A forward genetic screen identifies Dolk as a regulator of startle magnitude through the potassium channel subunit Kv1.1.

The acoustic startle response is an evolutionarily conserved avoidance behavior. Disruptions in startle behavior, particularly startle magnitude, are a hallmark of several human neurological disorders. While the neural circuitry underlying startle behavior has been studied extensively, the repertoire of genes and genetic pathways that regulate this locomotor behavior has not been explored using an unbiased genetic approach.

Pregnancy-associated plasma protein-aa supports hair cell survival by regulating mitochondrial function.

To support cell survival, mitochondria must balance energy production with oxidative stress. Inner ear hair cells are particularly vulnerable to oxidative stress; thus require tight mitochondrial regulation. We identified a novel molecular regulator of the hair cells' mitochondria and survival: Pregnancy-associated plasma protein-aa (Pappaa).

2,4-Dichlorophenoxyacetic acid containing herbicide impairs essential visually guided behaviors of larval fish.

Aquatic herbicides are used worldwide to eradicate nuisance and invasive plants despite limited knowledge of their toxicity to non-target organisms. 2,4-Dichlorophenoxyacetic acid (2,4-D) is a common active ingredient in commercial herbicide formulations, which triggers plant cell death by mimicking the plant-specific hormone auxin. Application practices of 2,4-D commercial herbicides typically coincide with yearly freshwater fish spawning periods.

Adult zebrafish primarily use vision to guide piscivorous foraging behavior.

The sensory modalities used by predatory fish to detect and capture prey are a key dimension of their foraging strategy. Determining the sensory cues that guide predation can also further conservation efforts under environmental change, and address the welfare of research animals. Here, we experimentally manipulated the sensory modalities used by adult zebrafish (Danio rerio) when foraging for larval conspecifics in captivity.

Zebrafish expression reporters and mutants reveal that the IgSF cell adhesion molecule Dscamb is required for feeding and survival.

Down syndrome cell adhesion molecules (DSCAMs) are broadly expressed in nervous systems and play conserved roles in programmed cell death, neuronal migration, axon guidance, neurite branching and spacing, and synaptic targeting. However, DSCAMs appear to have distinct functions in different vertebrate animals, and little is known about their functions outside the retina. We leveraged the genetic tractability and optical accessibility of larval zebrafish to investigate the expression and function of a DSCAM family member, dscamb.

Pregnancy-Associated Plasma Protein-aa Regulates Photoreceptor Synaptic Development to Mediate Visually Guided Behavior.

To guide behavior, sensory systems detect the onset and offset of stimuli and process these distinct inputs via parallel pathways. In the retina, this strategy is implemented by splitting neural signals for light onset and offset via synapses connecting photoreceptors to ON and OFF bipolar cells, respectively. It remains poorly understood which molecular cues establish the architecture of this synaptic configuration to split light-onset and light-offset signals.

A Forward Genetic Screen in Zebrafish Identifies the G-Protein-Coupled Receptor CaSR as a Modulator of Sensorimotor Decision Making.

Animals continuously integrate sensory information and select contextually appropriate responses. Here, we show that zebrafish larvae select a behavioral response to acoustic stimuli from a pre-existing choice repertoire in a context-dependent manner. We demonstrate that this sensorimotor choice is modulated by stimulus quality and history, as well as by neuromodulatory systems-all hallmarks of more complex decision making.

A Cyfip2-Dependent Excitatory Interneuron Pathway Establishes the Innate Startle Threshold.

Sensory experiences dynamically modify whether animals respond to a given stimulus, but it is unclear how innate behavioral thresholds are established. Here, we identify molecular and circuit-level mechanisms underlying the innate threshold of the zebrafish startle response. From a forward genetic screen, we isolated five mutant lines with reduced innate startle thresholds.

HuD and the Survival Motor Neuron Protein Interact in Motoneurons and Are Essential for Motoneuron Development, Function, and mRNA Regulation.

Motoneurons establish a critical link between the CNS and muscles. If motoneurons do not develop correctly, they cannot form the required connections, resulting in movement defects or paralysis. Compromised development can also lead to degeneration because the motoneuron is not set up to function properly.

