Biology subjects

Burgess, H. A.

Publications and source records attributed to Burgess, H. A..

9 recordsLinked to original sources

bioRxiv2025

Functional interrogation of neuronal connections by chemoptogenetic presynaptic ablation

Most neurons are embedded in multiple circuits, with signaling to distinct postsynaptic partners playing functionally different roles. The function of specific connections can be interrogated using synaptically localized optogenetic effectors, however these tools are often experimentally difficult to validate or produce paradoxical outcomes. We have developed a system for photoablation of synaptic connections originating from genetically defined neurons, based on presynaptic localization of the fluorogen activating protein dL5** that acts as a photosensitizer when bound to a cell-permeable dye. Using the well mapped zebrafish escape circuit as a readout, we first show that cytoplasmically expressed dL5** enables efficient spatially targeted neuronal ablation using near infra-red light. We then demonstrate that spatially patterned illumination of presynaptically localized dL5** can effectively disconnect neurons from selected downstream partners, producing precise behavioral deficits. This technique should be applicable to almost any genetically tractable neuronal circuit, enabling precise manipulation of functional connectivity within the nervous system.

neuroscience↗

bioRxiv2025

Elevated body temperature exacerbates arrhythmia and seizure-like activity in a zebrafish model of Timothy syndrome

Timothy syndrome (TS) is a multisystem disorder with autistic-like features, seizures and arrhythmia as the main symptoms. Most TS cases are caused by a de novo single amino acid substitution G406R in the CACNA1C gene that encodes the pore-forming subunit of the voltage-gated L-type calcium channel CaV1.2. We generated a zebrafish model of TS with a homologous amino acid substitution in the cacna1c-encoded protein. Unlike patients, heterozygous mutants showed only mild impairments with no changes in mortality. However, homozygous mutants showed increased mortality, arrhythmias, neural activity and sensitivity to pentylenetetrazole-induced seizure-like behavior. Mutants also exhibited microcephaly, cerebellar hypotrophy and abnormal development of GABAergic neuron populations, and transcriptomic analysis revealed dysregulated expression of neuropeptide genes (including bdnf and vgf). Consistent with the idea that CaV1.2 channels activate during fever, we found that heterozygous larvae manifested arrhythmia and seizure-like behavior when exposed to elevated environmental temperature, and homozygous larvae switched from bradycardia to tachycardia. These data provide a basis for using zebrafish to study the etiology of TS abnormalities and suggest t hat fever may be a particular risk for TS patients.

genetics↗

bioRxiv2024

Mutations in the microexon splicing regulator srrm4 have minor phenotypic effects on zebrafish neural development

Achieving a diversity of neuronal cell types and circuits during brain development requires alternative splicing of developmentally regulated mRNA transcripts. Microexons are a type of alternatively spliced exon that are 3-27 nucleotides in length and are predominantly expressed in neuronal tissues. A key regulator of microexon splicing is the RNA-binding protein Serine/arginine repetitive matrix 4 (Srrm4). Srrm4 is a highly conserved, vertebrate splicing factor that is part of an ancient family of splicing proteins. To better understand the function of Srrm4 during brain development, we examined neural expression of zebrafish srrm4 from days 1-5 of development using fluorescence in situ hybridization. We found that srrm4 has a dynamically changing expression pattern, with expression in diverse cell types and stages during development. We then used CRISPR-based mutagenesis to generate zebrafish srrm4 mutants. Unlike previously described morphant phenotypes, srrm4 mutants did not show overt morphological defects. Moreover, sequencing of wild-type and mutant transcriptomes revealed only minor changes in splicing. srrm4 thus appears to have a limited role in zebrafish neural development.

developmental biology↗

bioRxiv2024

Parp1 deletion rescues cerebellar hypotrophy in xrcc1 mutant zebrafish

Defects in DNA single-strand break repair are associated with neurodevelopmental and neurodegenerative disorders. One such disorder is that resulting from mutations in XRCC1, a scaffold protein that plays a central role in DNA single-strand base repair. XRCC1 is recruited at sites of single-strand breaks by PARP1, a protein that detects and is activated by such breaks and is negatively regulated by XRCC1 to prevent excessive PARP binding and activity. Loss of XRCC1 leads to the toxic accumulation and activity of PARP1 at single-strand breaks leading to base excision repair defects, a mechanism that may underlie pathological changes in patients carrying deleterious XRCC1 mutations. Here, we demonstrate that xrcc1 knockdown impairs development of the cerebellar plate in zebrafish. In contrast, parp1 knockdown alone does not significantly affect neural development, and instead rescues the cerebellar defects observed in xrcc1 mutant larvae. These findings support the notion that PARP1 inhibition may be a viable therapeutic candidate in neurological disorders.

