Asymmetric inheritance of radial glial fibers by cortical neurons

Recent studies demonstrated the neuronogenic role of radial glial cells (RGCs) in the rodent. To reveal the fate of radial glial processes, we intensively monitored divisions of RGCs in DiI-labeled slices from the embryonic day 14 mouse cortex. During RGC division, each pia-connected fiber becomes thin but is neither lost nor divided; it is inherited asymmetrically by one daughter cell. In divisions that produce a neuron and a progenitor, the neuron inherits the pial fiber, also grows a thick ventricular process for several hours, and is therefore indistinguishable from the progenitor RGC. The ventricular process in the radial glial-like neuron ("radial neuron") then collapses, leading to ascent of the neuron by using the "recycled" radial fiber.

In vitro neurogenesis by progenitor cells isolated from the adult human hippocampus

Neurogenesis persists in the adult mammalian hippocampus. To identify and isolate neuronal progenitor cells of the adult human hippocampus, we transfected ventricular zone-free dissociates of surgically-excised dentate gyrus with DNA encoding humanized green fluorescent protein (hGFP), placed under the control of either the nestin enhancer (E/nestin) or the Talpha1 tubulin promoter (P/Talpha1), two regulatory regions that direct transcription in neural progenitor cells. The resultant P/Talpha1:hGFP+ and E/nestin:enhanced (E)GFP+ cells expressed betaIII-tubulin or microtubule-associated protein-2; many incorporated bromodeoxyuridine, indicating their genesis in vitro. Using fluorescence-activated cell sorting, the E/nestin:EGFP+ and P/Talpha1:hGFP+ cells were isolated to near purity, and matured antigenically and physiologically as neurons. Thus, the adult human hippocampus contains mitotically competent neuronal progenitors that can be selectively extracted. The isolation of these cells may provide a cellular substrate for re-populating the damaged or degenerated adult hippocampus.

Musashi1: an evolutionally conserved marker for CNS progenitor cells including neural stem cells

In situ detection of neural progenitor cells including stem-like cells is essential for studying the basic mechanisms of the generation of cellular diversity in the CNS, upon which therapeutic treatments for CNS injuries, degenerative diseases, and brain tumors may be based. We have generated rat monoclonal antibodies (Mab 14H1 and 14B8) that recognize an RNA-binding protein Musashi1, but not a Musashi1-related protein, Musashi2. The amino acid sequences at the epitope sites of these anti-Musashi1 Mabs are remarkably conserved among the human, mouse, and Xenopus proteins. Spatiotemporal patterns of Musashi1 immunoreactivity in the developing and/or adult CNS tissues of frogs, birds, rodents, and humans indicated that our anti-Musashi1 Mabs reacted with undifferentiated, proliferative cells in the CNS of all the vertebrates tested. Double or triple immunostaining of embryonic mouse brain cells in monolayer cultures demonstrated strong Musashi1 expression in Nestin(+)/RC2(+) cells. The relative number of Musashi1(+)/Nestin(+)/RC2(+) cells increased fivefold when embryonic forebrain cells were cultured to form 'neurospheres' in which stem-like cells are known to be enriched through their self-renewing mode of growth. Nestin(+)/RC2(-) cells, which included Talpha1-GFP(+) neuronal progenitor cells and GLAST(+) astroglial precursor cells, were also Musashi1(+), as were GFAP(+) astrocytes. Young neurons showed a trace of Musashi1 expression. Cells committed to the oligodendroglial lineage were Musashi(-). Musashi1 was localized to the perikarya of CNS stem-like cells and non-oligodendroglial progenitor cells without shifting to cell processes or endfeet, and is therefore advantageous for identifying each cell and counting cells in situ.

