G Zhu

Albert Einstein College of Medicine, New York City, NY, United States

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Publications (5)20.14 Total impact

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    ABSTRACT: Multipotent neural progenitor cells become progressively more biased towards a glial fate during development coincident with an increase in expression of the epidermal growth factor receptor (EGFR). To determine whether differences in lineage commitment of neural progenitor cells from different stages are causally related to expression of the EGFR and whether generation of glia is EGFR-dependent, we used an EGFR-specific tyrosine kinase inhibitor, PD158780, to block the activation of EGFR in progenitor cells. Treatment of cultured neonatal progenitor cells with PD158780 completely blocked EGF-induced proliferation of the cells but did not affect bFGF-induced proliferation. Nevertheless, treatment with the inhibitor failed to inhibit the generation of astroglia in the presence of either EGF or bFGF. Treatment with bone morphogenetic protein-2 (BMP2) enhanced astroglial differentiation and suppressed oligodendroglial (OL) differentiation. PD158780 treatment had no effect on the BMP2-induced astroglial differentiation or OL suppression. These observations suggest that the generation of astroglia is not dependent on EGFR activation. Because it was still possible that the progenitor cell responses reflected a prior history of EGFR signaling, rat forebrain cells were cultured in the presence of PD158780 from a time (E12.5) preceding expression of the EGFR. After time in culture, the E12.5 cells expressed EGFR by Western analysis both in the presence and in the absence of PD158780, but activation of EGFR kinase (receptor autophosphorylation) was undetectable in the presence of PD158780 and the cells did not proliferate in response to EGF. Nevertheless, astroglial differentiation was normal in PD158780-treated cells both in the absence and in the presence of BMPs or CNTF. Furthermore, the propensity towards glial differentiation increased with time in culture even in the absence of EGFR signaling. This suggests that the increased bias towards glial differentiation during development does not depend on EGFR signaling.
    Journal of Neuroscience Research 03/2000; 59(3):312-20. · 2.97 Impact Factor
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    ABSTRACT: Although multipotent progenitor cells capable of generating neurons, astrocytes and oligodendrocytes are present within the germinal zones of the brain throughout embryonic, postnatal and adult life, the different neural cell types are generated within discrete temporospatial developmental windows. This might suggest that multipotent progenitor cells encounter different signals during each developmental stage, thus accounting for separate waves of lineage commitment and cellular differentiation. This study demonstrates, however, that progenitor cell responses to the same class of signals, the bone morphogenetic proteins (BMPs), change during ontogeny, and that these same signals may thus initiate progenitor cell elaboration of several different lineages. BMPs promote cell death and inhibit the proliferation of early (embryonic day 13, E13) ventricular zone progenitor cells. At later embryonic (E16) stages of cerebral cortical development, BMPs exhibit a concentration-dependent dissociation of cellular actions, with either enhancement of neuronal and astroglial elaboration (at 1-10 ng/ml) or potentiation of cell death (at 100 ng/ml). Finally, during the period of perinatal cortical gliogenesis, BMPs enhance astroglial lineage elaboration. By contrast, oligodendroglial lineage elaboration is inhibited by the BMPs at all stages. Further, application of the BMP antagonist noggin to cultured progenitors promotes the generation of oligodendrocytes, indicating that endogenous BMP signaling can actively suppress oligodendrogliogenesis. These observations suggest that developmental changes in neural progenitor cell responsiveness to the BMPs may represent a novel mechanism for orchestrating context-specific cellular events such as lineage elaboration and cellular viability.
    Developmental Neuroscience 02/2000; 22(1-2):74-85. · 3.41 Impact Factor
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    ABSTRACT: Although Sonic Hedgehog (Shh) plays a critical role in brain development, its actions on neural progenitor cell proliferation and differentiation have not been clearly defined. Transcripts for the putative Shh-receptor genes patched (Ptc) and smoothened (Smo) are expressed by embryonic, postnatal, and adult progenitor cells, suggesting that Shh can act directly on these cells. The recombinant human amino-terminal fragment of Shh protein (Shh-N) alone did not support the survival of cultured progenitor cells, but treatment with Shh-N in the presence of bFGF increased progenitor cell proliferation. Furthermore, treatment of embryonic rat progenitor cells propagated either in primary