Young Investigators

Natalia Andersen1,3, Tania Veuthey1,3, Gabriela Blanco1,3, Gustavo Silbestri2,4, Diego Rayes1,3 and María José De Rosa1,3

1 INIBIBB. CCT-CONICET.
2 INQUISUR. CCT-CONICET.
3 Departamento de Biología, Bioquímica y Farmacia, UNS. 4Departamento de Química, UNS

By using C. elegans, our work aimed to explore novel biological roles for imidazole-containing compounds. To this end, we have tested the in vivo anti-proteotoxic effects of imidazolium salts. Since neurodegenerative diseases have been largely linked to impaired antioxidant defense mechanisms, we focused on 1-Mesityl-3-(3-sulfonatopropyl) imidazolium (MSI), one of the imidazolium salts that we identified as capable of improving iron-induced oxidative stress resistance in wild-type animals. By combining mutant and gene expression analysis we have determined that this protective effect depends on the activation of the Heat Shock Transcription Factor (HSF-1), whereas it is independent of other canonical cytoprotective molecules such as abnormal Dauer Formation-16 (DAF-16/FOXO) and Skinhead-1 (SKN-1/Nrf2). To delve deeper into the biological roles of MSI, we analyzed the impact of this compound on previously established C. elegans models of protein aggregation. We found that MSI ameliorates β-amyloid-induced paralysis in worms expressing the pathological protein involved in Alzheimer’s Disease. Moreover, this compound also delays age-related locomotion decline in other proteotoxic C. elegans models, suggesting a broad protective effect.
Taken together, our results point to MSI as a promising anti-proteotoxic compound and provide proof of concept of the potential of imidazole derivatives in the development of novel therapies to retard age-related proteotoxic diseases.

N. W. Martínez (nmartinez@cienciavida.org)1,2,3,4, F.E. Gómez1, S. Matus1,2,3,4 and I. Alfaro1, 5.

1 Fundación Ciencia & Vida, Santiago, Chile.
2 Facultad de Medicina y Ciencia, Universidad San Sebastián.
3 Biomedical Neuroscience Institute, University of Chile.
4 Center for Geroscience, Brain Health and Metabolism.
5 Institute of Sciences and Innovation in Medicine, Faculty of Medicine, Clínica Alemana Universidad del Desarrollo (UDD).

Introduction: Cognitive dysfunction during Alzheimer ́s disease (AD) is correlated with synaptic loss. Interestingly, local amyloid-beta (Aβ) peptide accumulation is related to nearby spine density reduction. This antecedent suggests that Aβ local response mediates synapse degeneration, but the molecular mechanism remains unknown. Recently, the stress sensor/kinase PKR has been involved in the Aβ induced LTP and memory impairment.
However, PKR location and its role in Aβ synaptic changes remains unexplored. PKR operates through the eukaryotic translation initiation factor 2 alpha subunit (eIF2α) phosphorylation and regulates homeostasis. Here we studied PKR and eIF2α localization and explored PKR potential as a regulator of Aβ induced synaptotoxicity.
Methods: The localization and activation (phosphorylation) of PKR and eIF2α in response to Aβ at synapses was studied on hippocampal neurons by immunofluorescence (IF). Using genetic and pharmacological targeting tools, we tested the effect of PKR inhibition in preventing Aβ synaptotoxicity. Using western blot assays we analyzed eIF2α and PKR on synaptic fractions obtained from an AD mouse model (5xFAD).
Results: eIF2α and PKR were found partially colocalizing with synaptic markers. Moreover, Aβ oligomers induced eIF2α and PKR activation at synaptic compartments and decreased synapse density. Synaptotoxicity in response to Aβ was inhibited under PKR loss of function conditions. Finally, PKR was enriched and activated on 5xFAD synaptic fractions.
Discussion: Here, we show eIF2α and PKR at synapses. Our results place PKR as a novel mediator of Aβ induced synaptic stress and degeneration.
Acknowledgements: AFB-170004 (to FCV), FONDAP 15150012, P09-015-F, ANID
Postdoctoral 3200932 (NM).

M. Belén Pardi1, 2, Johanna Vogenstahl2, Tamas Dalmay2, Teresa Spanò2, De-Lin Pu1, 2, Laura B. Naumann3, 4, Friedrich Kretschmer2
, Henning Sprekeler3, 4 , Johannes J. Letzkus1, 2.

1Institute for Physiology, Faculty of Medicine, University of Freiburg, 79108 Freiburg, Germany.
2Max Planck Institute for Brain Research, 60438 Frankfurt, Germany.
3Bernstein Center for Computational Neuroscience Berlin, 10115 Berlin, Germany.
4Technische Universität Berlin, 10587 Berlin, Germany.

The sensory neocortex is a critical substrate for memory that strongly interconnects with the thalamus. However, the role of direct thalamocortical communication in memory remains elusive. In this talk, I will show you that the higher-order sensory thalamus is a highly plastic source of cortical top-down information. To find this, we performed chronic in vivo two-photon calcium imaging of thalamic synapses in mouse auditory cortex layer 1, a major locus of cortical associations. Combined with optogenetics, viral tracing, whole-cell recording, and computational modeling, we found that the higher- order thalamus is required for associative learning and transmits memory-related information that closely correlates with acquired behavioral relevance. In turn, these signals are tightly and dynamically controlled by local presynaptic inhibition. Our results thus reveal a level of computational flexibility in layer 1 that goes far beyond hard-wired connectivity.

