Retrograde and anterograde labeling of cerebellar afferent projection by the injection of recombinant adenoviral vectors into the mouse cerebellar cortex

Development of adenoviral vectors that transduce Purkinje cells and other cerebellar cell-types in the cerebellum of a humanized mouse model

Viral vector gene therapy has immense promise for treating central nervous system (CNS) disorders. Although adeno-associated virus vectors (AAVs) have had success, their small packaging capacity limits their utility to treat the root cause of many CNS disorders. Adenoviral vectors (Ad) have tremendous potential for CNS gene therapy approaches. Currently, the most common vectors utilize the Group C Ad5 serotype capsid proteins, which rely on the Coxsackievirus-Adenovirus receptor (CAR) to infect cells. However, these Ad5 vectors are unable to transduce many neuronal cell types that are dysfunctional in many CNS disorders. The human CD46 (hCD46) receptor is widely expressed throughout the human CNS and is the primary attachment receptor for many Ad serotypes. Therefore, to overcome the current limitations of Ad vectors to treat CNS disorders, we created chimeric first generation Ad vectors that utilize the hCD46 receptor. Using a "humanized" hCD46 mouse model, we demonstrate these Ad vectors transduce cerebellar cell types, including Purkinje cells, that are refractory to Ad5 transduction. Since Ad vector transduction properties are dependent on their capsid proteins, these chimeric first generation Ad vectors open new avenues for high-capacity helper-dependent adenovirus (HdAd) gene therapy approaches for cerebellar disorders and multiple neurological disorders.

One-year follow-up of transgene expression by integrase-defective lentiviral vectors and their therapeutic potential in spinocerebellar ataxia model mice

We examined integrase-defective lentiviral vectors (IDLVs) with a mutant (D64V) integrase in terms of their residual integration capability, the levels and duration of transgene expression and their therapeutic potential in comparison to wild-type lentiviral vectors (WTLVs) with a wild-type integrase gene. Compared with WTLVs, the IDLV-mediated proviral integration into host-cell chromosomes was approximately 1/3850 in HeLa cells and approximately 1/111 in mouse cerebellar neurons in vivo. At 2 months, transgene expression by IDLVs in the mouse cerebellum was comparable to that by WTLVs, but then significantly decreased. The mRNA levels at 6 and 12 months after injection in IDLV-infected cerebella were approximately 26% and 5%, respectively, of the mRNA levels in WTLV-injected cerebella. To examine the therapeutic potential, IDLVs or WTLVs expressing a molecule that enhances the ubiquitin-proteasome pathway were injected into the cerebella of spinocerebellar ataxia type 3 model mice (SCA3 mice). IDLV-injected SCA3 mice showed a significantly improved rotarod performance even at 1 year after-injection. Immunohistochemistry at 1 year after injection showed a drastic reduction of mutant aggregates in Purkinje cellsfrom IDLV-injected, as well as WTLV-injected, SCA3 mice. Our results suggest that because of the substantially reduced risk of insertional mutagenesis, IDLVs are safer and potentially effective as gene therapy vectors.

Visualization of cortical projection neurons with retrograde TET-off lentiviral vector

We are interested in identifying and characterizing various projection neurons that constitute the neocortical circuit. For this purpose, we developed a novel lentiviral vector that carries the tetracycline transactivator (tTA) and the transgene under the TET Responsive Element promoter (TRE) on a single backbone. By pseudotyping such a vector with modified rabies G-protein, we were able to express palmitoylated-GFP (palGFP) or turboFP635 (RFP) in corticothalamic, corticocortical, and corticopontine neurons of mice. The high-level expression of the transgene achieved by the TET-Off system enabled us to observe characteristic elaboration of neuronal processes for each cell type. At higher magnification, we were able to observe fine structures such as boutons and spines as well. We also injected our retrograde TET-Off vector to the marmoset cortex and proved that it can be used to label the long-distance cortical connectivity of millimeter scale. In conclusion, our novel retrograde tracer provides an attractive option to investigate the morphologies of identified cortical projection neurons of various species.

Epha4 controls the midline crossing and contralateral axonal projections of inferior olive neurons

The guidance of axonal projections to ipsilateral and contralateral regions is essential for integration of bilateral sensory information and coordination of movement. In the development of olivocerebellar projections, newborn neurons of inferior olivary (IO) nuclei ventrally migrate from the hindbrain rhombic lip to the floor plate (FP). The cell bodies of IO neurons cannot cross the FP but their axons can, and thus IO neurons project their axons only to the contralateral cerebellar cortex. The molecular mechanisms determining the contralateral axonal projections of IO neurons, however, are obscure. The IO neurons and their axons express EphA4, whereas the FP expresses an EphA4 ligand, EphrinB3, from embryonic day 12.5. Therefore, we tested whether EphA4-deficient mice (EphA4(-/-) ) would show impairment in the development of olivocerebellar projections. We found that, in EphA4(-/-) embryos, some of the IO neurons projected their axons to the ipsilateral cerebellar cortex because the cell bodies of the IO neurons abnormally crossed the FP. Furthermore, even in adults, EphA4(-/-) cerebella were bilaterally innervated by unilateral IO subnuclei. These observations indicate that EphA4 is involved in the contralateral axonal projections of IO neurons by preventing their cell bodies from crossing the midline FP.

