glutamate receptors as reported for dye-coupled astrocytes. However, they lack 100 microM Ba2+-sensitive inwardly rectifying K+ (K(IR)) currents expressed by astrocytes, but display delayed rectifying K+ currents and 1 mM Ba2+-sensitive K+ currents. These currents contribute to K+ transport at rest and maintain hyperpolarized resting potentials. GFAP-expressing cells stained positive for both K(IR)2.1 and K(IR)4.1 channels, two major K(IR) channels in astrocytes. Ependymal cells, which also derive from radial glia and express GFAP, display typical glial properties and K(IR) currents consistent with their postmitotic nature. Our results suggest that GFAP-expressing cells in concert with ependymal cells can perform typical astrocytic functions such as K+ and glutamate buffering in the postnatal SVZ but display a unique set of functional characteristics intermediate between astrocytes and radial glia. 2006 Wiley-Liss, Inc.

PMID: 16886203 [PubMed - indexed for MEDLINE]

Expression of a member of tumor necrosis factor receptor superfamily, TROY, in the developing olfactory system.

Department of Anatomy and Neurobiology, Wakayama Medical University, Kimiidera, Wakayama, Japan.

TROY is a recently identified member of the tumor necrosis factor (TNF) receptor superfamily. We have previously reported that TROY induces the activation of nuclear factor kappaB via TNF receptor-associated factor 2, 5, and 6, and is strongly expressed in the developing central nervous system, including the olfactory bulb. In this study, we investigated the detailed cellular characterization of TROY-expressing cells in the developing olfactory system of mice using in situ hybridization and immunohistochemistry. Both mRNA and protein of TROY were first detected in the olfactory nerve layer (ONL) of the olfactory bulb at embryonic day 13.5. During late embryogenesis, TROY expression was most intense in the inner ONL (ONL-i). In the postnatal olfactory bulb, TROY-expressing cells were also detected in the glomerular layer (GL), in addition to the ONL-i. The double-immunofluorescence method demonstrated that TROY was expressed in olfactory ensheathing cells (OECs) of the ONL-i, which were positive for neuropeptide Y (NPY), but neither S-100 nor p75 low-affinity nerve growth factor receptor. Some TROY-expressing cells in the ONL-i were observed with the astrocyte-like phenotype (GFAP+/NPY-). In addition, TROY was also detected in GFAP+ glial cells of the GL. Thus, TROY was expressed in some specific subsets of glial cells in the olfactory bulb, including OECs, suggesting that TROY may play some roles in the developing and adult olfactory system. Copyright 2004 Wiley-Liss, Inc.

PMID: 14966863 [PubMed - indexed for MEDLINE]

Bergmann glial development in the mouse cerebellum as revealed by tenascin expression.

Laboratory of Neural Information, National Institute for Physiological Sciences, Okazaki, Japan.

Tenascin, an astroglia-derived extracellular matrix molecule, is also expressed by radial glia of the embryonic mouse cerebellum. Expression of tenascin can thus be applied as a marker of astroglial development from an early stage, especially prior to the expression of the glial fibrillary acidic protein (GFAP) that can be detected in the postnatal cerebellum. The development of Bergmann glia, specialized cerebello-cortical astroglia with radial processes, was examined by tenascin immunohistochemistry and non-radioactive in situ hybridization histochemistry for tenascin mRNA in the developing mouse cerebellum. Tenascin-immunopositive radial glial processes extending from the ventricular zone to the pia mater retracted toward the cortex in the embryonic cerebellum and occupied a position corresponding to the Bergmann glial processes at the perinatal stage. Tenascin gene-expressing cells were generated in the ventricular zone of the cerbellar primordium and migrated radially toward the cortex. They were stratified in the layer of Bergmann glial somata at the early postnatal stage. They extended GFAP-immunopositive radial processes from the somata to the pia mater as revealed by double-labeling employing tenascin in situ hybridization histochemistry and GFAP-immunostaining. Bergmann glia are therefore considered to develop from cerebellar radial glia by migration of their somata and retraction of their processes. The tenascin gene-expressing cells displayed mitotic activity after alignment in the cortex as revealed by double-labeling by tenascin in situ hybridization histochemistry and immunohistochemical detection of the incorporated bromodeoxyuridine. The above findings suggest that the Bergmann glia in the cortex represent one of the origins of the astroglia in the developing cerebellum.

PMID: 8849669 [PubMed - indexed for MEDLINE]

Transgenic overexpression of BMP4 increases astroglial and decreases oligodendroglial lineage commitment.

Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461, USA.

