Effectiveness of zebrafish models in understanding human diseases-A review of models

Exploring the osteogenic potential of chitosan-quercetin bio-conjugate: In vitro and in vivo investigations in osteoporosis models

Anti-osteoporotic agents are clinically employed to improve bone health and prevent osteoporotic fractures. In the current study, we investigated the potential of chitosan-quercetin bio-conjugate as an anti-osteoporotic agent. The conjugate was prepared and characterized by FTIR and found notable interactions between chitosan and quercetin. Treating mouse MSCs with the bioconjugate in osteogenic conditions for a week led to elevated expression of differentiation markers Runx2, ALP, and Col-I, as determined by real-time PCR analysis. Evaluation at the cellular level using alizarin red staining demonstrated enhanced calcium deposition in MSCs following treatment with the bioconjugate. Likewise, ELISA analysis showed significantly elevated levels of secretory osteocalcin and osteonectin in groups treated with the conjugate. To broaden our comprehension, we utilized a zebrafish-based in vivo model of dexamethasone-induced osteoporosis to investigate bone regeneration. Toxicity profiling with zebrafish larvae confirmed the bio-conjugate's compatibility at a concentration of 25 μg/ml, underscoring the significance of finding the right dosage. Furthermore, in zebrafish models of osteoporosis, the bio-conjugate demonstrated significant potential for bone regeneration, as indicated by improved bone calcification, callus formation, and overall bone healing in a tail fin fracture model. Additionally, the study revealed that the bio-conjugate inhibited osteoclastic activity, leading to reduced TRAP activity and hydroxyproline release, suggesting its effectiveness in mitigating bone resorption. In conclusion, our research provides compelling evidence for the osteogenic capabilities of the chitosan-quercetin bio-conjugate, highlighting its promising applications in regenerative medicine and the treatment of conditions like osteoporosis.

Novel human neurodevelopmental and neurodegenerative disease associated with IRF2BPL gene variants-mechanisms and therapeutic avenues

Recently a broad range of phenotypic abnormalities related to the neurodevelopmental and neurodegenerative disorder NEDAMSS (Neurodevelopmental Disorder with Regression, Abnormal Movements, Loss of Speech, and Seizures) have been associated with rare single-nucleotide polymorphisms (SNPs) or insertion and deletion variants (Indel) in the intron-less gene IRF2BPL. Up to now, 34 patients have been identified through whole exome sequencing carrying different heterozygous pathogenic variants spanning the intron-less gene from the first polyglutamine tract at the N-terminus to the C3HC4 RING domain of the C-terminus of the protein. As a result, the phenotypic spectrum of the patients is highly heterogeneous and ranges from abnormal neurocognitive development to severe neurodegenerative courses with developmental and seizure-related encephalopathies. While the treatment of IRF2BPL-related disorders has focused on alleviating the patient's symptoms by symptomatic multidisciplinary management, there has been no prospect of entirely relieving the symptoms of the individual patients. Yet, the recent advancement of CRISPR-Cas9-derived gene editing tools, leading to the generation of base editors (BEs) and prime editors (PEs), provide an encouraging new therapeutic avenue for treating NEDAMSS and other neurodevelopmental and neurodegenerative diseases, which contain SNPs or smaller Indels in post-mitotic cell populations of the central nervous system, due to its ability to generate site-specific DNA sequence modifications without creating double-stranded breaks, and recruiting the non-homologous DNA end joining repair mechanism.

Modelling phenotypes, variants and pathomechanisms of syndromic diseases in different systems

In this review we describe different model organisms and systems that are commonly used to study syndromic disorders. Different use cases in modeling diseases, underlying pathomechanisms and specific effects of certain variants are elucidated. We also highlight advantages and limitations of different systems. Models discussed include budding yeast, the nematode worm, the fruit fly, the frog, zebrafish, mice and human cell-based systems.

