Moderate developmental alcohol exposure reduces repetitive alternation in a zebrafish model of fetal alcohol spectrum disorders

Ontogeny of working memory and behavioural flexibility in the free movement pattern (FMP) Y-maze in zebrafish

The acquisition of executive skills such as working memory, decision-making and adaptive responding occur at different stages of central nervous system development. Zebrafish (Danio rerio) are increasingly used in behavioural neuroscience for complex behavioural tasks, and there is a critical need to understand the ontogeny of their executive functions. Zebrafish across developmental stages (4, 7, 14, 30 and 90 days post fertilisation (dpf)), were assessed to track development of working memory (WM) and behavioural flexibility (BF) using the free movement pattern Y-maze (FMP Y-maze). Several differences in both WM and BF were identified during the transition from yolk-dependent to independent feeding. Specifically, WM is evident in all age groups, even from 4 dpf. However, BF is not developed until larvae start free feeding, and show significant improvement thereafter, with young adults (90 dpf) demonstrating the most well-defined BF. We demonstrate, for the first time, objective WM processes in 4 dpf zebrafish larvae. This suggests that those wishing to study WM in zebrafish may be able to do so from 4 dpf, thus drastically increasing throughput. In addition, we show that zebrafish follow distinct stages of cognitive development and age-related changes during the early developmental period. Finally, our findings indicate distinct WM and BF mechanisms, which may be useful to study for translational purposes.

Obesity Impairs Cognitive Function with No Effects on Anxiety-like Behaviour in Zebrafish

Over the last decade, the zebrafish has emerged as an important model organism for behavioural studies and neurological disorders, as well as for the study of metabolic diseases. This makes zebrafish an alternative model for studying the effects of energy disruption and nutritional quality on a wide range of behavioural aspects. Here, we used the zebrafish model to study how obesity induced by overfeeding regulates emotional and cognitive processes. Two groups of fish (n = 24 per group) were fed at 2% (CTRL) and 8% (overfeeding-induced obesity, OIO) for 8 weeks and tested for anxiety-like behaviour using the novel tank diving test (NTDT). Fish were first tested using a short-term memory test (STM) and then trained for four days for a long-term memory test (LTM). At the end of the experiment, fish were euthanised for biometric sampling, total lipid content, and triglyceride analysis. In addition, brains (eight per treatment) were dissected for HPLC determination of monoamines. Overfeeding induced faster growth and obesity, as indicated by increased total lipid content. OIO had no effect on anxiety-like behaviour. Animals were then tested for cognitive function (learning and memory) using the aversive learning test in Zantiks AD units. Results show that both OIO and CTRL animals were able to associate the aversive stimulus with the conditioned stimulus (conditioned learning), but OIO impaired STM regardless of fish sex, revealing the effects of obesity on cognitive processes in zebrafish. Obese fish did not show a deficiency in monoaminergic transmission, as revealed by quantification of total brain levels of dopamine and serotonin and their metabolites. This provides a reliable protocol for assessing the effect of metabolic disease on cognitive and behavioural function, supporting zebrafish as a model for behavioural and cognitive neuroscience.

Zebrafish: A Pharmacological Model for Learning and Memory Research

Learning and memory are essential to organism survival and are conserved across various species, especially vertebrates. Cognitive studies involving learning and memory require using appropriate model organisms to translate relevant findings to humans. Zebrafish are becoming increasingly popular as one of the animal models for neurodegenerative diseases due to their low maintenance cost, prolific nature and amenability to genetic manipulation. More importantly, zebrafish exhibit a repertoire of neurobehaviors comparable to humans. In this review, we discuss the forms of learning and memory abilities in zebrafish and the tests used to evaluate the neurobehaviors in this species. In addition, the pharmacological studies that used zebrafish as models to screen for the effects of neuroprotective and neurotoxic compounds on cognitive performance will be summarized here. Lastly, we discuss the challenges and perspectives in establishing zebrafish as a robust model for cognitive research involving learning and memory. Zebrafish are becoming an indispensable model in learning and memory research for screening neuroprotective agents against cognitive impairment.