Selective and regulated gene expression in murine Purkinje cells by in utero electroporation

Cerebellar Purkinje cells, which convey the only output from the cerebellar cortex, play an essential role in cerebellar functions, such as motor coordination and motor learning. To understand how Purkinje cells develop and function in the mature cerebellum, an efficient method for molecularly perturbing them is needed. Here we demonstrate that Purkinje cell progenitors at embryonic day (E)11.5 could be efficiently and preferentially transfected by spatially directed in utero electroporation (IUE) with an optimized arrangement of electrodes. Electrophysiological analyses indicated that the electroporated Purkinje cells maintained normal membrane properties, synaptic responses and synaptic plasticity at postnatal days 25-28. By combining the L7 promoter and inducible Cre/loxP system with IUE, transgenes were expressed even more specifically in Purkinje cells and in a temporally controlled manner. We also show that three different fluorescent proteins could be simultaneously expressed, and that Bassoon, a large synaptic protein, could be expressed in the electroporated Purkinje cells. Moreover, phenotypes of staggerer mutant mice, which have a deletion in the gene encoding retinoid-related orphan receptor α (RORα1), were recapitulated by electroporating a dominant-negative form of RORα1 into Purkinje cells at E11.5. Together, these results indicate that this new IUE protocol, which allows the selective, effective and temporally regulated expression of multiple foreign genes transfected into Purkinje cell progenitors in vivo, without changing the cells' physiological characteristics, is a powerful tool for elucidating the molecular mechanisms underlying early Purkinje cell developmental events, such as dendritogenesis and migration, and synaptic plasticity in mature Purkinje cells.

Gene transfer to the cerebellum

There are several diseases for which gene transfer therapy to the cerebellum might be practicable. In these studies, we used recombinant Tag-deleted SV40-derived vectors (rSV40s) to study gene delivery targeting the cerebellum. These vectors transduce neurons and microglia very effectively in vitro and in vivo, and so we tested them to evaluate gene transfer to the cerebellum in vivo. Using a rSV40 vector carrying human immunodeficiency virus (HIV)-Nef with a C-terminal FLAG epitope, we characterized the distribution, duration, and cell types transduced. Rats received test and control vectors by stereotaxic injection into the cerebellum. Transgene expression was assessed 1, 2, and 4 weeks later by immunostaining of serial brain sections. FLAG epitope-expressing cells were seen, at all times after vector administration, principally detected in the Purkinje cells of the cerebellum, identified as immunopositive for calbindin. Occasional microglial cells were tranduced; transgene expression was not detected in astrocytes or oligodendrocytes. No inflammatory or other reaction was detected at any time. Thus, SV40-derived vectors can deliver effective, safe, and durable transgene expression to the cerebellum.

High transgene expression by lentiviral vectors causes maldevelopment of Purkinje cells in vivo

Lentiviral vectors are promising as gene-transfer vehicles for gene therapy targeted to intractable brain diseases. Although lentiviral vectors are thought to exert little toxicity on infected cells, the adverse influence of viral infection on vulnerable developing neurons has not been well studied. Here, we examined whether lentiviral vector infection and subsequent transgene expression affected the morphological and functional maturation of vigorously developing cerebellar Purkinje cells in vivo. Lentiviral vectors expressing GFP under the control of the murine stem cell virus (MSCV) promoter were injected into the cerebellar cortex of neonatal rat pups. Three weeks after treatment, GFP-expressing Purkinje cells were compared with control Purkinje cells from phosphate-buffered saline-injected rats. Analysis of the dendritic tree showed that total dendrite length in GFP-expressing Purkinje cells was almost 80% that in control Purkinje cells. Electrophysiological examination showed that short-term synaptic plasticity at parallel fiber-Purkinje cell synapses and climbing fiber-Purkinje cell synapses was significantly altered in GFP-expressing Purkinje cells. In contrast, maldevelopment of infected Purkinje cells was substantially attenuated when lentiviral vectors with much weaker promoter activity were used. These results suggest that the maldevelopment of Purkinje cells was mainly caused by subsequent expression of a high amount of GFP driven by the strong MSCV promoter. Thus, the use of lentiviral vectors carrying a strong promoter may require particular precautions when applying them to neurological disorders of infants.

Inositol 1,4,5-trisphosphate signaling maintains the activity of glutamate uptake in Bergmann glia

The maintenance of synaptic functions is essential for neuronal information processing in the adult brain. Astrocytes express glutamate transporters that rapidly remove glutamate from the extracellular space and they play a critical role in the precise operation of glutamatergic transmission. However, how the glutamate clearance function of astrocytes is maintained remains elusive. Here, we describe a maintenance mechanism for the glutamate uptake capacity of Bergmann glial cells (BGs) in the cerebellum. When inositol 1,4,5-trisphosphate (IP(3) ) signaling was chronically and selectively inhibited in BGs in vivo, the retention time of glutamate around parallel fiber-Purkinje cell synapses was increased. Under these conditions, a decrease in the level of the glutamate/aspartate transporter (GLAST) in BGs was observed. The same effects were observed after chronic in vivo inhibition of purinergic P2 receptors in the cerebellar cortex. These results suggest that the IP(3) signaling cascade is involved in regulating GLAST levels in BGs to maintain glutamate clearance in the mature cerebellum.

A bicistronic lentiviral vector-based method for differential transsynaptic tracing of neural circuits

We developed a bicistronic HIV1-derived lentiviral vector system co-expressing green fluorescent protein (AcGFP1) and wheat germ agglutinin (WGA) mediated by picornaviral 2A peptide. This system was first applied to the analysis of the rat cerebellar efferent pathways. When the lentiviral vector was injected into a specific lobule, the local Purkinje cell population (first-order neurons) was efficiently infected and co-expressed both AcGFP1 and WGA protein. In the second-order neurons in the cerebellar and vestibular nuclei, WGA but not AcGFP1 protein was differentially detected, demonstrating that the presence of AcGFP1 protein enables discrimination of first-order neurons from second-order neurons. Furthermore, WGA protein was detected in the contralateral ventrolateral thalamic nucleus (third-order nucleus). This system also successfully labeled rat cortical pathways from the primary somatosensory cortex and monkey cerebellar efferent pathways. Thus, this bicistronic lentiviral vector system is a useful tool for differential transsynaptic tracing of neural pathways originating from local brain regions.