Mouse-Musashi-1, a neural RNA-binding protein highly enriched in the mammalian CNS stem cell

There is increasing interest in the role of RNA-binding proteins during neural development. Drosophila Musashi is one of the neural RNA-binding proteins essential for neural development and required for asymmetric cell divisions in the Drosophila adult sensory organ development. Here, a novel mammalian neural RNA-binding protein, mouse-Musashi-1, was identified based on the homology to Drosophila Musashi and Xenopus NRP-1. In the developing CNS, mouse-Musashi-1 protein was highly enriched in the CNS stem cell. Single-cell culture experiments indicated that mouse-Musashi-1 expression is associated with neural precursor cells that are capable of generating neurons and glia. In contrast, in fully differentiated neuronal and glial cells mouse-Musashi-1 expression is lost. This expression pattern of mouse-Musashi-1 is complementary to that of another mammalian neural RNA-binding protein, Hu (a mammalian homologue of a Drosophila neuronal RNA-binding protein Elav), that is expressed in postmitotic neurons within the CNS. In vitro studies indicated that mouse-Musashi-1 possesses binding preferences on poly(G) RNA homopolymer, whereas Hu is known to preferentially bind to short A/U-rich regions in RNA. Based on their differential expression patterns and distinct preferential target RNA sequences, we believe that the mouse-Musashi-1 and Hu proteins may play distinct roles in neurogenesis, either through sequential regulatory mechanisms or differential sorting of mRNA populations during asymmetric division of neural precursor cells.

Transplantation of in vitro-expanded fetal neural progenitor cells results in neurogenesis and functional recovery after spinal cord contusion injury in adult rats

Neural progenitor cells, including neural stem cells, are a potential expandable source of graft material for transplantation aimed at repairing the damaged CNS. Here we present the first evidence that in vitro-expanded fetus-derived neurosphere cells were able to generate neurons in vivo and improve motor function upon transplantation into an adult rat spinal-cord-contusion injury model. As the source of graft material, we used a neural stem cell-enriched population that was derived from rat embryonic spinal cord (E14.5) and expanded in vitro by neurosphere formation. Nine days after contusion injury, these neurosphere cells were transplanted into adult rat spinal cord at the injury site. Histological analysis 5 weeks after the transplantation showed that mitotic neurogenesis occurred from the transplanted donor progenitor cells within the adult rat spinal cord, a nonneurogenic region; that these donor-derived neurons extended their processes into the host tissues; and that the neurites formed synaptic structures. Furthermore, analysis of motor behavior using a skilled reaching task indicated that the treated rats showed functional recovery. These results indicate that in vitro-expanded neurosphere cells derived from the fetal spinal cord are a potential source for transplantable material for treatment of spinal cord injury.

The neural RNA-binding protein Musashi1 translationally regulates mammalian numb gene expression by interacting with its mRNA

Musashi1 (Msi1) is an RNA-binding protein that is highly expressed in neural progenitor cells, including neural stem cells. In this study, the RNA-binding sequences for Msi1 were determined by in vitro selection using a pool of degenerate 50-mer sequences. All of the selected RNA species contained repeats of (G/A)U(n)AGU (n = 1 to 3) sequences which were essential for Msi1 binding. These consensus elements were identified in some neural mRNAs. One of these, mammalian numb (m-numb), which encodes a membrane-associated antagonist of Notch signaling, is a likely target of Msi1. Msi1 protein binds in vitro-transcribed m-numb RNA in its 3'-untranslated region (UTR) and binds endogenous m-numb mRNA in vivo, as shown by affinity precipitation followed by reverse transcription-PCR. Furthermore, adenovirus-induced Msi1 expression resulted in the down-regulation of endogenous m-Numb protein expression. Reporter assays using a chimeric mRNA that combined luciferase and the 3'-UTR of m-numb demonstrated that Msi1 decreased the reporter activity without altering the reporter mRNA level. Thus, our results suggested that Msi1 could regulate the expression of its target gene at the translational level. Furthermore, we found that Notch signaling activity was increased by Msi1 expression in connection with the posttranscriptional down-regulation of the m-numb gene.

Ataxia and epileptic seizures in mice lacking type 1 inositol 1,4,5-trisphosphate receptor

The inositol 1,4,5-trisphosphate (InsP3) receptor acts as an InsP3-gated Ca2+ release channel in a variety of cell types. Type 1 InsP3 receptor (IP3R1) is the major neuronal member of the IP3R family in the central nervous system, predominantly enriched in cerebellar Purkinje cells but also concentrated in neurons in the hippocampal CA1 region, caudate-putamen, and cerebral cortex. Here we report that most IP3R1-deficient mice generated by gene targeting die in utero, and born animals have severe ataxia and tonic or tonic-clonic seizures and die by the weaning period. An electroencephalogram showed that they suffer from epilepsy, indicating that IP3R1 is essential for proper brain function. However, observation by light microscope of the haematoxylin-eosin staining of the brain and peripheral tissues of IP3R1-deficient mice showed no abnormality, and the unique electrophysiological properties of the cerebellar Purkinje cells of IP3R1-deficient mice were not severely impaired.

