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Ahmed T.,Catholic University of Leuven | Van der Jeugd A.,Catholic University of Leuven | Blum D.,French Institute of Health and Medical Research | Blum D.,University of Lille Nord de France | And 9 more authors.
Neurobiology of Aging | Year: 2014

Tau has been implicated in the organization, stabilization, and dynamics of microtubules. In Alzheimer's disease and more than 20 neurologic disorders tau missorting, hyperphosphorylation, and aggregation is a hallmark. They are collectively referred to as tauopathies. Although the impact of human tauopathies on cognitive processes has been explored in transgenic mouse models, the functional consequences of tau deletion on cognition are far less investigated. Here, we subjected tau knock-out (KO) mice to a battery of neurocognitive, behavioral, and electrophysiological tests. Although KO and wild-type mice were indistinguishable in motor abilities, exploratory and anxiety behavior, KO mice showed impaired contextual and cued fear conditioning. In contrast, extensive spatial learning in the water maze resulted in better performance of KO mice during acquisition. In electrophysiological experiments, basal synaptic transmission and paired-pulse facilitation in the hippocampal CA1-region were unchanged. Interestingly, deletion of tau resulted in severe deficits in long-term potentiation but not long-term depression. Our results suggest a role of tau in certain cognitive functions and implicate long-term potentiation as the relevant physiological substrate. © 2014 Elsevier Inc.

Batailler M.,CNRS Physiology of Reproduction and Behaviors | Batailler M.,University of Tours | Batailler M.,Institute Francais Du Cheval Et Of Lequitation Ifce | Droguerre M.,CNRS Physiology of Reproduction and Behaviors | And 8 more authors.
Journal of Comparative Neurology | Year: 2014

Neural stem and precursor cells persist postnatally throughout adulthood and are capable of responding to numerous endogenous and exogenous signals by modifying their proliferation and differentiation. Whereas adult neurogenesis has been extensively studied in the dentate gyrus of the hippocampal formation and in the subventricular zone adjacent to the wall of the lateral ventricles, we and others have recently reported constitutive adult neurogenesis in other brain structures, including the hypothalamus. In this study, we used immunohistochemistry to study the expression of the neuroblast marker doublecortin (DCX), and compared its expression pattern in adult ovine, mouse, and human hypothalamic tissues. Our results indicate that DCX-positive cells resembling immature and developing neurons occur in a wide range of hypothalamic nuclei in all three species, although with different distribution patterns. In addition, the morphology of DCX-positive cells varied depending on their location. DCX-positive cells near the third ventricle had the morphology of very immature neuroblasts, a round shape with no processes, whereas those located deeper in the parenchyma such as in the ventromedial nucleus were fusiform and showed a bipolar morphology. Extending this observation, we showed that among the cohort of immature neurons entering the ventromedial nucleus, some appeared to undergo maturation, as revealed by the partial colocalization of DCX with markers of more mature neurons, e.g., human neuronal protein C and D (HuC/D). This study provides further confirmation of the existence of an adult hypothalamic neurogenic niche and argues for the potential existence of a migratory path within the hypothalamus. © 2013 Wiley Periodicals, Inc.

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