Improved spatial learning in aged rats by genetic activation of protein kinase C in small groups of hippocampal neurons

Connected neurons in multiple neocortical areas, comprising parallel circuits, encode essential information for visual shape learning

Neocortical areas comprised of multiple neuronal circuits which are encoded with innumerable advanced cognitive tasks. Studies focused on neuronal network and synaptic plasticity has hypothesized that every specific neuron and the circuit process the explicit essential information for the specific tasks. However, the structure of these circuits and the involved critical neurons remain to be elucidated. Considering our previous studies, showing the specificity of rat postrhinal cortex comprising specific neuronal circuit for encoding both the learning and recall of shape discrimination through a fast neurotransmitter release from the transduced neurons, here we have demonstrated that postsynaptic neurons in two distinct areas, perirhinal cortex and the ventral temporal association areas are required for the specific visual shape discriminations learning. The constitutively active PKC was delivered into neuronal cells in postrhinal cortex, and the animals were allowed to learn the new shape discriminations, and then the silencing siRNA was delivered into postsynaptic neurons in either perirhinal cortex or ventral temporal association areas, using a novel technology for gene transfer into connected neurons. We observed that expression of the siRNA caused the deficits in visual performance, via blocking the activity in the neurons, as displayed by activity-dependent gene imaging, and also subsequently obstructed the activation of specific signaling pathways required for further learning, and dendritic protein synthesis and CREB. Thus, ratifying the conclusion that the two parallel circuits are both required for the visual shape discrimination learning.

An identified ensemble within a neocortical circuit encodes essential information for genetically-enhanced visual shape learning

Advanced cognitive tasks are encoded in distributed neocortical circuits that span multiple forebrain areas. Nonetheless, synaptic plasticity and neural network theories hypothesize that essential information for performing these tasks is encoded in specific ensembles within these circuits. Relatively simpler subcortical areas contain specific ensembles that encode learning, suggesting that neocortical circuits contain such ensembles. Previously, using localized gene transfer of a constitutively active protein kinase C (PKC), we established that a genetically-modified circuit in rat postrhinal cortex, part of the hippocampal formation, can encode some essential information for performing specific visual shape discriminations. However, these studies did not identify any specific neurons that encode learning; the entire circuit might be required. Here, we show that both learning and recall require fast neurotransmitter release from an identified ensemble within this circuit, the transduced neurons; we blocked fast release from these neurons by coexpressing a Synaptotagmin I siRNA with the constitutively active PKC. During learning or recall, specific signaling pathways required for learning are activated in this ensemble; during learning, calcium/calmodulin-dependent protein kinase II, MAP kinase, and CREB are activated; and, during recall, dendritic protein synthesis and CREB are activated. Using activity-dependent gene imaging, we showed that during learning, activity in this ensemble is required to recruit and activate the circuit. Further, after learning, during image presentation, blocking activity in this ensemble reduces accuracy, even though most of the rest of the circuit is activated. Thus, an identified ensemble within a neocortical circuit encodes essential information for performing an advanced cognitive task.

In silico identification of critical proteins associated with learning process and immune system for Down syndrome

Understanding expression levels of proteins and their interactions is a key factor to diagnose and explain the Down syndrome which can be considered as the most prevalent reason of intellectual disability in human beings. In the previous studies, the expression levels of 77 proteins obtained from normal genotype control mice and from trisomic Ts65Dn mice have been analyzed after training in contextual fear conditioning with and without injection of the memantine drug using statistical methods and machine learning techniques. Recent studies have also pointed out that there may be a linkage between the Down syndrome and the immune system. Thus, the research presented in this paper aim at in silico identification of proteins which are significant to the learning process and the immune system and to derive the most accurate model for classification of mice. In this paper, the features are selected by implementing forward feature selection method after preprocessing step of the dataset. Later, deep neural network, gradient boosting tree, support vector machine and random forest classification methods are implemented to identify the accuracy. It is observed that the selected feature subsets not only yield higher accuracy classification results but also are composed of protein responses which are important for the learning and memory process and the immune system.

