Biomedical subjects

Harley I Kornblum

Publications and source records attributed to Harley I Kornblum.

At least 19 recordsLinked to original sources

PubMed2006

Phenotypic and functional heterogeneity of GFAP-expressing cells in vitro: differential expression of LeX/CD15 by GFAP-expressing multipotent neural stem cells and non-neurogenic astrocytes.

Recent findings show that the predominant multipotent neural stem cells (NSCs) isolated from postnatal and adult mouse brain express glial fibrillary acid protein (GFAP), a protein commonly associated with astrocytes, and that primary astrocyte cultures can contain GFAP-expressing cells that act as multipotent NSCs when transferred to neurogenic conditions. The relationship of GFAP-expressing NSCs to GFAP-expressing astrocytes is unclear, but has important implications. We compared the phenotype and neurogenic potential of GFAP-expressing cells derived from different CNS regions and maintained in vitro under different conditions. Multiple labeling immunohistochemistry revealed that both primary astrocyte cultures and adherent neurogenic cultures derived from postnatal or adult periventricular tissue contained subpopulations of GFAP-expressing cells that co-expressed nestin and LeX/CD15, two molecules associated with NSCs. In contrast, GFAP-expressing cells in similar cultures prepared from adult cerebral cortex did not express detectable levels of LeX/CD15, and exhibited no neurogenic potential. Fluorescence-activated cell sorting (FACS) of both primary astrocyte cultures and adherent neurogenic cultures for LeX/CD15 showed that GFAP-expressing cells competent to act as multipotent NSCs were concentrated in the LeX-positive fraction. Using neurosphere assays and a transgenic ablation strategy, we confirmed that the predominant NSCs in primary astrocyte and adherent neurogenic cultures were GFAP-expressing cells. These findings demonstrate that GFAP-expressing cells derived from postnatal and adult forebrain are heterogeneous in both molecular phenotype and neurogenic potential in vitro, and that this heterogeneity exists before exposure to neurogenic conditions. The findings provide evidence that GFAP-expressing NSCs are phenotypically and functionally distinct from non-neurogenic astrocytes.

Animals↗

PubMed2006

Brain tumor stem cells.

Cancers are composed of heterogeneous cell populations ranging from highly proliferative immature cells to more differentiated cells of various cell lineages. Recent advances in stem cell research have allowed for the demonstration of the existence of cancer stem cells in acute myeloid leukemia, breast cancer, and, most recently, in brain tumors. Each of these has some similarities with the normal stem cells in the corresponding organs. In brain tumors, putative cancer stem cells have been identified from glioblastoma multiforme, medulloblastoma and ependymoma. These tumor-derived cells self-renew under clonal conditions, and differentiate into neuron- and glia-like cells as well as into abnormal cells with mixed phenotypes. The tumor stem cells, but not the rest of tumor cells form secondary tumors by transplantation into immunodeficient mouse brain. In this review, we discuss the cellular and molecular relationships between brain tumor stem cells and normal neural stem cells, and also the possible clinical implications of brain tumor stem cells.

Brain Neoplasms↗

PubMed2005

PTEN negatively regulates neural stem cell self-renewal by modulating G0-G1 cell cycle entry.

Previous studies have demonstrated that a small subpopulation of brain tumor cells share key characteristics with neural stem/progenitor cells in terms of phenotype and behavior. These findings suggest that brain tumors might contain "cancer stem cells" that are critical for tumor growth. However, the molecular pathways governing such stem cell-like behavior remain largely elusive. Our previous study suggests that the phosphatase and tensin homologue deleted on chromosome 10 (PTEN) tumor suppressor gene, one of the most frequently mutated genes in glioblastomas, restricts neural stem/progenitor cell proliferation in vivo. In the present study, we sought to determine the role of PTEN in long-term maintenance of stem cell-like properties, cell cycle entry and progression, and growth factor dependence and gene expression. Our results demonstrate an enhanced self-renewal capacity and G(0)-G(1) cell cycle entry and decreased growth factor dependency of Pten null neural/stem progenitor cells. Therefore, loss of PTEN leads to cell physiological changes, which collectively are sufficient to increase the pool of self-renewing neural stem cells and promote their escape from the homeostatic mechanisms of proliferation control.