Viral strategies for studying the brain, including a replication-restricted self-amplifying delta-G vesicular stomatis virus that rapidly expresses transgenes in brain and can generate a multicolor golgi-like expression

Viruses have substantial value as vehicles for transporting transgenes into neurons. Each virus has its own set of attributes for addressing neuroscience-related questions. Here we review some of the advantages and limitations of herpes, pseudorabies, rabies, adeno-associated, lentivirus, and others to study the brain. We then explore a novel recombinant vesicular stomatitis virus (dG-VSV) with the G-gene deleted and transgenes engineered into the first position of the RNA genome, which replicates only in the first brain cell infected, as corroborated with ultrastructural analysis, eliminating spread of virus. Because of its ability to replicate rapidly and to express multiple mRNA copies and additional templates for more copies, reporter gene expression is amplified substantially, over 500-fold in 6 hours, allowing detailed imaging of dendrites, dendritic spines, axons, and axon terminal fields within a few hours to a few days after inoculation. Green fluorescent protein (GFP) expression is first detected within 1 hour of inoculation. The virus generates a Golgi-like appearance in all neurons or glia of regions of the brain tested. Whole-cell patch-clamp electrophysiology, calcium digital imaging with fura-2, and time-lapse digital imaging showed that neurons appeared physiologically normal after expressing viral transgenes. The virus has a wide range of species applicability, including mouse, rat, hamster, human, and Drosophila cells. By using dG-VSV, we show efferent projections from the suprachiasmatic nucleus terminating in the periventricular region immediately dorsal to the nucleus. DG-VSVs with genes coding for different color reporters allow multicolor visualization of neurons wherever applied.

Progress in transduction of cerebellar Purkinje cells in vivo using viral vectors

Expression of a foreign gene in cerebellar Purkinje cells in vivo is a powerful method for exploring the pathophysiology of the cerebellum. Although using developmental engineering many gene-modified mice have been generated, this approach is time-consuming and requires a lot of effort for crossing different lines of mice, genotyping and maintenance of animals. If a gene of interest can be transferred to and efficiently expressed in Purkinje cells of developing and mature animals, it saves much time, effort and money. Recent advances in viral vectors have markedly contributed to selective and efficient gene transfer to Purkinje cells in vivo. There are two approaches for selective gene expression in Purkinje cells: one is to take advantage of the viral tropism for Purkinje cells, which includes the tropism of adeno-associated virus and the vesicular stomatitis virus glycoprotein (VSV-G)-pseudotyped lentivirus. Another method, which might be used in combination with the first one, is utilization of a Purkinje-cell-specific promoter. Focusing mainly on these points, recent progress in viral-vector-mediated transduction of Purkinje cells in vivo is reviewed.

Potential usefulness of D2R reporter gene imaging by IBF as gene therapy monitoring for cerebellar neurodegenerative diseases

We investigated a gene expression imaging method to examine the level of therapeutic gene expression in the cerebellum. Using a human immunodeficiency virus derived lentivial vector, we expressed the dopamine D(2) receptor (D(2)R) as a reporter protein to mouse cerebellar Purkinje cells. Biodistribution and ex vivo autoradiography studies were performed by giving [(125)I]5-iodo-7-N-[(1-ethyl-2-pyrrolidinyl)methyl]carboxamide-2,3-dihydrobenzofuran ([(125)I]IBF) (1.85 MBq), as a radioactive D(2)R ligand, to model mice expressing the D(2)R with an HA tag (HA-D(2)R) in the cerebellum. In this study, [(125)I]IBF was bound to the D(2)R expressed in the cerebellum of the model mice selectively. Immunostaining was performed to confirm the HA-D(2)R expression in the cerebellum of the model mice. A significant correlation (r=0.900, P<0.001) between areas that expressed HA-D(2)R by immunostaining and areas in which [(125)I]IBF accumulated by the ex vivo autoradiograms was found. These results indicated that radioiodinated IBF is useful as a reporter probe to detect D(2)R reporter gene expression, which can be used for monitoring therapeutic gene expression in the cerebellum.

Retrograde infection of precerebellar nuclei neurons by injection of a recombinant adenovirus into the cerebellar cortex of normal and reeler mice

The reeler mouse is an autosomal recessive mutant mouse caused by mutation of the reelin gene and characterized by cerebellar ataxia. To determine whether the distribution pattern of precerebellar nuclei neurons in the brainstem of the reeler mouse changes, we injected a small volume of a replication-defective recombinant adenovirus carrying E. coli beta-galactosidase (lacZ) into the cerebellar cortex of normal and reeler mice. Five days later, the mice were transcardially perfused by a fixative solution. X-gal staining of coronal or sagittal sections of the brainstem revealed that many origins for reticulocerebellar, cuneocerebellar, trigeminocerebellar, and pontocerebellar projections were retrogradely labeled, but only a few olivocerebellar neurons were labeled. Retrogradely labeled neurons in the lateral reticular nucleus tended to locate more laterally and be more condensed into a small compartment in the reeler compared with their normal counterparts. Retrogradely labeled neurons in the external cuneate nucleus were more dorsally shifted in the reeler mice compared with their normal counterparts. We could not find any differences between the normal and reeler mice in the distribution patterns of their trigeminocerebellar projection neurons. Retrogradely labeled pontocerebellar neurons in the basilar pons of the reeler mouse were reduced in number compared with their normal counterparts in addition to being more ventrally and laterally shifted. These findings strongly suggest that the migration of some precerebellar nuclei neurons from the rhombic lip to their final loci may be obstructed in the reeler mice.

Migration and nucleogenesis of mouse precerebellar neurons visualized by in utero electroporation of a green fluorescent protein gene

Neural migration is a critical step for accurate CNS development, but the molecular mechanisms that regulate migration, settlement and nucleogenesis remain largely unknown. The precerebellar neurons (PCNs), generated in the lower rhombic lip (LRL), migrate towards their destinations: some neurons form the pontine gray nucleus (PGN) and reticulotegmental nucleus (RTN) in the ipsilateral pons, while others form the lateral reticular and external cuneate nuclei in the contralateral medulla after crossing the midline. Here, by introducing an EGFP gene into a unilateral LRL of mouse embryos by in utero electroporation, we specifically labeled and tracked the PCNs in vivo. We found that a substantial number of the labeled neurons crossed the midline and formed PGN/RTN on the contralateral side. In addition, we found that a subpopulation of the interpolar subnucleus of the spinal trigeminal nucleus, which projects the axons to the cerebellum, was one of the PCNs derived from the LRL. Furthermore, because the electroporated mice were born and grew up healthy, we could visualize the PCNs and their mossy fibers in the adult brain. Therefore, the EGFP labeling of PCNs can be applied to studying the physiology of the mossy fiber system as well as PCN development in embryos.