A Calcium- and Diacylglycerol-Stimulated Protein Kinase C (PKC), Caenorhabditis elegans PKC-2, Links Thermal Signals to Learned Behavior by Acting in Sensory Neurons and Intestinal Cells

Ca²⁺- and diacylglycerol (DAG)-activated protein kinase C (cPKC) promotes learning and behavioral plasticity. However, knowledge of in vivo regulation and exact functions of cPKCs that affect behavior is limited. We show that PKC-2, a Caenorhabditis elegans cPKC, is essential for a complex behavior, thermotaxis. C. elegans memorizes a nutrient-associated cultivation temperature (T_c ) and migrates along the T_c within a 17 to 25°C gradient. pkc-2 gene disruption abrogated thermotaxis; a PKC-2 transgene, driven by endogenous pkc-2 promoters, restored thermotaxis behavior in pkc-2^-/- animals. Cell-specific manipulation of PKC-2 activity revealed that thermotaxis is controlled by cooperative PKC-2-mediated signaling in both AFD sensory neurons and intestinal cells. Cold-directed migration (cryophilic drive) precedes T_c tracking during thermotaxis. Analysis of temperature-directed behaviors elicited by persistent PKC-2 activation or inhibition in AFD (or intestine) disclosed that PKC-2 regulates initiation and duration of cryophilic drive. In AFD neurons, PKC-2 is a Ca²⁺ sensor and signal amplifier that operates downstream from cyclic GMP-gated cation channels and distal guanylate cyclases. UNC-18, which regulates neurotransmitter and neuropeptide release from synaptic vesicles, is a critical PKC-2 effector in AFD. UNC-18 variants, created by mutating Ser³¹¹ or Ser³²², disrupt thermotaxis and suppress PKC-2-dependent cryophilic migration.

Characteristic and intermingled neocortical circuits encode different visual object discriminations

Synaptic plasticity and neural network theories hypothesize that the essential information for advanced cognitive tasks is encoded in specific circuits and neurons within distributed neocortical networks. However, these circuits are incompletely characterized, and we do not know if a specific discrimination is encoded in characteristic circuits among multiple animals. Here, we determined the spatial distribution of active neurons for a circuit that encodes some of the essential information for a cognitive task. We genetically activated protein kinase C pathways in several hundred spatially-grouped glutamatergic and GABAergic neurons in rat postrhinal cortex, a multimodal associative area that is part of a distributed circuit that encodes visual object discriminations. We previously established that this intervention enhances accuracy for specific discriminations. Moreover, the genetically-modified, local circuit in POR cortex encodes some of the essential information, and this local circuit is preferentially activated during performance, as shown by activity-dependent gene imaging. Here, we mapped the positions of the active neurons, which revealed that two image sets are encoded in characteristic and different circuits. While characteristic circuits are known to process sensory information, in sensory areas, this is the first demonstration that characteristic circuits encode specific discriminations, in a multimodal associative area. Further, the circuits encoding the two image sets are intermingled, and likely overlapping, enabling efficient encoding. Consistent with reconsolidation theories, intermingled and overlapping encoding could facilitate formation of associations between related discriminations, including visually similar discriminations or discriminations learned at the same time or place.

Molecular and cellular aspects of age-related cognitive decline and Alzheimer's disease

As the population of people aged 60 or older continues to rise, it has become increasingly important to understand the molecular basis underlying age-related cognitive decline. In fact, a better understanding of aging biology will help us identify ways to maintain high levels of cognitive functioning throughout the aging process. Many cellular and molecular aspects of brain aging are shared with other organ systems; however, certain age-related changes are unique to the nervous system due to its structural, cellular and molecular complexity. Importantly, the brain appears to show differential changes throughout the aging process, with certain regions (e.g. frontal and temporal regions) being more vulnerable than others (e.g. brain stem). Within the medial temporal lobe, the hippocampus is especially susceptible to age-related changes. The important role of the hippocampus in age-related cognitive decline and in vulnerability to disease processes such as Alzheimer's disease has prompted this review, which will focus on the complexity of changes that characterize aging, and on the molecular connections that exist between normal aging and Alzheimer's disease. Finally, it will discuss behavioral interventions and emerging insights for promoting healthy cognitive aging.