Zebrafish Modeling of Autism Spectrum Disorders, Current Status and Future Prospective

Autism spectrum disorder (ASD) refers to a complicated range of childhood neurodevelopmental disorders which can occur via genetic or non-genetic factors. Clinically, ASD is associated with problems in relationships, social interactions, and behaviors that pose many challenges for children with ASD and their families. Due to the complexity, heterogeneity, and association of symptoms with some neuropsychiatric disorders such as ADHD, anxiety, and sleep disorders, clinical trials have not yielded reliable results and there still remain challenges in drug discovery and development pipeline for ASD patients. One of the main steps in promoting lead compounds to the suitable drug for commercialization is preclinical animal testing, in which the efficacy and toxicity of candidate drugs are examined in vivo. In recent years, zebrafish have been able to attract the attention of many researchers in the field of neurological disorders such as ASD due to their outstanding features. The presence of orthologous genes for ASD modeling, the anatomical similarities of parts of the brain, and similar neurotransmitter systems between zebrafish and humans are some of the main reasons why scientists draw attention to zebrafish as a prominent animal model in preclinical studies to discover highly effective treatment approaches for the ASD through genetic and non-genetic modeling methods.

Long-lasting implications of embryonic exposure to alcohol: Insights from zebrafish research

The harmful consumption of ethanol is associated with significant health problems and social burdens. This drug activates a complex network of reward mechanisms and habit formation learning that is supposed to contribute to the consumption of increasingly high and frequent amounts, ultimately leading to addiction. In the context of fetal alcohol spectrum disorders, fetal alcohol syndrome (FAS) is a consequence of the harmful use of alcohol during pregnancy, which affects the embryonic development of the fetus. FAS can be easily reproduced in zebrafish by exposing the embryos to different concentrations of ethanol in water. In this regard, the aim of the present review is to discuss the late pathological implications in zebrafish exposed to ethanol at the embryonic stage, providing information in the context of human fetal alcoholic spectrum disorders. Experimental FAS in zebrafish is associated with impairments in the metabolic, morphological, neurochemical, behavioral, and cognitive domains. Many of the pathways that are affected by ethanol in zebrafish have at least one ortholog in humans, collaborating with the wider adoption of zebrafish in studies on alcohol disorders. In fact, zebrafish present validities required for the study of these conditions, which contributes to the use of this species in research, in addition to studies with rodents.

Tricaine Methanesulfonate (MS222) Has Short-Term Effects on Young Adult Zebrafish (Danio rerio) Working Memory and Cognitive Flexibility, but Not on Aging Fish

Exposure to anesthetic drugs is common in biomedical sciences being part of routine procedures in different translational species, however its impacts on memory and cognition are still debated, having different impacts depending on drug and age. The zebrafish (Danio rerio) is a translational species widely used in behavioral neuroscience, where tricaine methanesulfonate (MS222) is the most acceptable and used drug when conducting routine procedures. Based on this, we investigated the effects of MS222 (100 mg/l) in young adults and aging zebrafish 1, 2, 3, and 7 days after exposure. Animals' were submitted to the anesthetic procedure until loss of body posture, slowing of opercular movements and lack of response to tail touch with a plastic pipette were achieved, then further left in the drug for 3 min. After that, animals (6 mpf vs. 24 mpf) were transferred to a recovery tank until fully recovered and transferred back to their housing system until further testing in the free movement pattern (FMP) Y-maze, which assesses zebrafish working memory and cognitive lexibility. Young animals had significant impairment in their working memory and cognitive flexibility 1 and 2 days after the exposure to MS222, being fully recovered by day 3 and with no effects 7 days post drug exposure. Increased repetitions were also observed for animals exposed to MS222 which could indicate increased stress-related response in animals up to 2 days after drug exposure. No drug effect was observed in aging animals besides their natural decreased alternations and working memory. Overall, behavioral experiments after routine procedures using MS222 should be performed with caution and need to be delayed, at least 3 days after exposure where working memory, cognitive flexibility, and repetitive behavior are back to normal.