repo encodes a glial-specific homeo domain protein required in the Drosophila nervous system

We report the identification of a Drosophila locus, reversed polarity (repo). Weak repo alleles were viable but affected glia in the optic lobe, resulting in a reversal in polarity of the electrophysiological to light in the adult. Strong repo alleles caused defects in embryonic glia and resulted in embryonic lethality. Expression of repo appeared to be specific to glia throughout development. In the adult visual system, repo was expressed in laminal glia, medullar glia, and subretinal cells; in the embryo, repo was expressed in nearly all of the identified glia in the central and peripheral nervous systems except midline glia. The repo gene encoded a homeo domain protein suggesting that it might be a transcriptional regulator of genes required for glial development.

Transplantation of human neural stem cells for spinal cord injury in primates

Recent studies have shown that delayed transplantation of neural stem/progenitor cells (NSPCs) into the injured spinal cord can promote functional recovery in adult rats. Preclinical studies using nonhuman primates, however, are necessary before NSPCs can be used in clinical trials to treat human patients with spinal cord injury (SCI). Cervical contusion SCIs were induced in 10 adult common marmosets using a stereotaxic device. Nine days after injury, in vitro-expanded human NSPCs were transplanted into the spinal cord of five randomly selected animals, and the other sham-operated control animals received culture medium alone. Motor functions were evaluated through measurements of bar grip power and spontaneous motor activity, and temporal changes in the intramedullary signals were monitored by magnetic resonance imaging. Eight weeks after transplantation, all animals were sacrificed. Histologic analysis revealed that the grafted human NSPCs survived and differentiated into neurons, astrocytes, and oligodendrocytes, and that the cavities were smaller than those in sham-operated control animals. The bar grip power and the spontaneous motor activity of the transplanted animals were significantly higher than those of sham-operated control animals. These findings show that NSPC transplantation was effective for SCI in primates and suggest that human NSPC transplantation could be a feasible treatment for human SCI.

Musashi, a neural RNA-binding protein required for Drosophila adult external sensory organ development

A family of neural RNA-binding proteins has recently been described in both vertebrates and invertebrates. We have identified a new member of this family, the Drosophila musashi (msi) locus, which is required for development of adult external sensory organs (sensilla). In contrast with wild-type sensilla, which contain two outer support cells, the msi mutation typically results in the appearance of extra outer support cells. The msi putative RNA-binding protein is localized to the nucleus and appears to be expressed in all cells in each sensillum and predominantly in neurons during embryogenesis. We propose that the msi protein regulates sensillum development by controlling the expression of target genes at the posttranscriptional level.

Nestin-EGFP transgenic mice: visualization of the self-renewal and multipotency of CNS stem cells

We generated transgenic mice carrying enhanced green fluorescent protein (EGFP) under the control of the nestin second-intronic enhancer (E/nestin:EGFP). Flow cytometry followed by in vitro assays revealed that in situ EGFP expression in the embryonic brain correlated with the mitotic index, the cogeneration of both neurons and glia, and the frequency of neurosphere formation in vitro. High-level EGFP expressors derived from embryos included a distinct subpopulation of cells that were self-renewable and multipotent, criteria that define neural stem cells (NSCs). Such cells were largely absent among lower-level or non-EGFP expressors, thereby permitting us to enrich for NSCs using EGFP expression level. In adults, although E/nestin:EGFP-positive cells included the NSC population, the frequency of neurosphere formation did not correlate directly with the level of EGFP expression. However, moderately EGFP-expressing cells in adults gained EGFP intensity when they formed neurospheres, suggesting embryonic and adult NSCs exist in different microenvironments in vivo.

Neurogenesis by progenitor cells in the ischemic adult rat hippocampus

BACKGROUND AND PURPOSE

Recently, there has been great interest in adult neurogenesis. We investigated whether transient forebrain ischemia could influence the proliferation of neuronal progenitor in the subgranular zone (SGZ) of the rat hippocampus and whether aging could influence the neurogenesis after ischemia.

