BMC Neuroscience

Dynamics of peptidergic secretory granule transport are regulated by neuronal stimulation.

Publication Date: 2010 Mar 4 PMID: 20202202
Authors: Sobota, J. A. - Mohler, W. A. - Cowan, A. E. - Eipper, B. A. - Mains, R. E.
Journal: BMC Neurosci

ABSTRACT: BACKGROUND: Peptidergic neurons store and secrete the contents of large dense core vesicles (LDCVs) from axon terminals and from dendrites. Secretion of peptides requires a highly regulated exocytotic mechanism, plus coordinated synthesis and transport of LDCVs to their sites of release. Although these trafficking events are critical to function, little is known regarding the dynamic behavior of LDCVs and the mechanisms by which their transport is regulated. Sensory neurons also package opiate receptors in peptide-containing LDCVs, which is thought to be important in pain sensation. Since peptide granules cannot be refilled locally after their contents are secreted, it is particularly important to understand how neurons support regulated release of peptides. RESULTS: A vector encoding soluble peptidylglycine alpha-hydroxylating monooxygenase fused to green fluorescent protein was constructed to address these questions in cultured primary peptidergic neurons of the trigeminal ganglion using time lapse confocal microscopy. The time course of release differs with secretagogue; the secretory response to depolarization with K+ is rapid and terminates within 15 minutes, while phorbol ester stimulation of secretion is maintained over a longer period. The data demonstrate fundamental differences between LDCV dynamics in axons and growth cones under basal conditions. CONCLUSIONS: Under basal conditions, LDCVs move faster away from the soma than toward the soma, but fewer LDCVs travel anterograde than retrograde. Stimulation decreases average anterograde velocity and increases granule pausing. Data from antibody uptake, quantification of enzyme secretion and appearance of pHluorin fluorescence demonstrate distributed release of peptides all along the axon, not just at terminals.

post to: CiteULike

Neuroprotective effects of bis(7)-tacrine against glutamate-induced retinal ganglion cells damage.

Publication Date: 2010 Mar 3 PMID: 20199668
Authors: Fang, J. H. - Wang, X. H. - Xu, Z. R. - Jiang, F. G.
Journal: BMC Neurosci

ABSTRACT: BACKGROUND: Glutamate-mediated excitotoxicity, primarily through N-methyl-D-aspartate (NMDA) receptors, may be an important cause of retinal ganglion cells (RGCs) death in glaucoma and several other retinal diseases. Bis(7)-tacrine is a noncompetitive NMDA receptors antagonist that can prevent glutamate-induced hippocampal neurons damage. We tested the effects of bis(7)-tacrine against glutamate-induced rat RGCs damage in vitro and in vivo.Results:In cultured neonatal rats RGCs, the MTT assay showed that glutamate induced a concentration- and time-dependent toxicity. Bis(7)-tacrine and memantine prevented glutamate-induced cell death in a concentration-dependent manner with IC50 values of 0.028microM and 0.834microM, respectively. The anti-apoptosis effects of bis(7)-tacrine were confirmed by annexin V-FITC/PI staining. In vivo, TUNEL analysis and retrograde labeling analysis found that pretreatment with bis(7)-tacrine(0.2mg/kg) induced a significant neuroprotective effect against glutamate-induced RGCs damage.Conclusions:Our results showed that bis(7)-tacrine had neuroprotective effects against glutamate-induced RGCs damage in vitro and in vivo, possibly through the drug's anti-NMDA receptor effects. These findings make bis(7)-tacrine potentially useful for treating a variety of ischemic or traumatic retinopathies inclusive of glaucoma.

post to: CiteULike

Components of acquisition-to-acquisition variance in continuous arterial spin labelling (CASL) imaging.