Antonella Soledad Rios1, Ana Paula De Vincenti2, Pablo Brumovsky3, Jorge Aquino3, Gustavo Paratcha2, Fernanda Ledda1.

1 Fundación Instituto Leloir, Instituto de Investigaciones Bioquímicas de Buenos Aires, CONICET, Buenos Aires, Argentina.
2 División de Neurociencia Molecular y Celular, Instituto de Biología Celular y Neurociencias, Universidad de Buenos Aires, CONICET, Buenos Aires, Argentina.,
3 Developmental Biology & Regenerative Medicine Laboratory, Instituto de Investigaciones en Medicina Traslacional (IIMT), CONICET-Universidad Austral, Derqui-Pilar, Buenos Aires, Argentina

The perception of noxious environmental stimuli by nociceptive sensory neurons is an essential mechanism for the prevention of tissue damage (1,2). Etv4 is a transcriptional factor expressed in most nociceptors in dorsal root ganglia (DRG) during the embryonic development (3). However, its physiological role remains unclear. Here, we show that Etv4 ablation results in
defects in the development of the peripheral peptidergic projections in vivo and deficits in axonal elongation and growth cone morphology in cultured sensory neurons in response to NGF. From a mechanistic point of view, our findings reveal that NGF regulates Etv4-dependent gene expression of molecules involved in extracellular matrix (ECM) remodeling. Etv4-null mice were less sensitive to noxious heat stimuli and chemical pain and this behavioral phenotype correlates with a significant reduction in the expression of the pain-transducing ion channel TRPV1 in mutant mice. Together, our data demonstrate that Etv4 is required for the correct innervation and function of peptidergic sensory neurons, regulating a transcriptional program that involves
molecules associated to axonal growth and pain transduction.

(1) Einarsdottir, E. et al (2004).. Hum Mol Genet 13, 799-805.
(2) Indo, Y. (2010). Expert Rev Neurother 10, 1707-1724.
(3) Fontanet, P. et al (2013). J Neurosci 33, 15940-15951.

Mariela F. Trinchero

Laboratorio de Plasticidad Neuronal, Fundación Instituto Leloir – Buenos Aires – (CONICET)

Aging induces changes that result in a decrease in circuit plasticity and ultimately impaired cognitive capacity. Adult hippocampal neurogenesis is also affected with age. Neurons born in 8‐month‐old (8M) mice are scarce and exhibit slow development. However, when animals are exposed to a running wheel or enriched environment, neuronal development and integration
are largely accelerated. These results indicate that stimuli which enhance hippocampal activity trigger high levels of plasticity in the aging hippocampus. Sensory stimulation at gamma frequency has recently been shown to activate the hippocampus, reduce levels of amyloid beta peptide and improve memory performance in aging animals and mouse models of Alzheimer’s disease. We studied the impact of audiovisual stimulation (sound and light flickering) at 40 Hz on the development of neurons born in the dentate gyrus of 8M mice. Gamma flickering boosted circuit remodeling by adult neurogenesis, as shown by a significant increase in the dendritic tree length and complexity of newly generated neurons. These results reveal that audiovisual stimuli awaken mechanisms that promote neuronal plasticity not only under pathological conditions, but also in the healthy aging brain.

Andres P Varani1, Romain W Sala1 , Caroline Mailhes-Hamon1 , Jimena L Frontera1 , Daniela Popa1 , Clément Léna1

(1) Institut de biologie de l’Ecole normale supérieure (IBENS), Ecole normale supérieure, CNRS, INSERM, PSL Research University, 75005 Paris, France.

The contribution of the cerebellum to motor learning is often considered to be limited to adaptation, a short-timescale tuning of reflexes and learned skills. Yet, the cerebellum is reciprocally connected to two main players of motor learning, the motor cortex and the basal ganglia, via the ventral and midline thalamus respectively. Here, we evaluated the contribution of cerebellar neurons projecting to these thalamic nuclei in a skilled locomotion task in mice. In the cerebellar nuclei, we found task- specific neuronal activities during the task, and lasting changes following execution suggesting an offline processing of task-related information. Using pathway-specific inhibition, we found that
Dentate Nucleus neurons projecting to the midline thalamus contribute to learning and retrieval, while Interposed Nucleus neurons projecting to the ventral thalamus contribute to the offline consolidation of savings. Our results thus show that two parallel cerebello-thalamic pathways support distinct computations operating on different timescales in motor learning.

Leonardo Versaci
Universidad Nacional de Quilmes

Temporal cognition is involved in the representation of the temporal structure of events in our environment (ordering events in time, perceiving durations, producing rhythms, thinking about the past or the future, etc). In the hundred millisecond range, temporal cognition is linked to motor control, speech and music performance. A paradigmatic phenomenon in this timing range is sensorimotor synchronization, that is the synchronization of movements with an external periodic stimulus as in paced finger tapping. The effect of
attention when oriented to temporal aspects of a task is well established for reaction time tasks, yet it is reasonable to hypothesize that time-oriented attention could also have an influence on sensorimotor synchronization. In this work we show that attention can be oriented to the purely temporal aspects of a paced finger-tapping task and that it affects performance. Specifically, time-oriented attention improves the accuracy in paced finger tapping and it also increases the resynchronization efficiency after a period perturbation. We
use two markers of the attention level: auditory ERPs and subjective report of the mental workload. In addition, we propose a novel algorithm to separate the auditory, stimulus-related components from the somatosensory, response-related ones, which are naturally overlapped in the recorded EEG.