Evading or escaping from predators is one of the most crucial issues for survival across the animal kingdom. The timely detection of predators and the initiation of appropriate fight-or-flight responses are innate capabilities of the nervous system. Here we review recent progress in our understanding of innate visually-triggered defensive behaviors and the underlying neural circuit mechanisms, and a comparison among vinegar flies, zebrafish, and mice is included. This overview covers the anatomical and functional aspects of the neural circuits involved in this process, including visual threat processing and identification, the selection of appropriate behavioral responses, and the initiation of these innate defensive behaviors. The emphasis of this review is on the early stages of this pathway, namely, threat identification from complex visual inputs and how behavioral choices are influenced by differences in visual threats. We also briefly cover how the innate defensive response is processed centrally. Based on these summaries, we discuss coding strategies for visual threats and propose a common prototypical pathway for rapid innate defensive responses.
Mice ; Animals ; Zebrafish ; Neurons/physiology* ; Visual Perception/physiology*

Predatory hunting is an important type of innate behavior evolutionarily conserved across the animal kingdom. It is typically composed of a set of sequential actions, including prey search, pursuit, attack, and consumption. This behavior is subject to control by the nervous system. Early studies used toads as a model to probe the neuroethology of hunting, which led to the proposal of a sensory-triggered release mechanism for hunting actions. More recent studies have used genetically-trackable zebrafish and rodents and have made breakthrough discoveries in the neuroethology and neurocircuits underlying this behavior. Here, we review the sophisticated neurocircuitry involved in hunting and summarize the detailed mechanism for the circuitry to encode various aspects of hunting neuroethology, including sensory processing, sensorimotor transformation, motivation, and sequential encoding of hunting actions. We also discuss the overlapping brain circuits for hunting and feeding and point out the limitations of current studies. We propose that hunting is an ideal behavioral paradigm in which to study the neuroethology of motivated behaviors, which may shed new light on epidemic disorders, including binge-eating, obesity, and obsessive-compulsive disorders.
Animals ; Zebrafish ; Hunting ; Predatory Behavior/physiology* ; Neurons/physiology* ; Motivation

Mammals exhibit limited heart regeneration ability, which can lead to heart failure after myocardial infarction. In contrast, zebrafish exhibit remarkable cardiac regeneration capacity. Several cell types and signaling pathways have been reported to participate in this process. However, a comprehensive analysis of how different cells and signals interact and coordinate to regulate cardiac regeneration is unavailable. We collected major cardiac cell types from zebrafish and performed high-precision single-cell transcriptome analyses during both development and post-injury regeneration. We revealed the cellular heterogeneity as well as the molecular progress of cardiomyocytes during these processes, and identified a subtype of atrial cardiomyocyte exhibiting a stem-like state which may transdifferentiate into ventricular cardiomyocytes during regeneration. Furthermore, we identified a regeneration-induced cell (RIC) population in the epicardium-derived cells (EPDC), and demonstrated Angiopoietin 4 (Angpt4) as a specific regulator of heart regeneration. angpt4 expression is specifically and transiently activated in RIC, which initiates a signaling cascade from EPDC to endocardium through the Tie2-MAPK pathway, and further induces activation of cathepsin K in cardiomyocytes through RA signaling. Loss of angpt4 leads to defects in scar tissue resolution and cardiomyocyte proliferation, while overexpression of angpt4 accelerates regeneration. Furthermore, we found that ANGPT4 could enhance proliferation of neonatal rat cardiomyocytes, and promote cardiac repair in mice after myocardial infarction, indicating that the function of Angpt4 is conserved in mammals. Our study provides a mechanistic understanding of heart regeneration at single-cell precision, identifies Angpt4 as a key regulator of cardiomyocyte proliferation and regeneration, and offers a novel therapeutic target for improved recovery after human heart injuries.
Humans ; Mice ; Rats ; Cell Proliferation ; Heart/physiology* ; Mammals ; Myocardial Infarction/metabolism* ; Myocytes, Cardiac/metabolism* ; Pericardium/metabolism* ; Single-Cell Analysis ; Zebrafish/metabolism*

Recording the highly diverse and dynamic activities in large populations of neurons in behaving animals is crucial for a better understanding of how the brain works. To meet this challenge, extensive efforts have been devoted to developing functional fluorescent indicators and optical imaging techniques to optically monitor neural activity. Indeed, optical imaging potentially has extremely high throughput due to its non-invasive access to large brain regions and capability to sample neurons at high density, but the readout speed, such as the scanning speed in two-photon scanning microscopy, is often limited by various practical considerations. Among different imaging methods, light field microscopy features a highly parallelized 3D fluorescence imaging scheme and therefore promises a novel and faster strategy for functional imaging of neural activity. Here, we briefly review the working principles of various types of light field microscopes and their recent developments and applications in neuroscience studies. We also discuss strategies and considerations of optimizing light field microscopy for different experimental purposes, with illustrative examples in imaging zebrafish and mouse brains.
Animals ; Mice ; Microscopy/methods* ; Zebrafish ; Neurons/physiology* ; Brain/physiology* ; Neurosciences