Animals↗

PubMed2005

Neural progenitor implantation restores metabolic deficits in the brain following striatal quinolinic acid lesion.

Neural progenitor transplantation is a potential treatment for neurodegenerative diseases, including Huntington's disease (HD). In the current study, we tested the potential of rat embryonic neural progenitors expanded in vitro as therapy in the rat quinolinic acid-lesioned striatum, a model that demonstrates some of the pathological features of HD. We used positron emission tomography (PET) to demonstrate that the intrastriatal injection of cultured rat neural progenitors results in improved metabolic function in the striatum and overlying cortex when compared to media-injected controls. Transplanted progenitors were capable of surviving, migrating long distances and differentiating into neurons and glia. The cortices of transplanted animals contained greater numbers of neurons in regions that had shown metabolic improvement. However, histological analysis revealed that only a small fraction of these increased neurons could be accounted for by engrafted cells, indicating that the metabolic sparing was likely the result of a trophic action of the transplanted cells on the host. Behavioral testing of the implanted animals did not reveal improvement in apomorphine-induced rotation. These data demonstrate that progenitor cell implantation results in enhanced metabolic function and sparing of neuron number, but that these functions do not necessarily result in the restoration of complex circuitry.

Analysis of Variance↗

PubMed2005

Maternal embryonic leucine zipper kinase (MELK) regulates multipotent neural progenitor proliferation.

Maternal embryonic leucine zipper kinase (MELK) was previously identified in a screen for genes enriched in neural progenitors. Here, we demonstrate expression of MELK by progenitors in developing and adult brain and that MELK serves as a marker for self-renewing multipotent neural progenitors (MNPs) in cultures derived from the developing forebrain and in transgenic mice. Overexpression of MELK enhances (whereas knockdown diminishes) the ability to generate neurospheres from MNPs, indicating a function in self-renewal. MELK down-regulation disrupts the production of neurogenic MNP from glial fibrillary acidic protein (GFAP)-positive progenitors in vitro. MELK expression in MNP is cell cycle regulated and inhibition of MELK expression down-regulates the expression of B-myb, which is shown to also mediate MNP proliferation. These findings indicate that MELK is necessary for proliferation of embryonic and postnatal MNP and suggest that it regulates the transition from GFAP-expressing progenitors to rapid amplifying progenitors in the postnatal brain.

Animals↗

PubMed2005

Developmental profile of ErbB receptors in murine central nervous system: implications for functional interactions.

The ErbB family, ErbB1 (also known as the epidermal growth factor receptor EGFR), ErbB2, ErbB3, and ErbB4 comprise a group of receptor tyrosine kinases that interact with ligands from the epidermal growth factor (EGF) superfamily, subsequently dimerize, catalytically activate each other by cross-phosphorylation, and then stimulate various signaling pathways. To gain a better understanding of in vivo functions of ErbB receptors in the central nervous system, the current study examined their mRNA expression throughout development in the mouse brain via in situ hybridization. EGFR, ErbB2, and ErbB4 exhibited distinct but sometimes overlapping distributions in multiple cell types within germinal zones, cortex, striatum, and hippocampus in prenatal and postnatal development. In addition, a subpopulation of cells positive for ErbB4 mRNA in postnatal cortex and striatum coexpressed mRNA for either EGFR or GAD67, a marker for gamma-aminobutyric acid (GABA)ergic interneurons, suggesting that both ErbB4 and EGFR are coexpressed in GABAergic interneurons. In contrast, ErbB3 mRNA was not detected within the brain during development and only appeared in white matter tracts in adulthood. Together, these findings suggest that ErbB receptors might mediate multiple functions in central nervous system development, some of which may be initiated by EGFR/ErbB4 heterodimers in vivo.