Environmentally Relevant Concentrations of Triphenyl Phosphate (TPhP) Impact Development in Zebrafish

A common flame-retardant and plasticizer, triphenyl phosphate (TPhP) is an aryl phosphate ester found in many aquatic environments at nM concentrations. Yet, most studies interrogating its toxicity have used µM concentrations. In this study, we used the model organism zebrafish (Danio rerio) to uncover the developmental impact of nM exposures to TPhP at the phenotypic and molecular levels. At concentrations of 1.5-15 nM (0.5 µg/L-5 µg/L), chronically dosed 5dpf larvae were shorter in length and had pericardial edema phenotypes that had been previously reported for exposures in the µM range. Cardiotoxicity was observed but did not present as cardiac looping defects as previously reported for µM concentrations. The RXR pathway does not seem to be involved at nM concentrations, but the tbx5a transcription factor cascade including natriuretic peptides (nppa and nppb) and bone morphogenetic protein 4 (bmp4) were dysregulated and could be contributing to the cardiac phenotypes. We also demonstrate that TPhP is a weak pro-oxidant, as it increases the oxidative stress response within hours of exposure. Overall, our data indicate that TPhP can affect animal development at environmentally relevant concentrations and its mode of action involves multiple pathways.

Indigo dyes: Toxicity, teratogenicity, and genotoxicity studies in zebrafish embryos

Wastewater released by textile dyeing industries is a major source of pollution. Untreated wastewater released from indigo dyeing operations affects aquatic ecosystems and threatens their biodiversity. We have assessed the toxicity of natural and synthetic indigo dye in zebrafish embryos, using the endpoints of teratogenicity, genotoxicity, and histopathology. The zebrafish embryo toxicity test (ZFET) was conducted, exposing embryos to ten concentrations of natural and synthetic indigo dyes; the 96-hour LC50 values were approximately 350 and 300 mg/L, respectively. Both dyes were teratogenic, causing egg coagulation, tail detachment, yolk sac edema, pericardial edema, and tail bend, with no significant difference in effects between the natural and synthetic dyes. Both dyes were genotoxic (using comet assay for DNA damage). Real-time RT-PCR studies showed upregulation of the DNA-repair genes FEN1 and ERCC1. Severe histological changes were seen in zebrafish larvae following exposure to the dyes. Our results show that indigo dyes may be teratogenic and genotoxic to aquatic organisms, underscoring the need for development of sustainable practices and policies for mitigating the environmental impacts of textile dyeing.

Reversible Influence of Hemipiperazine Photochromism on the Early Development of Zebrafish Embryo

This study explores the potential of controlling organismal development with light by using reversible photomodulation of activity in bioactive compounds. Specifically, our research focuses on plinabulin 1, an inhibitor of tubulin dynamics that contains a photochromic motif called hemipiperazine. The two isomeric forms, Z-1 and E-1, can partially interconvert with light, yet show remarkable thermal stability in darkness. The Z-isomer exhibits higher cytotoxicity due to stronger binding to α-tubulin's colchicine site. The less toxic E-1 form, considered a "pro-drug", can be isolated in vitro and stored. Upon activation by blue or cyan light, it predominantly generates the more toxic Z-1 form. Here we demonstrate that 1 can effectively photomodulate epiboly, a critical microtubule-dependent cell movement during gastrulation in zebrafish embryos. This research highlights the potential of photomodulation for precise and reversible control of cellular activities and organismal development.

Sub-chronic exposure to paroxetine disrupts ecologically relevant behaviours in fish

The functional conservation of important selective serotonin reuptake inhibitor (SSRI) targets in non-target organisms raises concerns about their potential adverse effects on the ecosystems. Although the environmental levels of SSRIs like paroxetine (PAR) have risen, the knowledge regarding the effects of long-term exposure to PAR is limited. This study investigated the impact of sub-chronic exposure (21 days) to two sub-lethal concentrations of PAR (40 and 400 μg/L) on the behaviour of adult zebrafish in different scenarios: basal activity (under dark and light conditions), stress response (evoked by sudden light transitions) and stress response recovery. A new framework was employed for the integrative study of fish's swimming performance based on their innate ability to respond to light shifts. Several swimming-associated parameters (e.g., total swimming distance, time of inactivity, swimming angles) and thigmotaxis were monitored for an integrated analysis in each scenario. Data revealed reduced swimming activity, impaired behavioural response to stress and alterations in stress recovery of PAR-exposed fish. An anxiolytic effect was particularly noticeable in fish basal swimming activity in the dark at 400 μg/L and in the behavioural response to stress (from dark to light) and stress recovery (from light to dark) for organisms exposed to 40 μg/L. The detected PAR-induced behavioural modifications suggest a disruption of brain glucocorticoid signalling that may have implications at the individual level (e.g., changing behavioural responses to predators), with potential repercussions on the population and community levels. Therefore, the applied protocol proved sensitive in detecting behavioural changes induced by PAR.