In vivo transduction of murine cerebellar Purkinje cells by HIV-derived lentiviral vectors

Cerebellar Purkinje cells are key elements in motor learning and motor coordination, and therefore, it is important to clarify the mechanisms by which Purkinje cells integrate information and control cerebellar function. Gene transfer into neurons, followed by the assessment of the effects on neural function, is an effective approach for examining gene function. However, this method has not been used fully in the study of the cerebellum because adenovirus vectors, the vectors most commonly used for in vivo gene transfer, have very low affinity for Purkinje cells. In this study, we used a human immunodeficiency virus (HIV)-derived lentiviral vector and examined the transduction profile of the vector in the cerebellum. A lentiviral vector carrying the GFP gene was injected into the cerebellar cortex. Seven days after the injection, Purkinje cells were efficiently transduced without significant influence on the cell viability and synaptic functions. GFP was also expressed, though less efficiently, in other cortical interneurons and Bergmann glias. In contrast to reported findings with other viral vectors, no transduced cells were observed outside of the cerebellar cortex. Thus, when HIV-derived lentiviral vectors were injected into the cerebellar cortex, transduction was limited to the cells in the cerebellar cortex, with the highest tropism for Purkinje cells. These results suggest that HIV-derived lentiviral vectors are useful for the study of gene function in Purkinje cells as well as for application as a gene therapy tool for the treatment of diseases that affect Purkinje cells.

Improved Golgi-like Visualization in Retrogradely Projecting Neurons after EGFP-Adenovirus Infection in Adult Rat and Monkey

An adenovirus vector was generated using a neuron-specific promoter synapsin I and enhanced green fluorescent protein (EGFP) reporter (AdSynEGFP). In addition, two modifications were identified that resulted in robust and reliable retrograde transport and EGFP expression after injection of the virus into three different brain regions in adult rats (medial prefrontal cortex, posterior thalamic nuclear group, and CA1). These are post-injection survival times of 14 days and addition of high concentrations of NaCl (≥600 mM) to the injection buffer. These modifications resulted in obvious improvement in the intensity of the EGFP signal and in the number of labeled cells. Use of anti-EGFP in immunofluorescence or immunoperoxidase processing further enhanced the signal so that Golgi-like filling of dendritic spines and axon collaterals was routinely achieved. Effectiveness of the AdSynEGFP for Golgi-like filling was confirmed in one rhesus monkey with injections in visual area V4. Because of the long-term viability of the infected neurons (at least up to 28 days in rats and 22 days in monkey), this AdSynEGFP is suitable for use in microcircuitry studies in combination with other fluorescently tagged elements, including anterogradely labeled extrinsic projections. The native EGFP signal (without antibody enhancement) may be sufficient for studies involving cultured cells or slices. (J Histochem Cytochem 54:539-548, 2006)

In vivo Evidence for Radial Migration of Neurons by Long-Distance Somal Translocation in the Developing Ferret Visual Cortex

During the development of the cerebral cortex, neurons generated in the cortical ventricular zone migrate radially toward the marginal zone. Radially migrating neurons are thought to display 1 of 2 morphologies: cells with a long, pia-contacting, apical process utilized for somal translocation early in development, when the cortex is still relatively thin; or cells with a short leading process, abundant at late stages of corticogenesis when neurons need to travel for longer distances. In large convoluted brains, like those of many primates and carnivores, radially migrating neurons must travel distances up to several millimeters before reaching their final destination, often following curvilinear trajectories. Here we analyze modes and morphologies of radially migrating neurons in convoluted brains by studying the visual cortex of developing ferrets. We provide in vivo and in vitro evidence for the existence of late-born cortical neurons that migrate radially by long-distance somal translocation within a long apical process extended to the cortical plate, in contrast to the early somal translocation observed in rodents. Long-distance translocating neurons in the ferret show a discontinuous rhythm of migration, alternating periods of advance with periods of stall. Furthermore, by combining different labeling methods we find the simultaneous presence in the developing ferret cortex of long-distance translocating neurons and neurons migrating within a short leading process.

Adenovirus-mediated gene transfer in olfactory epithelium and olfactory bulb: a long-term study

OBJECTIVES

We sought to study the spatiotemporal gene expression mediated by adenoviral vector in the olfactory pathways.

METHODS

The replication-defective adenoviral vector AxCALacZ, which encodes the enzyme Escherichia coli beta-galactosidase, was applied to mouse olfactory epithelium by intranasal instillation.

RESULTS

The LacZ gene product, beta-galactosidase, was expressed not only in the olfactory receptor neurons and their axons, but also in the olfactory bulbs. The first evidence of anterograde labeling was observed at postinfection day (PID) 2. At PID 3, beta-galactosidase was strongly expressed in olfactory nerve axons, as well as their terminal glomeruli, in the olfactory bulbs. beta-Galactosidase expression persisted up to PID 90, and there was a significant decrease in the number of labeled neurons at PID 30.

CONCLUSIONS

These results suggest possible long-term effects of adenovirus-mediated gene transfer on the olfactory neurons, as well as the olfactory bulbs.

