deletion rescues cerebellar hypotrophy in 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 , 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.

Brain Imaging and Registration in Larval Zebrafish.

Registration of larval zebrafish brain scans to a common reference brain enables comparison of transgene and gene expression patterns, neuroanatomy, and morphometry. Here we describe methods for staining and mounting larval zebrafish to facilitate whole-brain fluorescence imaging. Following image acquisition, we provide a template for aligning brain images to a reference atlas using nonlinear registration with the ANTs software package.

A Critical Review of Zebrafish Neurological Disease Models-1. The Premise: Neuroanatomical, Cellular and Genetic Homology and Experimental Tractability.

The last decade has seen a dramatic rise in the number of genes linked to neurological disorders, necessitating new models to explore underlying mechanisms and to test potential therapies. Over a similar period, many laboratories adopted zebrafish as a tractable model for studying brain development, defining neural circuits and performing chemical screens. Here we discuss strengths and limitations of using the zebrafish system to model neurological disorders.

A Critical Review of Zebrafish Neurological Disease Models-2. Application: Functional and Neuroanatomical Phenotyping Strategies and Chemical Screens.

Extensive phylogenetic conservation of molecular pathways and neuroanatomical structures, associated with efficient methods for genetic modification, have been exploited increasingly to generate zebrafish models of human disease. A range of powerful approaches can be deployed to analyze these models with the ultimate goal of elucidating pathogenic mechanisms and accelerating efforts to find effective treatments. Unbiased neurobehavioral assays can provide readouts that parallel clinical abnormalities found in patients, although some of the most useful assays quantify responses that are not routinely evaluated clinically, and differences between zebrafish and human brains preclude expression of the full range of neurobehavioral abnormalities seen in disease.

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

Sudden changes in the environment are frequently perceived as threats and provoke defensive behavioral states. One such state is tonic immobility, a conserved defensive strategy characterized by powerful suppression of movement and motor reflexes. Tonic immobility has been associated with multiple brainstem regions, but the underlying circuit is unknown.

Disruption of grin2B, an ASD-associated gene, produces social deficits in zebrafish.

Background: Autism spectrum disorder (ASD), like many neurodevelopmental disorders, has complex and varied etiologies. Advances in genome sequencing have identified multiple candidate genes associated with ASD, including dozens of missense and nonsense mutations in the NMDAR subunit GluN2B, encoded by GRIN2B. NMDARs are glutamate-gated ion channels with key synaptic functions in excitatory neurotransmission.

The X-linked acrogigantism-associated gene gpr101 is a regulator of early embryonic development and growth in zebrafish.

We recently described X-linked acrogigantism (X-LAG), a condition of early childhood-onset pituitary gigantism associated with microduplications of the GPR101 receptor. The expression of GPR101 in hyperplastic pituitary regions and tumors in X-LAG patients, and GPR101's normally transient pituitary expression during fetal development, suggest a role in the regulation of growth. Nevertheless, little is still known about GPR101's physiological functions, especially during development.

A Model to Study NMDA Receptors in Early Nervous System Development.

-methyl-D-aspartate receptors (NMDARs) are glutamate-gated ion channels that play critical roles in neuronal development and nervous system function. Here, we developed a model to study NMDARs in early development in zebrafish, by generating CRISPR-mediated lesions in the NMDAR genes, and , which encode the obligatory GluN1 subunits. While receptors containing or show high Ca permeability, like their mammalian counterpart, is expressed earlier and more broadly in development than Both and zebrafish are viable.

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.

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.

Agouti-Related Protein 2 Is a New Player in the Teleost Stress Response System.

Agouti-related protein (AgRP) is a hypothalamic regulator of food consumption in mammals. However, AgRP has also been detected in circulation, but a possible endocrine role has not been examined. Zebrafish possess two agrp genes: hypothalamically expressed agrp1, considered functionally equivalent to the single mammalian agrp, and agrp2, which is expressed in pre-optic neurons and uncharacterized pineal gland cells and whose function is not well understood.

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.

Startling responses of zebrafish: an interview with Harold Burgess.

Harold Burgess is a Senior Investigator at the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), part of the National Institutes of Health. Work in his lab combines genetic and imaging techniques to study neural circuits required for sensory guided behavior in zebrafish. In this interview Harold shares his thoughts on the changing field of neural development, pre-publication review, and 'Darwinian experiments' of peer review.

Presynaptic Inhibition Selectively Gates Auditory Transmission to the Brainstem Startle Circuit.

