Astrocytes are the predominant glial cell population in the central nervous system (CNS). Once considered only passive scaffolding elements, astrocytes are now recognised as cells playing essential roles in CNS development and function. They control extracellular water and ion homeostasis, provide substrates for energy metabolism, and regulate neurogenesis, myelination and synaptic transmission. Due to these multiple activities astrocytes have been implicated in almost all brain pathologies, contributing to various aspects of disease initiation, progression and resolution. Evidence is emerging that astrocyte dysfunction can be the direct cause of neurodegeneration, as shown in Alexander’s disease where myelin degeneration is caused by mutations in the gene encoding the astrocyte-specific cytoskeleton protein glial fibrillary acidic protein. Recent studies point to a primary role for astrocytes in the pathogenesis of other genetic leukodystrophies such as megalencephalic leukoencephalopathy with subcortical cysts and vanishing white matter disease. The aim of this review is to summarize current knowledge of the pathophysiological role of astrocytes focusing on their contribution to the development of the above mentioned leukodystrophies and on new perspectives for the treatment of neurological disorders.
Leukodystrophies; Glial cells; Myelin; Ion homeostasis; CNS diseases; Alexander’s disease; Megalencephalic leukoencephalopathy with subcortical cysts (MLC); Vanishing white matter disease
Computational methods have complemented experimental and clinical neurosciences and led to improvements in our understanding of the nervous systems in health and disease. In parallel, neuromodulation in form of electric and magnetic stimulation is gaining increasing acceptance in chronic and intractable diseases. In this paper, we firstly explore the relevant state of the art in fusion of both developments towards translational computational neuroscience. Then, we propose a strategy to employ the new theoretical concept of dynamical network biomarkers (DNB) in episodic manifestations of chronic disorders. In particular, as a first example, we introduce the use of computational models in migraine and illustrate on the basis of this example the potential of DNB as early-warning signals for neuromodulation in episodic migraine.
Migraine; Neuromodulation; Nonlinear dynamics; Biomarkers; Spreading depression; Hodgkin-Huxley models; Central pattern generator; Pain
Alzheimer’s disease (AD) is an age-related dementia, with the pathological hallmarks of neuritic plaques and neurofibrillary tangles, brain atrophy and loss of synaptic terminals. Dysfunctional mitochondrial bioenergetics is implicated as a contributing factor to the cognitive decline observed in AD. We hypothesized that, in the presence of the AD neurotoxic peptide beta-amyloid, mitochondrial respiration is impaired early in synaptic terminals, which are vital to cognitive performance, preferentially in cognitive centers of the brain. We compared oxygen consumption in synaptosomal and perikaryal mitochondria prepared from the cerebral cortex and cerebellum of wild type (WT) and AD transgenic Tg2576 mice. Compared to WT mice, Tg2576 mice showed decreased mitochondrial respiration in the cerebral cortex specifically in synaptosomal fraction, while the perikaryal mitochondria were unaffected. Neither mitochondrial fraction was affected in the cerebellum of Tg2576 mice as compared to WT. The occurrence of a bioenergetic defect in synaptic terminals of mice overexpressing mutant beta-amyloid, in particular in an area of the brain important to cognition, points to an early role of mitochondrial defects in the onset of cognitive deficits in AD.
Alzheimer’s disease; Amyloid; Dementia; Energy Metabolism; Memory; Mitochondria; Oxidative phosphorylation; Oxygen Consumption; Tg2576
Vertebrate brains share many features in common. Early in development, both the hindbrain and diencephalon are built similarly. Only later in time do differences in morphology occur. Factors that could potentially influence such changes include certain physiological properties of neurons. As an initial step to investigate this problem, embryonic Alligator brain neurons were cultured and calcium responses were characterized. The present report is the first to document culture of Alligator brain neurons in artificial cerebrospinal fluid (ACSF) as well as in standard mammalian tissue culture medium supplemented with growth factors. Alligator brain neuron cultures were viable for at least 1 week with unipolar neurites emerging by 24 hours. Employing Fura-2 AM, robust depolarization-induced calcium influx, was observed in these neurons. Using selective blockers of the voltage-gated calcium channels, the contributions of N-, P/Q-, R-, T-, and L-type channels in these neurons were assessed and their presence documented. Lastly, Alligator brain neurons were challenged with an excitotoxic stimulus (glutamate + glycine) where delayed calcium deregulation could be prevented by a classical NMDA receptor antagonist.