Cytoplasmic dynein mediates adenovirus binding to microtubules

During infection, adenovirus (Ad) capsids undergo microtubule-dependent retrograde transport as part of a program of vectorial transport of the viral genome to the nucleus. The microtubule-associated molecular motor, cytoplasmic dynein, has been implicated in the retrograde movement of Ad. We hypothesized that cytoplasmic dynein constituted the primary mode of association of Ad with microtubules. To evaluate this hypothesis, an Ad-microtubule binding assay was established in which microtubules were polymerized with taxol, combined with Ad in the presence or absence of microtubule-associated proteins (MAPs), and centrifuged through a glycerol cushion. The addition of purified bovine brain MAPs increased the fraction of Ad in the microtubule pellet from 17.3% +/- 3.5% to 80.7% +/- 3.8% (P < 0.01). In the absence of tubulin polymerization or in the presence of high salt, no Ad was found in the pellet. Ad binding to microtubules was not enhanced by bovine brain MAPs enriched for tau protein or by the addition of bovine serum albumin. Enhanced Ad-microtubule binding was also observed by using a fraction of MAPs purified from lung A549 epithelial cell lysate which contained cytoplasmic dynein. Ad-microtubule interaction was sensitive to the addition of ATP, a hallmark of cytoplasmic dynein-dependent microtubule interactions. Immunodepletion of cytoplasmic dynein from the A549 cell lysate abolished the MAP-enhanced Ad-microtubule binding. The interaction of Ad with both dynein and dynactin complexes was demonstrated by coimmunoprecipitation. Partially uncoated capsids isolated from cells 40 min after infection also exhibited microtubule binding. In summary, the primary mode of Ad attachment to microtubules occurs though cytoplasmic dynein-mediated binding.

Spinal 5-HT2A receptors regulate cutaneous sympathetic vasomotor outflow in rabbits and rats; relevance for cutaneous vasoconstriction elicited by MDMA (3,4-methylenedioxymethamphetamine, “Ecstasy”) and its reversal by clozapine

We determined whether spinal 5-hydroxytryptamine 2A (5-HT2A) receptors contribute to resting cutaneous sympathetic vasomotor activity, and to increases in activity elicited by electrical stimulation of the medullary raphe/parapyramidal region, and whether these receptors are involved in the cutaneous vasoconstricting action of systemically administered MDMA (3,4-methylenedioxymethamphetamine, "Ecstasy") and its reversal by clozapine. Experiments were conducted in urethane-anesthetized rabbits and rats. Administration of the 5-HT2A antagonist, trans-4-((3Z)3-[(2-Dimethylaminoethyl)oxyimino]-3-(2-fluorophenyl)propen-1-yl)-phenol, hemifumarate (SR 46349B, 0.1 mg/kg, i.v.) inhibited resting ear pinna sympathetic vasomotor nerve discharge and reduced the extent to which raphe/parapyramidal electrical stimulation caused ear pinna (rabbit) and tail (rat) artery blood flow to fall. Clozapine (0.125-0.5 mg/kg, i.v.) also reduced the fall in ear pinna blood flow elicited by raphe/parapyramidal stimulation. In rabbits, after inactivation of raphe/parapyramidal function by local microinjection of muscimol (1 nmol in 100 nl), the 5-HT2A agonist R(-)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane hydrochloride (DOI, 50 microg/kg, i.v.) increased ear pinna sympathetic nerve activity from 3+/-2% to 129+/-5% of pre-muscimol levels (P<0.01, n=6), and this increase was abolished by section of the ipsilateral cervical sympathetic nerve trunk. MDMA (2 mg/kg, i.v.) after muscimol decreased ear pinna blood flow from 33+/-10 to 2+/-1 cm/s (P<0.01, n=5) and increased ear pinna sympathetic nerve activity from 8+/-4% to 120+/-41% of pre-muscimol levels (P<0.01, n=6). The MDMA-elicited increase in nerve activity was abolished by SR 46349B. Data suggest that spinal 5-HT2A receptors contribute to sympathetically induced cutaneous vasoconstriction regulated by raphe/parapyramidal neurons in the brainstem, and that these receptors contribute to the cutaneous vasoconstricting action of MDMA and its reversal by clozapine.

Retrograde labeling of mouse spinal descending tracts by a recombinant adenovirus

The present study tested whether a gene-transfer based upon the retrograde axonal transport of the lacZ adenovirus is effective in the spinal descending tracts of the adult mouse. A small volume of a replication-defective recombinant adenovirus encoding E. coli beta-galactosidase was injected into the upper lumbar cord, and, seven days later, the mice were transcardially perfused by a fixative solution. X-gal staining of coronal or sagittal sections of the spinal cord and the brain revealed that many sites of origin for rubrospinal, vestibulospinal, and reticulospinal tracts were retrogradely labeled, whereas few of the corticospinal tract neurons were retrogradely labeled. Ependymal cells surrounding the central canal of the spinal cord, which were located far from the injection site, showed a high expression of beta-galactosidase activity. Motoneurons around the injection site were strongly stained by X-gal staining, and their axons in the ventral root were anterogradely labeled. Afferent fibers in the dorsal root were labeled by the transganglionic transport of beta-galactosidase. To examine the efficacy of the uptake and retrograde transport of HRP and adenovirus, we injected a mixed solution of 10% HRP and recombinant adenovirus. The number of HRP-labeled corticospinal neurons overwhelmed the number of X-gal stained ones, while the numbers of HRP-labeled rubrospinal and subcoeruleus-spinal neurons were smaller in comparison with the numbers of beta-galactosidase-positive counterparts. The present study revealed that the origins for the spinal descending tracts except for corticospinal neurons could be efficiently gene-transferred by the retrograde infection of a recombinant adenovirus. Such a difference in efficacy of retrograde infection among the spinal descending tracts is practically important when an adenovirus-mediated gene transfer is designed to treat certain neurological diseases affecting the spinal descending tracts.

