Biology subjects

Bergeron, S. A.

Publications and source records attributed to Bergeron, S. A..

3 recordsLinked to original sources

bioRxiv2021

Environmental and molecular modulation of motor individuality in larval zebrafish

Innate behavioral biases such as human handedness are a ubiquitous form of inter-individual variation that are not strictly hardwired into the genome and are influenced by diverse internal and external cues. Yet, genetic and environmental factors modulating behavioral variation remain poorly understood, especially in vertebrates. To identify genetic and environmental factors that influence behavioral variation, we take advantage of larval zebrafish light-search behavior. During light-search, individuals preferentially turn in leftward or rightward loops, in which directional bias is sustained and non-heritable, and maintained by a habenula-rostral PT circuit. Here we use a medium-throughput recording strategy and unbiased analysis to show that significant individual to individual variation exists in wildtype larval zebrafish turning preference. We classify stable left, right, and unbiased turning types, with most individuals exhibiting a directional preference. Raising larvae at elevated temperature selectively reduces the leftward turning type and impacts rostral PT neurons, specifically. Exposure to conspecifics, variable salinity, environmental enrichment, and physical disturbance does not significantly impact inter-individual turning bias. Pharmacological manipulation of Notch signaling and carrying a mutant allele of a known Notch pathway affecter gene, gsx2, disrupted turn bias individuality in a dose-dependent manner. These results establish that larval zebrafish is a powerful vertebrate model for inter-individual variation with sensitivity to specific environmental perturbations and gene dosage.

neuroscience↗

bioRxiv2021

Gsx2 but not Gsx1 is necessary for early forebrain patterning and long-term survival in zebrafish

Central nervous system (CNS) development is regulated by regionally expressed transcription factors that impart initial cell identity, connectivity, and function to neural circuits through complex molecular genetic cascades. genomic screen homeobox 1 and 2 (gsx1 and gsx2) encode homeobox transcription factors expressed in the developing CNS in multiple vertebrates examined to date. However, we have limited knowledge of the expression of these transcription factors and the gene networks that they regulate across developing brain regions in zebrafish. The objective of this study was to comprehensively examine gsx1 and gsx2 expression throughout neurodevelopment and characterize gsx1 and gsx2 mutants to study the essential roles of these closely related transcription factors. Using RT-PCR, whole-mount in situ hybridization (WISH), and fluorescence in situ hybridization, we examine gsx1 and gsx2 expression from early embryonic to late larval stages. gsx1 is expressed initially in the hindbrain and diencephalon and later in the optic tectum, pretectum, and cerebellar plate. Comparatively, gsx2 is expressed in the early telencephalon and later in the pallium and olfactory bulb. gsx1 and gsx2 are regionally co-expressed in the hypothalamus, preoptic area, and hindbrain, however rarely co-localize in the same cells. To identify forebrain target genes, we utilize mutants made with Transcription activator-like effector nucleases (TALEN). gsx1 mutant zebrafish exhibit stunted growth, however, they survive through adulthood and are fertile. gsx2 mutant zebrafish experience swim bladder inflation failure that prevents survival past larval stage. Using WISH and RT-qPCR we demonstrate altered expression of genes including, distal-less homeobox genes and forkhead box gene foxp2. This work provides novel tools with which other target genes and functions of Gsx1 and Gsx2 can be characterized across the CNS to better understand the unique and overlapping roles of these highly conserved transcription factors.

developmental biology↗

bioRxiv2019

Prepontine non-giant neurons drive flexible escape behavior in zebrafish

Many species execute ballistic escape reactions to avoid imminent danger. Despite fast reaction times, responses are often highly regulated, reflecting a trade-off between costly motor actions and perceived threat level. However, how sensory cues are integrated within premotor escape circuits remains poorly understood. Here we show that in zebrafish, less precipitous threats elicit a delayed escape, characterized by flexible trajectories, that are driven by a cluster of 38 prepontine neurons that are completely separate from the fast escape pathway. Whereas neurons that initiate rapid escapes receive direct auditory input and drive motor neurons, input and output pathways for delayed escapes are indirect, facilitating integration of cross-modal sensory information. Rapid decision making in the escape system is thus enabled by parallel pathways for ballistic responses and flexible delayed actions.

neuroscience↗