METHODS

Male Wistar rats were subjected to 4-vessel occlusion model. We used a bromodeoxyuridine (BrdU) labeling method to identify the postproliferation cells and double-immunostaining with confocal microscopy to determine the cell phenotype.

RESULTS

The number of BrdU-positive cells in the SGZ increased approximately 5.7-fold 8 days after ischemia, compared with the control. BrdU-positive cells formed clusters, which suggested that these cells had divided from an original progenitor cell, and expressed Musashi1 (Msi1), a marker of neural stem/progenitor cells. Although astrocytes also expressed Msi1 in the adult brain, Msi1-positive cells that formed clusters in the SGZ did not express glial fibrillary acidic protein, an astrocyte marker. About 70% of all BrdU-positive cells in the SGZ represented the neuronal phenotype 4 weeks after the BrdU injection. Although proliferation of progenitor cells was stimulated in both young and older animals, aging accelerated the reduction in newborn cells after ischemia.

CONCLUSIONS

Our results indicate that ischemic stress stimulated the proliferation of neuronal progenitor cells in the SGZ of both young and old rats but resulted in increased neurogenesis only in young animals. Our findings will be important in developing therapeutic intervention to enhance endogenous neurogenesis after brain injury.

WRM-1 activates the LIT-1 protein kinase to transduce anterior/posterior polarity signals in C. elegans

During C. elegans development, Wnt/WG signaling is required for differences in cell fate between sister cells born from anterior/posterior divisions. A beta-catenin-related gene, wrm-1, and the lit-1 gene are effectors of this signaling pathway and appear to downregulate the activity of POP-1, a TCF/LEF-related protein, in posterior daughter cells. We show here that lit-1 encodes a serine/threonine protein kinase homolog related to the Drosophila tissue polarity protein Nemo. We demonstrate that the WRM-1 protein binds to LIT-1 in vivo and that WRM-1 can activate the LIT-1 protein kinase when coexpressed in vertebrate tissue culture cells. This activation leads to phosphorylation of POP-1 and to apparent changes in its subcellular localization. Our findings provide evidence for novel regulatory avenues for an evolutionarily conserved Wnt/WG signaling pathway.

Brain from bone: efficient "meta-differentiation" of marrow stroma-derived mature osteoblasts to neurons with Noggin or a demethylating agent

Bone marrow stromal cells are able to differentiate into adipogenic, chondrogenic, myogenic, osteogenic, and cardiomyogenic lineages, all of which are limited to a mesoderm-derived origin. In this study, we showed that neurons, which are of an ectoderm-origin, could be generated from marrow-derived stromal cells by specific inducers, fibronectin/ornithine coating, and neurosphere formation. The neurons generated from marrow stroma formed neurites, expressed neuron-specific markers and genes, and started to respond to depolarizing stimuli as functional mature neurons. Among stromal cells, isolated mature osteoblasts which had strong in vivo osteogenic activity could be efficiently converted into functional neurons. This transdifferentiation or meta-differentiation was enhanced by Noggin, an inhibitor of bone morphogenetic proteins, in comparison with 5-azacytidine, a demethylating agent capable of altering the gene expression pattern. Marrow stroma is therefore a potential source of cells for neural cell transplantation.

Glial cell degeneration and hypomyelination caused by overexpression of myelin proteolipid protein gene

Myelin proteolipid protein (PLP), the major myelin protein in the CNS, has been thought to function in myelin assembly. Thus, mutations within the gene coding for PLP (Plp) cause hypomyelination, such as the jimpy phenotype in mice and Pelizaeus-Merzbacher disease in humans. However, these mutants often exhibit premature death of oligodendrocytes, which form CNS myelin. To elucidate the functional roles of Plp gene products in the maturation and/or survival of oligodendrocytes, we produced transgenic mice overexpressing the Plp gene by introducing extra wild-type mouse Plp genes. Surprisingly, transgenic mice bearing 4 more Plp genes exhibited dysmyelination in the CNS, whereas those with 2 more Plp genes showed normal myelination at an early age (3 weeks after birth), but later developed demyelination. Overexpression of the Plp gene resulted in arrested maturation of oligodendrocytes, and the severity of arrest was dependent on the extent of overexpression. Overexpression also led to oligodendrocyte cell death, apparently caused by abnormal swelling of the Golgi apparatus. Thus, tight regulation of Plp gene expression is necessary for normal oligodendrocyte differentiation and survival, and its overexpression can be the cause of both dys- and demyelination.