Expression of the activating transcription factor 3 prevents c-Jun N-terminal kinase-induced neuronal death by promoting heat shock protein 27 expression and Akt activation

Activating transcription factor 3 (ATF3) is induced and functions both as a cellular response to stress and to stimulate proliferation in multiple tissues. However, in the nervous system ATF3 is expressed only in injured neurons. Here we reveal a function of ATF3 in neurons under death stress. Overexpression of ATF3 by adenovirus inhibits the mitogen-activated kinase kinase kinase 1 (MEKK1)-c-Jun N-Terminal Kinase (JNK)-induced apoptosis and induces neurite elongation via Akt activation in PC12 cells and superior nerve ganglion neurons. A DNA microarray study reveals that ATF3 expression and JNK activation induce expression of the heat shock protein 27 (Hsp27). Immunoprecipitation analysis and promoter assay for Hsp27 expression suggest that both ATF3 and c-Jun are necessary for transcriptional activation of Hsp27. Hsp27 expression significantly inhibits JNK-induced apoptosis as well as Akt activation in PC12 cells and superior cervical ganglion neurons. We conclude that the combination of ATF3 and c-Jun induces the anti-apoptotic factor Hsp27, which directly or indirectly activates Akt, and thereby possibly inhibits apoptosis and induces nerve elongation. Our results suggest that ATF3- and c-Jun-induced Hsp27 expression is a novel survival response in neurons under death stress such as nerve injury.

Transneuronal tracing of diverse CNS circuits by Cre-mediated induction of wheat germ agglutinin in transgenic mice

Systems neuroscience addresses the complex circuits made by populations of neurons in the CNS and the cooperative function of these neurons. Improved approaches to the neuroanatomical analysis of CNS circuits are thus of great interest. In fact, significant advances in tract-tracing methods have recently been made by using transgenic mice that express transneuronal lectin tracers under the control of neuron-specific promoters. The utility of those animals, however, is limited to the CNS circuit influenced by the particular promoter. Here, we describe a new transgenic mouse that can be used for transneuronal tracing analysis of circuits in any region of the brain or spinal cord. The transgene in these mice results in expression of LacZ in neurons throughout the CNS. Excision of the LacZ gene by Cre-mediated recombination initiates expression of the lectin, wheat germ agglutinin (WGA). To illustrate the diverse uses of these ZW (LacZ-WGA) mice, we triggered WGA expression either by crossing the mice with two Cre-expressing transgenic mouse lines or by microinjecting a Cre-expressing adeno-associated virus into the cerebellum or cerebral cortex. Both approaches resulted in extensive WGA expression in the cell bodies and dendrites of neurons in which the recombination event occurred, as well as anterograde and transneuronal transport of the lectin to second and third order neurons. Because the lectin can be induced in developing and adult animals, and in all regions of the brain and spinal cord, these ZW may prove extremely valuable for numerous studies of CNS circuit analysis.

Developmental alteration of nerve injury induced glial cell line-derived neurotrophic factor (GDNF) receptor expression is crucial for the determination of injured motoneuron fate

Axotomy-induced neuronal death occurs in neonatal motoneurons, but not in adult rat. Here we demonstrated that during the course of postnatal development, nerve injury induced down-regulation of the glial cell line-derived neurotrophic factor (GDNF) receptor GFRalpha1 in axotomized hypoglossal motoneurons of rat are gradually converted to the adult up-regulation pattern of response. The compensatory expression of GFRalpha1 specifically in the injured motoneurons of neonates by adenovirus succeeded in rescuing the injured neurons without an application of growth factors. To the contrary, the nuclear antisense RNA for GFRalpha1 expression accelerates the axotomy-induced neuronal death in pups. These findings suggest that the receptor expression response after nerve injury is critical for the determination of injured motoneuron fate.

Corticostriatopallidal neuroprotection by adenovirus-mediated ciliary neurotrophic factor gene transfer in a rat model of progressive striatal degeneration

Ciliary neurotrophic factor (CNTF) is a potent protective factor for striatal neurons in animal models of Huntington's disease (HD). Clinical application of this potential therapeutic still requires the design and optimization of delivery systems. In the case of HD, spatial spread in the vast volume occupied by the striatum and long-term delivery of the factor are particular challenges for these systems. We explored the potential of adenovirus-mediated gene transfer to fulfill these requirements by studying the functional and anatomical effects of single-site striatal delivery of CNTF recombinant vectors in a rat model of HD. In an initial series of experiments, unilateral injections of CNTF adenovirus were performed in rats 10, 30, or 90 d before a 5 d neurotoxic treatment with systemic 3-nitropropionic acid (3NP). Preservation of striatal neurons was observed at all time points, demonstrating temporally extended neuroprotective effects of the CNTF adenovirus. In a second series of experiments, bilateral injections of CNTF adenovirus were performed in the medial aspect of the striatum 10 d before starting 3NP intoxication. Despite placement of the CNTF-producing vector outside the lateral striatal area susceptible to lesion, massive protection of corticostriatopallidal circuits was observed, associated with significant behavioral benefits. This spatial spread of neuroprotection is discussed with reference to the retrograde transport of the adenovirus vector and the anterograde transport of the transgenic CNTF. Overall, adenovirus-mediated CNTF gene transfer appears to be a potentially useful delivery system for widespread, long-term circuit neuroprotection in HD patients.

Highly efficient and specific gene transfer to Purkinje cells in vivo using a herpes simplex virus I amplicon

The transduction of cerebellar neurons in vivo with herpes simplex virus 1 (HSV-1) amplicon carrying the lacZ gene has been investigated after injection of the vector in the cerebellar cortex, ventricles, and inferior olive of adult rats. Injection into the cerebellar cortex resulted in transduction of Purkinje cells near the needle tract and injection into the ventricles yielded no transduced neurons. In contrast, high transduction efficiency was achieved by vector injection into the inferior olive, resulting in one of three positive Purkinje cells all over the ipsilateral and contralateral cerebellar hemispheres. Because neurons in the deep cerebellar nuclei are also transduced, we suggest that the vector is delivered from the inferior olive to the cerebellar nuclei and then to Purkinje cells by retrograde axonal transport. Expression of the lacZ gene within Purkinje cells was surprisingly persistent and was maintained at the same level for at least 40 days. Importantly, no signs of either toxicity or inflammation were observed in the cerebellum after vector injection, except for the borders of the needle tract where some reactive astrocytes were detected. Indeed, motor coordination of treated animals was entirely normal, as assessed by the rota-rod test. These results demonstrate that HSV-1 amplicon vectors can effect safe and stable transgene expression in Purkinje cells in vivo, raising the possibility of using these vectors for long-term gene therapy of human cerebellar disorders.