Animals↗

PubMed2004

Developmental expression of glial fibrillary acidic protein mRNA in mouse forebrain germinal zones--implications for stem cell biology.

Postnatal neural stem cells (NSCs) express the "traditional" astrocyte marker, glial fibrillary acidic protein (GFAP). Here, we analyze the ontogeny of GFAP mRNA in mouse forebrain germinal zones (GZ). On embryonic day 15, mRNA distribution is highly restricted. Subsequently, expression expands to include many cells in the GZ regions adjacent to the cortex and septum but not to the striatum. Double immunostaining for GFAP and nestin did not demonstrate extensive overlap in the GZ of adult rats, suggesting that either few of the GFAP-expressing cells are stem cells, or that nestin is not a reliable marker for stem cells in the adult rat brain. The current findings indicate that while some GFAP-expressing cells in the GZ may be NSCs, most are not likely to function in a neurogenic capacity.

Animals↗

PubMed2004

Developmental expression of OAP-1/Tspan-3, a member of the tetraspanin superfamily.

OSP/claudin-11-associated protein (OAP-1/Tspan-3), originally isolated by yeast two-hybrid screening using OSP/claudin-11 (oligodendrocyte-specific protein) as bait, is a member of the tetraspanin superfamily and OAP-1/Tspan-3, OSP/claudin-11, and beta1 integrin form a protein complex that seems to be involved in oligodendrocyte proliferation and migration. This study investigated the temporal and regional expression, glycosylation status, and tissue distribution of OAP-1/Tspan-3. OAP-1/Tspan-3 mRNA was expressed as a single transcript throughout brain development, with high levels of expression in the germinal zones. OAP-1/Tspan-3 protein contains N-terminal glycosylation sites in extracellular loop 2 and deglycosylation studies indicated a decrease in apparent molecular weight of OAP-1/Tspan-3, consistent with removal of N-glycans. Similar to OSP/claudin-11, OAP-1/Tspan-3 is expressed in all stages of oligodendrocyte development and in the myelin sheath. Unlike OSP/claudin-11, however, it is expressed in all cell types tested in the central nervous system (CNS), including neurons and astrocytes. The association of OAP-1/Tspan-3 with OSP/claudin-11 and beta1 integrin, its subcellular distribution as a cell surface, membrane-spanning glycoprotein, and its widespread distribution supports its potential role in cell migration, proliferation, and interactions between cells and extracellular matrix.

Animals↗

PubMed2004

Metabolic correlates of lesion-specific plasticity: an in vivo imaging study.

High-resolution positron emission tomography (microPET) allows for repeated observations of brain function in the same animal. In a previous study, using [(18)F] fluorodeoxyglucose (FDG) microPET, we demonstrated diminished glucose metabolism and subsequent recovery in the Neostriatum and thalamus ipsilateral to cortical aspiration (ASP) lesions. Thermocoagulation (TCL) of pial vessels has been shown to result in the same degree of cortical injury but induce more compensatory re-organization than ASP. In the present work, FDG microPET was used to compare glucose metabolism following both TCL and ASP lesions in order to determine whether metabolic differences correlate with the previously described anatomical and functional changes in the two lesion models. Animals were scanned 3-day, 10-day and 1-month post-injury. Estimated cortical lesion size did not differ between the two models at 1 month following injury. Both lesions induced ipsilateral neostriatal and thalamic hypometabolism 3-day post-injury, with subsequent metabolic improvement over time. However, complete recovery was not observed by 1 month in either group. ASP lesions resulted in an overall greater metabolic deficit in the subcortical structures and a greater cortical deficit 1 month following injury when compared to the TCL. Contralateral cortical glucose metabolism at 3 days following injury was not different in the two lesions. These data demonstrate that the two lesions differ somewhat in their metabolic response to injury, and that the relative hypometabolism observed following ASP may be a reflection of the diminished capacity of the contralateral cortex to compensate for ASP as compared to TCL.

Animals↗

PubMed2004

Evolution of diaschisis in a focal stroke model.