Blockade of interleukin-6 receptor suppresses reactive astrogliosis and ameliorates functional recovery in experimental spinal cord injury

Endogenous neural stem/progenitor cells (NSPCs) have recently been shown to differentiate exclusively into astrocytes, the cells that are involved in glial scar formation after spinal cord injury (SCI). The microenvironment of the spinal cord, especially the inflammatory cytokines that dramatically increase in the acute phase at the injury site, is considered to be an important cause of inhibitory mechanism of neuronal differentiation following SCI. Interleukin-6 (IL-6), which has been demonstrated to induce NSPCs to undergo astrocytic differentiation selectively through the JAK/STAT pathway in vitro, has also been demonstrated to play a critical role as a proinflammatory cytokine and to be associated with secondary tissue damage in SCI. In this study, we assessed the efficacy of rat anti-mouse IL-6 receptor monoclonal antibody (MR16-1) in the treatment of acute SCI in mice. Immediately after contusive SCI with a modified NYU impactor, mice were intraperitoneally injected with a single dose of MR16-1 (100 microg/g body weight), the lesions were assessed histologically, and the functional recovery was evaluated. MR16-1 not only suppressed the astrocytic diffentiation-promoting effect of IL-6 signaling in vitro but inhibited the development of astrogliosis after SCI in vivo. MR16-1 also decreased the number of invading inflammatory cells and the severity of connective tissue scar formation. In addition, we observed significant functional recovery in the mice treated with MR16-1 compared with control mice. These findings suggest that neutralization of IL-6 signaling in the acute phase of SCI represents an attractive option for the treatment of SCI.

Visualization, direct isolation, and transplantation of midbrain dopaminergic neurons

To visualize and isolate live dopamine (DA)-producing neurons in the embryonic ventral mesencephalon, we generated transgenic mice expressing green fluorescent protein (GFP) under the control of the rat tyrosine hydroxylase gene promoter. In the transgenic mice, GFP expression was observed in the developing DA neurons containing tyrosine hydroxylase. The outgrowth and cue-dependent guidance of GFP-labeled axons was monitored in vitro with brain culture systems. To isolate DA neurons expressing GFP from brain tissue, cells with GFP fluorescence were sorted by fluorescence-activated cell sorting. More than 60% of the sorted GFP(+) cells were positive for tyrosine hydroxylase, confirming that the population had been successfully enriched with DA neurons. The sorted GFP(+) cells were transplanted into a rat model of Parkinson's disease. Some of these cells survived and innervated the host striatum, resulting in a recovery from Parkinsonian behavioral defects. This strategy for isolating an enriched population of DA neurons should be useful for cellular and molecular studies of these neurons and for clinical applications in the treatment of Parkinson's disease.

Mammalian ELAV-like neuronal RNA-binding proteins HuB and HuC promote neuronal development in both the central and the peripheral nervous systems

Hu proteins are mammalian embryonic lethal abnormal visual system (ELAV)-like neuronal RNA-binding proteins that contain three RNA recognition motifs. Although Drosophila ELAV is required for the correct differentiation and survival of neurons, the roles played by the Hu genes in the mammalian nervous system remain largely unknown. To explore the in vivo functions of mouse Hu proteins, we overexpressed them in rat pheochromocytoma PC12 cells, where they induced neuronal phenotype in the absence of nerve growth factor. We have characterized the functions of various forms of mHuB and mHuC bearing point mutations or deletions. Mutants of mHuC that had amino acid exchanges in the RNP1 domain of the first or second RNA recognition motifs (RRMs) lost biologic activity as well as RNA-binding activity. In addition, the mutants containing only the third RRM failed to induce the neuronal phenotype in PC12 cells and inhibited the biologic activity of cotransfected wild-type mHuB and mHuC, thus acting as a dominant-negative form. However, these mutants could not suppress the nerve growth factor-induced differentiation of PC12 cells. Further, we misexpressed wild-type and dominant-negative Hu in E9.5 mouse embryos, by using electroporation into the neural tube at the level of the rhombencephalon. mHuB and mHuC induced the ectopic expression of neuronal markers, whereas the dominant-negative forms of mHuB and mHuC suppressed the differentiation of central nervous system motor neurons. From these results, we suggest that Hu proteins are required for neuronal differentiation in the mammalian nervous system.

