Biology subjects

Portugues, R.

Publications and source records attributed to Portugues, R..

22 records · Page 2Linked to original sources

bioRxiv2019

Localized calcium accumulations prime synapses for phagocyte removal in cortical neuroinflammation

Cortical pathology contributes to chronic cognitive impairment of patients suffering from the neuroinflammatory disease multiple sclerosis (MS). How such gray matter inflammation affects neuronal structure and function is not well understood. Here we use functional and structural in vivo imaging in a mouse model of cortical MS to demonstrate that bouts of cortical inflammation disrupt cortical circuit activity coincident with a widespread but transient loss of dendritic spines. Spines destined for removal show a local calcium accumulation and are subsequently removed by invading macrophages and activated microglia. Targeting phagocyte activation with a new antagonist of the colony-stimulating factor 1 receptor prevents cortical synapse loss. Overall, our study identifies synapse loss as a key pathological feature of inflammatory gray matter lesions that is amenable to immunomodulatory therapy.\n\nHIGHLIGHTSO_LIWidespread, but transient loss of synapses in inflammatory lesions and beyond\nC_LIO_LIReversible impairment of neuronal firing and circuit function in the inflamed cortex\nC_LIO_LICalcium dyshomeostasis of single spines precedes swift synapse loss\nC_LIO_LIPhagocyte-mediated spine pruning as targetable mechanism of synapse loss\nC_LI

neuroscience↗

bioRxiv2018

Stytra: an open-source, integrated system for stimulation, tracking and closed-loop behavioral experiments

We present Stytra, a flexible, open-source software package, written in Python, that we designed to cover all the general requirements involved in larval zebrafish behavioral experiments. It allows timed stimulus presentation, interfacing with external devices and simultaneous real-time tracking of position, tail and eye motion in both freely-swimming and head-restrained preparations. It logs in standardized formats all recorded quantities, metadata, and code version to allow full provenance tracking, from data acquisition through analysis to publication. The package is modular and expandable for different experimental protocols and setups. Current releases can be found at https://github.com/portugueslab/stytra. We also provide complete documentation with examples for extending the package to new stimuli and hardware, as well as a schema and parts list for behavioral setups. We showcase Stytra by reproducing two previously behavioral protocols, one with head-restrained and the other with freely-swimming larvae, as well as an experiment in which the software is used in the context of a calcium imaging experiment, where it can trigger and communicate with other acquisition devices. Our aims are to help laboratories with little or no experience in the field to start implementing behavioral experiments and to provide a platform for sharing stimulus protocols to enable easy reproduction of experiments and straightforward validation. In addition, Stytra can easily serve as a base platform to design behavioral experiments in other model organisms.

neuroscience↗

bioRxiv2018

Motor context dominates output from Purkinje cell functional regions during reflexive visuomotor behaviors

The cerebellum integrates sensory stimuli and motor actions to enable smooth coordination and motor learning. Here we harness the innate behavioral repertoire of the larval zebrafish to characterize the spatiotemporal dynamics of feature coding across the entire Purkinje cell population during visual stimuli and the reflexive behaviors that they elicit. Population imaging reveals three spatially-clustered regions of Purkinje cell activity along the rostrocaudal axis. Complementary single-cell electrophysiological recordings assign these Purkinje cells to one of three functional phenotypes that encode a specific visual, and not motor, signal via complex spikes. In contrast, simple spike output of most Purkinje cells is strongly driven by motor-related tail and eye signals. Interactions between complex and simple spikes show heterogeneous modulation patterns across different Purkinje cells, which become temporally restricted during swimming episodes. Our findings reveal how sensorimotor information is encoded by individual Purkinje cells and organized into behavioral modules across the entire cerebellum.

neuroscience↗

bioRxiv2017

Whole-Brain Serial-Section Electron Microscopy In Larval Zebrafish

Investigating the dense meshwork of wires and synapses that form neuronal circuits is possible with the high resolution of serial-section electron microscopy (ssEM)1. However, the imaging scale required to comprehensively reconstruct axons and dendrites is more than 10 orders of magnitude smaller than the spatial extents occupied by networks of interconnected neurons2--some of which span nearly the entire brain. The difficulties in generating and handling data for relatively large volumes at nanoscale resolution has thus restricted all studies in vertebrates to neuron fragments, thereby hindering investigations of complete circuits. These efforts were transformed by recent advances in computing, sample handling, and imaging techniques1, but examining entire brains at high resolution remains a challenge. Here we present ssEM data for a complete 5.5 days post-fertilisation larval zebrafish brain. Our approach utilizes multiple rounds of targeted imaging at different scales to reduce acquisition time and data management. The resulting dataset can be analysed to reconstruct neuronal processes, allowing us to, for example, survey all the myelinated axons (the projectome). Further, our reconstructions enabled us to investigate the precise projections of neurons and their contralateral counterparts. In particular, we observed that myelinated axons of reticulospinal and lateral line afferent neurons exhibit remarkable bilateral symmetry. Additionally, we found that fasciculated reticulospinal axons maintain the same neighbour relations throughout the extent of their projections. Furthermore, we use the dataset to set the stage for whole-brain comparisons of structure and function by co-registering functional reference atlases and in vivo two-photon fluorescence microscopy data from the same specimen. We provide the complete dataset and reconstructions as an open-access resource for neurobiologists and others interested in the ultrastructure of the larval zebrafish.

neuroscience↗