Expression of human cystatin A by keratinocytes is positively regulated via the Ras/MEKK1/MKK7/JNK signal transduction pathway but negatively regulated via the Ras/Raf-1/MEK1/ERK pathway

Cystatin A, a cysteine proteinase inhibitor, is a cornified cell envelope constituent expressed in the upper epidermis. We previously reported that a potent protein kinase C activator, 12-O-tetradecanoylphorbol-13-acetate, increases human cystatin A expression by the activation of AP-1 proteins. Here, we delineate the signaling cascade responsible for this regulation. Co-transfection of the cystatin A promoter into normal human keratinocytes together with a dominant active form of ras increased the promoter activity by 3-fold. In contrast, a dominant negative form of ras suppressed basal cystatin A promoter activity. Further analyses disclosed that transfection of dominant negative forms of raf-1, MEK1, ERK1, ERK2, or wild-type MEKK1 all increased cystatin A promoter activity in normal human keratinocytes, whereas wild-type raf-1, ERK1, ERK2, or dominant negative forms of MEKK1, MKK7, or JNK1 suppressed the promoter activity. The increased or decreased promoter activity reflected the expression of cystatin A on mRNA and protein levels. These effects were not observed when a cystatin A promoter with a T2 (-272 to -278) deletion was used. In contrast, transfection of dominant negative forms of MKK3, MKK4, or p38 did not affect cystatin A promoter activity. Immunohistochemical analyses revealed that phosphorylated active extracellular signal-regulated kinases and c-Jun N-terminal kinase were expressed in the nuclei of basal cells and cells in the suprabasal-granular cell layer, respectively. These results indicate that the expression of cystatin A is regulated via mitogen-activated protein kinase pathways positively by Ras/MEKK1/MKK7/JNK and negatively by Ras/Raf/MEK1/ERK.

Callosal commissural neurons of Dab1 deficient mutant mouse, yotari

The yotari mouse is an autosomal recessive mutant mouse, caused by mutation of disabled homolog 1 (Dab1) gene. The mutant mouse is recognized by unstable gait and tremor and by early deaths around at the time of weaning. The cytoarchitectures of cerebeller and cerebral cortices and hippocampal formation of the yotari mouse are abnormal. These malformations strikingly resemble those of reeler mouse. In the present study we examined the callosal commissural (CC) neurons of yotari, reeler and normal mice with the injection of recombinant adenovirus into the frontal area 1 (Fr1) to find some possible phenotypes specific for the yotari mouse. The distribution pattern of CC neurons of the yotari was similar to that of the reeler: retrogradely labeled CC neurons were seen throughout all depths of the contralateral Fr1. However, the present statistical analysis revealed that the difference of the mean intracortical position of the CC neurons between the yotari and the reeler is significantly different (Student's t-test), suggesting that the phenotype of the yotari is clearly different from that of the reeler.

Tracing axons in the peripheral nerve using lacZ gene recombinant adenovirus and its application to regeneration of the peripheral nerve

The usefulness of recombinant adenovirus with LacZ to trace axons in the peripheral nervous system was investigated. Recombinant adenovirus with LacZ was applied to the cut end of the tibial nerve in rats. The LacZ gene product (B-galactosidase) filled axons of the tibial nerve, which permitted the continuous long-range tracing of axons. Further, the branching and the direction of the branches could also be examined. Labeled axons in the tibial nerves ran parallel to each other without branching and kept this relative position in the tibial and the sciatic nerve. When the virus was introduced to the regenerating nerve using a silicon tube, the regenerating fibers grew tortuously with short branches in the bulge at the proximal end of the silicon tube. The fibers grew straight in the tube and passed through the bulge at the distal end of the tube without branching. These observations indicate that the LacZ gene recombinant adenovirus is a useful tracer for the study of the peripheral nervous system and of the regeneration processes.

Adenovirus-mediated transfer and expression of beta-gal in injured hippocampus after traumatic brain injury in mice

In models of focal cerebral ischemia, adenoviral gene transfer is often attenuated or delayed versus naive. After controlled cortical impact (CCI)-induced traumatic brain injury in mice, CA1 and CA3 hippocampus exhibit delayed neuronal death by 3 days, with subsequent near complete loss of hippocampus by 21 days. We hypothesized that adenoviral-mediated expression of the reporter gene beta-Galactosidase (beta-Gal) in hippocampus would be attenuated after CCI in mice. C57BL6 mice (n = 16) were subjected to either CCI to left parietal cortex or sham (burr hole). Adenovirus carrying the beta-Gal gene (AdlacZ; 1 x 10(9) plaque-forming units [pfu]/mL) was then injected into left dorsal hippocampus. At 24 or 72 h, beta-Gal expression was quantified (mU/mg protein). Separate mice (n = 10) were used to study beta-Gal spatial distribution in brain sections. Beta-Gal expression in left hippocampus was similar in shams at 24 h (48.4 +/- 4.1) versus 72 h (68.8 +/- 8.8, not significant). CCI did not reduce beta-Gal expression in left hippocampus (68.8 +/- 8.8 versus 88.1 +/- 7.0 at 72 h, sham versus CCI, not significant). In contrast, CCI reduced beta-Gal expression in right (contralateral) hippocampus versus sham (p < 0.05 at both 24 and 72 h). Beta-Gal was seen in many cell types in ipsilateral hippocampus, including CA3 neurons. Despite eventual loss of ipsilateral hippocampus, adenovirus-mediated gene transfer was surprisingly robust early after CCI providing an opportunity to test novel genes targeting delayed hippocampal neuronal death.