Behavioral Characteristics of Adult Zebrafish () after MS222 Anesthesia for Fin Excision.

The health of laboratory animals is an ethical responsibility of researchers and a critical determinant of experimental outcome. Therefore, all husbandry procedures should be evaluated for their effects on mortality, behavior, and physiology to maximize animal welfare and minimize experimental variability. For adult zebrafish, the excision of a small portion of the caudal fin (that is, 'fin clipping') under MS222 anesthesia is a common procedure to obtain tissue for genotyping.

Novel roles for the radial spoke head protein 9 in neural and neurosensory cilia.

Cilia are cell surface organelles with key roles in a range of cellular processes, including generation of fluid flow by motile cilia. The axonemes of motile cilia and immotile kinocilia contain 9 peripheral microtubule doublets, a central microtubule pair, and 9 connecting radial spokes. Aberrant radial spoke components RSPH1, 3, 4a and 9 have been linked with primary ciliary dyskinesia (PCD), a disorder characterized by ciliary dysmotility; yet, radial spoke functions remain unclear.

Protocadherins control the modular assembly of neuronal columns in the zebrafish optic tectum.

Cell-cell recognition guides the assembly of the vertebrate brain during development. δ-Protocadherins comprise a family of neural adhesion molecules that are differentially expressed and have been implicated in a range of neurodevelopmental disorders. Here we show that the expression of δ-protocadherins partitions the zebrafish optic tectum into radial columns of neurons.

Carbamate nerve agent prophylatics exhibit distinct toxicological effects in the zebrafish embryo model.

Pyridostigmine bromide (PB) is an FDA-approved drug for the treatment of myasthenia gravis and a prophylactic pre-treatment for organophosphate nerve agent poisoning. Current methods for evaluating nerve agent treatments include enzymatic studies and mammalian models. Rapid whole animal screening tools for assessing the effects of nerve agent pre-treatment and post-exposure drugs represent an underdeveloped area of research.

A genome-wide screen identifies PAPP-AA-mediated IGFR signaling as a novel regulator of habituation learning.

Habituation represents a fundamental form of learning, yet the underlying molecular genetic mechanisms are not well defined. Here we report on a genome-wide genetic screen, coupled with whole-genome sequencing, that identified 14 zebrafish startle habituation mutants including mutants of the vertebrate-specific gene pregnancy-associated plasma protein-aa (pappaa). PAPP-AA encodes an extracellular metalloprotease known to increase IGF bioavailability, thereby enhancing IGF receptor signaling.

Modulation of cAMP and ras signaling pathways improves distinct behavioral deficits in a zebrafish model of neurofibromatosis type 1.

Neurofibromatosis type 1 (NF1) is a common autosomal-dominant disorder associated with attention deficits and learning disabilities. The primary known function of neurofibromin, encoded by the NF1 gene, is to downregulate Ras activity. We show that nf1-deficient zebrafish exhibit learning and memory deficits and that acute pharmacological inhibition of downstream targets of Ras (MAPK and PI3K) restores memory consolidation and recall but not learning.

Temporal requirement for SMN in motoneuron development.

Proper function of the motor unit is dependent upon the correct development of dendrites and axons. The infant/childhood onset motoneuron disease spinal muscular atrophy (SMA), caused by low levels of the survival motor neuron (SMN) protein, is characterized by muscle denervation and paralysis. Although different SMA models have shown neuromuscular junction defects and/or motor axon defects, a comprehensive analysis of motoneuron development in vivo under conditions of low SMN will give insight into why the motor unit becomes dysfunctional.

The tumor suppressor gene retinoblastoma-1 is required for retinotectal development and visual function in zebrafish.

Mutations in the retinoblastoma tumor suppressor gene (rb1) cause both sporadic and familial forms of childhood retinoblastoma. Despite its clinical relevance, the roles of rb1 during normal retinotectal development and function are not well understood. We have identified mutations in the zebrafish space cadet locus that lead to a premature truncation of the rb1 gene, identical to known mutations in sporadic and familial forms of retinoblastoma.

Zebrafish neurofibromatosis type 1 genes have redundant functions in tumorigenesis and embryonic development.