Alligator; Calcium mobilization; Immunoblot; Neuronal culture; NMDA receptor; Voltage-gated calcium channels
Transcranial magnetic stimulation (TMS) is a neurostimulation and neuromodulation technique that has provided over two decades of data in focal, non-invasive brain stimulation based on the principles of electromagnetic induction. Its minimal risk, excellent tolerability and increasingly sophisticated ability to interrogate neurophysiology and plasticity make it an enviable technology for use in pediatric research with future extension into therapeutic trials. While adult trials show promise in using TMS as a novel, non-invasive, non-pharmacologic diagnostic and therapeutic tool in a variety of nervous system disorders, its use in children is only just emerging. TMS represents an exciting advancement to better understand and improve outcomes from disorders of the developing brain.
Transcranial magnetic stimulation; Non-invasive brain stimulation; Neuromodulation; Neurostimulation; Child; Pediatrics; Safety; Therapeutic trials
Accumulation of neurofibrillary tangles (NFT), intracellular inclusions of fibrillar forms of tau, is a hallmark of Alzheimer Disease. NFT have been considered causative of neuronal death, however, recent evidence challenges this idea. Other species of tau, such as soluble misfolded, hyperphosphorylated, and mislocalized forms, are now being implicated as toxic. Here we review the data supporting soluble tau as toxic to neurons and synapses in the brain and the implications of these data for development of therapeutic strategies for Alzheimer’s disease and other tauopathies.
Alzheimer; tauopathy; neurofibrillary tangle; hyperphosphorylated tau
A body of epidemiological literature has suggested an association between prenatal infection, subsequent maternal immune activation (MIA), and later risk of schizophrenia. These epidemiological studies have inspired preclinical research using rodent and primate models of prenatal infection and MIA. The findings from these preclinical studies indicate that severe infection and immune activation during pregnancy can negatively impact offspring brain development and impair adult behavior. This review aims to summarize the major epidemiological and preclinical findings addressing the connection between prenatal infection and immune activation and later risk of developing schizophrenia, as well as the more limited literature addressing the mechanisms by which this gestational insult might affect offspring neurodevelopment. Finally, directions for future research will be discussed.
Prenatal infection; Maternal immune activation; Schizophrenia; Polyinosinic-polycytosinic acid (Poly IC); Cytokines; Neurodevelopment
Gene products such as organelles, proteins and RNAs are actively transported to synaptic terminals for the remodeling of pre-existing neuronal connections and formation of new ones. Proteins described as molecular motors mediate this transport and utilize specialized cytoskeletal proteins that function as molecular tracks for the motor based transport of cargos. Molecular motors such as kinesins and dynein's move along microtubule tracks formed by tubulins whereas myosin motors utilize tracks formed by actin. Deficits in active transport of gene products have been implicated in a number of neurological disorders. We describe such disorders collectively as “transportopathies”. Here we review current knowledge of critical components of active transport and their relevance to neurodegenerative diseases.
Axonal transport; Neurodegenerative diseases
As a neurodegenerative disorder, Alzheimer disease (AD) is the most common form of dementia found in the aging population. Immunotherapy with passive or active immunizations targeting amyloid beta (Aβ) build-up in the brain may provide a possible treatment option and may help prevent AD from progressing. A number of passive immunizations with anti-Aβ42 antibodies are in different phases of clinical trials. One active immunization approach, AN-1792, was stopped after the development of autoimmune encephalitis in 6% of patients and a second one, CAD106, in which a small Aβ epitope is used, is currently in safety and tolerability studies. Besides active immunizations with proteins or peptides, active immunizations using DNA which codes for the protein against which the immune response will be directed, so called genetic immunizations, provide additional safety as the immune response in DNA immunizations differs quantitatively and qualitatively from the response elicited by peptide immunizations. In this review, we summarize our data using DNA Aβ42 immunizations in mouse models and discuss the results together with the results presented by other groups working on a DNA vaccine as treatment option for AD.