culture or after mitogen expansion significantly increased the proportions of both beta-tubulin- (neuronal marker) and O4- (oligodendroglial marker) immunoreactive cells and reduced the proportion of nestin- (uncommitted neural progenitor cell marker) immunoreactive cells. By contrast Shh-N had no effect on the elaboration of GFAP- (astroglial marker) immunoreactive cells. Cotreatment with Shh-N and bone morphogenetic protein-2 (BMP2) inhibited the anti-proliferative, astroglial-inductive, and oligodendroglial-suppressive effects of BMP2. Our observations suggest that Shh-N selectively promotes the elaboration of both neuronal and oligodendroglial lineage species and inhibits the effects of BMP2 on progenitor cell proliferation and astroglial differentiation.
    Developmental Biology 12/1999; 215(1):118-29. · 3.87 Impact Factor
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    ABSTRACT: Multipotent progenitor cells have been identified within periventricular generative zones of the developing and adult brain. To determine whether the environmental responsiveness of these cells changes during development, progenitor cells were cultured from embryonic, postnatal, and adult rat brain in the presence of either basic fibroblast growth factor (bFGF) or epidermal growth factor (EGF). Embryonic cells cultured as intact progenitor neurospheres proliferated more robustly in response to bFGF than to EGF, whereas proliferation of postnatal and adult progenitor cells was enhanced more by EGF than bFGF. Progenitor cells generated in the presence of either bFGF or EGF had the capacity to generate neurons, astrocytes, and oligodendrocytes at all developmental stages. Most embryonic and neonatal bFGF-generated cells differentiated predominantly into neurons, whereas late stage embryonic and neonatal EGF-generated progenitors largely remained in an undifferentiated state. However, later postnatal and adult progenitor species, irrespective of whether they were generated in the presence of bFGF or EGF, gave rise preferentially to astrocytes. Treatment with bone morphogenetic protein (BMP)2 or BMP7 enhanced astroglial differentiation and suppressed oligodendroglial differentiation of both EGF- and bFGF-generated progenitor species, suggesting that the effects of the BMPs are not dependent on EGF receptor activation. Thus, while central nervous system (CNS) progenitor cells retain multipotent capacity and responsiveness to the BMPs throughout development, they exhibit significant changes in other cellular response properties, perhaps reflecting differences in the requirements for specific generative versus regenerative events.
    Journal of Neuroscience Research 05/1999; 56(2):131-45. · 2.97 Impact Factor
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    ABSTRACT: We have previously isolated epidermal growth factor (EGF)-responsive multipotent progenitor cells from the early postnatal rodent cerebral cortex independent of generative zones. In this study we have examined the mechanisms regulating the generation of differentiated oligodendrocytes (OLs) from these multipotent cells. Although cultures of primary cortical OL progenitor cells propagated at clonal density spontaneously gave rise to differentiated OLs in defined medium, cultures of multipotent progenitors isolated from identical regions supported the elaboration of OL progenitors but not differentiated OLs. These observations indicate that the terminal maturation of OL progenitors derived from multipotent cells is dependent on signals present within the cellular environment. Application of cytokines such as basic fibroblast growth factor (bFGF), platelet-derived growth factor (PDGF), or neurotrophin 3 (NT3) to clonal density cultures of cortical multipotent progenitors increased the proportion of OL progenitors but failed to support the generation of differentiated OLs. By contrast, application of factors that activate gp130/leukemia inhibitory factor beta (LIFbeta) heterodimeric receptors, such as ciliary neurotrophic factor (CNTF), activated signal transducers and activators of transcription-3 in these OL progenitor cells and promoted the generation of differentiated OLs. Clonal analysis also demonstrated that CNTF directly targets OL progenitors derived from the multipotent cells. These observations suggest that two distinct progenitor cell pathways contribute to the generation of differentiated OLs during postnatal cortical gliogenesis. Although oligodendroglial maturation of classical OL progenitor cells is driven by cell autonomous mechanisms, our findings demonstrate that the generation of differentiated OLs from cortical multipotent progenitor cells is dependent on environmental cues, including activation of gp130/LIFbeta receptors.
    Journal of Neuroscience 01/1999; 18(23):9800-11. · 6.91 Impact Factor

Publication Stats

330 Citations
20.14 Total Impact Points

Institutions

  • 1999–2000
    • Albert Einstein College of Medicine
      • Department of Neuroradiology
      New York City, NY, United States