Biology subjects

Klann, E.

Publications and source records attributed to Klann, E..

24 records · Page 2Linked to original sources

bioRxiv2020

Genetic removal of p70 S6K1 corrects coding sequence length-dependent alterations in mRNA translation in fragile X syndrome mice

Loss of the fragile X mental retardation protein (FMRP) causes fragile X syndrome (FXS). FMRP is widely thought to repress protein synthesis, but its translational targets and modes of control remain in dispute. We previously showed that genetic removal of p70 S6 kinase 1 (S6K1) corrects altered protein synthesis as well as synaptic and behavioral phenotypes in FXS mice. In this study, we examined the gene-specificity of altered mRNA translation in FXS and the mechanism of rescue with genetic reduction of S6K1 by carrying out ribosome profiling and RNA-Seq on cortical lysates from wild-type, FXS, S6K1 knockout, and double knockout mice. We observed reduced ribosome footprint abundance in the majority of differentially translated genes in the cortices of FXS mice. We used molecular assays to discover evidence that the reduction in ribosome footprint abundance reflects an increased rate of ribosome translocation, which is captured as a decrease in the number of translating ribosomes at steady state, and is normalized by inhibition of S6K1. We also found that genetic removal of S6K1 prevented a positive-to-negative gradation of alterations in translation efficiencies (RF/mRNA) with coding sequence length across mRNAs in FXS mouse cortices. Our findings reveal the identities of dysregulated mRNAs and a molecular mechanism by which reduction of S6K1 prevents altered translation in FXS.

neuroscience↗

bioRxiv2020

De novo protein synthesis in distinct centrolateral amygdala interneurons is required for associative emotional memories

To survive in a dynamic environment, animals need to identify and appropriately respond to stimuli that signal danger1,2. At the same time, animal survival also depends on suppressing the threat response during a stimulus that predicts absence of threat, i.e. safety3-5. Understanding the biological substrates of differential threat memories in which animals learn to flexibly switch between expressing and suppressing defensive responses to a threat-predictive cue and a safety cue, respectively, is critical for developing treatments for memory disorders such as PTSD6. A key brain area for processing and storing threat memories is the centrolateral amygdala (CeL), which receives convergent sensory inputs from the parabrachial nucleus and the basolateral amygdala and connects directly to the output nucleus of amygdala, the centromedial nucleus, to mediate defensive responses7-9. Despite a plethora of studies on the importance of neuronal activity in specific CeL neuronal populations during memory acquisition and retrieval10-12, little is known about regulation of their protein synthesis machinery. Consolidation of long-term, but not short-term, threat memories requires de novo protein synthesis, which suggests that the translation machinery in CeL interneurons is tightly regulated in order to stabilize associative memories. Herein, we have applied intersectional chemogenetic strategies in CeL interneurons to block cell type-specific translation initiation programs that are sensitive to depletion of eukaryotic initiation factor 4E (eIF4E) and phosphorylation of eukaryotic initiation factor 2 (p-eIF2), respectively. We show that in a differential threat conditioning paradigm, de novo translation in somatostatin-expressing (SOM) interneurons in the CeL is necessary for long-term storage of conditioned threat response whereas de novo translation in protein kinase C{delta}-expressing (PKC{delta}) interneurons in the CeL is essential for storing conditioned response inhibition to a safety cue. Further, we show that oxytocinergic neuromodulation of PKC{delta} interneurons during differential threat learning is important for long-lasting cued threat discrimination. Our results indicate that the molecular elements of a differential threat memory trace are compartmentalized in distinct CeL interneuron populations and provide new mechanistic insight into the role of de novo protein synthesis in consolidation of long-term memories.

neuroscience↗

bioRxiv2020

Genetic reduction of PERK-eIF2α signaling in dopaminergic neurons drives cognitive and age-dependent motor dysfunction

An array of phenotypes in animal models of neurodegenerative disease have been shown to be reversed by neuronal inhibition of PERK, an eIF2 kinase that modulates the unfolded protein response (UPR). This suggests that targeting PERK therapeutically could be beneficial for treatment of human disease. Herein, using multiple genetic approaches we show that selective deletion of the PERK in mouse midbrain dopaminergic (DA) neurons results in multiple cognitive and age-dependent motor phenotypes. Conditional expression of phospho-mutant eIF2 in DA neurons recapitulated the phenotypes caused by deletion of PERK, consistent with a causal role of decreased eIF2 phosphorylation. In addition, deletion of PERK in DA neurons resulted in altered de novo translation, as well as age-dependent changes in axonal DA release and uptake in the striatum that mirror the pattern of motor changes observed. Taken together, our findings show that proper regulation of PERK-eIF2 signaling in DA neurons is required for normal cognitive and motor function across lifespan, and also highlight the need for caution in the proposed use of sustained PERK inhibition in neurons as a therapeutic strategy in the treatment of neurodegenerative disorders.