Combined toxicity of trifloxystrobin and fluopyram to zebrafish embryos and the effect on bone development

Trifloxystrobin (TRI) is a methacrylate fungicide, and fluopyram (FLU) is a new pyridylethylbenzamide fungicide and nematicide. Both are often detected in water bodies and may be highly toxic to many aquatic organisms. Unfortunately, the aquatic biological risks of single FLU or a mixture of trifloxystrobin and fluopyram have not been reported. In this study, zebrafish was selected as the test organism to investigate the combined toxicity of trifloxystrobin and fluopyram to zebrafish. After zebrafish embryos exposed to three pesticide solutions, Alcian-blue staining, Alizarin-red staining and quantitative PCR (qPCR) were performed. The results indicated that 96h-LC50 of TRI was 0.159 mg·L-1 to zebrafish embryo, which was highly toxic. The 96h-LC50 of FLU to zebrafish embryos was 4.375 mg·L-1, being moderately toxic. The joint toxicity to zebrafish embryos(FLU at 96h-LC50 and TRI at 96h-LC50 in a 1:1 weight ratio to form a series of concentration treatment groups) was antagonistic. Both trifloxystrobin and fluopyram also inhibited the skeletal development of zebrafish and showed to be antagonistic. The results of qPCR indicated upregulations of different genes upon three different treatments. TRI mainly induced Smads up-expression, which may affect the BMP-smads pathway. FLU mainly induced an up-expression of extracellular BMP ligands and type I receptor (Bmpr-1a), which may affect the BMP ligand receptor pathway. The 1:1 mixture (weight ratio) of trifloxystrobin and fluopyram induced a reduction of the genes of extracellular BMP ligand (Smads) and type I receptor (Bmpr1ba), which may down-regulate BMP signaling and thus attenuating cartilage hyperproliferation, hypertrophy and mineralization. The results warren an interest in further studying the effect of the two fungicides in a mixture on zebrafish.

Ecotoxicological Effects of TiO2 P25 Nanoparticles Aqueous Suspensions on Zebrafish (Danio rerio) Eleutheroembryos

Among nanoparticles (NPs), titanium dioxide is one of the most highly manufactured worldwide and widely used in multiple products for both industrial use and personal care products. This increases the probability of release into aquatic environments, potentially affecting these ecosystems. The present study aimed to evaluate TiO2 P25 NP toxicity in zebrafish embryos and eleutheroembryos by evaluating LC50, hatching rate, embryo development, and chemical analysis of the TiO2 concentration accumulated in eleutheroembryo tissues. Zebrafish embryos ~2 h post-fertilization (hpf) were exposed to 75, 100, 150, 200, and 250 mg/L TiO2 P25 NPs for 48 and 96 h. A total of 40-60 embryos were placed in each Petri dish for the respective treatments. Three replicates were used for each treatment group. Ti4+ concentrations were determined by inductively coupled plasma optical emission spectrometry (ICP-OES), and a conversion factor was used to calculate the TiO2 concentrations in the tissues. The highest calculated concentrations of TiO2 in zebrafish larvae were 1.0199 mg/L after 48 h and 1.2679 mg/L after 96 h of exposure. The toxicological results indicated that these NPs did not have a significant effect on the mortality and hatching of zebrafish embryos but did have an effect on their development. LC20 and LC30 were determined experimentally, and LC50 and LC80 were estimated using four different methods. Up to 11% of embryos also presented physical malformations. These effects can be detrimental to a species and affect ecosystems. Physical malformations were observed in all treatments, indicating teratogenic effects.