Bone morphogenetic proteins (BMPs) promote astrocytic differentiation of cultured subventricular zone stem cells. To determine whether BMPs regulate the astrocytic lineage in vivo, transgenic mice were constructed that overexpress BMP4 under control of the neuron-specific enolase (NSE) promoter. Overexpression of BMP4 was first detectable by Western analysis on embryonic day 16 and persisted into the adult. The overexpression of BMP4 resulted in a remarkable 40% increase in the density of astrocytes in multiple brain regions accompanied by a decrease in the density of oligodendrocytes ranging between 11 and 26%, depending on the brain region and the developmental stage. No changes in neuron numbers or the pattern of myelination were detected, and there were no gross structural abnormalities. Similar phenotypes were observed in three independently derived transgenic lines. Coculture of transgenic neurons with neural progenitor cells significantly enhanced astrocytic lineage commitment by the progenitors; this effect was blocked by the BMP inhibitor Noggin, indicating that the stimulation of astrogliogenesis was due to BMP4 release by the transgenic neurons. These observations suggest that BMP4 directs progenitor cells in vivo to commit to the astrocytic rather than the oligodendroglial lineage. Further, differentiation of radial glial cells into astrocytes was accelerated, suggesting that radial glia were a source of at least some of the supernumerary astrocytes. Therefore, BMPs are likely important mediators of astrocyte development in vivo.

PMID: 12618141 [PubMed - indexed for MEDLINE]

Erratum in:

Brain Res Mol Brain Res. 2003 Jun 10;114(2):177.

Expression of dystroglycan, fukutin and POMGnT1 during mouse cerebellar development.

Shriver Center for Mental Retardation, 200 Trapelo Road, Waltham, MA 02452, USA.

Dystroglycan (DG) plays a central role in linking the extracellular matrix to cellular cytoskeletal elements, and is required for proper neuromuscular junction organization and neural cell migration in the CNS. DG interactions with laminin and several other extracellular ligands are mediated through carbohydrates located in a densely glycosylated mucin core domain on alpha-DG. A hallmark of a number of congenital muscular dystrophies is abnormal alpha-DG glycosylation and disordered neuronal migration in both the cerebral cortex and cerebellum. The underlying genetic defects in two such diseases have been localized to the POMGnT1 glycosyltransferase and the putative glycosyltransferase fukutin. We report here the spatial expression pattern of DG together with its putative modifying enzymes during the period of peak neuronal migration in the cerebellum. All three genes are broadly expressed in late embryonic and early postnatal cerebellar neurons, including premigratory granule neurons of the external granule cell layer. Expression of POMGnT1 and fukutin is maintained in neurons of the internal granule cell layer after migration is complete, whereas DG mRNA is largely downregulated. Purkinje cells expressed all three genes throughout development at varying levels, ranging from weak expression of DG to a unique pattern of intense fukutin expression in irregularly spaced cell bodies that do not appear to correlate with known parasagittal stripes. Significantly, immunocytochemical analysis reveals that alpha- and beta-DG proteins are also present on the Bergmann glial scaffolds used by granule cells during early postnatal radial migration, and double-label in situ hybridization confirms that these cells also express POMGnT1 and fukutin. These results suggest that abnormal glycosylation of alpha-DG on glial scaffolds and neurons and their processes could affect interactions with alpha-DG ligands expressed by migrating granule cells, and be a potential mechanism through which neuronal migration is compromised in CMD disease.

PMID: 12670716 [PubMed - indexed for MEDLINE]

Fgfr3 expression by astrocytes and their precursors: evidence that astrocytes and oligodendrocytes originate in distinct neuroepithelial domains.

Wolfson Institute for Biomedical Research and Department of Biology, University College London, Gower Street, London WC1E 6BT, UK.

The postnatal central nervous system (CNS) contains many scattered cells that express fibroblast growth factor receptor 3 transcripts (Fgfr3). They first appear in the ventricular zone (VZ) of the embryonic spinal cord in mid-gestation and then distribute into both grey and white matter - suggesting that they are glial cells, not neurones. The Fgfr3(+) cells are interspersed with but distinct from platelet-derived growth factor receptor alpha (Pdgfra)-positive oligodendrocyte progenitors. This fits with the observation that Fgfr3 expression is preferentially excluded from the pMN domain of the ventral VZ where Pdgfra(+) oligodendrocyte progenitors--and motoneurones--originate. Many glial fibrillary acidic protein (Gfap)- positive astrocytes co-express Fgfr3 in vitro and in vivo. Fgfr3(+) cells within and outside the VZ also express the astroglial marker glutamine synthetase (Glns). We conclude that (1) Fgfr3 marks astrocytes and their neuroepithelial precursors in the developing CNS and (2) astrocytes and oligodendrocytes originate in complementary domains of the VZ. Production of astrocytes from cultured neuroepithelial cells is hedgehog independent, whereas oligodendrocyte development requires hedgehog signalling, adding further support to the idea that astrocytes and oligodendrocytes can develop independently. In addition, we found that mice with a targeted deletion in the Fgfr3 locus strongly upregulate Gfap in grey matter (protoplasmic) astrocytes, implying that signalling through Fgfr3 normally represses Gfap expression in vivo.

