http://www.molecularbrain.com The most accessed research articles published by Molecular Brain 2010-02-05T00:00:00Z This is an RSS newsfeed from BioMed Central It is intended to be used with an RSS reader. For more information about RSS newsfeeds from BioMed Central, visit http://www.biomedcentral.com/info/about/rss/ The molecular mechanisms governing the differentiation of neural stem cells (NSCs) into neuronal progenitor cells and finally into neurons are gradually being revealed. The lack of convenient means for real-time determination of the stages of differentiation of individual neural cells, however, has been hindering progress in elucidating the mechanisms. In order to be able to easily identify the stages of differentiation of neural cells, we have been attempting to establish a mouse system that would allow progression of neuronal differentiation to be visualized based on transitions between fluorescence colors by using a combination of mouse genetics and the ever-expanding repertoire of fluorescent proteins. In this study we report the initial version of such a mouse system, which we call "Color Timer." We first generated transgenic (Tg; nestin/KOr Tg) mice in which production of the fluorescent protein Kusabira-Orange (KOr) is controlled by the gene regulatory elements within the 2nd intronic enhancer of the nestin gene, which is a good marker for NSCs, so that NSCs would emit orange fluorescence upon excitation. We then confirmed by immunohistochemical and immunocytochemical analyses that the KOr fluorescence closely reflected the presence of the Nestin protein. We also confirmed by a neurosphere formation assay that the intensity of the KOr fluorescence correlated with "stemness" of the cell and it was possible to readily identify NSCs in the two neurogenic regions, namely the dentate gyrus of the hippocampus and the subventricular zone of the lateral ventricle, in the brain of adult nestin/KOr Tg mice by the orange fluorescence they emitted. We then crossed nestin/KOr mice with doublecortin-enhanced Green Fluorescent Protein Tg mice, whose immature neurons emit green fluorescence upon excitation, and it was possible to visualize the progress of NSC-to-neuron differentiation by the transition between fluorescence colors from orange to green. This two-color initial version of the "Color Timer" mouse system will provide a powerful new tool for neurogenesis research. http://www.molecularbrain.com/content/3/1/5 Hiroaki Kanki Marilia Shimabukuro Atsushi Miyawaki Hideyuki Okano Molecular Brain 2010, 3:5 2010-02-02T00:00:00Z doi:10.1186/1756-6606-3-5 Molecular Brain 1756-6606 3 5 2010-02-02T00:00:00Z XML The presenilins form part of a complex of membrane proteins that are involved in the proteolytic cleavage of cell-surface molecules. This article reviews the history of the discovery of the presenilins, their role in the pathogenesis of Alzheimer's disease and in the metabolism of the amyloid-beta precursor protein. Unanswered questions about their biochemical mechanism of action and their effects on Ca2+ homeostasis are examined. http://www.molecularbrain.com/content/3/1/7 David Small David Klaver Lisa Foa Molecular Brain 2010, 3:7 2010-02-05T00:00:00Z doi:10.1186/1756-6606-3-7 Molecular Brain 1756-6606 3 7 2010-02-05T00:00:00Z PDF Direct interaction with the β subunit of the heterotrimeric G protein complex causes voltage-dependent inhibition of N-type calcium channels. To further characterize the molecular determinants of this interaction, we performed scanning mutagenesis of residues 372-387 and 410-428 of the N-type channel α1 subunit, in which individual residues were replaced by either alanine or cysteine. We coexpressed wild type Gβ1γ2 subunits with either wild type or point mutant N-type calcium channels, and voltage-dependent, G protein-mediated inhibition of the channels (VDI) was assessed using patch clamp recordings. The resulting data indicate that Arg376 and Val416 of the α1 subunit, residues which are surface-exposed in the presence of the calcium channel β subunit, contribute significantly to the functional inhibition by Gβ1. To further characterize the roles of Arg376 and Val416 in this interaction, we performed secondary mutagenesis of these residues, coexpressing the resulting mutants with wild type Gβ1γ2 subunits and with several isoforms of the auxiliary β subunit of the N-type channel, again assessing VDI using patch