Publication Date: 2010 Mar 2 PMID: 20196843
Authors: Viviani, R. - Beschoner, P. - Lo, H. - Osterfeld, N. - Thone, J. - Sim, E. J.
Journal: BMC Neurosci

ABSTRACT: BACKGROUND: Images of perfusion estimates obtained with the continuous arterial spin labelling technique are characterized by variation between single acquisitions. Little is known about the spatial determinants of this variation during the acquisition process and their impact on voxel-by-voxel estimates of effects. RESULTS: We show here that the spatial patterns of covariance between voxels arising during the acquisition of these images uncover distinct mechanisms through which this variance arises: through variation in global perfusion levels; through the action of large vessels and other, less well characterized, large anatomical structures; and through the effect of noisy areas such as the edges of the brain. CONCLUSIONS: Knowledge of these covariance patterns is important to experimenters for a correct interpretation of findings, especially for studies where relatively few acquisitions are made.

post to: CiteULike

Gene expression changes in the medial prefrontal cortex and nucleus accumbens following abstinence from cocaine self-administration.

Publication Date: 2010 Feb 26 PMID: 20187946
Authors: Freeman, W. M. - Lull, M. E. - Patel, K. M. - Brucklacher, R. M. - Morgan, D. - Roberts, D. C. - Vrana, K. E.
Journal: BMC Neurosci

ABSTRACT: BACKGROUND: Many studies of cocaine-responsive gene expression have focused on changes occurring during cocaine exposure, but few studies have examined the persistence of these changes with cocaine abstinence. Persistent changes in gene expression, as well as alterations induced during abstinence may underlie long-lasting drug craving and relapse liability. RESULTS: Whole-genome expression analysis was conducted on a rat cocaine binge-abstinence model that has previously been demonstrated to engender increased drug seeking and taking with abstinence. Gene expression changes in two mesolimbic terminal fields (mPFC and NAc) were identified in a comparison of cocaine-naive rats with rats after 10 days of cocaine self-administration followed by 1, 10, or 100 days of enforced abstinence (n=6-11 per group). A total of 1,461 genes in the mPFC and 414 genes in the NAc were altered between at least two time points (ANOVA, p<0.05; +/-1.4 fold-change). These genes can be subdivided into: 1) changes with cocaine self-administration that do not persist into periods of abstinence, 2) changes with cocaine self-administration that persist with abstinence, 3) and those not changed with cocaine self-administration, but changed during enforced abstinence. qPCR analysis was conducted to confirm gene expression changes observed in the microarray analysis. CONCLUSIONS: Together, these changes help to illuminate processes and networks involved in abstinence-induced behaviors, including synaptic plasticity, MAPK signaling, and TNF signaling.

post to: CiteULike

Calcium imaging in the ant Camponotus fellah reveals a conserved odour-similarity space in insects and mammals.

Publication Date: 2010 Feb 26 PMID: 20187931
Authors: Dupuy, F. - Josens, R. - Giurfa, M. - Sandoz, J. C.
Journal: BMC Neurosci

ABSTRACT: BACKGROUND: Olfactory systems create representations of the chemical world in the animal brain. Recordings of odour-evoked activity in the primary olfactory centres of vertebrates and insects have suggested similar rules for odour processing, in particular through spatial organization of chemical information in their functional units, the glomeruli. Similarity between odour representations can be extracted from across-glomerulus patterns in a wide range of species, from insects to vertebrates, but comparison of odour similarity in such diverse taxa has not been addressed. In the present study, we asked how 11 aliphatic odorants previously tested in honeybees and rats are represented in the antennal lobe of the ant Camponotus fellah, a social insect that relies on olfaction for food search and social communication. RESULTS: Using calcium imaging of specifically-stained second-order neurons, we show that these odours induce specific activity patterns in the ant antennal lobe. Using multidimensional analysis, we show that clustering of odours is similar in ants, bees and rats. Moreover, odour similarity is highly correlated in all three species. CONCLUSION: This suggests the existence of similar coding rules in the neural olfactory spaces of species among which evolutionary divergence happened hundreds of million years ago.

post to: CiteULike

JAM-A is a novel surface marker for NG2-Glia in the adult mouse brain.