Protein kinase-based neural signaling pathways for ginsenosides: a retrospective review

Ginsenosides are the main active components of ginseng, which have been reported to target brain tissues and produce multiple neuroprotective effects. Ginsenosides have been shown to improve learning ability and memory in normal aged animals, and in an animal model of memory impairment. However, its underlying pharmacological mechanisms are very complicated, especially with regard to its effects on the activation of protein kinases in neurons. Previous reports have shown that some protein kinases may be affected by ginsenosides, including protein kinase C, calcium/calmodulin-dependent protein kinase II, c-Jun-N terminal kinase, and protein tyrosine kinase. In this paper, protein kinases that may underlie the mechanisms of ginsenosides will be discussed.

The long-term impact of oxaliplatin chemotherapy on rodent cognition and peripheral neuropathy

Chemotherapy treatment is associated with cognitive dysfunction in cancer survivors after treatment completion. The duration of these impairments is unclear. Therefore this paper aims to evaluate the lasting impact of varying doses of the chemotherapy oxaliplatin (OX) on cognition and peripheral neuropathy. In Experiment 1 rats were treated once a week for 3 weeks with either physiological saline (control) or 6 mg/kg OX i.p. and were assessed for peripheral neuropathy, using von Frey filaments, and cognitive function, using novel object and location recognition, up to 2 weeks after treatment completion. For Experiment 2 rats received 3 weekly i.p. injections of either physiological saline (control), 0.6 mg/kg, 2mg/kg or 6 mg/kg OX and assessed for peripheral neuropathy and cognitive function up to 11 months after treatment completion. Systemic OX treatment induced lasting effects on cognitive function at 11 months after treatment, and peripheral neuropathy at 1 month after treatment and these were dose dependent; higher doses of OX resulted in worse cognitive outcomes and more severe peripheral neuropathy.

Neurons can be labeled with unique hues by helper virus-free HSV-1 vectors expressing Brainbow

BACKGROUND

A central problem in neuroscience is elucidating synaptic connections, the connectome. Because mammalian forebrains contain many neurons, labeling specific neurons with unique tags is desirable. A novel technology, Brainbow, creates hundreds of hues by combinatorial expression of multiple fluorescent proteins (FPs).

NEW METHOD

We labeled small numbers of neurons, and their axons, with unique hues, by expressing Brainbow from a helper virus-free Herpes Simplex Virus (HSV-1) vector.

RESULTS

The vector expresses a Brainbow cassette containing four FPs from a glutamatergic-specific promoter. Packaging HSV-Brainbow produced arrays of seven to eight Brainbow cassettes, and using Cre, each FP gene was in a position to be expressed, in different cassettes. Delivery into rat postrhinal (POR) cortex or hippocampus labeled small numbers of neurons with different, often unique, hues. An area innervated by POR cortex, perirhinal (PER) cortex, contained axons with different hues. Specific axons in PER cortex were matched to specific cell bodies in POR cortex, using hue.

COMPARISON WITH EXISTING METHODS

HSV-Brainbow is the only technology for labeling small numbers of neurons with unique hues. In Brainbow mice, many neurons contain the same hue. Brainbow-adeno-associated virus vectors require transduction of the same neuron with multiple vector particles, confounding neuroanatomical studies. Replication-competent Brainbow-pseudorabies virus vectors label multiple neurons with the same hue.

CONCLUSIONS

Attractive properties of HSV-Brainbow include each vector particle contains multiple cassettes, representing numerous hues, recombination products are stabile, and experimental control of the number of labeled neurons. Labeling neurons with unique hues will benefit mapping forebrain circuits.