Fibroblast growth factor-2/brain-derived neurotrophic factor-associated maturation of new neurons generated from adult human subependymal cells

The adult mammalian forebrain harbors neuronal precursor cells in the subependymal zone (SZ). Neuronal progenitors also persist in the adult human SZ and have been cultured from epileptic temporal lobe. In the present study, we sought to identify these neural progenitors in situ, and to direct their expansion and neuronal differentiation in vitro. We prepared explants of adult human SZ, obtained from temporal lobe resections of refractory epileptics. The resultant cultures were treated with fibroblast growth factor-2 (FGF-2) for a week, with concurrent exposure to [3H]thymidine, then switched to media containing brain-derived neurotrophic factor (BDNF) for up to 2 months. Sporadic neuronal outgrowth, verified antigenically and physiologically, was observed from SZ cultures regardless of FGF-2/BDNF treatment; however, only FGF-2/BDNF-treated cultures exhibited profuse outgrowth, and these displayed neuronal survival as long as 9 weeks in vitro. In addition, cortical cultures derived from two brains generated microtubule-associated protein-2+ neurons, which incorporated [3H]thymidine and exhibited significant calcium increments to depolarization. In histological sections of the subependyma, both uncommitted and restricted progenitors, defined respectively by musashi and Hu protein expression, were identified. Thus, the adult human subependyma harbors neural progenitors, which are able to give rise to neurons whose numbers can be supported for prolonged periods in vitro.

Control of the cell death pathway by Dapaf-1, a Drosophila Apaf-1/CED-4-related caspase activator

We identified a Drosophila Apaf-1/CED-4 homolog gene, dapaf-1. Alternative splicing results in two dapaf-1 mRNA species, which encode distinct forms of caspase activator, Dapaf-1L (Apaf-1 type) and Dapaf-1S (CED-4 type). Distinct caspases were activated by these Dapaf-1 isoforms. Loss of Dapaf-1 function resulted in defective cytochrome c-dependent caspase activities and reduced apoptosis in embryo and in larval brain. Dapaf-1 activities were also involved in cell death induced by ectopic expression of reaper in the compound eye. These data suggest that Dapaf-1/cytochrome c-dependent cell death-inducing machinery is present in Drosophila, and the requirement of Dapaf-1/Apaf-1 in neural cell death is conserved through evolution.

The Xenopus IP3 receptor: structure, function, and localization in oocytes and eggs

To study the role of the IP3 receptor (IP3R) upon egg activation, cDNA clones encoding IP3R expressed in the Xenopus oocytes were isolated. By analyses of the primary structure and functional expression of the cDNA, Xenopus IP3R (XIP3R) was shown to have an IP3-binding domain and a putative Ca2+ channel region. Immunocytochemical studies revealed polarized distribution of XIP3R in the cytoplasm of the animal hemisphere in a well-organized endoplasmic reticulum-like structure and intensive localization in the perinuclear region of stage VI immature oocytes. In ovulated unfertilized eggs, XIP3R was densely enriched in the cortical region of both hemispheres in addition to its polarized localization. After fertilization, XIP3R showed a drastic change in its distribution in the cortical region. These results imply the predominant role of the XIP3R in both the formation and propagation of Ca2+ waves at fertilization.

The subtypes of the mouse inositol 1,4,5-trisphosphate receptor are expressed in a tissue-specific and developmentally specific manner

Additional subtypes of the inositol 1,4,5-trisphosphate (InsP3) receptor are expressed in a tissue-specific and developmentally specific manner. They differ from the InsP3 receptor structure previously reported in two small variably spliced segments. One segment (SI) is located within the InsP3 binding site, whereas another segment (SII) is located near putative sites for phosphorylation and ATP binding to modulate InsP3 action on Ca2+ flux. Therefore, we speculate that selective use of InsP3 receptor subtypes permits a tissue-specific and developmentally specific expression of functionally distinct channels.