Publication Date: 2010 Feb 26 PMID: 20184779
Authors: Stelzer, S. - Ebnet, K. - Schwamborn, J. C.
Journal: BMC Neurosci

ABSTRACT: BACKGROUND: Junctional adhesion molecule-A (JAM-A) is an adhesive protein expressed in various cell types. JAM-A localizes to the tight junctions between contacting endothelial and epithelial cells, where it contributes to cell-cell adhesion and to the control of paracellular permeability. RESULTS: So far, the expression pattern of JAM-A has not been described in detail for the different cell types of the adult brain. Here we show that a subset of proliferating cells in the adult mouse brain express JAM-A. We further clarify that these cells belong to the lineage of NG2-glia cells. Although these mitotic NG2-glia cells express JAM-A, the protein never shows a polarized subcellular distribution. Also non-mitotic NG2-glia cells express JAM-A in a non-polarized pattern on their surface. CONCLUSIONS: Our data show that JAM-A is a novel surface marker for NG2-glia cells of the adult brain.

post to: CiteULike

Novel lines of Pax6-/- embryonic stem cells exhibit reduced neurogenic capacity without loss of viability.

Publication Date: 2010 Feb 24 PMID: 20178645
Authors: Quinn, J. C. - Molinek, M. - Nowakowski, T. J. - Mason, J. O. - Price, D. J.
Journal: BMC Neurosci

ABSTRACT: BACKGROUND: Embryonic stem (ES) cells can differentiate into all cell types and have been used extensively to study factors affecting neuronal differentiation. ES cells containing mutations in known genes have the potential to provide useful in vitro models for the study of gene function during neuronal differentiation. Recently, mouse ES cell lines lacking the neurogenic transcription factor Pax6 were reported; neurons derived from these Pax6-/- ES cells died rapidly after neuronal differentiation in vitro. RESULTS: Here we report the derivation of new lines of Pax6-/- ES cells and the assessment of their ability to survive and differentiate both in vitro and in vivo. Neurons derived from our new Pax6-/- lines were viable and continued to elaborate processes after culture under conditions that resulted in the death of neurons derived from previously reported Pax6-/- ES cell lines. The new lines of Pax6-/- ES cells showed reduced neurogenic potential, mimicking the effects of loss of Pax6 in vivo. We used our new lines to generate Pax6-/- <-> Pax6+/+ chimeras in which the mutant cells survived and displayed the same phenotypes as Pax6-/- cells in Pax6-/- <-> Pax6+/+ chimeras made by embryo aggregation. CONCLUSIONS: We suggest that loss of Pax6 from ES cells reduces their neurogenic capacity but does not necessarily result in the death of derived neurons. We offer these new lines as additional tools for those interested in the generation of chimeras and the analysis of in vitro ES cell models of Pax6 function during neuronal differentiation, embryonic and postnatal development.

post to: CiteULike

G-CSF protects motoneurons against axotomy-induced apoptotic death in neonatal mice.

Publication Date: 2010 Feb 23 PMID: 20178614
Authors: Henriques, A. - Pitzer, C. - Dupuis, L. - Schneider, A.
Journal: BMC Neurosci

ABSTRACT: BACKGROUND: Granulocyte colony stimulating factor (G-CSF) is a growth factor essential for generation of neutrophilic granulocytes. Apart from this hematopoietic function, we have recently uncovered potent neuroprotective and regenerative properties of G-CSF in the central nervous system (CNS). The G-CSF receptor and G-CSF itself are expressed in motoneurons, G-CSF protects motoneurons, and improves outcome in the SOD1(G93A) transgenic mouse model for amyotrophic lateral sclerosis (ALS). In vitro, G-CSF acts anti-apoptotically on motoneuronal cells. Due to the pleiotropic effects of G-CSF and the complexity of the SOD1 transgenic ALS models it was however not possible to clearly distinguish between directly mediated anti-apoptotic and indirect protective effects on motoneurons. Here we studied whether G-CSF is able to protect motoneurons from purely apoptotic cell death induced by a monocausal paradigm, neonatal sciatic nerve axotomy. RESULTS: We performed sciatic nerve axotomy in neonatal mice overexpressing G-CSF in the CNS and found that G-CSF transgenic mice displayed significantly higher numbers of surviving lumbar motoneurons 4 days following axotomy than their littermate controls. Also, surviving motoneurons in G-CSF overexpressing animals were larger, suggesting additional trophic effects of this growth factor. CONCLUSIONS: In this model of pure apoptotic cell death the protective effects of G-CSF indicate direct actions of G-CSF on motoneurons in vivo. This shows that G-CSF exerts potent anti-apoptotic activities towards motoneurons in vivo and suggests that the protection offered by G-CSF in ALS mouse models is due to its direct neuroprotective activity.

post to: CiteULike

Sensitivity of the human auditory cortex to acoustic degradation of speech and non-speech sounds.