Signaling pathways relevant to cognition-enhancing drug targets

Aging is generally associated with a certain cognitive decline. However, individual differences exist. While age-related memory deficits can be observed in humans and rodents in the absence of pathological conditions, some individuals maintain intact cognitive functions up to an advanced age. The mechanisms underlying learning and memory processes involve the recruitment of multiple signaling pathways and gene expression, leading to adaptative neuronal plasticity and long-lasting changes in brain circuitry. This chapter summarizes the current understanding of how these signaling cascades could be modulated by cognition-enhancing agents favoring memory formation and successful aging. It focuses on data obtained in rodents, particularly in the rat as it is the most common animal model studied in this field. First, we will discuss the role of the excitatory neurotransmitter glutamate and its receptors, downstream signaling effectors [e.g., calcium/calmodulin-dependent protein kinase II (CaMKII), protein kinase C (PKC), extracellular signal-regulated kinases (ERK), mammalian target of rapamycin (mTOR), cAMP response element-binding protein (CREB)], associated immediate early gene (e.g., Homer 1a, Arc and Zif268), and growth factors [insulin-like growth factors (IGFs) and brain-derived neurotrophic factor (BDNF)] in synaptic plasticity and memory formation. Second, the impact of the cholinergic system and related modulators on memory will be briefly reviewed. Finally, since dynorphin neuropeptides have recently been associated with memory impairments in aging, it is proposed as an attractive target to develop novel cognition-enhancing agents.

PKC in developmental hypothyroid rat brain

Thyroid hormone (TH) is essential for the proper development of mammalian central nervous system. TH deficiency during the critical period of brain development results in permanent cognitive and neurological impairments. Members of the protein kinase C (PKC) family play a key role in the regulation of cellular functions in the nervous system. Alteration of PKC can be involved in the pathogenesis of neuronal disorders. This review details recent progress made in determining the roles played by PKC isoforms in developing hypothyroid rat brain. Evidence indicates that hippocampus down-regulation of PKCβ and PKCγ may be related to impaired learning and memory observed in perinatal hypothyroid rats. Enhanced PKCα activity in neonatal hypothyroid brain may bring about oxidative stress and cause brain damage. The activated pro-apoptotic PKCs including PKCδ can cause extensive apoptosis in the hypothyroid rat brain.

Age-dependent alterations in cAMP signaling contribute to synaptic plasticity deficits following traumatic brain injury

The elderly have comparatively worse cognitive impairments from traumatic brain injury (TBI) relative to younger adults, but the molecular mechanisms that underlie this exacerbation of cognitive deficits are unknown. Experimental models of TBI have demonstrated that the cyclic AMP-protein kinase A (cAMP-PKA) signaling pathway is downregulated after brain trauma. Since the cAMP-PKA signaling pathway is a key mediator of long-term memory formation, we investigated whether the TBI-induced decrease in cAMP levels is exacerbated in aged animals. Aged (19 months) and young adult (3 months) male Fischer 344 rats received sham surgery or mild (1.4-1.6 atmospheres, atm) or moderate (1.7-2.1 atm) parasagittal fluid-percussion brain injury. At various time points after surgery, the ipsilateral parietal cortex, hippocampus, and thalamus were assayed for cAMP levels. Mild TBI lowered cAMP levels in the hippocampus of aged, but not young adult animals. Moderate TBI lowered cAMP levels in the hippocampus and parietal cortex of both age groups. In the thalamus, cAMP levels were significantly lowered after moderate, but not mild TBI. To determine if the TBI-induced decreases in cAMP had physiological consequences in aged animals, hippocampal long-term potentiation (LTP) in the Schaffer collateral pathway of the CA1 region was assessed. LTP was significantly decreased in both young adult and aged animals after mild and moderate TBI as compared to sham surgery animals. Rolipram rescued the LTP deficits after mild TBI for young adult animals and caused a partial recovery for aged animals. However, rolipram did not rescue LTP deficits after moderate TBI in either young adult or aged animals. These results indicate that the exacerbation of cognitive impairments in aged animals with TBI may be due to decreased cAMP levels and deficits in hippocampal LTP.