Filtering mechanisms prevent a continuous stream of sensory information from swamping perception, leading to diminished focal attention and cognitive processing. Mechanisms for sensory gating are commonly studied using prepulse inhibition, a paradigm that measures the regulated transmission of auditory information to the startle circuit; however, the underlying neuronal pathways are unresolved. Using large-scale calcium imaging, optogenetics, and laser ablations, we reveal a cluster of 30 morphologically identified neurons in zebrafish that suppress the transmission of auditory signals during prepulse inhibition.

Morphometric analysis and neuroanatomical mapping of the zebrafish brain.

Large-scale genomic studies have recently identified genetic variants causative for major neurodevelopmental disorders, such as intellectual disability and autism. However, determining how underlying developmental processes are affected by these mutations remains a significant challenge in the field. Zebrafish is an established model system in developmental neurogenetics that may be useful in uncovering the mechanisms of these mutations.

Generation and characterization of Kctd15 mutations in zebrafish.

Potassium channel tetramerization domain containing 15 (Kctd15) was previously found to have a role in early neural crest (NC) patterning, specifically delimiting the region where NC markers are expressed via repression of transcription factor AP-2a and inhibition of Wnt signaling. We used transcription activator-like effector nucleases (TALENs) to generate null mutations in zebrafish kctd15a and kctd15b paralogs to study the in vivo role of Kctd15. We found that while deletions producing frame-shift mutations in each paralog showed no apparent phenotype, kctd15a/b double mutant zebrafish are smaller in size and show several phenotypes including some affecting the NC, such as expansion of the early NC domain, increased pigmentation, and craniofacial defects.

High-precision registration between zebrafish brain atlases using symmetric diffeomorphic normalization.

Atlases provide a framework for spatially mapping information from diverse sources into a common reference space. Specifically, brain atlases allow annotation of gene expression, cell morphology, connectivity, and activity. In larval zebrafish, advances in genetics, imaging, and computational methods now allow the collection of such information brain-wide.

Search strategy is regulated by somatostatin signaling and deep brain photoreceptors in zebrafish.

Background: Animals use sensory cues to efficiently locate resources, but when sensory information is insufficient, they may rely on internally coded search strategies. Despite the importance of search behavior, there is limited understanding of the underlying neural mechanisms in vertebrates.

Results: Here, we report that loss of illumination initiates sophisticated light-search behavior in larval zebrafish.

Genetically Blocking the Zebrafish Pineal Clock Affects Circadian Behavior.

The master circadian clock in fish has been considered to reside in the pineal gland. This dogma is challenged, however, by the finding that most zebrafish tissues contain molecular clocks that are directly reset by light. To further examine the role of the pineal gland oscillator in the zebrafish circadian system, we generated a transgenic line in which the molecular clock is selectively blocked in the melatonin-producing cells of the pineal gland by a dominant-negative strategy.

Genetic Ablation, Sensitization, and Isolation of Neurons Using Nitroreductase and Tetrodotoxin-Insensitive Channels.

Advances in genetic technologies enable the highly selective expression of transgenes in targeted neuronal cell types. Transgene expression can be used to noninvasively ablate, silence or activate neurons, providing a tool to probe their contribution to the control of behavior or physiology. Here, we describe the use of the tetrodotoxin (TTX)-resistant voltage-gated sodium channel Nav1.

Motivated state control in larval zebrafish: behavioral paradigms and anatomical substrates.

Over the course of each day, animals prioritize different objectives. Immediate goals may reflect fluctuating internal homeostatic demands, prompting individuals to seek out energy supplies or warmth. At other times, the environment may present temporary challenges or opportunities.

A 3D Searchable Database of Transgenic Zebrafish Gal4 and Cre Lines for Functional Neuroanatomy Studies.

Transgenic methods enable the selective manipulation of neurons for functional mapping of neuronal circuits. Using confocal microscopy, we have imaged the cellular-level expression of 109 transgenic lines in live 6 day post fertilization larvae, including 80 Gal4 enhancer trap lines, 9 Cre enhancer trap lines and 20 transgenic lines that express fluorescent proteins in defined gene-specific patterns. Image stacks were acquired at single micron resolution, together with a broadly expressed neural marker, which we used to align enhancer trap reporter patterns into a common 3-dimensional reference space.

Increased functional protein expression using nucleotide sequence features enriched in highly expressed genes in zebrafish.

Many genetic manipulations are limited by difficulty in obtaining adequate levels of protein expression. Bioinformatic and experimental studies have identified nucleotide sequence features that may increase expression, however it is difficult to assess the relative influence of these features. Zebrafish embryos are rapidly injected with calibrated doses of mRNA, enabling the effects of multiple sequence changes to be compared in vivo.