Developmental Toxicity of PEDOT:PSS in Zebrafish: Effects on Morphology, Cardiac Function, and Intestinal Health

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is a conductive polymer commonly used in various technological applications. However, its impact on aquatic ecosystems remains largely unexplored. In this study, we investigated the toxicity effects of PEDOT:PSS on zebrafish. We first determined the lethal concentration (LC50) of PEDOT:PSS in zebrafish and then exposed AB-type zebrafish embryos to different concentrations of PEDOT:PSS for 120 h. Our investigation elucidated the toxicity effects of zebrafish development, including morphological assessments, heart rate measurements, behavioral analysis, transcriptome profiling, and histopathological analysis. We discovered that PEDOT:PSS exhibited detrimental effects on the early developmental stages of zebrafish, exacerbating the oxidative stress level, suppressing zebrafish activity, impairing cardiac development, and causing intestinal cell damage. This study adds a new dimension to the developmental toxicity of PEDOT:PSS in zebrafish. Our findings contribute to our understanding of the ecological repercussions of PEDOT:PSS and highlight the importance of responsible development and application of novel materials in our rapidly evolving technological landscape.

MEndoB, a chimeric lysin featuring a novel domain architecture and superior activity for the treatment of staphylococcal infections

Bacterial infections are a growing global healthcare concern, as an estimated annual 4.95 million deaths are associated with antimicrobial resistance (AMR). Methicillin-resistant Staphylococcus aureus is one of the deadliest pathogens and a high-priority pathogen according to the World Health Organization. Peptidoglycan hydrolases (PGHs) of phage origin have been postulated as a new class of antimicrobials for the treatment of bacterial infections, with a novel mechanism of action and no known resistances. The modular architecture of PGHs permits the creation of chimeric PGH libraries. In this study, the chimeric enzyme MEndoB was selected from a library of staphylococcal PGHs based on its rapid and sustained activity against staphylococci in human serum. The benefit of the presented screening approach was illustrated by the superiority of MEndoB in a head-to-head comparison with other PGHs intended for use against staphylococcal bacteremia. MEndoB displayed synergy with antibiotics and rapid killing in human whole blood with complete inhibition of re-growth over 24 h at low doses. Successful treatment of S. aureus-infected zebrafish larvae with MEndoB provided evidence for its in vivo effectiveness. This was further confirmed in a lethal systemic mouse infection model in which MEndoB significantly reduced S. aureus loads and tumor necrosis factor alpha levels in blood in a dose-dependent manner, which led to increased survival of the animals. Thus, the thorough lead candidate selection of MEndoB resulted in an outstanding second-generation PGH with in vitro, ex vivo, and in vivo results supporting further development.IMPORTANCEOne of the most pressing challenges of our era is the rising occurrence of bacteria that are resistant to antibiotics. Staphylococci are prominent pathogens in humans, which have developed multiple strategies to evade the effects of antibiotics. Infections caused by these bacteria have resulted in a high burden on the health care system and a significant loss of lives. In this study, we have successfully engineered lytic enzymes that exhibit an extraordinary ability to eradicate staphylococci. Our findings substantiate the importance of meticulous lead candidate selection to identify therapeutically promising peptidoglycan hydrolases with unprecedented activity. Hence, they offer a promising new avenue for treating staphylococcal infections.

Design of an automated robotic microinjection system for batch injection of zebrafish embryos and larvae

This paper presents the design of a vision-based automated robotic microinjection system for batch injection of both zebrafish embryos and larvae. A novel visual recognition algorithm based on an automatic threshold and excessive dilatation is introduced to accurately identify the center of zebrafish embryos and larval yolks. A corresponding software system is developed using the producer-consumer model as the framework structure, and a friendly user interface is designed to allow operators to choose from a range of desired functions according to their different needs. In addition, a novel microstructural agarose device is designed and fabricated to simultaneously immobilize mixed batches of embryos and larvae. Moreover, a prototype microinjection system is fabricated by integrating hardware devices with visual algorithms. An experimental study is conducted to verify the performance of the robotic microinjection system. The results show that the reported system can accurately identify zebrafish embryos and larvae and efficiently complete batch microinjection tasks of the mixtures with an injection success rate of 92.05% in 13.88 s per sample. Compared with manual and existing microinjection systems, the proposed system demonstrates the merits of versatility, excellent efficiency, high success rate, high survival rate, and sufficient stability.