clamp recordings. The results confirm the importance of Arg376 for G protein-mediated inhibition and show that a single amino acid substitution to phenylalanine drastically alters the abilities of auxiliary calcium channel subunits to regulate G protein inhibition of the channel. http://www.molecularbrain.com/content/3/1/6 Hugo Tedford Alexandra Kisilevsky Lucienne Vieira Diego Varela Lina Chen Gerald Zamponi Molecular Brain 2010, 3:6 2010-02-03T00:00:00Z doi:10.1186/1756-6606-3-6 Molecular Brain 1756-6606 3 6 2010-02-03T00:00:00Z XML Elucidating the neural and genetic factors underlying psychiatric illness is hampered by current methods of clinical diagnosis. The identification and investigation of clinical endophenotypes may be one solution, but represents a considerable challenge in human subjects. Here we report that mice heterozygous for a null mutation of the alpha-isoform of calcium/calmodulin-dependent protein kinase II (alpha-CaMKII+/-) have profoundly dysregulated behaviours and impaired neuronal development in the dentate gyrus (DG). The behavioral abnormalities include a severe working memory deficit and an exaggerated infradian rhythm, which are similar to symptoms seen in schizophrenia, bipolar mood disorder and other psychiatric disorders. Transcriptome analysis of the hippocampus of these mutants revealed that the expression levels of more than 2000 genes were significantly changed. Strikingly, among the 20 most downregulated genes, 5 had highly selective expression in the DG. Whereas BrdU incorporated cells in the mutant mouse DG was increased by more than 50 percent, the number of mature neurons in the DG was dramatically decreased. Morphological and physiological features of the DG neurons in the mutants were strikingly similar to those of immature DG neurons in normal rodents. Moreover, c-Fos expression in the DG after electric footshock was almost completely and selectively abolished in the mutants. Statistical clustering of human post-mortem brains using 10 genes differentially-expressed in the mutant mice were used to classify individuals into two clusters, one of which contained 16 of 18 schizophrenic patients. Nearly half of the differentially-expressed probes in the schizophrenia-enriched cluster encoded genes that are involved in neurogenesis or in neuronal migration/maturation, including calbindin, a marker for mature DG neurons. Based on these results, we propose that an "immature DG" in adulthood might induce alterations in behavior and serve as a promising candidate endophenotype of schizophrenia and other human psychiatric disorders. http://www.molecularbrain.com/content/1/1/6 Nobuyuki Yamasaki Motoko Maekawa Katsunori Kobayashi Yasushi Kajii Jun Maeda Miho Soma Keizo Takao Koichi Tanda Koji Ohira Keiko Toyama Kouji Kanzaki Kohji Fukunaga Yusuke Sudo Hiroshi Ichinose Masashi Ikeda Nakao Iwata Norio Ozaki Hidenori Suzuki Makoto Higuchi Tetsuya Suhara Shigeki Yuasa Tsuyoshi Miyakawa Molecular Brain 2008, 1:6 2008-09-10T00:00:00Z doi:10.1186/1756-6606-1-6 Molecular Brain 1756-6606 1 6 2008-09-10T00:00:00Z XML The downstream regulatory element antagonist modulator (DREAM), a multifunctional Ca2+-binding protein, binds specifically to DNA and several nucleoproteins regulating gene expression and with proteins outside the nucleus to regulate membrane excitability or calcium homeostasis. DREAM is highly expressed in the central nervous system including the hippocampus and cortex; however, the roles of DREAM in hippocampal synaptic transmission and plasticity have not been investigated. Taking advantage of transgenic mice overexpressing a Ca2+-insensitive DREAM mutant (TgDREAM), we used integrative methods including electrophysiology, biochemistry, immunostaining, and behavior tests to study the function of DREAM in synaptic transmission, long-term plasticity and fear memory in hippocampal CA1 region. We found that NMDA receptor but not AMPA receptor-mediated current was decreased in TgDREAM mice. Moreover, synaptic plasticity, such as long-term depression (LTD) but not long-term potentiation (LTP), was impaired in TgDREAM mice. Biochemical experiments found that DREAM interacts with PSD-95 and may inhibit NMDA receptor function through this interaction. Contextual fear memory was significantly impaired in TgDREAM mice. By contrast, sensory responses to noxious stimuli were not affected. Our results demonstrate that DREAM