Biology subjects

Israely, I.

Publications and source records attributed to Israely, I..

5 recordsLinked to original sources

bioRxiv2026

Dysfunctional synaptic competition at dendritic spines in Fragile X syndrome

Dendritic spines are highly dynamic structures whose morphology and lifespan are modified in response to synaptic efficacy changes. Structural modifications following activity support the long-term encoding of information and could allow for the remodeling of neural circuits. Long-term depression (LTD) is a key mechanism for synaptic weight regulation, yet its structural correlates -- particularly for long-lasting, protein synthesis dependent forms -- remain poorly understood. Furthermore, in humans, this type of plasticity is often disrupted in neurodevelopmental disorders, correlating with cognitive dysfunction and structural abnormalities. Fragile X Syndrome (FXS) is the most common inherited form of intellectual disability and is characterized by excessive metabotropic receptor-mediated synaptic depression, excessive protein synthesis, and spine abnormalities. Here, we investigate the relationship between long lasting synaptic depression and structural plasticity, as well as the role of protein availability in determining how many spines can simultaneously undergo structural changes during LTD in both healthy and FXS mutant neurons. Using high resolution optical methods, we developed and tested a method for inducing metabotropic glutamate receptor (mGluR)-dependent depression at single spines via glutamate uncaging in mouse hippocampal neurons. We found that this form of activity leads to robust spine shrinkage, which requires new protein synthesis. However, when we induced this depression at multiple spines, they competed for structural changes and only one spine shrank. We hypothesized that this was due to limited resources, in the form of newly made proteins, and therefore, we decided to test if spine competition would be altered in the mouse model of FXS, where protein levels are abnormally elevated. Indeed, we found that competition was absent in FXS mutant neurons, and all of the stimulated spines underwent shrinkage following LTD induction. Importantly, we found that single spine structural plasticity in FXS was expressed to the same degree as in WT controls. Taken together, these findings suggest that the hallmark phenotype of excess mGluR LTD in FXS may result from a greater number of inputs undergoing synaptic depression, rather than excessive LTD at individual synapses. By probing plasticity at the level of individual inputs, our findings highlight the importance of evaluating activity across groups of synapses, in order to uncover plasticity interactions that are critical for learning. Understanding how these mechanisms are disrupted in neurodevelopmental disorders such as FXS can inform the development of effective therapeutic strategies.

neuroscience↗

bioRxiv2021

Temporal Pattern of Synaptic Activation Determines the Longevity of Structural Plasticity at Single Dendritic Spines

Individual synapses are the points at which information is passed between neurons, yet it is unknown how the diverse patterns of activity that are observed in vivo effect plasticity at the level of single inputs. Here, we aimed to determine what are the structural plasticity consequences of naturalistic patterns of activity at single spines, as these reflect changes in synaptic efficacy. Utilizing two- photon fluorescence imaging and glutamate uncaging, we studied structural plasticity of individual CA1 hippocampal dendritic spines using activation patterns sampled from a Poisson distribution, which resemble endogenous firing patterns from their CA3 inputs. We found that while the majority of inputs initially undergo structural changes, the robustness of this plasticity is determined by the timing structure of the Poisson sampled naturalistic stimulation patterns. Further, we found that structural plasticity elicited by these naturalistic patterns is both NMDAR and protein synthesis dependent, consistent with requirements for other forms of plasticity. Lastly, we found that during the delivery of naturalistic activity patterns, spines underwent rapid and dynamic structural growth that predicted the longevity of plasticity, which was not the case during non-naturalistic stimulation protocols. These data suggest that dendritic spines are able to integrate incoming temporal information and accordingly modulate the longevity of plasticity that is induced. HighlightsO_LINaturalistic stimulation of single dendritic spines of CA1 hippocampal neurons induces long lasting structural plasticity that depends on the temporal distribution of the synaptic events. C_LIO_LIStructural plasticity induced by naturalistic stimulation patterns requires NMDA receptor activation and new protein-synthesis. C_LIO_LIRapid spine structural dynamics during naturalistic activity, but not regular patterns, predict the longevity of subsequent structural plasticity. C_LI

neuroscience↗

bioRxiv2020

Pyramidal tract neurons drive feed-forward excitation of striatum through cholinergic interneurons