Publication Date: 2010 Feb 22 PMID: 20175890
Authors: Miettinen, I. - Tiitinen, H. - Alku, P. - May, P. J.
Journal: BMC Neurosci

ABSTRACT: BACKGROUND: Recent studies have shown that the human right-hemispheric auditory cortex is particularly sensitive to reduction in sound quality, with an increase in distortion resulting in an amplification of the auditory N1m response measured in the magnetoencephalography (MEG). Here, we examined whether this sensitivity is specific to the processing of acoustic properties of speech or whether it can be observed also in the processing of sounds with a simple spectral structure. We degraded speech stimuli (vowel /a/), complex non-speech stimuli (a composite of five sinusoidals), and sinusoidal tones by decreasing the amplitude resolution of the signal waveform. The amplitude resolution was impoverished by reducing the number of bits to represent the signal samples. Auditory evoked magnetic fields (AEFs) were measured in the left and right hemisphere of sixteen healthy subjects. RESULTS: We found that the AEF amplitudes increased significantly with stimulus distortion for all stimulus types, which indicates that the right-hemispheric N1m sensitivity is not related exclusively to degradation of acoustic properties of speech. In addition, the P1m and P2m responses were amplified with increasing distortion similarly in both hemispheres. The AEF latencies were not systematically affected by the distortion. CONCLUSIONS: We propose that the increased activity of AEFs reflects cortical processing of acoustic properties common to both speech and non-speech stimuli. More specifically, the enhancement is most likely caused by spectral changes brought about by the decrease of amplitude resolution, in particular the introduction of periodic, signal-dependent distortion to the original sound. Converging evidence suggests that the observed AEF amplification could reflect cortical sensitivity to periodic sounds.

post to: CiteULike

Apolipoprotein-E forms dimers in human frontal cortex and hippocampus.

Publication Date: 2010 Feb 20 PMID: 20170526
Authors: Elliott, D. A. - Halliday, G. M. - Garner, B.
Journal: BMC Neurosci

ABSTRACT: BACKGROUND: Apolipoprotein-E (apoE) plays important roles in neurobiology and the apoE4 isoform increases risk for Alzheimer's disease (AD). ApoE3 and apoE2 are known to form disulphide-linked dimers in plasma and cerebrospinal fluid whereas apoE4 cannot form these dimers as it lacks a cysteine residue. Previous in vitro research indicates dimerisation of apoE3 has a significant impact on its functions related to cholesterol homeostasis and amyloid-beta peptide degradation. The possible occurrence of apoE dimers in cortical tissues has not been examined and was therefore assessed. Human frontal cortex and hippocampus from control and AD post-mortem samples were homogenised and analysed for apoE by western blotting under both reducing and non-reducing conditions. RESULTS: In apoE3 homozygous samples, ~12% of apoE was present as a homodimer and ~2% was detected as a 43 kDa heterodimer. The level of dimerisation was not significantly different when control and AD samples were compared. As expected, these dimerised forms of apoE were not detected in apoE4 homozygous samples but were detected in apoE3/4 heterozygotes at a level ~60% lower than seen in the apoE3 homozygous samples. Similar apoE3 dimers were also detected in lysates of SK-N-SH neuroblastoma cells and in freshly prepared rabbit brain homogenates. The addition of the thiol trapping agent, iodoacetamide, to block reactive thiols during both human and rabbit brain sample homogenisation and processing did not reduce the amount of apoE homodimer recovered. These data indicate that the apoE dimers we detected in the human brain are not likely to be post-mortem artefacts. CONCLUSION: The identification of disulphide-linked apoE dimers in human cortical and hippocampal tissues represents a distinct structural difference between the apoE3 and apoE4 isoforms that may have functional consequences.

post to: CiteULike

A comparison of experience-dependent locomotory behaviors and biogenic amine neurons in nematode relatives of Caenorhabditis elegans.