PMID: 12441294 [PubMed - indexed for MEDLINE]

Developmental and spatial expression pattern of syntaxin 13 in the mouse central nervous system.

Institut de Biologie Cellulaire et de Morphologie (IBCM), Rue du Bugnon 9, 1005 Lausanne, Switzerland.

Vesicular transport involves SNARE (soluble- N-ethylmaleimide-sensitive-factor-attachment-protein-receptor) proteins on transport vesicles and on target membranes. Syntaxin 13 is a SNARE enriched in brain, associated with recycling endosomes; its overexpression in PC12 cells promotes neurite outgrowth. This suggests an important role for receptor recycling during neuronal differentiation. Here we describe the spatiotemporal pattern of syntaxin 13 expression during mouse brain development. During early embryogenesis (E12-E15), it was found in the forebrain ventricular zone and in primary motor and sensory neurons in the brainstem, spinal cord and sensory ganglia. In the forebrain at E15, syntaxin 13 was not detected in neuroblasts in the intermediate zone of the embryonic hemispheric wall, while there was labeling in cortical neurons in deeper layers starting at E15-18, and progressively in later-generated neurons up to layer II around P6. Syntaxin 13 reached maximal expression in all brain divisions at about P7, followed by a decrease, with heterogeneous neuron populations displaying various staining intensities in adult brain. While usually restricted to the soma of neurons, we transiently detected syntaxin 13 in dendrites of pyramidal neurons during the first postnatal week. In conclusion, the developmentally regulated syntaxin 13 expression in various neuronal populations is consistent with its involvement in endocytic trafficking and neurite outgrowth.

PMID: 12172780 [PubMed - indexed for MEDLINE]

Localization of oncostatin M receptor beta in adult and developing CNS.

Department of Anatomy and Neurobiology, Wakayama Medical University, 811-1 Kimiidera, 641-8509, Wakayama, Japan.

Oncostatin M (OSM) is a member of the interleukin-6 cytokine family, which is involved in definitive hematopoiesis, the development of liver, and local inflammation. However, little is known about the role of OSM in the murine CNS. Using Northern blot analysis, we examined the regional distribution of OSM receptor beta (OSMRbeta) mRNA in the adult CNS. OSMRbeta mRNA was observed predominantly in the olfactory bulb, and with low levels in the other regions. In situ hybridization shows that OSMRbeta gene expression was found in astrocytes of olfactory bulb, epithelial cells of choroid plexus, and meningeal cells in pia mater. In addition, we investigated the gene expression of OSMRbeta in the developing CNS at different time points. Its gene expression was first observed in large neurons of the hypoglossal nucleus at 14.5 days postcoitum, which was sustained until neonatal mice. OSMRbeta mRNA and protein were mainly localized in the ventral subnucleus of the developing hypoglossal nucleus. Our results suggest that OSM contributes to the development of specific subpopulations of both neurons and astrocytes in the murine CNS.

PMID: 12831858 [PubMed - indexed for MEDLINE]

Transcriptional regulation of glial fibrillary acidic protein (GFAP)-mRNA expression during postnatal development of mouse brain.

INSERM U. 282, Hôpital H. Mondor, Créteil, France.

During mouse brain maturation, GFAP-mRNA undergoes a two-step developmental expression. It increases between birth and day 15 (period of astrocytic proliferation) and then decreases until day 55 (period of astrocytic morphological differentiation). We have developed an in vitro transcription procedure, as a mean to study the part of transcriptional control in this biphasic expression. After RNA synthesis by endogenous RNA polymerases in nuclei isolated from mouse brain (of 3 to 55 days and 217 days), the relative rates of GFAP-mRNA transcripts were analysed by hybridization with a specific cDNA probe. As early as 3 days after birth, the rate of GFAP-mRNA transcripts was maximal, whereas unexpectedly, it showed a significant decrease in mice of 15 days and stayed low until the 55th day. Therefore, a transcriptional control may take place early in mouse brain postnatal development by increasing the transcriptional rate of the GFAP gene in astrocytes, and during the transition from proliferation to differentiation phase of astrocytes (that occurs at the 15th day after birth) by decreasing this rate. However, posttranscriptional events may also occur to modulate the level of the cytoplasmic GFAP-mRNA. In older mice (217 days), the low rate of GFAP-mRNA transcripts found is not concordant with the high cytoplasmic level generally observed in gliosis of the aging brain. Our data suggest posttranscriptional events at this age.

PMID: 1629945 [PubMed - indexed for MEDLINE]