Generation of a Zebrafish Knock-In Model Recapitulating Childhood ETV6::RUNX1-Positive B-Cell Precursor Acute Lymphoblastic Leukemia

Approximately 25% of children with B-cell precursor acute lymphoblastic leukemia (pB-ALL) harbor the t(12;21)(p13;q22) translocation, leading to the ETV6::RUNX1 (E::R) fusion gene. This translocation occurs in utero, but the disease is much less common than the prevalence of the fusion in newborns, suggesting that secondary mutations are required for overt leukemia. The role of these secondary mutations remains unclear and may contribute to treatment resistance and disease recurrence. We developed a zebrafish model for E::R leukemia using CRISPR/Cas9 to introduce the human RUNX1 gene into zebrafish etv6 intron 5, resulting in E::R fusion gene expression controlled by the endogenous etv6 promoter. As seen by GFP fluorescence at a single-cell level, the model correctly expressed the fusion protein in the right places in zebrafish embryos. The E::R fusion expression induced an expansion of the progenitor cell pool and led to a low 2% frequency of leukemia. The introduction of targeted pax5 and cdkn2a/b gene mutations, mimicking secondary mutations, in the E::R line significantly increased the incidence in leukemia. Transcriptomics revealed that the E::R;pax5mut leukemias exclusively represented B-lineage disease. This novel E::R zebrafish model faithfully recapitulates human disease and offers a valuable tool for a more detailed analysis of disease biology in this subtype.

Zebrafish as an Emerging Model for Sarcopenia: Considerations, Current Insights, and Future Directions

Sarcopenia poses a significant challenge to public health and can severely impact the quality of life of aging populations. Despite extensive efforts to study muscle degeneration using traditional animal models, there is still a lack of effective diagnostic tools, precise biomarkers, and treatments for sarcopenia. Zebrafish models have emerged as powerful tools in biomedical research, providing unique insights into age-related muscle disorders like sarcopenia. The advantages of using zebrafish models include their rapid growth outside of the embryo, optical transparency during early developmental stages, high reproductive potential, ease of husbandry, compact size, and genetic tractability. By deepening our understanding of the molecular processes underlying sarcopenia, we may develop novel diagnostic tools and effective treatments that can improve the lives of aging individuals affected by this condition. This review aims to explore the unique advantages of zebrafish as a model for sarcopenia research, highlight recent breakthroughs, outline potential avenues for future investigations, and emphasize the distinctive contributions that zebrafish models offer. Our research endeavors to contribute significantly to address the urgent need for practical solutions to reduce the impact of sarcopenia on aging populations, ultimately striving to enhance the quality of life for individuals affected by this condition.

Kif21a deficiency leads to impaired glomerular filtration barrier function

The renal glomerulus represents the major filtration body of the vertebrate nephron and is responsible for urine production and a number of other functions such as metabolic waste elimination and the regulation of water, electrolyte and acid-base balance. Podocytes are highly specialized epithelial cells that form a crucial part of the glomerular filtration barrier (GFB) by establishing a slit diaphragm for semipermeable plasma ultrafiltration. Defects of the GFB lead to proteinuria and impaired kidney function often resulting in end-stage renal failure. Although significant knowledge has been acquired in recent years, many aspects in podocyte biology are still incompletely understood. By using zebrafish as a vertebrate in vivo model, we report a novel role of the Kinesin-like motor protein Kif21a in glomerular filtration. Our studies demonstrate specific Kif21a localization to the podocytes. Its deficiency resulted in altered podocyte morphology leading to podocyte foot process effacement and altered slit diaphragm formation. Finally, we proved considerable functional consequences of Kif21a deficiency by demonstrating a leaky GFB resulting in severe proteinuria. Conclusively, our data identified a novel role of Kif21a for proper GFB function and adds another piece to the understanding of podocyte architecture and regulation.