BACKGROUND AND PURPOSE: Stroke produces diaschisis in adjacent and connected regions. The sequential changes in diaschisis over time and the relationship of regions of diaschisis to functional cortical areas and regions of poststroke neuroplasticity have not been determined. METHODS: Small cortical strokes were produced in the barrel cortex of rats. Relative glucose metabolism was determined in vivo over time with [18F]fluorodeoxyglucose small-animal positron emission tomography. Cerebral blood flow was measured with [14C]iodoantipyrine. Regions of hypometabolism and hypoperfusion were compared with histological damage in the same animals. RESULTS: Small cortical strokes produce an initial network of hypometabolism in a broad region of cortex adjacent to the stroke and in the striatum and thalamus on day 1. Cerebral blood flow is diminished only immediately around the cortical infarct on day 1. A substantial area of cortex adjacent to the stroke remains hypometabolic on day 8. This persistent cortical hypometabolism occupies the somatosensory cortex, forelimb motor cortex, and second somatosensory area. CONCLUSIONS: Focal stroke produces ipsilateral diaschisis in connected cortical regions that is clearly distant from subtotal damage and may play a role in poststroke neuroplasticity.

Animals↗

PubMed2004

Patterns of Jagged1, Jagged2, Delta-like 1 and Delta-like 3 expression during late embryonic and postnatal brain development suggest multiple functional roles in progenitors and differentiated cells.

The Notch-DSL signaling system, consisting of multiple receptors and ligands, inhibits neurogenesis and promotes gliogenesis during embryonic development, but the specific function of the various ligands and receptors at later developmental stages are unknown. Here, we examined the expression pattern of four Delta, Serrate and Lag-2 (DSL) ligands, Jagged1, Jagged2, Delta-like1 (Dl1) and Delta-like 3 (Dl3), in late embryonic and postnatal rat brain by in situ hybridization. In late embryos, Jagged1, Dl1 and Dl3 mRNAs were present in the periventricular germinal epithelia, but this expression diminished during postnatal ages. Jagged1 mRNA was also expressed in the inner aspect of the dentate gyrus at early postnatal times. Dl3 was detectable in the external granule cell layer (EGL) of the cerebellum, another site of postnatal neurogenesis. Jagged2 mRNA was expressed in virtually all postnatal neurons. Jagged1 mRNA was highly expressed in several brain nuclei during postnatal development, with lower levels of expression in other grey matter regions. In white matter, Dl1 and Dl3 mRNAs were expressed during the first week of postnatal development but only the expression of Dl1 mRNA persisted through the second week. Dl1 mRNA was present at lower levels throughout grey matter during the first few weeks of development. Jagged1 mRNA was expressed in blood vessels, choroid plexus, and menninges throughout development and in the adult. Jagged2 mRNA was transiently expressed in cerebral blood vessels and choroid plexus during the first postnatal week. Taken together, these results support multiple and differing roles for the various ligands during and after central nervous system (CNS) development.

Animals↗

PubMed2004

[Cancer stem cells in pediatric brain tumors].

Cancers are formed by heterogeneous cell types from immature highly proliferative cells to lineage-committed differentiated cells. Transplantation studies have suggested the existence of "cancer stem cells", individual cells capable of producing an entire tumor. Recent advances in stem cell research have allowed for the demonstration of the existence of cancer stem cells in acute myeloid leukemia, breast cancer, and, most recently, in pediatric brain tumors. Each of these has some similarities with the normal stem cells in the corresponding organs. For example, leukemia stem cells express some, but not all, markers of hematopoietic stem cells. Regarding pediatric brain tumors, putative cancer stem cells were identified from medulloblastoma and also from glioma. These tumor-derived cells self-renew under clonal conditions, and differentiate into neurons and glia as well as into abnormal cells with mixed phenotypes. Interestingly, the tumor stem/progenitors, enriched in culture, maintained proliferation after 4 weeks from transplantation into neonatal rat brain. In this review, we discuss the difference as well as the similarity between tumor and normal stem cells, and also the possible clinical implication of cancer stem cells.