plays a novel role in postsynaptic modulation of the NMDA receptor, and contributes to synaptic plasticity and behavioral memory. http://www.molecularbrain.com/content/3/1/3 Long-Jun Wu Britt Mellstrom Hansen Wang Ming Ren Sofia Domingo Susan Kim Xiang-Yao Li Tao Chen Jose Naranjo Min Zhuo Molecular Brain 2010, 3:3 2010-01-21T00:00:00Z doi:10.1186/1756-6606-3-3 Molecular Brain 1756-6606 3 3 2010-01-21T00:00:00Z XML Background: Diurnal rhythm-mediated endogenous cortisol levels in humans are characterised by a peak in secretion after awakening that declines throughout the day to an evening trough. However, a significant proportion of the population exhibits an atypical cycle of diurnal cortisol due to shift work, jet-lag, aging, and mental illness. Results: The present study has demonstrated a correlation between elevation of cortisol in the evening and deterioration of visual object recognition memory. However, high evening cortisol levels have no effect on spatial memory. Conclusion: This study suggests that atypical evening salivary cortisol levels have an important role in the early deterioration of recognition memory. The loss of recognition memory, which is vital for everyday life, is a major symptom of the amnesic syndrome and early stages of Alzheimer's disease. Therefore, this study will promote a potential physiologic marker of early deterioration of recognition memory and a possible diagnostic strategy for Alzheimer's disease. http://www.molecularbrain.com/content/1/1/4 Heather Gilpin Daniel Whitcomb Kwangwook Cho Molecular Brain 2008, 1:4 2008-08-21T00:00:00Z doi:10.1186/1756-6606-1-4 Molecular Brain 1756-6606 1 4 2008-08-21T00:00:00Z XML Background: Glycogen synthase kinase-3 (GSK-3) is a widely expressed and highly conserved serine/threonine protein kinase encoded by two genes that generate two related proteins: GSK-3α and GSK-3β. Mice lacking a functional GSK-3α gene were engineered in our laboratory; they are viable and display insulin sensitivity. In this study, we have characterized brain functions of GSK-3α KO mice by using a well-established battery of behavioral tests together with neurochemical and neuroanatomical analysis. Results: Similar to the previously described behaviours of GSK-3β+/-mice, GSK-3α mutants display decreased exploratory activity, decreased immobility time and reduced aggressive behavior. However, genetic inactivation of the GSK-3α gene was associated with: decreased locomotion and impaired motor coordination, increased grooming activity, loss of social motivation and novelty; enhanced sensorimotor gating and impaired associated memory and coordination. GSK-3α KO mice exhibited a deficit in fear conditioning, however memory formation as assessed by a passive avoidance test was normal, suggesting that the animals are sensitized for active avoidance of a highly aversive stimulus in the fear-conditioning paradigm. Changes in cerebellar structure and function were observed in mutant mice along with a significant decrease of the number and size of Purkinje cells. Conclusion: Taken together, these data support a role for the GSK-3α gene in CNS functioning and possible involvement in the development of psychiatric disorders. http://www.molecularbrain.com/content/2/1/35 Oksana Kaidanovich-Beilin Tatiana Lipina Keizo Takao Matthijs van Eede Satoko Hattori Christine Laliberte Mustafa Khan Kenichi Okamoto John Chambers Paul Fletcher Katrina MacAulay Bradley Doble Mark Henkelman Tsuyoshi Miyakawa John Roder James Woodgett Molecular Brain 2009, 2:35 2009-11-19T00:00:00Z doi:10.1186/1756-6606-2-35 Molecular Brain 1756-6606 2 35 2009-11-19T00:00:00Z XML Glutamatergic synapses play critical roles in brain functions and diseases. Long-term potentiation (LTP) is a most effective cellular model for investigating the synaptic changes that underlie learning as well as brain disease – although different molecular mechanisms are likely involved in LTP in physiological and pathological conditions. In the case of learning, N-methyl-D-aspartate (NMDA) receptor is known to be important for triggering learning-related plasticity; alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic (AMPA) receptors are thought to be important for the expression of synaptic changes. In this review, I will examine recent evidence on the novel roles of NMDA receptors, in particular NR2B subunit-containing NMDA receptors in learning and chronic pain. A