Corticostriatal connectivity is central for many cognitive and motor processes, such as reinforcement or action initiation and invigoration. The cortical input to the striatum arises from two main cortical populations: intratelencephalic (IT) and pyramidal tract (PT) neurons. We uncovered a new feedforward excitatory circuit, supported by a polysynaptic motif from PT neurons to cholinergic interneurons (ChIs) to excitatory inputs, which runs in parallel to the canonical monosynaptic corticostriatal connection. This new motif conveys a delayed second phase of excitation to striatal spiny projection neurons (SPNs), through an acetylcholine-dependent glutamate release mechanism, resulting in biphasic corticostriatal signals. These biphasic signals are a hallmark of PT, but not IT, corticostriatal inputs, due to a stronger relative input from PT neurons to ChIs. These results uncover a novel feed-forward circuit mechanism by which PT activity differentially gates excitatory inputs to the striatum, with potential implications for behavior, plasticity and learning. HighlightsO_LIPT, but not IT, corticostriatal inputs convey biphasic excitation to SPNs via a disynaptic circuit involving striatal ChIs. C_LIO_LIPT neurons recruit ChIs more efficiently than IT neurons due to a stronger relative input to ChIs. C_LIO_LIThe second phase of SPN excitation is mediated by nicotinic receptors at long-range glutamatergic axons in the striatum. C_LIO_LISuprathreshold depolarizations of SPNs by PT inputs depend on ChI[->]SPN excitation and result in delayed spiking. C_LI

neuroscience↗

bioRxiv2020

SpineS: An interactive time-series analysis software for dendritic spines

Live fluorescence imaging has shown the dynamic nature of dendritic spines, with changes in shape occurring both during development and in response to activity. The structure of a dendritic spine positively correlates with its functional efficacy. Learning and memory studies have shown that great deal of the information stored by a neuron is contained in the synapses. High precision tracking of synaptic structures can give hints about the dynamic nature of memory and help us to understand how memories evolve both in biological and artificial neural networks. Experiments that aim to investigate the dynamics behind the structural changes of dendritic spines require the collection and analysis of large time-series datasets. In this paper, we present an open-source software called SpineS for the automatic longitudinal structural analysis of dendritic spines with additional features for manual intervention to ensure optimal analysis. Our extensive experimental analyses on multiple datasets demonstrate that SpineS can achieve a high-level performance on samples collected both by two-photon and confocal imaging systems.

neuroscience↗

bioRxiv2018

Homeostatic plasticity scales dendritic spine volumes and changes the threshold and specificity of Hebbian plasticity

Information is encoded within neural networks through synaptic weight changes. Synaptic learning rules involve a combination of rapid Hebbian plasticity with slower homeostatic synaptic plasticity (HSP) that regulates neuronal activity through global synaptic scaling. While Hebbian plasticity has been extensively investigated, much less is known about HSP. Here we investigate the structural and functional consequences of HSP at dendritic spines of mouse hippocampal neurons. We find that prolonged activity blockade induces spine growth, paralleling synaptic strength increases. Following activity blockade, glutamate uncaging-mediated long-term potentiation at single spines leads to size-dependent structural plasticity: smaller spines undergo robust growth, while larger spines remain unchanged. Moreover, we find that neighboring spines in the vicinity of the stimulated spine exhibit volume changes following HSP, indicating that plasticity has spread across a group of synapses. Overall, these findings demonstrate that Hebbian and homeostatic plasticity shape neural connectivity through coordinated structural plasticity of clustered inputs.

neuroscience↗