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Vilas-Boas F.,University of Lisbon | Vilas-Boas F.,Champalimaud Neuroscience Programme At Instituto Gulbenkian Of Ciencia | Fior R.,University of Lisbon | Swedlow J.R.,University of Dundee | And 3 more authors.
BMC Biology | Year: 2011

Background: Building the complex vertebrate nervous system involves the regulated production of neurons and glia while maintaining a progenitor cell population. Neurogenesis starts asynchronously in different regions of the embryo and occurs over a long period of time, allowing progenitor cells to be exposed to multiple extrinsic signals that regulate the production of different cell types. Notch-mediated cell-cell signalling is one of the mechanisms that maintain the progenitor pool, however, little is known about how the timing of Notch activation is related to the cell cycle and the distinct modes of cell division that generate neurons. An essential tool with which to investigate the role of Notch signalling on cell by cell basis is the development a faithful reporter of Notch activity.Results: Here we present a novel reporter for Notch activity based on the promoter of the well characterised Notch target chick Hes5-1, coupled with multiple elements that confer instability, including a destabilized nuclear Venus fluorescent protein and the 3' untranslated region (UTR) of Hes5-1. We demonstrate that this reporter faithfully recapitulates the endogenous expression of Hes5-1 and that it robustly responds to Notch activation in the chick neural tube. Analysis of the patterns of Notch activity revealed by this reporter indicates that although Notch is most frequently activated prior to mitosis it can be activated at any time within the cell cycle. Notch active progenitors undergoing mitosis generate two daughters that both continue to experience Notch signalling. However, cells lacking Notch activity before and during mitosis generate daughters with dissimilar Notch activity profiles.Conclusions: A novel Notch reporter with multiple destabilisation elements provides a faithful read-out of endogenous Notch activity on a cell-by-cell basis, as neural progenitors progress through the cell cycle in the chick neural tube. Notch activity patterns in this cell population provide evidence for distinct Notch signalling dynamics underlying different cell division modes and for the involvement of random initiation of Notch signalling within the neuroepithelium. These findings highlight the importance of single-cell analysis in the study of the complexity of Notch activity and provide new insights into the mechanisms underlying cell fate decisions in neural progenitors. © 2011 Vilas-Boas et al; licensee BioMed Central Ltd.

Ramiro-Cortes Y.,Champalimaud Neuroscience Programme At Instituto Gulbenkian Of Ciencia | Ramiro-Cortes Y.,Champalimaud Center for the Unknown | Israely I.,Champalimaud Neuroscience Programme At Instituto Gulbenkian Of Ciencia | Israely I.,Champalimaud Center for the Unknown
PLoS ONE | Year: 2013

Neuronal circuits modify their response to synaptic inputs in an experience-dependent fashion. Increases in synaptic weights are accompanied by structural modifications, and activity dependent, long lasting growth of dendritic spines requires new protein synthesis. When multiple spines are potentiated within a dendritic domain, they show dynamic structural plasticity changes, indicating that spines can undergo bidirectional physical modifications. However, it is unclear whether protein synthesis dependent synaptic depression leads to long lasting structural changes. Here, we investigate the structural correlates of protein synthesis dependent long-term depression (LTD) mediated by metabotropic glutamate receptors (mGluRs) through two-photon imaging of dendritic spines on hippocampal pyramidal neurons. We find that induction of mGluR-LTD leads to robust and long lasting spine shrinkage and elimination that lasts for up to 24 hours. These effects depend on signaling through group I mGluRs, require protein synthesis, and activity. These data reveal a mechanism for long lasting remodeling of synaptic inputs, and offer potential insights into mental retardation. © 2013 Ramiro-Cortés, Israely.

PubMed | Champalimaud Neuroscience Programme At Instituto Gulbenkian Of Ciencia
Type: Comment | Journal: Neuron | Year: 2011

High-frequency open-loop deep brain stimulation (DBS) has been used to alleviate Parkinsons symptoms for almost 20 years. In this issue of Neuron, Rosin etal. present a closed-loop real-time approach that improves DBS and shines light on the etiology of motor symptoms in Parkinsons disease.