Group 1 metabotropic glutamate receptor function and its regulation of learning and memory in the aging brain

Normal aging is generally characterized by a slow decline of cognitive abilities albeit with marked individual differences. Several animal models have been studied to explore the molecular and cellular mechanisms underlying this phenomenon. The excitatory neurotransmitter glutamate and its receptors have been closely linked to spatial learning and hippocampus-dependent memory processes. For decades, ionotropic glutamate receptors have been known to play a critical role in synaptic plasticity, a form of adaptation regulating memory formation. Over the past 10 years, several groups have shown the importance of group 1 metabotropic glutamate receptor (mGluR) in successful cognitive aging. These G-protein-coupled receptors are enriched in the hippocampal formation and interact physically with other proteins in the membrane including glutamate ionotropic receptors. Synaptic plasticity is crucial to maintain cognitive abilities and long-term depression (LTD) induced by group 1 mGluR activation, which has been linked to memory in the aging brain. The translation and synthesis of proteins by mGluR-LTD modulate ionotropic receptor trafficking and expression of immediate early genes related to cognition. Fragile X syndrome, a genetic form of autism characterized by memory deficits, has been associated to mGluR receptor malfunction and aberrant activation of its downstream signaling pathways. Dysfunction of mGluR could also be involved in neurodegenerative disorders like Alzheimer’s disease (AD). Indeed, beta-amyloid, the main component of insoluble senile plaques and one of the hallmarks of AD, occludes mGluR-dependent LTD leading to diminished functional synapses. This review highlights recent findings regarding mGluR signaling, related synaptic plasticity, and their potential involvement in normal aging and neurological disorders.

Cognitive impairments caused by oxaliplatin and 5-fluorouracil chemotherapy are ameliorated by physical activity

RATIONALE

Studies in women with breast cancer, and in animal models, have demonstrated that chemotherapy can have a negative impact on cognitive function. Which chemotherapy agents cause problems with cognition and the aetiology of the impairment is unknown. Furthermore, there is no proven treatment.

OBJECTIVES

This study aimed to evaluate the effects of 5-fluorouracil (5FU) and oxaliplatin (OX) chemotherapy agents commonly used to treat colorectal cancer on cognition in laboratory rodents. Furthermore, we assessed physical activity as a potential remedy for the observed chemotherapy-induced cognitive deficits.

RESULTS

In rodents, treatment with 5FU and OX alone impairs memory as measured by novel object recognition. But combined treatment appears to have greater detrimental effects on hippocampal-dependent tasks, contextual fear recall and spatial reference memory (water maze), yet had no effect on cued fear recall, a non-hippocampal task. These impairments were prevented by 4 weeks of wheel running overnight after 5FU/OX treatment. We found a significant interaction between chemotherapy and exercise: rats receiving both 5FU/OX and exercise had improved cognition relative to non-exercising 5FU/OX rats on novel object recognition and spatial reference memory.

CONCLUSIONS

The combination 5FU/OX had a significant impact on cognition. However, rats treated with 5FU/OX that exercised post chemotherapy had improved cognition relative to non-exercising rats. This suggests that physical activity may prove useful in ameliorating the cognitive impairments induced by 5FU/OX.