Alzheimer’s disease; amyloid-beta; immunotherapy; vaccination
Osteopontin (OPN) is a pro-inflammatory cytokine that can be secreted from many cells including activated macrophages and T-lymphocytes. Elevated levels of osteopontin in the plasma, cerebrospinal fluid or brain of individuals with neurodegenerative diseases such as multiple sclerosis (MS), Parkinson’s and Alzheimer’s disease and more recently in HIV-associated neurocognitive disorder has been reported. However, except for the case of MS, little is known regarding the molecular mechanisms by which OPN may exacerbate disease. Alternatively, OPN through its ability to promote cell survival may in some contexts function in the brain in a protective capacity. OPN has several protein motifs that allow it to engage with several different signaling pathways involved in immunity and inflammation. A better understanding of the cellular pathways that are regulated by OPN in cells of the central nervous system is required to uncover its putative role in neuronal homeostasis.
Neurodegeneration; Integrin; CD44; HIV-associated neurocognitive disorder; Macrophage; Microglia
Alterations in gyral form and complexity have been consistently noted in both autism and dyslexia. In this present study, we apply spherical harmonics, an established technique which we have exapted to estimate surface complexity of the brain, in order to identify abnormalities in gyrification between autistics, dyslexics, and controls. On the order of absolute surface complexity, autism exhibits the most extreme phenotype, controls occupy the intermediate ranges, and dyslexics exhibit lesser surface complexity. Here, we synthesize our findings which demarcate these three groups and review how factors controlling neocortical proliferation and neuronal migration may lead to these distinctive phenotypes.
Cerebral cortex; Gyral window; Gyrification index; Minicolumn; Neurogenesis
Diffuse axonal injury is a common pathological consequence of Traumatic Brain Injury (TBI). Diffusion Tensor Imaging is an ideal technique to study white matter integrity using the Fractional Anisotropy (FA) index which is a measure of axonal integrity and coherence. There have been several reports showing reduced FA in individuals with TBI, which suggest demyelination or reduced fiber density in white matter tracts secondary to injury. Individuals with TBI are usually diagnosed with cognitive deficits such as reduced attention span, memory and executive function. In this study we sought to investigate correlations between brain functional networks, white matter integrity, and TBI severity in individuals with TBI ranging from mild to severe. A resting state functional magnetic resonance imaging protocol was used to study the default mode network in subjects at rest. FA values were decreased throughout all white matter tracts in the mild to severe TBI subjects. FA values were also negatively correlated with TBI injury severity ratings. The default mode network showed several brain regions in which connectivity measures were higher among individuals with TBI relative to control subjects. These findings suggest that, subsequent to TBI, the brain may undergo adaptation responses at the cellular level to compensate for functional impairment due to axonal injury.
Traumatic Brain Injury (TBI); Functional magnetic resonance imaging (fMRI); DTI; Cognitive Function
The name astroglia unifies many non-excitable neural cells that act as primary homeostatic cells in the nervous system. Neuronal activity triggers multiple homeostatic responses of astroglia that include increase in metabolic activity and synthesis of neuronal preferred energy substrate lactate, clearance of neurotransmitters and buffering of extracellular K+ ions to name but a few. Many (if not all) of astroglial homeostatic responses are controlled by dynamic changes in the cytoplasmic concentration of two cations, Ca2+ and Na+. Intracellular concentration of these ions is tightly controlled by several transporters and can be rapidly affected by the activation of respective fluxes through ionic channels or ion exchangers. Here, we provide a comprehensive review of astroglial Ca2+ and Na+ signalling.