OBJECTIVE: To determine if ARHGEF10 has a haploinsufficient effect and provide evidence to evaluate the severity, if any, during prenatal consultation. METHODS: Zebrafish was used as a model for generating mutant. The pattern of arhgef10 expression in the early stages of zebrafish development was observed using whole-mount in situ hybridization (WISH). CRISPR/Cas9 was applied to generate a zebrafish model with a single-copy or homozygous arhgef10 deletion. Activity and light/dark tests were performed in arhgef10 ^-/-, arhgef10 ^+/-, and wild-type zebrafish larvae. ARHGEF10 was knocked down using small interferon RNA (siRNA) in the SH-SY5Y cell line, and cell proliferation and apoptosis were determined using the CCK-8 assay and Annexin V/PI staining, respectively. RESULTS: WISH showed that during zebrafish embryonic development arhgef10 was expressed in the midbrain and hindbrain at 36-72 h post-fertilization (hpf) and in the hemopoietic system at 36-48 hpf. The zebrafish larvae with single-copy and homozygous arhgef10 deletions had lower exercise capacity and poorer responses to environmental changes compared to wild-type zebrafish larvae. Moreover, arhgef10 ^-/- zebrafish had more severe symptoms than arhgef10 ^+/- zebrafish. Knockdown of ARHGEF10 in human neuroblastoma cells led to decreased cell proliferation and increased cell apoptosis. CONCLUSION Based on our findings, ARHGEF10 appeared to have a haploinsufficiency effect.
Animals ; Annexin A5 ; Apoptosis ; Blotting, Western ; CRISPR-Associated Protein 9 ; CRISPR-Cas Systems ; Cell Line ; Cell Proliferation ; Cells, Cultured ; Flow Cytometry ; Genotype ; Humans ; In Situ Hybridization ; Larva/physiology* ; Phenotype ; RNA/isolation & purification* ; Real-Time Polymerase Chain Reaction/standards* ; Rho Guanine Nucleotide Exchange Factors/metabolism* ; Sincalide/analysis* ; Spectrophotometry/methods* ; Zebrafish/physiology*

PURPOSE: microRNAs (miRNAs) are non-coding RNAs composed of 20 to 22 nucleotides that regulate development and differentiation in various organs by silencing specific RNAs and regulating gene expression. In the present study, we show that the microRNA (miR)-183 cluster is upregulated during hair cell regeneration and that its inhibition reduces hair cell regeneration following neomycin-induced ototoxicity in zebrafish. MATERIALS AND METHODS: miRNA expression patterns after neomycin exposure were analyzed using microarray chips. Quantitative polymerase chain reaction was performed to validate miR-183 cluster expression patterns following neomycin exposure (500 µM for 2 h). After injection of an antisense morpholino (MO) to miR-183 (MO-183) immediately after fertilization, hair cell regeneration after neomycin exposure in neuromast cells was evaluated by fluorescent staining (YO-PRO1). The MO-183 effect also was assessed in transgenic zebrafish larvae expressing green fluorescent protein (GFP) in inner ear hair cells. RESULTS: Microarray analysis clearly showed that the miR-183 cluster (miR-96, miR-182, and miR-183) was upregulated after neomycin treatment. We also confirmed upregulated expression of the miR-183 cluster during hair cell regeneration after neomycin-induced ototoxicity. miR-183 inhibition using MO-183 reduced hair cell regeneration in both wild-type and GFP transgenic zebrafish larvae. CONCLUSION: Our work demonstrates that the miR-183 cluster is essential for the regeneration of hair cells following ototoxic injury in zebrafish larvae. Therefore, regulation of the miR-183 cluster can be a novel target for stimulation of hair cell regeneration.
Animals ; Animals, Genetically Modified ; Cell Count ; Gene Expression Profiling ; Gene Expression Regulation/drug effects ; Gene Knockdown Techniques ; Green Fluorescent Proteins/metabolism ; Hair Cells, Auditory/drug effects ; Hair Cells, Auditory/physiology ; Larva/drug effects ; Larva/genetics ; MicroRNAs/genetics ; MicroRNAs/metabolism ; Morpholinos/pharmacology ; Neomycin/toxicity ; Regeneration/drug effects ; Regeneration/genetics ; Zebrafish/genetics

OBJECTIVETo investigate the pro-angiogenic effects of paeoniflorin (PF) in a vascular insufficiency model of zebrafish and in human umbilical vein endothelial cells (HUVECs).

METHODSIn vivo, the pro-angiogenic effects of PF were tested in a vascular insufficiency model in the Tg(fli-1:EGFP)y1 transgenic zebrafish. The 24 h post fertilization (hpf) embryos were pretreated with vascular endothelial growth factor (VEGF) receptor tyrosine kinase inhibitor II (VRI) for 3 h to establish the vascular insufficiency model and then post-treated with PF for 24 h. The formation of intersegmental vessels (ISVs) was observed with a fluorescence microscope. The mRNA expression of fms-like tyrosine kinase-1 (flt-1), kinase insert domain receptor (kdr), kinase insert domain receptor like (kdrl) and von Willebrand factor (vWF) were analyzed by real-time polymerase chain reaction (PCR). In vitro, the pro-angiogenic effects of PF were observed in HUVECs in which cell proliferation, migration and tube formation were assessed.