Screening of Tnfaip1-Interacting Proteins in Zebrafish Embryonic cDNA Libraries Using a Yeast Two-Hybrid System

TNFAIP1 regulates cellular biological functions, including DNA replication, DNA repair, and cell cycle, by binding to target proteins. Identification of Tnfaip1-interacting proteins contributes to the understanding of the molecular regulatory mechanisms of their biological functions. In this study, 48 hpf, 72 hpf, and 96 hpf wild-type zebrafish embryo mRNAs were used to construct yeast cDNA library. The library titer was 1.12 × 107 CFU/mL, the recombination rate was 100%, and the average length of the inserted fragments was greater than 1000 bp. A total of 43 potential interacting proteins of Tnfaip1 were identified using zebrafish Tnfaip1 as a bait protein. Utilizing GO functional annotation and KEGG signaling pathway analysis, we found that these interacting proteins are mainly involved in translation, protein catabolic process, ribosome assembly, cytoskeleton formation, amino acid metabolism, and PPAR signaling pathway. Further yeast spotting analyses identified four interacting proteins of Tnfaip1, namely, Ubxn7, Tubb4b, Rpl10, and Ybx1. The Tnfaip1-interacting proteins, screened from zebrafish embryo cDNA in this study, increased our understanding of the network of Tnfaip1-interacting proteins during the earliest embryo development and provided a molecular foundation for the future exploration of tnfaip1's biological functions.

Assessing Drug Administration Techniques in Zebrafish Models of Neurological Disease

Neurological diseases, including neurodegenerative and neurodevelopmental disorders, affect nearly one in six of the world's population. The burden of the resulting deaths and disability is set to rise during the next few decades as a consequence of an aging population. To address this, zebrafish have become increasingly prominent as a model for studying human neurological diseases and exploring potential therapies. Zebrafish offer numerous benefits, such as genetic homology and brain similarities, complementing traditional mammalian models and serving as a valuable tool for genetic screening and drug discovery. In this comprehensive review, we highlight various drug delivery techniques and systems employed for therapeutic interventions of neurological diseases in zebrafish, and evaluate their suitability. We also discuss the challenges encountered during this process and present potential advancements in innovative techniques.

Data on plasma cortisol levels in nibbler fish Girella punctata reared under high-density conditions in either surface seawater or deep ocean water

Deep ocean water (DOW) is the water obtained from depth of >200 m below the surface of Earth's oceans and is characterized by rich nutrients and cleanliness [1,2]. We have recently reported that DOW suppresses the high-density-induced increase of plasma cortisol levels (i.e., a stress marker) in Japanese flounder (Paralichthys olivaceus) [1]. The current study aimed to examine whether the cortisol-reducing effect of DOW was observed in other marine organisms as well by comparing the plasma cortisol levels of nibbler fish Girella punctata reared under high-density conditions between surface seawater (SSW) and DOW. The nibbler fish were caught from Tsukumo Bay of Noto Peninsula (Ishikawa Prefecture, Japan). The DOW was obtained from seawater 320 m below the Noto Bay surface at a facility (Aquas Noto, Ishikawa Prefecture, Japan), whereas SSW was obtained from Tsukumo Bay (Noto Peninsula, Ishikawa Prefecture). The dissolved oxygen was maintained at approximately 7 mg/L in DOW as well as in SSW. Before they were transferred to the high-density condition, nibbler fish were acclimated in SSW at 20°C for 1 week at a mean density of 100 g/62.5 L. To expose them to the high-density stress, each of fish was kept at a density of 10 kg/m³ in a single aquarium (60 × 25 × 30 cm) containing either SSW or DOW (n = 8). Subsequently, the fish were reared with SSW or DOW for 10 days at 20°C ± 1°C under a 12:12-h light-dark cycle. A heparin containing syringe was used to obtain the blood samples from the caudal vessels of the fish anesthetized with a 0.04% 2-phenoxyethanol (FUJIFILM Wako Pure Chemical Corporation). The blood sampling was performed on days 0, 5, and 10 after rearing in the small aquaria. The plasma samples were prepared from the collected blood by centrifuging it at 5200 × g for 5 min and the cortisol concentrations were determined using an enzyme-linked immunosorbent assay (ELISA) kit (Cosmo Bio Co. Ltd., Tokyo, Japan) from those samples. The plasma cortisol concentration of nibbler fish reared in SSW on day 10 was significantly higher than that on day 0, whereas those reared in DOW did not show significant difference on the respective days. The current data contributes to the generalization of the cortisol-reducing effect of DOW on fish, which has been proposed in Japanese flounder [1]. These data could be used for developing and designing experiments to analyze the mechanisms underlying the cortisol-reducing effects by using small fish such as zebrafish, a well-established animal model.