Astrocyte; Homeostasis; Excitability; Ca2+ signalling; Na+ signalling
Based on evidence suggesting that deep brain stimulation (DBS) may promote certain cognitive processes, we have been interested in developing DBS as a means of mitigating memory and learning impairments in Alzheimer’s disease (AD). In this study we used an animal model of AD (TgCRND8 mice) to determine the effects of high-frequency stimulation (HFS) on non-amyloidogenic α-secretase activity and DBS in short-term memory. We tested our hypothesis using hippocampal slices (in vitro studies) from TgCRND8 mice to evaluate whether HFS increases α-secretase activity (non-amyloidogenic pathway) in the CA1 region. In a second set of experiments, we performed in vivo studies to evaluate whether DBS in midline thalamic region re-establishes hippocampal dependent short-term memory in TgCRND8 mice. The results showed that application of HFS to isolated hippocampal slices significantly increased synaptic plasticity in the CA1 region and promoted a 2-fold increase of non-amyloidogenic α-secretase activity, in comparison to low frequency stimulated controls from TgCRND8 mice. In the in vivo studies, DBS treatment facilitated acquisition of object recognition memory in TgCRND8 mice, in comparison to their own baseline before treatment. These results provide evidence that DBS could enhance short-term memory in the CA1 region of hippocampus in a mouse model of AD.
Alzheimer’s disease; Deep brain stimulation; Hippocampus; LTP; Neuronal transmission Synaptic plasticity; Memory; TgCRND8 mice; Thalamus
The organization of the cortex can be understood as a complex system comprised of interconnected modules called minicolumns. Comparative anatomical studies suggest that evolution has prompted a scale free world network of connectivity within the white matter while simultaneously increasing the complexity of minicolumnar composition. It is this author’s opinion that this complex system is poised to collapse under the weight of environmental exigencies. Some mental disorders may be the manifestations of this collapse.
Minicolumn; Neocortex; Isocortex; Encephalization; Corticalization; Systems theory
Biological, genetic, and clinical data provide compelling proof for N-type voltage-gated calcium channels (CaV2.2) as therapeutic targets for chronic pain. While decreasing channel function is ultimately anti-nociceptive, directly targeting the channel can lead to multiple adverse effects. Targeting regulators of channel activity may facilitate improved analgesic properties associated with channel block and afford a broader therapeutic window. Towards this end, we recently identified a short peptide, designated CBD3, derived from collapsin response mediator protein 2 (CRMP-2) that suppressed inflammatory and neuropathic hypersensitivity by inhibiting CRMP-2 binding to CaV2.2 [Brittain et al., Nature Medicine 17:822–829 (2011)]. Rodents administered CBD3 intraperitoneally, fused to the HIV TAT protein cell penetrating domain, exhibited antinociception lasting ~4 hours highlighting potential instability, limited oral bioavailability, and/or rapid elimination of peptide. This report focuses on improving upon the parental CBD3 peptide. Using SPOTScan analysis of synthetic versions of the parental CBD3 peptide, we identified peptides harboring single amino acid mutations that bound with greater affinity to CaV2.2. One such peptide, harboring a phenylalanine instead of glycine (G14F), was tested in rodent models of migraine and neuropathic pain. In vivo laser Doppler blood flowmetry measure of capsaicin-induced meningeal vascular responses related to headache pain was almost completely suppressed by dural application of the G14F peptide. The G14F mutant peptide, administered intraperitoneally, also exhibited greater antinociception in Stavudine (2'-3'-didehydro-2'-3'-dideoxythymidine (d4T)/Zerit®) model of AIDS therapy-induced peripheral neuropathy compared to the parent CBD3 peptide. These results demonstrate the patent translational value of small biologic drugs targeting CaV2.2 for management of clinical pain.
N-type calcium channel; CRMP-2; Uncoupling peptide; Meningeal blood flow; Migraine model; d4T/Zerit/Stavudine; NTR; AIDS therapy-induced neuropathic pain; Chronic pain
Most psychiatric and neurological disorders exhibit sleep disorders, and in some cases presage the disease. Study of the control of sleep and waking has the potential for making a major impact on a number of disorders, making translational neuroscience research on this area critical. One element of the reticular activating system (RAS) is the pedunculopontine nucleus (PPN), which is the cholinergic arm of the RAS, and projects to the thalamus to trigger thalamocortical rhythms and to the brainstem to modulate muscle tone and locomotion. We developed a research program using brainstem slices containing the PPN to tell us about the cellular and molecular organization of this region. In addition, we developed the P13 midlatency auditory evoked potential, which is generated by PPN outputs, preparation in freely moving rats. This allows the study of PPN cellular and molecular mechanisms at the level of the whole animal. We also study the P50 midlatency auditory evoked potential, which is the human equivalent of the rodent P13 potential, allowing us to study processes detected in vitro, confirmed in the whole animal, and tested in humans. This translational research program led to the discovery of a novel mechanism of sleep-wake control, pointing the way to a number of new clinical applications in the development of novel stimulants and anesthetics.