Animals↗

PubMed2003

Neural progenitor genes. Germinal zone expression and analysis of genetic overlap in stem cell populations.

The identification of the genes regulating neural progenitor cell (NPC) functions is of great importance to developmental neuroscience and neural repair. Previously, we combined genetic subtraction and microarray analysis to identify genes enriched in neural progenitor cultures. Here, we apply a strategy to further stratify the neural progenitor genes. In situ hybridization demonstrates expression in the central nervous system germinal zones of 54 clones so identified, making them highly relevant for study in brain and neural progenitor development. Using microarray analysis we find 73 genes enriched in three neural stem cell (NSC)-containing populations generated under different conditions. We use the custom microarray to identify 38 "stemness" genes, with enriched expression in the three NSC conditions and present in both embryonic stem cells and hematopoietic stem cells. However, comparison of expression profiles from these stem cell populations indicates that while there is shared gene expression, the amount of genetic overlap is no more than what would be expected by chance, indicating that different stem cells have largely different gene expression patterns. Taken together, these studies identify many genes not previously associated with neural progenitor cell biology and also provide a rational scheme for stratification of microarray data for functional analysis.

Animals↗

PubMed2003

Cancerous stem cells can arise from pediatric brain tumors.

Pediatric brain tumors are significant causes of morbidity and mortality. It has been hypothesized that they derive from self-renewing multipotent neural stem cells. Here, we tested whether different pediatric brain tumors, including medulloblastomas and gliomas, contain cells with properties similar to neural stem cells. We find that tumor-derived progenitors form neurospheres that can be passaged at clonal density and are able to self-renew. Under conditions promoting differentiation, individual cells are multipotent, giving rise to both neurons and glia, in proportions that reflect the tumor of origin. Unlike normal neural stem cells, however, tumor-derived progenitors have an unusual capacity to proliferate and sometimes differentiate into abnormal cells with multiple differentiation markers. Gene expression analysis reveals that both whole tumors and tumor-derived neurospheres express many genes characteristic of neural and other stem cells, including CD133, Sox2, musashi-1, bmi-1, maternal embryonic leucine zipper kinase, and phosphoserine phosphatase, with variation from tumor to tumor. After grafting to neonatal rat brains, tumor-derived neurosphere cells migrate, produce neurons and glia, and continue to proliferate for more than 4 weeks. The results show that pediatric brain tumors contain neural stem-like cells with altered characteristics that may contribute to tumorigenesis. This finding may have important implications for treatment by means of specific targeting of stem-like cells within brain tumors.

AC133 Antigen↗

PubMed2003

Global analysis of gene expression in neural progenitors reveals specific cell-cycle, signaling, and metabolic networks.

The genetic programs underlying neural stem cell (NSC) proliferation and pluripotentiality have only been partially elucidated. We compared the gene expression profile of proliferating neural stem cell cultures (NS) with cultures differentiated for 24 h (DC) to identify functionally coordinated alterations in gene expression associated with neural progenitor proliferation. The majority of differentially expressed genes (65%) were upregulated in NS relative to DC. Microarray analysis of this in vitro system was followed by high throughput screening in situ hybridization to identify genes enriched in the germinal neuroepithelium, so as to distinguish those expressed in neural progenitors from those expressed in more differentiated cells in vivo. NS cultures were characterized by the coordinate upregulation of genes involved in cell cycle progression, DNA synthesis, and metabolism, not simply related to general features of cell proliferation, since many of the genes identified were highly enriched in the CNS ventricular zones and not widely expressed in other proliferating tissues. Components of specific metabolic and signal transduction pathways, and several transcription factors, including Sox3, FoxM1, and PTTG1, were also enriched in neural progenitor cultures. We propose a putative network of gene expression linking cell cycle control to cell fate pathways, providing a framework for further investigations of neural stem cell proliferation and differentiation.