Dissection of signaling cascades through gp130 in vivo: reciprocal roles for STAT3- and SHP2-mediated signals in immune responses

We generated a series of knockin mouse lines, in which the cytokine receptor gp130-dependent STAT3 and/or SHP2 signals were disrupted, by replacing the mouse gp130 gene with human gp130 mutant cDNAs. The SHP2 signal-deficient mice (gp130F759/F759 were born normal but displayed splenomegaly and lymphadenopathy and an enhanced acute phase reaction. In contrast, the STAT3 signal-deficient mice (gp130FXQ/FXXQ) died perinatally, like the gp130-deficient mice (gp130D/D). The gp130F759/F759 mice showed prolonged gp130-induced STAT3 activation, indicating a negative regulatory role for SHP2. Th1-type cytokine production and IgG2a and IgG2b production were increased in the gp130F759/F759 mice, while they were decreased in the gp130FXXQ/FXXQ immune system. These results indicate that the balance of positive and negative signals generated through gp130 regulates the immune responses.

Promoter-targeted selection and isolation of neural progenitor cells from the adult human ventricular zone

Adult humans, like their nonhuman mammalian counterparts, harbor persistent neural progenitor cells in the forebrain ventricular lining. In the absence of adequate surface markers, however, these cells have proven difficult to isolate for study. We have previously identified and selected neural progenitor cells from both the fetal and adult rodent ventricular zone (VZ), by sorting forebrain cells transfected with plasmid DNA encoding the gene for green fluorescent protein driven by the early neuronal promoter for Talpha1 tubulin (P/Talpha1:hGFP). We have now extended this approach by purifying both P/Talpha1:hGFP tubulin-defined neuronal progenitors, as well as potentially less committed E/nestin:hGFP-defined neural progenitor cells, from the adult human VZ. The ventricular wall of the temporal horn of the lateral ventricle was dissected from temporal lobes obtained from four adult patients undergoing therapeutic lobectomy. These samples were dissociated, and the cultured cells transduced with either P/Talpha1:hGFP or E/nestin:EGFP plasmid DNA. A week later, the cells were redissociated, selected via fluorescence-activated cell sorting (FACS) on the basis of neural promoter-driven GFP expression, and replated. The majority of these cells expressed the early neuronal protein betaIII-tubulin upon FACS; within the week thereafter, most matured as morphologically evident neurons that coexpressed betaIII-tubulin and microtubule-associated protein (MAP)-2. Many of these neurons had incorporated bromodeoxyuridine in vitro in the days before FACS, indicating their mitogenesis in vitro. Thus, the use of fluorescent transgenes under the control of early neural promoters permits the enrichment of neuronal progenitor cells from the adult human ventricular zone. The specific acquisition, in both purity and number, of residual neural progenitor cells from the adult human brain may now permit hitherto unfeasible studies of both their biology and practical application.

Requirement of AP-1 for ceramide-induced apoptosis in human leukemia HL-60 cells

Ceramide has emerged as a novel lipid mediator in cell proliferation, differentiation, and apoptosis. In this work, we demonstrate that the levels of c-jun mRNA, c-Jun protein, and DNA binding activity of a nuclear transcription factor AP-1 to 12-o-tetradecanoylphorbol 13-acetate responsive elements all increased following treatment with the cell-permeable ceramide, N-acetylsphingosine in human leukemia HL-60 cells. N-Acetylsphingosine (1-10 microM) increased the levels of c-jun mRNA in a dose-dependent manner, and maximal expression was achieved 1 h after treatment. Increase of c-jun expression treated with 5 microM N-acetyldihydrosphingosine, which could not induce apoptosis, was one third of that with 5 microM N-acetylsphingosine. Ceramide-induced growth inhibition and DNA fragmentation were both prevented by treatment with curcumin, 1,7-bis[4-hydroxy-3-methoxy-phenyl]-1,6-heptadiene-3,5-dione (an inhibitor of AP-1 activation), or antisense oligonucleotides for c-jun. These results suggest that the transcription factor AP-1 is critical for apoptosis in HL-60 cells and that an intracellular sphingolipid mediator, ceramide, modulates a signal transduction inducing apoptosis through AP-1 activation.