Biology subjects

Segebarth, D.

Publications and source records attributed to Segebarth, D..

4 recordsLinked to original sources

bioRxiv2022

Integrated cardio-behavioural defensive states

Fear and anxiety are brain states that evolved to mediate defensive responses to threat. While it is clear that the defense reaction includes multiple interacting behavioural, autonomic and endocrine adjustments, their integrative nature is poorly understood. In particular, threat has been associated with various cardiac changes, yet a clear consensus on their relevance for the integrated defense reaction is missing. We here define rapid microstates associated with specific behaviours and heart rate dynamics, both affected by long-lasting macrostates and reflecting context-dependent threat levels. In addition, we demonstrate that one of the most commonly used defensive behavioural responses, freezing measured by immobility, is part of an integrated cardio-behavioural microstate mediated by specific midbrain circuit elements. Our work puts forth a framework for systematic integration of cardiac and behavioural readouts that presents the basis for a better understanding of complex neural defensive states and their associated systemic functions.

neuroscience↗

bioRxiv2020

Constitutively active TrkB kinase signalling reduces actin filopodia dynamics and cell migration

Trk receptors and gene fusions of NTRK are targets in precision oncology. Classical Trk signalling concepts fail to explain ligand-independent signalling of intracellular TrkB or NTRK fusion proteins. Here, we show that abundance of the intracellular domain of TrkB is sufficient for ligand-independent autophosphorylation. This constitutive TrkB signalling reduced actin filopodia dynamics, could phosphorylate FAK, and changed cell morphology. Mutating Y705 in the kinase domain of TrkB alone specifically blocked these pathways. Engineered intracellular kinase domain proteins and a cancer-related intracellular NTRK2-fusion protein (SQSTM1-NTRK2) also underwent constitutive activation. In migrating glioblastoma-like U87MG cells, self-active TrkB kinase reduced cell migration. Moreover, we found evidences for constitutively active, intracellular TrkB in tissue of human grade IV glioblastoma. Structural modelling of the kinase domain let us postulate that release from cis-autoinhibition by abundance is sufficient for TrkB/FAK/Actin signalling via Y705. These constitutive signalling pathways could be fully blocked within minutes by clinically approved, anti-tumorigenic Trk inhibitors. In conclusion, our data provide an explanation and biological function for TrkB kinase domain signalling in the absence of a ligand.

neuroscience↗

bioRxiv2018

DeepFLaSh, a deep learning pipeline for segmentation of fluorescent labels in microscopy images

Fluorescent labeling of biomolecules is widely used for bioimage analyses throughout the life sciences. Recent advances in deep learning (DL) have opened new possibilities to scale the image analysis processes through automation. However, the annotation of fluorescent features with a low signal-to-noise ratio is frequently based on subjective criteria. Training on subjective annotations may ultimately lead to biased DL models yielding irreproducible results. An end-to-end analysis process that integrates data annotation, ground truth estimation, and model training can mitigate this risk. To highlight the importance of this integrated process, we compare different DL-based analysis approaches. Based on data from different laboratories, we show that ground truth estimation from multiple human annotators is indispensable to establish objectivity in fluorescent feature annotations. We demonstrate that ensembles of multiple models trained on the estimated ground truth establish reliability and validity. Our research provides guidelines for reproducible and transparent bioimage analyses using DL methods.

neuroscience↗

bioRxiv2018

Reward signaling in a recurrent circuit of dopaminergic neurons and Kenyon cells

1.Dopaminergic neurons in the brain of the Drosophila larva play a key role in mediating reward information to the mushroom bodies during appetitive olfactory learning and memory. Using optogenetic activation of Kenyon cells we provide evidence that a functional recurrent signaling loop exists between Kenyon cells and dopaminergic neurons of the primary protocerebral anterior (pPAM) cluster. An optogenetic activation of Kenyon cells paired with an odor is sufficient to induce appetitive memory, while a simultaneous impairment of the dopaminergic pPAM neurons abolishes memory expression. Thus, dopaminergic pPAM neurons mediate reward information to the Kenyon cells, but in turn receive feedback from Kenyon cells. We further show that the activation of recurrent signaling routes within mushroom body circuitry increases the persistence of an odor-sugar memory. Our results suggest that sustained activity in a neuronal circuitry is a conserved mechanism in insects and vertebrates to consolidate memories.

neuroscience↗