Overexpression of either lysine-specific demethylase-1 or CLOCK, but not Co-Rest, improves long-term expression from a modified neurofilament promoter, in a helper virus-free HSV-1 vector system

Long-term expression from helper virus-free Herpes Simplex Virus (HSV-1) vectors is required for many specific neural gene therapies and studies on neuronal physiology. We previously developed a promoter that supports long-term, neuron-specific expression by fusing the chicken ß-globin insulator (INS), followed by an upstream enhancer from the rat tyrosine hydroxylase (TH) promoter, to a neurofilament heavy gene (NFH) promoter. Here, we examined the capability of specific transcription factors to further improve long-term expression from this promoter. Following a HSV-1 virus infection, the virus genome is localized to promyelocytic leukemia protein (PML) nuclear bodies (NB). At these sites, specific cellular transcription factors interact with HSV-1 encoded transcription factors, and together regulate HSV-1 gene expression. Importantly, lysine-specific demethylase-1 (LSD1), CLOCK, and Co-Rest each activate HSV-1 gene expression. However, gene expression from HSV-1 vectors differs in a number of important aspects from the virus, including no HSV-1 genes are expressed. Nonetheless, these observations raise the possibility that specific transcription factors may improve long-term expression from specific promoters in HSV-1 vectors. Here, we show that overexpression of either LSD1 or CLOCK improves long-term expression from the INS-TH-NFH promoter, but overexpression of Co-Rest supports levels of long-term expression similar to those supported by a control vector. Further, overexpression of LSD1 is compatible with neuron-specific expression. Thus, overexpressing specific transcription factors can improve long-term expression from specific cellular promoters in HSV-1 vectors, and the chromatin structure of the vector has an important role in enabling expression.

A 16 bp upstream sequence from the rat tyrosine hydroxylase promoter supports long-term expression from a neurofilament promoter, in a helper virus-free HSV-1 vector system

Helper virus-free Herpes Simplex Virus vector-mediated gene transfer has supported studies on neuronal physiology, and may support specific gene therapies. Long-term, neuron-specific expression is required for many of these applications. A neurofilament heavy gene (NFH) promoter does not support long-term expression. We previously developed a promoter that supports long-term expression by fusing 6.3 kb of upstream sequences from the rat tyrosine hydroxylase (TH) promoter to a NFH promoter, and this promoter has supported physiological studies. The TH promoter fragment contains an enhancer, as it has activity in both orientations and at a distance from the basal promoter. Identifying this enhancer may support further improvements in long-term expression. A previous deletion analysis identified two ~100 bp fragments that each support long-term expression, and are contained within an ~320 bp fragment located ~3 kb from the TH promoter transcription start site. As this analysis used overlapping fragments, the two ~100 bp fragments contained 44 or 23 bp of unique sequence. Here, we used mutagenesis to identify a short sequence that supports long-term expression. We studied a 42 bp sequence, centered on the 23 bp unique sequence. Analysis of the wt sequence, and five mutations containing clustered changes that spanned the sequence, identified two adjacent mutations that do not support long-term expression, which together defined a 16 bp maximum essential sequence. This 16 bp sequence contains a putative E2F-1/DP-1 transcription factor binding site, and this transcription factor is expressed in many brain areas.

Antibody-mediated targeted gene transfer of helper virus-free HSV-1 vectors to rat neocortical neurons that contain either NMDA receptor 2B or 2A subunits

Because of the numerous types of neurons in the brain, and particularly the forebrain, neuron type-specific expression will benefit many potential applications of direct gene transfer. The two most promising approaches for achieving neuron type-specific expression are targeted gene transfer to a specific type of neuron and using a neuron type-specific promoter. We previously developed antibody-mediated targeted gene transfer with Herpes Simplex Virus (HSV-1) vectors by modifying glycoprotein C (gC) to replace the heparin binding domain, which mediates the initial binding of HSV-1 particles to many cell types, with the Staphylococcus A protein ZZ domain, which binds immunoglobulin (Ig) G. We showed that a chimeric gC-ZZ protein is incorporated into vector particles and binds IgG. As a proof-of-principle for antibody-mediated targeted gene transfer, we isolated complexes of these vector particles and an anti-NMDA NR1 subunit antibody, and demonstrated targeted gene transfer to neocortical cells that contain NR1 subunits. However, because most forebrain neurons contain NR1, we obtained only a modest increase in the specificity of gene transfer, and this targeting specificity is of limited utility for physiological experiments. Here, we report efficient antibody-mediated targeted gene transfer to NMDA NR2B- or NR2A-containing cells in rat postrhinal cortex, and a neuron-specific promoter further restricted recombinant expression to neurons. Of note, because NR2A-containing neurons are relatively rare, these results show that antibody-mediated targeted gene transfer with HSV-1 vectors containing neuron type-specific promoters can restrict recombinant expression to specific types of forebrain neurons of physiological significance.