Chronic unpredictable early-life stress (CUELS) protocol: Early-life stress changes anxiety levels of adult zebrafish

Early-life stress can lead to two different behavioral responses: (1) increased susceptibility to psychiatric disorders or (2) resilience. Here, we created a chronic unpredictable early-life stress (CUELS) protocol to assess the effects of early experiences in adult zebrafish. Animals were exposed to mild stressors twice a day and the duration was varied between groups (0, 1, 3, 7 and 14 days of stress). The stressor consisted of light/dark cycle changes; social isolation; overcrowding; water changes; water cooling; mechanical stirring; water heating; and immersion in shallow water. Behavior was assessed at young stages (21 days post-fertilization - open field analysis) and adulthood (4-months-old - novel tank diving test, light/dark task, shoaling, free movement pattern Y-maze and Pavlovian fear conditioning). Cortisol levels were assessed to evaluate the impact of CUELS in the HPI axis. Zebrafish exposed to 7 days of CUELS showed a decreased anxiety-like phenotype in two behavioral tasks, presenting increased time spent in top and decreased time spent in the dark area. Animals exposed to 14 days of CUELS showed an opposite anxious phenotype compared to 3 and 7 days of CUELS. No significant changes were observed in memory and cognition, social behavior and cortisol levels. In general, 7 days of CUELS protocol decreased anxiety in young and adult zebrafish, and could be used to understand the mechanisms underlying early-life experiences-derived alterations in neural circuits of anxiety.

Swimming in the maze: An overview of maze apparatuses and protocols to assess zebrafish behavior

Most preclinical behavioral assays use rodents as model animals, leaving room for species-specific biases that could be avoided by an expanded cross-species approach. In this context, zebrafish emerges as an alternative model organism to study neurobiological mechanisms of anxiety, preference, learning, and memory, as well as other phenotypes with relevance to neuropsychiatric disorders. In recent years, several zebrafish studies using different types of mazes have been published. However, the protocols and apparatuses' shapes and dimensions vary widely in the literature. This variation may puzzle researchers attempting to implement maze behavioral assays and challenges the reproducibility across institutions. This review aims to provide an overview of the behavioral paradigms assessed in different types of mazes in zebrafish reported in the last couple of decades. Also, this review aims to contribute to a better characterization of multi-behavioral assessment in zebrafish.

Automated Operant Conditioning Devices for Fish. Do They Work?

Simple Summary

Automated training devices are commonly used for investigating learning, memory, and other cognitive functions in warm-blood vertebrates, whereas manual training procedures are the standard in fish and other lower vertebrates, thus limiting comparison among species. Here, we directly compared the two different approaches to training in guppies (Poecilia reticulata) by administering numerical discrimination tasks of increasing difficulty. The automated device group showed a much lower performance compared to the traditionally-trained group. We modified some features of the automated device in order to improve its efficiency. Increasing the decision time or inter-trial interval was ineffective, while reducing the cognitive load and allowing subjects to reside in the test tank improved numerical performance. Yet, in no case did subjects match the performance of traditionally-trained subjects, suggesting that small teleosts may be limited in their capacity to cope with operant conditioning devices.

Abstract

The growing use of teleosts in comparative cognition and in neurobiological research has prompted many researchers to develop automated conditioning devices for fish. These techniques can make research less expensive and fully comparable with research on warm-blooded species, in which automated devices have been used for more than a century. Tested with a recently developed automated device, guppies (Poecilia reticulata) easily performed 80 reinforced trials per session, exceeding 80% accuracy in color or shape discrimination tasks after only 3–4 training session, though they exhibit unexpectedly poor performance in numerical discrimination tasks. As several pieces of evidence indicate, guppies possess excellent numerical abilities. In the first part of this study, we benchmarked the automated training device with a standard manual training procedure by administering the same set of tasks, which consisted of numerical discriminations of increasing difficulty. All manually-trained guppies quickly learned the easiest discriminations and a substantial percentage learned the more difficult ones, such as 4 vs. 5 items. No fish trained with the automated conditioning device reached the learning criterion for even the easiest discriminations. In the second part of the study, we introduced a series of modifications to the conditioning chamber and to the procedure in an attempt to improve its efficiency. Increasing the decision time, inter-trial interval, or visibility of the stimuli did not produce an appreciable improvement. Reducing the cognitive load of the task by training subjects first to use the device with shape and color discriminations, significantly improved their numerical performance. Allowing the subjects to reside in the test chamber, which likely reduced the amount of attentional resources subtracted to task execution, also led to an improvement, although in no case did subjects match the performance of fish trained with the standard procedure. Our results highlight limitations in the capacity of small laboratory teleosts to cope with operant conditioning automation that was not observed in laboratory mammals and birds and that currently prevent an easy and straightforward comparison with other vertebrates.