Publication Date: 2010 Feb 19 PMID: 20167133
Authors: Rivard, L. - Srinivasan, J. - Stone, A. - Ochoa, S. - Sternberg, P. W. - Loer, C. M.
Journal: BMC Neurosci

ABSTRACT: BACKGROUND: Survival of an animal depends on its ability to match its responses to environmental conditions. To generate an optimal behavioral output, the nervous system must process sensory information and generate a directed motor output in response to stimuli. The nervous system should also store information about experiences to use in the future. The diverse group of free-living nematodes provides an excellent system to study macro- and microevolution of molecular, morphological and behavioral character states associated with such nervous system function. We asked whether an adaptive behavior would vary among bacterivorous nematodes and whether differences in the neurotransmitter systems known to regulate the behavior in one species would reflect differences seen in the adaptive behavior among those species. Caenorhabditis elegans worms slow in the presence of food; this 'basal' slowing is triggered by dopaminergic mechanosensory neurons that detect bacteria. Starved worms slow more dramatically; this 'enhanced' slowing is regulated by serotonin. RESULTS: We examined seven nematode species with known phylogenetic relationship to C. elegans for locomotory behaviors modulated by food, and by the worm's recent history of feeding (being well-fed or starved). We found that locomotory behavior in some species was modulated by food and recent feeding experience in a manner similar to C. elegans, but not all the species tested in our analyses exhibited these food-modulated behaviors. Using histochemical and immunological staining, we found that dopaminergic neurons were very similar among all species. For instance, we saw likely homologs of four bilateral pairs of dopaminergic cephalic and deirid neurons known from C. elegans in all seven species examined. In contrast, there was greater variation in the patterns of serotonergic neurons. The presence of presumptive homologs of dopaminergic and serotonergic neurons in a given species did not correlate with the observed differences in locomotory behaviors. CONCLUSION: This study demonstrates that behaviors can differ significantly between species that appear morphologically very similar, and therefore it is important to consider factors, such as ecology of a species in the wild, when formulating hypotheses about the adaptive significance of a behavior. Our results suggest that evolutionary changes in locomotory behaviors are less likely to be caused by changes in neurotransmitter expression of neurons. Such changes could caused either by subtle changes in neural circuitry or in the function of the signal transduction pathways mediating these behaviors.

post to: CiteULike

Acute NMDA toxicity in cultured rat cerebellar granule neurons is accompanied by autophagy induction and late onset autophagic cell death phenotype.

Publication Date: 2010 Feb 18 PMID: 20167092
Authors: Sadasivan, S. - Zhang, Z. - Larner, S. F. - Liu, M. C. - Zheng, W. - Kobeissy, F. H. - Hayes, R. L. - Wang, K. K.
Journal: BMC Neurosci

ABSTRACT: BACKGROUND: Autophagy, an intracellular response to stress, is characterized by double membrane cytosolic vesicles called autophagosomes. Prolonged autophagy is known to result in autophagic (Type II) cell death. This study examined the potential role of an autophagic response in cultured cerebellar granule neurons challenged with excitotoxin N-methyl-D-aspartate (NMDA). Results: NMDA exposure induced light chain-3 (LC-3)-immunopositive and monodansylcadaverine (MDC) fluorescent dye-labeled autophagosome formation in both cell bodies and neurites as early as 3 hours post-treatment. Elevated levels of Beclin-1 and the autophagosome-targeting LC3-II were also observed following NMDA exposure. Prolonged exposure of the cultures to NMDA (8-24 h) generated MDC-, LC3-positive autophagosomal bodies, concomitant with the neurodegenerative phase of NMDA challenge. Lysosomal inhibition studies also suggest that NMDA-treatment diverted the autophagosome-associated LC3-II from the normal lysosomal degradation pathway. Autophagy inhibitor 3-methyladenine significantly reduced NMDA-induced LC3-II/LC3-I ratio increase, accumulation of autophagosomes, and suppressed NMDA-mediated neuronal death. ATG7 siRNA studies also showed neuroprotective effects following NMDA treatment. Conclusions: Collectively, this study shows that autophagy machinery is robustly induced in cultured neurons subjected to prolonged exposure to excitotoxin, while autophagosome clearance by lysosomal pathway might be impaired. Our data further show that prolonged autophagy contributes to cell death in NMDA-mediated excitotoxicity.