PubMed | Champalimaud Neuroscience Programme At Instituto Gulbenkian Of Ciencia
Type: Journal Article | Journal: Philosophical transactions of the Royal Society of London. Series B, Biological sciences | Year: 2013

Connections between neurons can undergo long-lasting changes in synaptic strength correlating with changes in structure. These events require the synthesis of new proteins, the availability of which can lead to cooperative and competitive interactions between synapses for the expression of plasticity. These processes can occur over limited spatial distances and temporal periods, defining dendritic regions over which activity may be integrated and could lead to the physical rewiring of synapses into functional groups. Such clustering of inputs may increase the computational power of neurons by allowing information to be combined in a greater than additive manner. The availability of new proteins may be a key modulatory step towards activity-dependent, long-term growth or elimination of spines necessary for remodelling of connections. Thus, the aberrant growth or shrinkage of dendritic spines could occur if protein levels are misregulated. Indeed, such perturbations can be seen in several mental retardation disorders, wherein either too much or too little protein translation exists, matching an observed increase or decrease in spine density, respectively. Cellular events which alter protein availability could relieve a constraint on synaptic competition and disturb synaptic clustering mechanisms. These changes may be detrimental to modifications in neural circuitry following activity.

PubMed | Champalimaud Neuroscience Programme At Instituto Gulbenkian Of Ciencia
Type: Journal Article | Journal: The Journal of neuroscience : the official journal of the Society for Neuroscience | Year: 2010

The auditory system has two parallel streams in the brain that have been implicated in auditory fear learning. The lemniscal stream has selective neurons that are tonotopically organized and is thought to be important for sound discrimination. The nonlemniscal stream has less selective neurons, which are not tonotopically organized, and is thought to be important for multimodal processing and for several forms of learning. Therefore, it has been hypothesized that the lemniscal, but not the nonlemniscal, pathway supports discriminative fear to auditory cues. To test this hypothesis we assessed the effect of electrolytic lesions to the ventral, or medial, division of the medial geniculate nucleus (MGv or MGm, which correspond, respectively, to the lemniscal and the nonlemniscal auditory pathway to amygdala) on the acquisition, expression and extinction of fear responses in discriminative auditory fear conditioning, where one tone is followed by shock (conditioned stimulus, CS(+)), and another is not (CS(-)). Here we show that with single-trial conditioning control, MGv- and MGm-lesioned male rats acquire nondiscriminative fear of both the CS(+) and the CS(-). However, after multiple-trial conditioning, control rats discriminate between the CS(+) and CS(-), whereas MGv- and MGm-lesioned do not. Furthermore, post-training lesions of MGm, but not MGv, lead to impaired expression of discriminative fear. Finally, MGm-lesioned rats display high levels of freezing to both the CS(+) and CS(-) even after an extinction session to the CS(+). In summary, our findings suggest that the lemniscal pathway is important for discriminative learning, whereas the nonlemniscal is important for negatively regulating fear responses.

PubMed | Champalimaud Neuroscience Programme At Instituto Gulbenkian Of Ciencia
Type: Journal Article | Journal: The European journal of neuroscience | Year: 2012

The maintenance of long-lasting forms of plasticity, such as long-term potentiation (LTP) is dependent on the capture of plasticity-related proteins (PRPs) in an input-specific manner - synaptic capture. Here, it is shown that LTP, induced at Schaffer collaterals-CA1 synapses in acute rat hippocampal slice preparation, is not sensitive to protein synthesis inhibition if N-methyl-d-aspartate (NMDA) receptors are blocked, suggesting that synaptic activation is involved in the modulation of LTP maintenance. Similarly, it was found that synaptic activation also determines the sensitivity of LTP to manipulations of the actin cytoskeleton dynamics. Suspending synaptic activation or concomitant NMDA receptor inhibition is sufficient to rescue the impairment on LTP maintenance induced by actin polymerization blockade. Additionally, concomitant inhibition of protein degradation can partially prevent the LTP decay observed under actin polymerization blockade, suggesting that protein degradation is involved in the destabilization of LTP maintenance induced by actin polymerization blockade. Taken together, these observations suggest that LTP maintenance is determined by a balance of synthesis and degradation of PRPs modulated by synaptic activation and actin dynamics. Finally, it was uncovered that inhibition of actin depolymerization blocks synaptic capture, whereas inhibition of actin polymerization can extend the temporal window for synaptic capture. Additionally, inhibition of actin polymerization can rescue the impairment in synaptic capture induced by CaMKII inhibition, suggesting a link between CaMKII activation and modulation of actin dynamics during synaptic capture. These results show that an activity-dependent regulation of actin dynamics plays a critical role in LTP maintenance and synaptic capture.

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