Brainstem slices; Electrical coupling; Gap junctions; Modafinil; P13 potential; P50 potential
It has been reported that individuals with autism spectrum disorder (ASD) have abnormal responses to the sensory environment. For these individuals sensory overload can impair functioning, raise physiological stress, and adversely affect social interaction. Early-stage (i.e. within 200ms of stimulus onset) auditory processing abnormalities have been widely examined in ASD using event-related potentials (ERP), while ERP studies investigating early-stage visual processing in ASD are less frequent. We wanted to test the hypothesis of early-stage visual processing abnormalities in ASD by investigating ERPs elicited in a visual oddball task using illusory figures. Our results indicate that individuals with ASD have abnormally large cortical responses to task irrelevant stimuli over both parieto-occipital and frontal regions-of-interest (ROI) during early stages of visual processing compared to the control group. Furthermore, ASD patients showed signs of an overall disruption in stimulus discrimination, and had a significantly higher rate of motor response errors.
Autism; event-related potentials; EEG; visual processing; evoked potentials
Using the NIH Pediatric MRI Data Repository for normative developmental studies, white matter depth within the gyri of the frontal, temporal, parietal, and occipital lobes, and of the left and right hemisphere was identified for 312 typically developing children and young adults (168 male and 144 female) between 4 and 23 years of age. There was no significant age difference between male and female groups overall (F1,867 = 0.0002; p = 0.99) or per-visit (F2,867 = 2.18; p = 0.86). There was significant dependence of gyral window upon age (F1,6544 = 115, p < 0.0001), lobe (F3,6544 = 229, p < 0.0001), hemisphere (F1,6544 = 5.23, p = 0.022), age*sex (F1,6544 = 13.8, p = 0.0002), age*lobe (F3,6544 = 120, p = 0.0001), and age*hemisphere (F1,6544 = 4.41, p = 0.036). Gyrification increased with age in both males and females in the frontal, temporal and parietal lobes with opposite effects observed in the occipital lobe. Relative gyral depth, as measured in this study, was significantly (p < 0.0001) inversely correlated with gyrification index. Previous studies relate gyral window measurements to the differential expression of short and long corticocortical projections. Our results therefore suggest that the pattern of corticocortical connections is malleable during the first two decades of development.
cerebral cortex; gyral window; gyrification index; magnetic resonance imaging
Morphometric studies of the corpus callosum suggest its involvement in a number of psychiatric conditions. In the present study we introduce a novel pattern recognition technique that offers a point-by-point shape descriptor of the corpus callosum. The method uses arc lengths of electric field lines in order to avoid discontinuities caused by folding anatomical contours. We tested this technique by comparing the shape of the corpus callosum in a series of dyslexic men (n = 16) and age-matched controls (n = 14). The results indicate a generalized increase in size of the corpus callosum in dyslexia with a concomitant diminution at its rostral and caudal poles. The reported shape analysis and 2D-reconstruction provide information of anatomical importance that would otherwise passed unnoticed when analyzing size information alone.
Brain mapping; Corpus callosum; Dyslexia; Magnetic resonance imaging
The brain of the bottlenose dolphin exhibits patterns of isocortical parcellation and cytoarchitecture distinct from those seen in primates, yet cell clusters in anterior insula are comparable in scale to module-like cell arrangements found throughout isocortex in other placental mammalian species with long divergent evolutionary histories. This similarity may be due to common ancestry, or to convergence as a result of selective constraints on organization of connections within such modules. Differences reflect alternate arrangements of minicolumns, an elemental cytoarchitectonic motif of isocortex defined by radially oriented pyramidal cell arrays. In contrast with larger modular structures incorporating them, minicolumns have been highly conserved in mammalian evolution. In this study a previously validated imaging method was employed to assess verticality, D, a parameter indicating radial bias of isocortex. Photomicrographs of coronal Nissl-stained sections of dolphin anterior insular cortex were compared with sections from human brains of putatively homologous areas as well as other isocortical areas differing in modular organization. Dolphin insula exhibited a high degree of verticality consistent with conserved minicolumnar organization. Our findings indicate that a basic structural motif of isocortex is synapomorphic in a species of marine mammal exhibiting unique phylogenetically derived isocortical characteristics.