The vesicular glutamate transporter-1 upstream promoter and first intron each support glutamatergic-specific expression in rat postrhinal cortex

Multiple applications of direct gene transfer into neurons require restricting expression to glutamatergic neurons, or specific subclasses of glutamatergic neurons. Thus, it is desirable to develop and analyze promoters that support glutamatergic-specific expression. The three vesicular glutamate transporters (VGLUTs) are found in different populations of neurons, and VGLUT1 is the predominant VGLUT in the neocortex, hippocampus, and cerebellar cortex. We previously reported on a plasmid (amplicon) Herpes Simplex Virus vector that contains a VGLUT1 promoter. This vector supports long-term expression in VGLUT1-containing glutamatergic neurons in rat postrhinal (POR) cortex, but does not support expression in VGLUT2-containing glutamatergic neurons in the ventral medial hypothalamus. This VGLUT1 promoter contains both the VGLUT1 upstream promoter and the VGLUT1 first intron. In this study, we begin to isolate and analyze the glutamatergic-specific regulatory elements in this VGLUT1 promoter. We show that the VGLUT1 upstream promoter and first intron each support glutamatergic-specific expression. We isolated a small, basal VGLUT1 promoter that does not support glutamatergic-specific expression. Next, we fused either the VGLUT1 upstream promoter or the first intron to this basal promoter. The VGLUT1 upstream promoter or the first intron, fused to the basal promoter, each supported glutamatergic-specific expression in POR cortex.

Genetic labeling of both the axons of transduced, glutamatergic neurons in rat postrhinal cortex and their postsynaptic neurons in other neocortical areas by herpes simplex virus vectors that coexpress an axon-targeted β-galactosidase and wheat germ agglutinin from a vesicular glutamate transporter-1 promoter

Neuronal circuits comprise the foundation for neuronal physiology and synaptic plasticity, and thus for consequent behaviors and learning, but our knowledge of neocortical circuits is incomplete. Mapping neocortical circuits is a challenging problem because these circuits contain large numbers of neurons, a high density of synapses, and numerous classes and subclasses of neurons that form many different types of synapses. Expression of specific genetic tracers in small numbers of specific subclasses of neocortical neurons has the potential to map neocortical circuits. Suitable genetic tracers have been established in neurons in subcortical areas, but application to neocortical circuits has been limited. Enabling this approach, Herpes Simplex Virus (HSV-1) plasmid (amplicon) vectors can transduce small numbers of neurons in a specific neocortical area. Further, expression of a particular genetic tracer can be restricted to specific subclasses of neurons; in particular, the vesicular glutamate transporter-1 (VGLUT1) promoter supports expression in VGLUT1-containing glutamatergic neurons in rat postrhinal (POR) cortex. Here, we show that expression of an axon-targeted β-galactosidase (β-gal) from such vectors supports mapping specific commissural and associative projections of the transduced neurons in POR cortex. Further, coexpression of wheat germ agglutinin (WGA) and an axon-targeted β-gal supports mapping both specific projections of the transduced neurons and identifying specific postsynaptic neurons for the transduced neurons. The neocortical circuit mapping capabilities developed here may support mapping specific neocortical circuits that have critical roles in cognitive learning.