Neurons in Golgi-stain-like images revealed by GFP-adenovirus infection in vivo

Neurons in the adult brain have a very complex morphology with many processes, including tremendously long axons. Since dendrites and axons play key roles in the input and output of neural information, respectively, the visualization of complete images of these processes is necessary to reveal the mechanism of neural information processing. Here we made a recombinant adenovirus vector which encodes green fluorescent protein (GFP) tagged with a palmitoylation site, a membrane-targeting signal, produced specific antibodies to GFP, and used them as probes for staining the nervous system. In the neocortex, after injection of the recombinant virus and immunoperoxidase staining with the antibodies, many different types of cells were labeled in a Golgi stain-like fashion. Although the number of labeled cells varied depending on the amount of virus injected, the recombinant virus was considered to be infectious to cortical neurons of all cell types without selectivity. In contrast, the viral infection in the cerebellar cortex and superior cervical ganglion showed some selectivity toward the cell type. It is expected that this recombinant virus will be a useful tool for the morphological analysis of neuronal connections, especially the analysis of microcircuitry in the cerebral cortex.

In vivo transduction of cerebellar Purkinje cells using adeno-associated virus vectors

We investigated whether adenovirus or adeno-associated virus vectors can transduce cerebellar Purkinje cells (PCs) in vivo. Mice were injected in the deep cerebellar nuclei (DCN) with lacZ-transducing adenovirus (Ad.RSV-betagal) or a recombinant AAV serotype 2 (rAAV2) vector (vTR-CMVbeta) mixed with wild-type adenovirus type 5 (Ad5). One week later, Ad.RSV-betagal transduced cells were found throughout the cerebellar white matter in a dose-dependent manner, but few transduced PCs were evident. In contrast, vTR-CMVbeta with Ad5 transduced several hundred PCs throughout the injected hemisphere. Using an rAAV2 vector transducing a CMV-regulated green fluorescent protein gene, we again found PC transduction, but only with Ad5 coinjection. To assess the effect of injection site and to determine whether the apparent requirement for Ad5 coinfection is observed with other promoters, a beta-actin-regulated vector was injected with or without Ad5 to DCN or cerebellar cortical sites. Thousands of transduced PCs were observed under each condition. Cortical injection yielded greater numbers of transduced cells. Injection of rAAV2 without Ad5 led to greater specificity for PC transduction. We conclude that injection of rAAV2 vectors into the cerebellum is an effective means for transferring genes into substantial numbers of Purkinje cells in vivo.

Akt/protein kinase B prevents injury-induced motoneuron death and accelerates axonal regeneration

Motoneurons require neurotrophic factors for their survival and axonal projection during development, as well as nerve regeneration. By using the axotomy-induced neuronal death paradigm and adenovirus-mediated gene transfer, we attempted to gain insight into the functional significances of major growth factor receptor downstream cascades, Ras-extracellular signal-regulated kinase (Ras-ERK) pathway and phosphatidylinositol-3 kinase-Akt (PI3K-Akt) pathway. After neonatal hypoglossal nerve transection, the constitutively active Akt-overexpressing neurons could survive as well as those overexpressing Bcl-2, whereas the constitutively active ERK kinase (MEK)-overexpressing ones failed to survive. A dominant negative Akt experiment demonstrated that inhibition of Akt pathway hastened axotomy-induced neuronal death in the neonate. In addition, the dominant active Akt-overexpressing adult hypoglossal neurons showed accelerated axonal regeneration after axotomy. These results suggest that Akt plays dual roles in motoneuronal survival and nerve regeneration in vivo and that PI3K-Akt pathway is probably more vital in neuronal survival after injury than Ras-ERK pathway.

Adenovirus-mediated gene delivery to hypothalamic magnocellular neurons in mice

Vasopressin is synthesized by magnocellular neurons in supraoptic (SON) and paraventricular (PVN) hypothalamic nuclei and released by their axon terminals in the neurohypophysis (NH). With its actions as an antidiuretic hormone and vasoactive agent, vasopressin plays a pivotal role in the control of body fluids and cardiovascular homeostasis. Because of its well-defined neurobiology and functional importance, the SON/PVN-NH system is ideal to establish methods for gene transfer of genetic material into specific pathways in the mouse central nervous system. In these studies, we compared the efficiency of transferring the gene lacZ, encoding for beta-galactosidase (beta-gal), versus a gene encoding for green fluorescent protein by using replication-deficient adenovirus (Ad) vectors in adult mice. Transfection with viral concentrations up to 2 x 10(7) plaque-forming units per coverslip of NH, PVN, and SON in dissociated, cultured cells caused efficient transfection without cytotoxicity. However, over an extended period of time, higher levels (50% to 75% of the cells) of beta-gal expression were detected in comparison with green fluorescent protein (5% to 50% of the cells). With the use of a stereotaxic approach, the pituitary glands of mice were injected with Ad (4 x 10(6) plaque-forming units). In material from these animals, we were able to visualize the expression of the beta-gal gene in the NH and in magnocellular neurons of both the PVN and SON. The results of these experiments indicate that Ad-Rous sarcoma virus promoter-beta-gal is taken up by nerve terminals at the injection site (NH) and retrogradely transported to the soma of the neurons projecting to the NH. We conclude that the application of these experimental approaches will provide powerful tools for physiological studies and potential approaches to deliver therapeutic genes to treat diseases.

Ambiguus nucleus neurons innervating the abdominal esophagus are malpositioned in the reeler mouse

To examine whether the migration of ambiguus nucleus (NA) neurons is affected in the reeler mouse, recombinant replication-deficient adenoviral vector carrying E. coli-galactosidase gene (lacZ) was injected into the abdominal esophagus of the reeler mouse and normal control at two months of age prior to 5 days of sacrifice of the animals. In the normal control, lacZ-positive neurons were found in the compact formation of the NA, whereas, in the reeler, they were scattered from the base of the fourth ventricle to the ventro-lateral margin of the medulla. The present study confirmed that NA neurons are malpositioned in the reeler mouse, suggesting that the migration of NA neurons is guided by the reelin-related protein (Reelin).