RESULTSPF (6.25-100 μmol/L) could rescue VRI-induced blood vessel loss in zebrafish and PF (25-100 μmol/L), thereby restoring the mRNA expressions of flt-1, kdr, kdrl and vWF, which were down-regulated by VRI treatment. In addition, PF (0.001-0.03 μmol/L) could promote the proliferation of HUVECs while PF stimulated HUVECs migration at 1.0-10 μmol/L and tube formation at 0.3 μmol/L.

CONCLUSIONPF could promote angiogenesis in a vascular insufficiency model of zebrafish in vivo and in HUVECs in vitro.

Angiogenesis Inducing Agents ; pharmacology ; therapeutic use ; Animals ; Animals, Genetically Modified ; Cells, Cultured ; Disease Models, Animal ; Drugs, Chinese Herbal ; pharmacology ; therapeutic use ; Embryo, Nonmammalian ; Glucosides ; pharmacology ; therapeutic use ; Human Umbilical Vein Endothelial Cells ; drug effects ; physiology ; Humans ; Monoterpenes ; pharmacology ; therapeutic use ; Neovascularization, Physiologic ; drug effects ; Phytotherapy ; Vascular Diseases ; drug therapy ; pathology ; Zebrafish

Schisandra chinensis, a traditional Chinese medicine (TCM), has been used to treat sleep disorders. Zebrafish sleep/wake behavioral profiling provides a high-throughput platform to screen chemicals, but has never been used to study extracts and components from TCM. In the present study, the ethanol extract of Schisandra chinensis and its two main lignin components, schisandrin and schisandrin B, were studied in zebrafish. We found that the ethanol extract had bidirectional improvement in rest and activity in zebrafish. Schisandrin and schisandrin B were both sedative and active components. We predicted that schisandrin was related to serotonin pathway and the enthanol extract of Schisandra chinensis was related to seoronin and domapine pathways using a database of zebrafish behaviors. These predictions were confirmed in experiments using Caenorhabditis elegans. In conclusion, zebrafish behavior profiling could be used as a high-throughput platform to screen neuroactive effects and predict molecular pathways of extracts and components from TCM.
Animals ; Behavior, Animal ; drug effects ; Caenorhabditis elegans ; Central Nervous System Agents ; chemistry ; isolation & purification ; pharmacology ; Cyclooctanes ; analysis ; isolation & purification ; pharmacology ; Drugs, Chinese Herbal ; chemistry ; pharmacology ; Lignans ; analysis ; isolation & purification ; pharmacology ; Plant Extracts ; chemistry ; isolation & purification ; pharmacology ; Polycyclic Compounds ; analysis ; isolation & purification ; pharmacology ; Schisandra ; chemistry ; Zebrafish ; physiology

We propose that locations of genes on chromosomes can contribute to the prediction of gene regulatory relationships. We constructed a time-based gene regulatory network of zebrafish cardiogenesis on the basis of a spatio-temporal neighborhood method. Through the network, specific regulatory pathways and order of gene expression during zebrafish cardiogenesis were obtained. By comparing the order with locations of these genes on chromosomes, we discovered that there exists a reversal phenomenon between the order and order of gene locations. The discovery provides an inherent rule to instruct exploration of gene regulatory relationships. Specifically, the discovery can help to predict if regulatory relationships between genes exist and contribute to evaluating the correctness of discovered gene regulatory relationships.
Algorithms ; Animals ; Chromosome Mapping ; Chromosomes ; Gene Expression ; Gene Regulatory Networks ; Heart/physiology* ; Zebrafish/genetics*

This study aimed to investigate the expression of the natriuretic peptide precursor C coding gene nppc and its role in angiogenesis during embryonic period of the zebrafish. Whole mount in situ hybridization was performed to detect the expression pattern of nppc. nppc specific morpholino and nppc mRNA were injected respectively into the one-cell stage embryo to specifically knock-down and rescue the expression of nppc in Tg (flk1:GFP) and Tg (fli1a:nGFP) transgenic lines. The morphology and endothelial cell number of intersegmental vessel (ISV) were analyzed after imaging using the laser scanning confocal microscope. The results revealed that nppc was expressed in the brain, heart and vasculature of zebrafish larvae at 24 and 48 hours post-fertilization (hpf). Knock-down of nppc affected the development of ISV. Endothelial cell number was reduced after the knock-down of nppc. These results suggest that nppc controls zebrafish angiogenesis by affecting the endothelial cell proliferation and migration.
Animals ; Animals, Genetically Modified ; Cell Movement ; Cell Proliferation ; Endothelial Cells ; physiology ; Gene Knockdown Techniques ; Heart ; physiology ; Larva ; Natriuretic Peptides ; genetics ; physiology ; Neovascularization, Physiologic ; RNA, Messenger ; Zebrafish ; genetics ; physiology ; Zebrafish Proteins ; genetics ; physiology