Age-related defects in sensorimotor activity, spatial learning, and memory in C57BL/6 mice

Impaired locomotor activity and spatial memory are common features in the natural aging process, and aging is an important risk factor for neurodegenerative disease and postoperative cognitive dysfunction. To characterize age-related changes in psychomotor performance, we assessed sensorimotor activity, spatial learning, and memory in C57BL/6 mice using the Rotarod, foot fault, and Barnes Maze tests. Old mice exhibit significant deficits in locomotor activity and spatial memory relative to young mice, but improve with training. These tests will be useful to assess outcome in neurodegenerative disease and postoperative cognitive dysfunction models carried out in aged mice.

Antibody-mediated targeted gene transfer to NMDA NR1-containing neurons in rat neocortex by helper virus-free HSV-1 vector particles containing a chimeric HSV-1 glycoprotein C-staphylococcus A protein

Because of the heterogeneous cellular composition of the brain, and especially the forebrain, cell type-specific expression will benefit many potential applications of direct gene transfer. The two prevalent approaches for achieving cell type-specific expression are using a cell type-specific promoter or targeting gene transfer to a specific cell type. Targeted gene transfer with Herpes Simplex Virus (HSV-1) vectors modifies glycoprotein C (gC) to replace the heparin binding domain, which binds to many cell types, with a binding activity for a specific cell surface protein. We previously reported targeted gene transfer to nigrostriatal neurons using chimeric gC-glial cell line-derived neurotrophic factor or gC-brain-derived neurotrophic factor protein. Unfortunately, this approach is limited to cells that express the cognate receptor for either neurotrophic factor. Thus, a general strategy for targeting gene transfer to many different types of neurons is desirable. Antibody-mediated targeted gene transfer has been developed for targeting specific virus vectors to specific peripheral cell types; a specific vector particle protein is modified to contain the Staphylococcus A protein ZZ domain, which binds immunoglobulin (Ig) G. Here, we report antibody-mediated targeted gene transfer of HSV-1 vectors to a specific type of forebrain neuron. We constructed a chimeric gC-ZZ protein, and showed this protein is incorporated into vector particles and binds Ig G. Complexes of these vector particles and an antibody to the NMDA receptor NR1 subunit supported targeted gene transfer to NR1-containing neocortical neurons in the rat brain, with long-term (2 months) expression.

A helper virus-free HSV-1 vector containing the vesicular glutamate transporter-1 promoter supports expression preferentially in VGLUT1-containing glutamatergic neurons

Multiple potential uses of direct gene transfer into neurons require restricting expression to specific classes of glutamatergic neurons. Thus, it is desirable to develop vectors containing glutamatergic class-specific promoters. The three vesicular glutamate transporters (VGLUTs) are expressed in distinct populations of neurons, and VGLUT1 is the predominant VGLUT in the neocortex, hippocampus, and cerebellar cortex. We previously reported a plasmid (amplicon) Herpes Simplex Virus (HSV-1) vector that placed the Lac Z gene under the regulation of the VGLUT1 promoter (pVGLUT1lac). Using helper virus-free vector stocks, we showed that this vector supported approximately 90% glutamatergic neuron-specific expression in postrhinal (POR) cortex, in rats sacrificed at either 4 days or 2 months after gene transfer. We now show that pVGLUT1lac supports expression preferentially in VGLUT1-containing glutamatergic neurons. pVGLUT1lac vector stock was injected into either POR cortex, which contains primarily VGLUT1-containing glutamatergic neurons, or into the ventral medial hypothalamus (VMH), which contains predominantly VGLUT2-containing glutamatergic neurons. Rats were sacrificed at 4 days after gene transfer, and the types of cells expressing ss-galactosidase were determined by immunofluorescent costaining. Cell counts showed that pVGLUT1lac supported expression in approximately 10-fold more cells in POR cortex than in the VMH, whereas a control vector supported expression in similar numbers of cells in these two areas. Further, in POR cortex, pVGLUT1lac supported expression predominately in VGLUT1-containing neurons, and, in the VMH, pVGLUT1lac showed an approximately 10-fold preference for the rare VGLUT1-containing neurons. VGLUT1-specific expression may benefit specific experiments on learning or specific gene therapy approaches, particularly in the neocortex.