Identifying knowledge gaps in understanding the effects of selective serotonin reuptake inhibitors (SSRIs) on fish behaviour

Selective serotonin reuptake inhibitors (SSRIs) are a class of antidepressants increasingly prescribed to treat patients with clinical depression. As a result of the significant negative impact of the COVID-19 pandemic on the population's mental health, its consumption is expected to increase even more. The high consumption of these substances leads to their environmental dissemination, with evidence of their ability to compromise molecular, biochemical, physiological, and behavioural endpoints in non-target organisms. This study aimed to provide a critical review of the current knowledge regarding the effects of SSRI antidepressants on fish ecologically relevant behaviours and personality-dependent traits. A literature review shows limited data concerning the impact of fish personality on their responses to contaminants and how such responses could be influenced by SSRIs. This lack of information may be attributable to a lack of widely adopted standardized protocols for evaluating behavioural responses in fish. The existing studies examining the effects of SSRIs across various biological levels overlook the intra-specific variations in behaviour and physiology associated with different personality patterns or coping styles. Consequently, some effects may remain undetected, such as variations in coping styles and the capacity to handle environmental stressors. This oversight could potentially result in long-term effects with ecological implications. Data support the need for more studies to understand the impact of SSRIs on personality-dependent traits and how they may impair fitness-related behaviours. Given the considerable cross-species similarity in the personality dimensions, the collected data may allow new insights into the correlation between personality and animal fitness.

Different housing conditions for zebrafish: what are the effects?

Zebrafish is a popular experimental model in several research areas but little is known about the effects of using different strains or housing conditions. Poor control of genetic background and housing conditions could affect experimental results and data reproducibility. Here we investigated the effects of two possible sources of variation on zebrafish behaviour: fish origin and environmental parameters (light intensity, water temperature and noise). Zebrafish behaviour was then examined using the 'novel tank test', one of the most common paradigms used to assess anxiety-like behaviours in zebrafish. Our results show that an increase in light intensity alters fish behaviour, particularly freezing duration and distance from the bottom of the tank, indicating increased anxiety. Swimming activity increased at the lowest temperature (25°C). However, different levels of background noise did not cause any significant changes in behaviour. Differences were also found between zebrafish strains and populations: while the AB strain from laboratory 1 was minimally influenced by variation in holding conditions, the AB strain from laboratory 2 was highly affected by changes in temperature, light, and background noise. Our study shows that variation in strains and holding conditions can significantly influence the results of behavioural testing and should be carefully considered in the experimental design and properly reported to improve data interpretation and reproducibility.

Principles of Zebrafish Nephron Segment Development

Nephrons are the functional units which comprise the kidney. Each nephron contains a number of physiologically unique populations of specialized epithelial cells that are organized into discrete domains known as segments. The principles of nephron segment development have been the subject of many studies in recent years. Understanding the mechanisms of nephrogenesis has enormous potential to expand our knowledge about the basis of congenital anomalies of the kidney and urinary tract (CAKUT), and to contribute to ongoing regenerative medicine efforts aimed at identifying renal repair mechanisms and generating replacement kidney tissue. The study of the zebrafish embryonic kidney, or pronephros, provides many opportunities to identify the genes and signaling pathways that control nephron segment development. Here, we describe recent advances of nephron segment patterning and differentiation in the zebrafish, with a focus on distal segment formation.