Contributions of Zebrafish Studies on the Behavioural Consequences of Early Alcohol Exposure: A Systematic Review

BACKGROUND

The consequences of mild to severe exposure to alcohol during brain development is still a matter of debate and scientific investigation. The long-term behavioural effects of ethanol exposure have been related to impaired social skills and cognition. Zebrafish have become a suitable animal model to investigate the effects of early ethanol exposure because it is very feasible to promote drug delivery during early development.

OBJECTIVE

The goal of the current report is to review existing behavioural studies addressing the impact of early alcohol exposure using zebrafish to determine whether these models resemble the behavioural effects of early alcohol exposure in humans.

METHODS

A comprehensive search of biomedical databases was performed using the operation order: "ZEBRAFISH AND BEHAV* AND (ETHANOL OR ALCOHOL)". The eligibility of studies was determined using the PICOS strategy, contemplating the population as zebrafish, intervention as exposure to ethanol, comparison with a non-exposed control animal, and outcomes as behavioural parameters.

RESULTS

The systematic search returned 29 scientific articles as eligible. The zebrafish is presented as a versatile animal model that is useful to study FASD short and long-term behaviour impairments, such as anxiety, impaired sociability, aggressiveness, learning problems, memory impairment, seizure susceptibility, sleep disorders, motivational problems, and addiction.

CONCLUSION

This systematic review serves to further promote the use of zebrafish as a model system to study the pathophysiological and behavioural consequences of early alcohol exposure.

Does early ethanol exposure increase seeking-like behavior in zebrafish?

Fetal alcohol spectrum disorder (FASD) is the most common cause of birth defects. The severe variations are in fetal alcohol syndrome (FAS) but the most frequent cases are alcohol-related neurodevelopmental disorder (ARND), which is of a difficult diagnosis. ARND characteristics include impaired social behavior, anxiety and depression prevalence, cognitive deficits, and an increased chance for drug addiction. Here, we aimed to test whether early alcohol exposure leads to later alcohol preference. We hypothesize that early alcohol exposure increases the reinforcing effects on later experiences, raising the chance of addiction in adult life. Lately, the zebrafish has been a valuable model on alcohol research, allowing embryonic exposure and the study of the ontogenetic effects. For this, embryos were exposed to three different alcohol treatments: 0.0%, 0.25% and 0.5%, for 2 hr, at 24-hr post-fertilization. Then we evaluated the effects of embryonic alcohol exposure on conditioned place preference in two developmental stage: fry (10 days post-fertilization (dpf)) and young (90 dpf) zebrafish. Results show that control fish presented alcohol associative learning, which means, changes in place preference due to alcohol exposure, at both ontogenetic phases. However, zebrafish exposed to 0.25 and 0.5% alcohol during embryogenesis did not show conditioning response at any evaluated stage. These results suggest perception and cognitive deficits due to embryonic alcohol exposure that can alter alcohol responsiveness throughout a lifetime. Although low alcohol doses do not provoke malformation, it has been shown to induce several neurological and behavioral changes that are termed as Alcohol-Related Neurodevelopmental Disorders. These results may contribute to future investigations on how embryonic exposure affects the neurocircuitry related to perception and associative learning processing.

The Free-movement pattern Y-maze: A cross-species measure of working memory and executive function

Numerous neurodegenerative and psychiatric disorders are associated with deficits in executive functions such as working memory and cognitive flexibility. Progress in developing effective treatments for disorders may benefit from targeting these cognitive impairments, the success of which is predicated on the development of animal models with validated behavioural assays. Zebrafish offer a promising model for studying complex brain disorders, but tasks assessing executive function are lacking. The Free-movement pattern (FMP) Y-maze combines aspects of the common Y-maze assay, which exploits the inherent motivation of an organism to explore an unknown environment, with analysis based on a series of sequential two-choice discriminations. We validate the task as a measure of working memory and executive function by comparing task performance parameters in adult zebrafish treated with a range of glutamatergic, cholinergic and dopaminergic drugs known to impair working memory and cognitive flexibility. We demonstrate the cross-species validity of the task by assessing performance parameters in adapted versions of the task for mice and Drosophila, and finally a virtual version in humans, and identify remarkable commonalities between vertebrate species' navigation of the maze. Together, our results demonstrate that the FMP Y-maze is a sensitive assay for assessing working memory and cognitive flexibility across species from invertebrates to humans, providing a simple and widely applicable behavioural assay with exceptional translational relevance.