Animals↗

PubMed2003

Expression patterns of epidermal growth factor receptor and fibroblast growth factor receptor 1 mRNA in fetal human brain.

Factors that interact with the epidermal growth factor and fibroblast growth factor receptors have numerous effects in the central nervous system (CNS), inducing the proliferation of CNS stem cells and astrocytes and the survival and differentiation of neurons. Both receptors are expressed in the embryonic rodent brain in proliferative and nonproliferative regions, suggesting roles in numerous developmental processes. However, the roles of these factors in human brain development are not known. In the current study, we examined the expression of human epidermal growth factor receptor (HEGFR) and human fibroblast growth factor receptor 1 (HFGFR1) mRNAs in the human fetal brain. The expression of both receptors is strikingly conserved relative to previously reported patterns in the rodent. In the germinal zones, the sites of cellular proliferation, HFGFR1 was expressed primarily in the ventricular zone, whereas HEGFR was expressed in the subventricular zone, suggesting different roles in CNS progenitor proliferation. Differential expression was also observed in other brain areas examined, including the hippocampus and the cerebellum. The current study suggests that HEGFR and HFGFR1 are likely to play different roles during human brain development, but that these roles will be similar to those observed in the rodent brain.

Brain↗

PubMed2003

The predominant neural stem cell isolated from postnatal and adult forebrain but not early embryonic forebrain expresses GFAP.

Periventricular germinal zones (GZs) of developing and adult brain contain neural stem cells (NSCs), the cellular identities and origins of which are not defined completely. We used tissue culture techniques and transgenic mice expressing herpes simplex virus thymidine kinase (HSV-TK) from the mouse glial fibrillary acid protein (GFAP) promoter to test the hypothesis that certain NSCs express GFAP. To do so, we determined the relative proportions of multipotent neurospheres that are formed by GFAP-expressing cells derived from GZs at different stages of development. In this transgenic model, dividing GFAP-expressing cells are ablated selectively by treatment with the antiviral agent ganciclovir (GCV). Single-cell analysis showed that transgene-derived HSV-TK was present only in GFAP-expressing cells. GCV applied in vitro eliminated growth of multipotent neurospheres from GZs of postnatal and adult transgenic mice but not early embryonic (embryonic day 12.5) transgenic mice. GCV prevented growth of secondary multipotent neurospheres prepared after passage of primary transgenic neurospheres derived from all three of these developmental stages. In addition, GCV prevented growth of multipotent neurospheres from transgenic astrocyte-enriched cell cultures derived from postnatal GZ, and elaidic acid GCV given for 4 d to adult transgenic mice in vivo abolished the ability to grow multipotent neurospheres from GZ. Extensive control experiments, including clonal analysis, demonstrated that failure of neurosphere growth was not merely secondary to loss of GFAP-expressing support cells or the result of a nonspecific toxic effect. Our findings demonstrate that the predominant multipotent NSCs isolated from postnatal and adult but not early embryonic GZs express GFAP, and that NSCs exhibit heterogeneous expression of intermediate filaments during developmental maturation.

Animals↗

PubMed2003

The RAS effector RIN1 modulates the formation of aversive memories.

RAS proteins are critical regulators of mitosis and are mutationally activated in many human tumors. RAS signaling is also known to mediate long-term potentiation (LTP) and long-term memory formation in postmitotic neurons, in part through activation of the RAF-MEK-ERK pathway. The RAS effector RIN1 appears to function through competitive inhibition of RAS-RAF binding and also through diversion of RAS signaling to alternate pathways. We show that RIN1 is preferentially expressed in postnatal forebrain neurons in which it is localized in dendrites and physically associated with RAS, suggesting a role in RAS-mediated postsynaptic neuronal plasticity. Mice with an Rin1 gene disruption showed a striking enhancement in amygdala LTP. In addition, two independent behavioral tests demonstrated elevated amygdala-dependent aversive memory in Rin1(-/-) mice. These results indicate that RIN1 serves as an inhibitory modulator of neuronal plasticity in aversive memory formation.

Amygdala↗