Cetaceans; Neocortex; Minicolumns; Pyramidal cells; Tursiops truncatus
While a distinct minicolumnar phenotype seems to be an underlying factor in a significant portion of cases of autism, great attention is being paid not only to genetics but to epigenetic factors which may lead to development of the conditions. Here we discuss the indivisible role the molecular environment plays in cellular function, particularly the pivotal position which the transcription factor and adhesion molecule, β-catenin, occupies in cellular growth. In addition, the learning environment is not only integral to postnatal plasticity, but the prenatal environment plays a vital role during corticogenesis, neuritogenesis, and synaptogenesis as well. To illustrate these points in the case of autism, we review important findings in genetics studies (e.g., PTEN, TSC1/2, FMRP, MeCP2, Neurexin-Neuroligin) and known epigenetic factors (e.g., valproic acid, estrogen, immune system, ultrasound) which may predispose towards the minicolumnar and connectivity patterns seen in the conditions, showing how one-gene mutational syndromes and exposure to certain CNS teratogens may ultimately lead to comparable phenotypes. This in turn may shed greater light on how environment and complex genetics combinatorially give rise to a heterogenetic group of conditions such as autism.
beta catenin; minicolumns; neural stem cells; Rett syndrome; fragile X syndrome; tuberous sclerosis; valproic acid; PTEN phosphohydrolase; ultrasonography; cell adhesion molecules; neuronal
Gene expression was investigated in the major brain subdivisions (telencephalon, diencephalon, midbrain and hindbrain) in a representative reptile, Alligator mississipiensis, during the later stages of embryonic development. The following genes were examined: voltage-gated sodium channel isoforms: NaV1.1 and NaV1.2; synaptic vesicle 2a (SV2a); synaptophysin; and calbindin 2. With the exception of synaptophysin, which was only expressed in the telencephalon, all genes were expressed in all brain regions sampled at the time periods examined. For NaV1.1, gene expression varied according to brain area sampled. When compared with NaV1.1, the pattern of NaV1.2 gene expression differed appreciably. The gene expression of SV2a was the most robust of any of the genes examined. Of the other genes examined, although differences were noted, no statistically significant changes were found either between brain part or time interval. Although limited, the present analysis is the first quantitative mRNA gene expression study in any reptile during development. Together with future experiments of a similar nature, the present gene expression results should determine which genes are expressed in major brain areas at which times during development in Alligator. When compared with other amniotes, these results will prove useful for determining how gene expression during development influences adult brain structure.
Alligator; Calbindin 2; qPCR; Synaptic vesicle protein 2; Synaptophysin; Voltage-gated sodium channel
Autism spectrum disorders (ASD) represent complex neurodevelopmental disorders characterized by impairments in reciprocal social interactions, abnormal development and use of language, and monotonously repetitive behaviors. With an estimated heritability of more than 90%, it is the most strongly genetically influenced psychiatric disorder of the young age. In spite of the complexity of this disorder, there has recently been much progress in the research on etiology, early diagnosing, and therapy of autism. Besides already advanced neuropathologic research, several new technological innovations, such as sleep functional MRI, diffusion tensor imaging (DTI) and proton magnetic resonance spectroscopy imaging (1H-MRS) divulged promising breakthroughs in exploring subtle morphological and neurochemical changes in the autistic brain. This review provides a comprehensive summary of morphological and neurochemical alterations in autism known to date, as well as a short introduction to the functional research that has begun to advance in the last decade. Finally, we mention the progress in establishing new standardized diagnostic measures and its importance in early recognition and treatment of ASD.
Autism; Autism spectrum disorder