neuroscience↗

bioRxiv2021

A cerebellar-prepontine circuit for tonic immobility triggered by inescapable threat

Sudden changes in the sensory environment are frequently perceived as threats and may provoke defensive behavioral states. One such state is tonic immobility, a conserved defensive strategy characterized by a powerful suppression of movement and motor reflexes. Tonic immobility has been associated with multiple brainstem regions and cell types, but the underlying circuit is not known. Here, we demonstrate that a strong vibratory stimulus evokes tonic immobility in larval zebrafish defined by suppression of exploratory locomotion and sensorimotor responses. Using a circuit-breaking screen and targeted neuron ablations, we show that cerebellar granule cells and a cluster of glutamatergic ventral prepontine neurons (vPPNs) that express key stress-associated neuropeptides are critical components of the circuit that suppresses movement. The complete sensorimotor circuit transmits information from primary sensory neurons through the cerebellum to vPPNs to regulate reticulospinal premotor neurons. These results show that cerebellar regulation of a neuropeptide-rich prepontine structure governs a conserved and ancestral defensive behavior that is triggered by inescapable threat.

neuroscience↗

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↗

bioRxiv2019

Molecular and cellular determinants of motor asymmetry in zebrafish

Asymmetries in motor behavior, such as human hand preference, are observed throughout bilateria. However, neural substrates and developmental signaling pathways that impose underlying functional lateralization on a broadly symmetric nervous system are unknown. Here we report that in the absence of over-riding visual information, zebrafish larvae show intrinsic lateralized motor behavior that is mediated by a cluster of 60 posterior tuberculum (PT) neurons in the forebrain. PT neurons impose motor bias via a projection through the epithalamic commissure to the habenula. Acquisition of left/right identity is disrupted by heterozygous mutations in mosaic eyes and mindbomb, genes that regulate Notch signaling. These results define the neuronal substrate for motor asymmetry in a vertebrate and support the idea that developmental pathways that establish visceral asymmetries also govern acquisition of left/right identity.

neuroscience↗

bioRxiv2018

Brain-wide cellular resolution imaging of Cre transgenic zebrafish lines for functional circuit-mapping

Decoding the functional connectivity of the nervous system is facilitated by transgenic methods that express a genetically encoded reporter or effector in specific neurons; however, most transgenic lines show broad spatiotemporal and cell-type expression. Increased specificity can be achieved using intersectional genetic methods which restrict reporter expression to cells that co-express multiple drivers, such as Gal4 and Cre. To facilitate intersectional targeting in zebrafish, we have generated more than 50 new Cre lines, and co-registered brain expression images with the Zebrafish Brain Browser, a cellular resolution atlas of 264 transgenic lines. Lines labeling neurons of interest can be identified using a web-browser to perform a 3D spatial search (zbbrowser.com). This resource facilitates the design of intersectional genetic experiments and will advance a wide range of precision circuit-mapping studies.

neuroscience↗

bioRxiv2016

High precision registration between zebrafish brain atlases using symmetric diffeomorphic normalization

Atlases provide a framework for information from diverse sources to be spatially mapped and integrated into a common reference space. In particular, brain atlases allow regional annotation of gene expression, cell morphology, connectivity and activity. In larval zebrafish, advances in genetics, imaging and computational methods have enabled the collection of large datasets providing such information on a whole-brain scale. However, datasets from different sources may not be aligned to the same spatial coordinate system, because technical considerations may necessitate use of different reference templates. Two recent brain atlases for larval zebrafish exemplify this problem. The Z-Brain atlas contains information on gene expression, neural activity and neuroanatomical segmentation acquired using immunohistochemical staining of fixed tissue. In contrast, the Zebrafish Brain Browser (ZBB) atlas was constructed from live scans of fluorescent reporter genes in transgenic larvae. Although different reference brains were used, the two atlases included several transgene patterns in common that provided potential 'bridges' for transforming each into the others coordinate space. We therefore tested multiple bridging channels and registration algorithms. The symmetric diffeomorphic normalization (SyN) algorithm in ANTs improved the precision of live brain registration while better preserving cell morphology than the previously used B-spline elastic registration algorithm. SyN could also be calibrated to correct for tissue distortion introduced during fixation and permeabilization. Finally, multi-reference channel optimization provided a transformation matrix that enabled Z-Brain and ZBB to be co-aligned with acceptable precision and minimal perturbation of cell and tissue morphology. This study demonstrates the feasibility of integrating whole brain datasets, despite disparate acquisition protocols and reference templates, when sufficient information is present for bridging.\n\nAnatomical abbreviations

neuroscience↗