positive feedback control of NR2B receptor subunit is proposed to explain cortical sensitization involved in chronic pain, but not learning and memory. http://www.molecularbrain.com/content/2/1/4 Min Zhuo Molecular Brain 2009, 2:4 2009-02-03T00:00:00Z doi:10.1186/1756-6606-2-4 Molecular Brain 1756-6606 2 4 2009-02-03T00:00:00Z XML Group I metabotropic glutamate receptors (mGluRs) are coupled via Gαq/11 to the activation of phospholipase Cβ, which hydrolyzes membrane phospholipids to form inositol 1,4,5 trisphosphate and diacylglycerol. This results in the release of Ca2+ from intracellular stores and the activation of protein kinase C. The activation of Group I mGluRs also results in ERK1/2 phosphorylation. We show here, that the proline-rich tyrosine kinase 2 (Pyk2) interacts with both mGluR1 and mGluR5 and is precipitated with both receptors from rat brain. Pyk2 also interacts with GST-fusion proteins corresponding to the second intracellular loop and the distal carboxyl-terminal tail domains of mGluR1a. Pyk2 colocalizes with mGluR1a at the plasma membrane in human embryonic kidney (HEK293) cells and with endogenous mGluR5 in cortical neurons. Pyk2 overexpression in HEK293 results in attenuated basal and agonist-stimulated inositol phosphate formation in mGluR1 expressing cells and involves a mechanism whereby Pyk2 displaces Gαq/11 from the receptor. The activation of endogenous mGluR1 in primary mouse cortical neuron stimulates ERK1/2 phosphorylation. Treatments that prevent Pyk2 phosphorylation in cortical neurons, and the overexpression of Pyk2 dominant-negative and catalytically inactive Pyk2 mutants in HEK293 cells, prevent ERK1/2 phosphorylation. The Pyk2 mediated activation of ERK1/2 phosphorylation is also Src-, calmodulin- and protein kinase C-dependent. Our data reveal that Pyk2 couples the activation mGluRs to the mitogen-activated protein kinase pathway even though it attenuates mGluR1-dependent G protein signaling. http://www.molecularbrain.com/content/3/1/4 Alexander Nicodemo Macarena Pampillo Lucimar Ferreira Lianne Dale Tamara Cregan Fabiola Ribeiro Stephen Ferguson Molecular Brain 2010, 3:4 2010-01-21T00:00:00Z doi:10.1186/1756-6606-3-4 Molecular Brain 1756-6606 3 4 2010-01-21T00:00:00Z XML Background: In mammals, the synchronized activity of cell autonomous clocks in the suprachiasmatic nuclei (SCN) enables this structure to function as the master circadian clock, coordinating daily rhythms in physiology and behavior. However, the dominance of this clock has been challenged by the observations that metabolic duress can over-ride SCN controlled rhythms, and that clock genes are expressed in many brain areas, including those implicated in the regulation of appetite and feeding. The recent development of mice in which clock gene/protein activity is reported by bioluminescent constructs (luciferase or luc) now enables us to track molecular oscillations in numerous tissues ex vivo. Consequently we determined both clock activities and responsiveness to metabolic perturbations of cells and tissues within the mediobasal hypothalamus (MBH), a site pivotal for optimal internal homeostatic regulation. Results: Here we demonstrate endogenous circadian rhythms of PER2::LUC expression in discrete subdivisions of the arcuate (Arc) and dorsomedial nuclei (DMH). Rhythms resolved to single cells did not maintain long-term synchrony with one-another, leading to a damping of oscillations at both cell and tissue levels. Complementary electrophysiology recordings revealed rhythms in neuronal activity in the Arc and DMH. Further, PER2::LUC rhythms were detected in the ependymal layer of the third ventricle and in the median eminence/pars tuberalis (ME/PT). A high-fat diet had no effect on the molecular oscillations in the MBH, whereas food deprivation resulted in an altered phase in the ME/PT. Conclusion: Our results provide the first single cell resolution of endogenous circadian rhythms in clock gene expression in any intact tissue outside the SCN, reveal the cellular basis for tissue level damping in extra-SCN oscillators and demonstrate that an oscillator in the ME/PT is responsive to changes in metabolism. http://www.molecularbrain.com/content/2/1/28 Clare Guilding Alun Hughes Timothy Brown Sara Namvar Hugh Piggins Molecular Brain 2009, 2:28 2009-08-27T00:00:00Z doi:10.1186/1756-6606-2-28 Molecular Brain 1756-6606 2 28 2009-08-27T00:00:00Z XML