Neurofibromatosis type 1 (NF1) is a common, dominantly inherited genetic disorder that results from mutations in the neurofibromin 1 (NF1) gene. Affected individuals demonstrate abnormalities in neural-crest-derived tissues that include hyperpigmented skin lesions and benign peripheral nerve sheath tumors. NF1 patients also have a predisposition to malignancies including juvenile myelomonocytic leukemia (JMML), optic glioma, glioblastoma, schwannoma and malignant peripheral nerve sheath tumors (MPNSTs).

Survival motor neuron affects plastin 3 protein levels leading to motor defects.

The actin-binding protein plastin 3 (PLS3) has been identified as a modifier of the human motoneuron disease spinal muscular atrophy (SMA). SMA is caused by decreased levels of the survival motor neuron protein (SMN) and in its most severe form causes death in infants and young children. To understand the mechanism of PLS3 in SMA, we have analyzed pls3 RNA and protein in zebrafish smn mutants.

In vivo nerve-macrophage interactions following peripheral nerve injury.

In vertebrates, the peripheral nervous system has retained its regenerative capacity, enabling severed axons to reconnect with their original synaptic targets. While it is well documented that a favorable environment is critical for nerve regeneration, the complex cellular interactions between injured nerves with cells in their environment, as well as the functional significance of these interactions, have not been determined in vivo and in real time. Here we provide the first minute-by-minute account of cellular interactions between laser transected motor nerves and macrophages in live intact zebrafish.

Behavioral genetics in larval zebrafish: learning from the young.

Deciphering the genetic code that determines how the vertebrate nervous system assembles into neural circuits that ultimately control behavior is a fascinating and challenging question in modern neurobiology. Because of the complexity of this problem, successful strategies require a simple yet focused experimental approach without limiting the scope of the discovery. Unbiased, large-scale forward genetic screens in invertebrate organisms have yielded great insight into the genetic regulation of neural circuit assembly and function.

Molecular-genetic mapping of zebrafish mutants with variable phenotypic penetrance.

Forward genetic screens in vertebrates are powerful tools to generate models relevant to human diseases, including neuropsychiatric disorders. Variability in phenotypic penetrance and expressivity is common in these disorders and behavioral mutant models, making their molecular-genetic mapping a formidable task. Using a 'phenotyping by segregation' strategy, we molecularly map the hypersensitive zebrafish houdini mutant despite its variable phenotypic penetrance, providing a generally applicable strategy to map zebrafish mutants with subtle phenotypes.

Chemical modulation of memory formation in larval zebrafish.

Whole organism-based small-molecule screens have proven powerful in identifying novel therapeutic chemicals, yet this approach has not been exploited to identify new cognitive enhancers. Here we present an automated high-throughput system for measuring nonassociative learning behaviors in larval zebrafish. Using this system, we report that spaced training blocks of repetitive visual stimuli elicit protein synthesis-dependent long-term habituation in larval zebrafish, lasting up to 24 h.

The cell adhesion molecule Tag1, transmembrane protein Stbm/Vangl2, and Lamininalpha1 exhibit genetic interactions during migration of facial branchiomotor neurons in zebrafish.

Interactions between a neuron and its environment play a major role in neuronal migration. We show here that the cell adhesion molecule Transient Axonal Glycoprotein (Tag1) is necessary for the migration of the facial branchiomotor neurons (FBMNs) in the zebrafish hindbrain. In tag1 morphant embryos, FBMN migration is specifically blocked, with no effect on organization or patterning of other hindbrain neurons.

Transient axonal glycoprotein-1 (TAG-1) and laminin-alpha1 regulate dynamic growth cone behaviors and initial axon direction in vivo.

Background: How axon guidance signals regulate growth cone behavior and guidance decisions in the complex in vivo environment of the central nervous system is not well understood. We have taken advantage of the unique features of the zebrafish embryo to visualize dynamic growth cone behaviors and analyze guidance mechanisms of axons emerging from a central brain nucleus in vivo.

Results: We investigated axons of the nucleus of the medial longitudinal fascicle (nucMLF), which are the first axons to extend in the zebrafish midbrain.