neuroscience↗

bioRxiv2019

Chemogenetic evidence that rapid neuronal de novo protein synthesis is required for consolidation of long-term memory

Translational control of memory processes is a tightly regulated process where the coordinated interaction and modulation of translation factors provides a permissive environment for protein synthesis during memory formation. Existing methods used to block translation lack the spatiotemporal precision to investigate cell-specific contributions to consolidation of long-term memories. Here, we have developed a novel chemogenetic mouse resource for cell type-specific and drug-inducible protein synthesis inhibition (ciPSI) that utilizes an engineered version of the catalytic kinase domain of dsRNA-activated protein (PKR). ciPSI allows rapid and reversible phosphorylation of eIF2 causing a block on general translation by 50% in vivo. Using this resource, we discovered that temporally structured pan-neuronal protein synthesis is required for consolidation of long-term auditory threat memory. Targeted protein synthesis inhibition in CamK2 expressing glutamatergic neurons in lateral amygdala (LA) impaired long-term memory, which was recovered with artificial chemogenetic reactivation at the cost of stimulus generalization. Conversely, genetically reducing phosphorylation of eIF2 in CamK2 positive neurons in LA enhanced memory strength, but was accompanied with reduced memory fidelity and behavior inflexibility. Our findings provide evidence for a finely tuned translation program during consolidation of long-term threat memories.

neuroscience↗

bioRxiv2018

The translatome of adult cortical axons is regulated by learning in vivo

Local translation can support memory consolidation by supplying new proteins to synapses undergoing plasticity. Translation in adult forebrain dendrites is an established mechanism of synaptic plasticity and is regulated by learning, yet there is no evidence for learning-regulated protein synthesis in adult forebrain axons, which have traditionally been believed to be incapable of translation. Here we show that axons in the adult rat amygdala contain translation machinery, and use translating ribosome affinity purification (TRAP) with RNASeq to identify mRNAs in cortical axons projecting to the amygdala, over 1200 of which were regulated during consolidation of associative memory. Mitochondrial and translation-related genes were upregulated, whereas synaptic, cytoskeletal, and myelin-related genes were downregulated; the opposite effects were observed in the cortex. Our results demonstrate that learning-regulated axonal translation occurs in the adult forebrain, and support the likelihood that local translation is more a rule than an exception in neuronal processes.

neuroscience↗

bioRxiv2018

Compartmentalized nonsense-mediated mRNA decay regulates synaptic plasticity and cognitive function via GluR1 signaling

Synaptic plasticity relies on new protein synthesis in dendrites that involves the selective translation of specific mRNAs. This requires a tight control of mRNA levels in dendrites. Consistently, RNA translation and degradation pathways have been recently linked to neurodevelopmental and neuropsychiatric diseases, suggesting a role for RNA regulation in synaptic plasticity and cognition. Despite being the only RNA regulatory pathway that is associated with multiple mental illnesses, the Nonsense-Mediated mRNA Decay (NMD) pathway presents an unexplored regulatory mechanism for synaptic function and plasticity. NMD is a highly conserved and selective RNA degradation pathway that exerts its function in a cell- and spatiotemporally-specific manner. Here, we show that neuron-specific disruption of NMD in adulthood attenuates learning, memory, hippocampal LTP, and potentiates perseverative/repetitive behavior. While it is known that local translation of specific mRNAs in dendrites enables synaptic plasticity, the tightly-controlled mechanisms that regulate local quantity of specific mRNAs remains poorly understood. We report that the NMD pathway operates within dendrites to regulate GluR1 surface levels. Specifically, NMD modulates the internalization of GluR1 and promotes its local synthesis in dendrites. We identified AMPK as a mechanistic substrate for NMD that contributes to the NMD-mediated regulation of GluR1 by limiting total GluR1 levels. These data establish that NMD regulates synaptic plasticity, cognition, and local protein synthesis in dendrites, providing fundamental insight into the neuron-specific function of NMD within the brain.

neuroscience↗