Biology subjects

Vanwalleghem, G. C.

Publications and source records attributed to Vanwalleghem, G. C..

4 recordsLinked to original sources

bioRxiv2020

Calcium imaging and the curse of negativity

The imaging of neuronal activity using calcium indicators has become a staple of modern neuroscience. However, without ground truths, there is a real risk of missing a significant portion of the real responses. Here, we show that a common assumption, the non-negativity of the neuronal responses as detected by calcium indicators, biases all levels of the frequently used analytical methods for these data. From the extraction of meaningful fluorescence changes to spike inference and the analysis of inferred spikes, each step risks missing real responses because of the assumption of non-negativity. We first show that negative deviations from baseline can exist in calcium imaging of neuronal activity. Then, we use simulated data to test three popular algorithms for image analysis, finding that suite2p may be the best suited to large datasets. Spike inference algorithms also showed their limitations in dealing with inhibited neurons, and new approaches may be needed to address this problem. We further suggest avoiding data analysis approaches that may ignore inhibited responses in favor of a first exploratory step to ensure that none are present. Taking these steps will ensure that inhibition, as well as excitation, is detected in calcium imaging datasets.

neuroscience↗

bioRxiv2020

Functional melanoma cell heterogeneity is regulated by MITF-dependent cell-matrix interactions

Phenotypic heterogeneity of cancer cells plays a critical role in shaping treatment response. This type of heterogeneity is organized spatially with specific phenotypes, such as sharply demarcated clusters of proliferating and cell cycle-arrested cells, predominating within discrete domains within a tumor. What determines the occurrence of specific tumor cell phenotypes in distinct microdomains of solid cancers is poorly understood. Here, we show that in melanoma spatial organization of phenotypic heterogeneity is dictated by the expression and activity of MITF. We reveal that this lineage survival oncogene controls ECM composition and organization, and ROCK-driven mechanotransduction through focal adhesion maturation and actin cytoskeleton functionality. In turn, altered tumor microarchitecture and structural integrity impact tumor solid stress which then mediates phenotypic heterogeneity through p27Kip1. Rho-ROCK-myosin signaling is necessary to transmit the effect of the reciprocal cell-ECM regulation into phenotypic heterogeneity. Our findings place cell-ECM crosstalk as a central driver of phenotypic tumor heterogeneity. SignificancePhenotypic heterogeneity is a major culprit of cancer therapy failure. We demonstrate that phenotypic heterogeneity is controlled through tumor cell-ECM crosstalk resulting in altered tumor microarchitecture, mechanotransduction and Rho-ROCK-myosin signaling. Melanoma shares these physical properties with any solid cancer underscoring the importance of our findings for therapeutically targeting this phenomenon.

cancer biology↗

bioRxiv2020

Brain-wide mapping of water flow perception in zebrafish

Information about water flow, detected by lateral line organs, is critical to the behavior and survival of fish and amphibians. While certain specific aspects of water flow processing have been revealed through electrophysiology, we lack a comprehensive description of the neurons that respond to water flow and the network that they form. Here, we use brain-wide calcium imaging in combination with microfluidic stimulation to map out, at cellular resolution, all neurons involved in perceiving and processing water flow information in larval zebrafish. We find a diverse array of neurons responding to forward flow, reverse flow, or both. Early in this pathway, in the lateral line ganglia, these are almost exclusively neurons responding to the simple presence of forward or reverse flow, but later processing includes neurons responding specifically to flow onset, representing the accumulated volume of flow during a stimulus, or encoding the speed of the flow. The neurons reporting on these more nuanced details are located across numerous brain regions, including some not previously implicated in water flow processing. A graph theory-based analysis of the brain-wide water flow network shows that a majority of this processing is dedicated to forward flow detection, and this is reinforced by our finding that details like flow velocity and the total volume of accumulated flow are only encoded for the simulated forward direction. The results represent the first brain-wide description of processing for this important modality, and provide a departure point for more detailed studies of the flow of information through this network. Significance statementIn aquatic animals, the lateral line is important for detecting water flow stimuli, but the brain networks that interpret this information remain mysterious. Here, we have imaged the activity of individual neurons across the entire brains of larval zebrafish, revealing all response types and their brain locations as water flow processing occurs. We find some neurons that respond to the simple presence of water flow, and others that are attuned to the flows direction, speed, duration, or the accumulated volume of water that has passed during the stimulus. With this information, we modeled the underlying network, describing a system that is nuanced in its processing of water flow simulating forward motion but rudimentary in processing flow in the reverse direction.

neuroscience↗

bioRxiv2019

Early migration of precursor neurons initiates cellular and functional regeneration after spinal cord injury in zebrafish.

Zebrafish have a remarkable capacity to regenerate following spinal cord (SC) injury but the responsible cellular events are not well understood. We used in vivo imaging and genetics to pin-point specific cellular processes controlling SC regeneration in zebrafish. We identified two temporally and mechanistically distinct phases of cellular regeneration in the SC. The initial phase relies on migration of precursor neurons to the injury, enabling rapid functional recovery, and activation of quiescent neural progenitor cells (NPCs). A second phase of regenerative neurogenesis compensates for both the lost tissue and cells depleted due to precursor neuron migration. We propose a critical role of precursor neurons recruitment in initiating neuronal circuit recovery and buying sufficient time for regenerative neurogenesis to take place. Taken together, our data suggests an unanticipated role of precursor cell recruitment in driving neural repair and functional recovery during the regenerative response. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=110 SRC="FIGDIR/small/539940v1_ufig1.gif" ALT="Figure 1"> View larger version (45K): org.highwire.dtl.DTLVardef@12c5be9org.highwire.dtl.DTLVardef@1461e99org.highwire.dtl.DTLVardef@82d28aorg.highwire.dtl.DTLVardef@cc6870_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