The cognitive and behavioral effects of D-amphetamine and nicotine sensitization in adult zebrafish

BACKGROUND

Zebrafish are growing in use as a model for understanding drug dependence and addiction. Sensitization paradigms have been a useful tool in identifying mechanisms involved in drug-induced behavioral and neurological changes, but in zebrafish have tended to focus on locomotor, rather than cognitive, endpoints.

METHODS

Here, we used a novel method, the FMP Y-maze, which measures continuous performance through a series of repeated binary choices (L vs R), to establish a model for assessing parameters associated with psychostimulant-induced behavioral and cognitive sensitization in adult zebrafish.

RESULTS

Repeat, intermittent exposure to d-amphetamine (AMPH) for 14 days increased alternations (LRLR) in the maze, suggesting improved working memory, which was enhanced further following drug challenge after a short withdrawal period, suggesting behavioral sensitization. However, this cognitive enhancement coincided with a reduction in the use of other exploration strategies, hypolocomotion, and inhibition of cognitive flexibility. Like AMPH, exposure to nicotine (NIC) increased alternations following drug challenge after chronic treatment. Repeat NIC exposure appeared to induce both cognitive and psychomotor sensitization, as evidenced by increased working memory performance (alternations) and locomotor activity, without negatively impacting other search strategies or cognitive flexibility.

CONCLUSION

Chronic treatment with AMPH or NIC boosts cognitive performance in adult zebrafish. Cognitive sensitization occurred with both drugs, resulting in enhanced working memory; however, repeat AMPH exposure, following a withdrawal period, resulted in inhibited cognitive flexibility, an effect not evident with repeat NIC exposure. Cognitive and behavioral sensitization paradigms in zebrafish could serve as a useful tool for assessing cognitive states which result in cognitive enhancing or impairing effects of drugs.

Protective effects of quercetin, polydatin, and folic acid and their mixtures in a zebrafish (Danio rerio) fetal alcohol spectrum disorder model

Protective effects of quercetin (QUE), polydatin (POL), and folic acid (FA) and their mixtures were tested using zebrafish to model fetal alcohol spectrum disorder in this study. Zebrafish embryos were exposed to 150 mM ethanol for 6 or 22 h and co-treated with QUE, POL, FA, and their mixtures (37.5-100.0 μM). Epiboly progression, teratogenic effects, and behavior were evaluated. Ethanol exposure reduced epiboly, and FA and QUE protected against these ethanol-induced defects. POL did not reduce epiboly defects. The mixture QUE + FA showed a possible antagonistic effect. The observed teratogenic effects were similar in all ethanol exposed groups. QUE, FA and QUE + POL reduced the percentage of affected animals, but treatments did not eliminate teratogenic effects. Behavioral measurements were divided into small (between 4 and 8 mm/s) and high swimming activity (>8 mm/s). All experimental groups displayed a reduction in small swimming activity as compared to control and ethanol groups when exposed to bright light. Additionally, larvae exposed to ethanol were more inhibited than control, not showing a habituation period (after 60 min of experiment) in high swimming activity. Chemical treatments like QUE and POL reduced behavioral defects induced by ethanol exposure. In conclusion, this study presents new evidence that QUE, POL, FA and their mixtures partially protected epiboly, teratogenic, and behavioral defects induced by ethanol exposure. QUE, FA and QUE + POL were more effective in reducing these defects than the other studied compounds and mixtures.

Understanding the neurobiological effects of drug abuse: Lessons from zebrafish models

Drug abuse and brain disorders related to drug comsumption are public health problems with harmful individual and social consequences. The identification of therapeutic targets and precise pharmacological treatments to these neuropsychiatric conditions associated with drug abuse are urgently needed. Understanding the link between neurobiological mechanisms and behavior is a key aspect of elucidating drug abuse-related targets. Due to various molecular, biochemical, pharmacological, and physiological features, the zebrafish (Danio rerio) has been considered a suitable vertebrate for modeling complex processes involved in drug abuse responses. In this review, we discuss how the zebrafish has been successfully used for modeling neurobehavioral phenotypes related to drug abuse and review the effects of opioids, cannabinoids, alcohol, nicotine, and psychedelic drugs on the central nervous system (CNS). Moreover, we summarize recent advances in zebrafish-based studies and outline potential advantages and limitations of the existing zebrafish models to explore the neurochemical bases of drug abuse and addiction. Finally, we discuss how the use of zebrafish models may present fruitful approaches to provide valuable clinically translatable data.