post to: CiteULike

Cellular toxicity following application of adeno-associated viral vector-mediated RNA interference in the nervous system.

Publication Date: 2010 Feb 18 PMID: 20167052
Authors: Ehlert, E. M. - Eggers, R. - Niclou, S. P. - Verhaagen, J.
Journal: BMC Neurosci

ABSTRACT: BACKGROUND: After a spinal cord lesion, axon regeneration is inhibited by the presence of a diversity of inhibitory molecules in the lesion environment. At and around the lesion site myelin-associated inhibitors, condroitin sulfate proteoglycans and several axon guidance molecules, including all members of the secreted (Class 3) Semaphorins, are expressed. Interfering with multiple inhibitory signals could potentially enhance the previously reported beneficial effects of blocking single molecules. RNA interference (RNAi) is a tool that can be used to simultaneously silence expression of multiple genes. In this study we aimed to employ adeno-associated virus (AAV) mediated expression of short hairpin RNAs (shRNAs) to target all Semaphorin class 3 signaling by knocking down its receptors, Neuropilin 1 (Npn-1) and Neuropilin 2 (Npn-2). RESULTS: We have successfully generated shRNAs that knock down Npn-1 and Npn-2 in a neuronal cell line. We detected substantial knockdown of Npn-2 mRNA when AAV5 viral vector particles expressing Npn-2 specific shRNAs were injected in dorsal root ganglia (DRG) of the rat. Unexpectedly however, AAV1-mediated expression of Npn-2 shRNAs and a control shRNA in the red nucleus resulted in an adverse tissue response and neuronal degeneration. The observed toxicity was dose dependent and was not seen with control GFP expressing AAV vectors, implicating the shRNAs as the causative toxic agents. CONCLUSIONS: RNAi is a powerful tool to knock down Semaphorin receptor expression in neuronal cells in vitro and in vivo. However, when shRNAs are expressed at high levels in CNS neurons, they trigger an adverse tissue response leading to neuronal degradation.

post to: CiteULike

Abnormalities of cell packing density and dendritic complexity in the MeCP2 A140V mouse model of Rett syndrome/X-linked mental retardation.

Publication Date: 2010 Feb 17 PMID: 20163734
Authors: Jentarra, G. M. - Olfers, S. L. - Rice, S. G. - Srivastava, N. - Homanics, G. E. - Blue, M. - Naidu, S. - Narayanan, V.
Journal: BMC Neurosci

ABSTRACT: BACKGROUND: Rett syndrome (RTT), a common cause of mental retardation in girls, is associated with mutations in the MECP2 gene. Most human cases of MECP2 mutation in girls result in classical or variant forms of RTT. When these same mutations occur in males, they often present as severe neonatal encephalopathy. However, some MECP2 mutations can also lead to diseases characterized as mental retardation syndromes, particularly in boys. One of these mutations, A140V, is a common, recurring missense mutation accounting for about 0.6% of all MeCP2 mutations and ranking 21st by frequency. It has been described in familial X-linked mental retardation (XLMR), PPM-X syndrome (Parkinsonism, Pyramidal signs, Macroorchidism, X-linked mental retardation) and in other neuropsychiatric syndromes. Interestingly, this mutation has been reported to preserve the methyl-CpG binding function of the MeCP2 protein while compromising its ability to bind to the mental retardation associated protein ATRX. RESULTS: We report the construction and initial characterization of a mouse model expressing the A140V MeCP2 mutation. These initial descriptive studies in male hemizygous mice have revealed brain abnormalities seen in both RTT and mental retardation. The abnormalities found include increases in cell packing density in the brain and a significant reduction in the complexity of neuronal dendritic branching. In contrast to some MeCP2 mutation mouse models, the A140V mouse has an apparently normal lifespan and normal weight gain patterns with no obvious seizures, tremors, breathing difficulties or kyphosis. CONCLUSION: We have identified various neurological abnormalities in this mouse model of Rett syndrome/X-linked mental retardation which may help to elucidate the manner in which MECP2 mutations cause neuronal changes resulting in mental retardation without the confounding effects of seizures, chronic hypoventilation, or other Rett syndrome associated symptoms.