Moderate early life stress improves adult zebrafish (Danio rerio) working memory but does not affect social and anxiety-like responses

Early life stress (ELS) is defined as a short or chronic period of trauma, environmental or social deprivation, which can affect different neurochemical and behavioral patterns during adulthood. Zebrafish (Danio rerio) have been widely used as a model system to understand human neurodevelopmental disorders and display translationally relevant behavioral and stress-regulating systems. In this study, we aimed to investigate the effects of moderate ELS by exposing young animals (6-weeks postfertilization), for 3 consecutive days, to three stressors, and analyzing the impact of this on adult zebrafish behavior (16-week postfertilization). The ELS impact in adults was assessed through analysis of performance on tests of unconditioned memory (free movement pattern Y-maze test), exploratory and anxiety-related task (novel tank diving test), and social cohesion (shoaling test). Here, we show for the first time that moderate ELS increases the number of alternations in turn-direction compared to repetitions in the unconditioned Y-maze task, suggesting increased working memory, but has no effect on shoal cohesion, locomotor profile, or anxiety-like behavior. Overall, our data suggest that moderate ELS may be linked to adaptive flexibility which contributes to build "resilience" in adult zebrafish by improving working memory performance.

Zebrafish (Danio rerio) behavioral laterality predicts increased short-term avoidance memory but not stress-reactivity responses

Once considered a uniquely human attribute, behavioral laterality has proven to be ubiquitous among non-human animals, and is associated with several neurophenotypes in rodents and fishes. Zebrafish (Danio rerio) is a versatile vertebrate model system widely used in translational neuropsychiatric research owing to their highly conserved genetic homology, well-characterized physiological responses, and extensive behavioral repertoire. Although spontaneous left- and right-biased responses, and associated behavioral domains (e.g., stress reactivity, aggression, and learning), have previously been observed in other teleost species, no information relating to whether spontaneous motor left–right-bias responses of zebrafish predicts other behavioral domains has been described. Thus, we aimed to investigate the existence and incidence of natural left–right bias in adult zebrafish, exploiting an unconditioned continuous free movement pattern (FMP) Y-maze task, and to explore the relationship of biasedness on performance within different behavioral domains. This included learning about threat cues in a Pavlovian fear conditioning test, and locomotion and anxiety-related behavior in the novel tank diving test. Although laterality did not change locomotion or anxiety-related behaviors, we found that biased animals displayed a different search strategy in the Y-maze, making them easily discernable from their unbiased counterparts, and increased learning associated to fear cues. In conclusion, we showed, for the first time, that zebrafish exhibit a natural manifestation of motor behavioral lateralization which can influence aversive learning responses.

Molecular Characterization and Functional Analysis of Leucine Zipper Transcription Factor Like 1 in Zebrafish (Danio rerio)

Leucine zipper transcription factor like 1 (LZTFL1) is a member of the Bardet-Biedl syndrome gene family. LZTFL1-null mice show the phenotype of obesity, retinal degeneration, and abnormal cilia development. Functionally, LZTFL1 serves as a tumor suppressor and a negative regulator in the hedgehog signaling pathways. The biological function of mammalian LZTFL1 is partially addressed, but data on other model organisms are limited. Zebrafish (Danio rerio) is widely considered as a powerful model to understand the functions of genes implicated in obesity, disease, and cancer. In this study, LZTFL1 homologs were identified in zebrafish (zebrafish LZTFL1). The full-length cDNA of zebrafish LZTFL1 contained 897 bps encoding 298 amino acids. Zebrafish LZTFL1 displayed conserved domains of coil-coil and leucine zipper domain. PCR results showed that zebrafish LZTFL1 was widely distributed in various tissues. Western blot analysis further revealed that zebrafish LZTFL1 was detected to be ectopically expressed in HeLa cells with correct molecular weight. Fluorescence images showed as well that zebrafish LZTFL1 was localized in the cytoplasm. Furthermore, luciferase reporter assay indicated zebrafish LZTFL1 served as a negative regulator in the hedgehog signaling pathway. These data supported that zebrafish was a good model for understanding the biological roles of LZTFL1.