post to: CiteULike

Signaling involved in neurite outgrowth of postnatally born subventricular zone neurons in vitro.

Publication Date: 2010 PMID: 20146799
Authors: Khodosevich, K. - Monyer, H.
Journal: BMC Neurosci

ABSTRACT: BACKGROUND: Neurite outgrowth is a key process during neuronal migration and differentiation. Complex intracellular signaling is involved in the initiation of neurite protrusion and subsequent elongation. Although, in general many constituents of the machinery involved in this multi-stage process are common for neurons in distinct brain areas, there are notable differences between specific neuronal subtypes. RESULTS: We analyzed key intracellular components of neurite outgrowth signaling in postnatally born subventricular zone (SVZ) neurons in vitro. We showed that inhibitors of PI3K, Akt1, PKCzeta and small GTPases significantly reduced neurite outgrowth. Transfection of SVZ-derived neurons with inactive forms of Rac1 or Cdc42 also decreased neurite length whereas transfection with constitutively active forms of Rac1, Cdc42 or Akt1 as well as with full-length PI3K or PKCzeta increased neurite length. PI3K, Akt1 and PKCzeta acted upstream of the small GTPases Rac1 and Cdc42, which in turn modulate lamellipodia formation of SVZ-derived neurons. CONCLUSION: We showed the involvement of PI3K/Akt1/PKCzeta/Rac1/Cdc42 pathway in neurite outgrowth of postnatally born SVZ neurons.

post to: CiteULike

Sleep triggered by an immune response in Drosophila is regulated by the circadian clock and requires the NFkappaB Relish.

Publication Date: 2010 PMID: 20144235
Authors: Kuo, T. H. - Pike, D. H. - Beizaeipour, Z. - Williams, J. A.
Journal: BMC Neurosci

ABSTRACT: BACKGROUND: Immune challenge impacts behavior in many species. In mammals, this adaptive behavior is often manifested as an increase in sleep. Sleep has therefore been proposed to benefit the host by enhancing immune function and thereby overcome the challenge. To facilitate genetic studies on the relationship between sleep and immune function, we characterized the effect of the immune response on sleep in Drosophila melanogaster. Behavioral features of sleep as well as the innate immune response signaling pathways are well characterized in flies and are highly conserved in mammals. RESULTS: An immune response induced by infection with Gram-negative bacteria or by aseptic injury increased sleep in flies. The increase in sleep occurred during the morning hours after treatment and the magnitude of the effect was dependent on the time-of-day of inoculation or injury such that night-time treatment had a stronger effect than that during the daytime. This pattern persisted in constant darkness, indicating a role of the circadian clock. Mutants of the circadian clock gene, period, eliminated the increase in sleep observed in the morning, but instead showed enhanced sleep immediately after injury or infection.Null mutants of the Nuclear Factor kappaB (NFkappaB) Relish, which is central to the innate immune response, do not increase sleep in response to injury or infection at any time of day. Instead, they maintain a normal sleep pattern until they die. Expression of a full-length Relish transgene in the fat bodies of Relish mutants restored the morning increase in sleep during an immune response. Fat bodies are a major site of immune signalling in flies and have a key role in host defense. CONCLUSIONS: These data demonstrate that an immune response increases sleep in flies in a manner that is gated by the circadian clock and that requires the NFkappaB Relish. These findings support a role of sleep in a recovery process and demonstrate a conserved feature of the Drosophila model of sleep.

post to: CiteULike