Search

Heat shock factors (HSFs) are transcription factors that regulate responses to environmental changes and play roles in physiological mechanisms like spermatogenesis. This study analyzed the HSF gene family and their expression profiles in the European eel under different environmental conditions and during testis maturation. Six HSF genes were identified in the studied vertebrates, in which the eel presents two HSF1 paralogs (HSF1a and HSF1b), likely resulting from the teleost whole-genome duplication event, while only one paralog is present for the other HSF (HSF2, HSF4, and HSF5). All five HSF genes were highly expressed in the testis, but some were also detected in the brain, intestine, and gills. Our findings showed that HSF1 changed their expression in response to different temperature and salinity conditions, suggesting that these may support males in perceiving the temperature and salinity changes possibly found during reproductive migration. During hCGrec-induced spermatogenesis, HSF genes presented a decreasing expression profile throughout testis maturation (with significant differences in HSF1a and HSF4), except HSF5, which showed the highest levels after 4 weeks of hormonal treatment. Our study indicates that HSF genes are potentially implicated in the response to environmental changes perception and during gonadal maturation. [ABSTRACT FROM AUTHOR]

Trophic factors, such as neurotrophins, are fundamental for cellular processes including differentiation, growth, survival, and regeneration. These molecules exhibit significant morphological and phylogenetic conservation throughout the animal kingdom, indicating conserved functions. In fish, the oldest and most diverse group of vertebrates, neurotrophins, and their receptors play pivotal roles not only within the central nervous system but also in various peripheral tissues. They are distributed in mechanosensory, muscle, skin, respiratory, circulatory, digestive, endocrine, urinary, reproductive, and immune systems, suggesting their involvement in the development and maintenance of all tissues/organs/systems. Despite this broad distribution, studies focusing on these molecules outside of the central nervous system have been limited to just 12 fish species. These investigations have revealed diverse expression patterns across different ages and tissues/organs/systems, expanding our comprehension of their functions beyond the central and peripheral nervous systems. Notably, BDNF and NT-3 are prominently expressed outside the central nervous system, particularly in mechanosensory and digestive tissues, whereas NGF is predominantly observed in mechanosensory and urinary systems. The expression and localization of neurotrophins and their receptors vary among organs, underscoring tissue-specific roles. Further research is imperative to decipher the precise functions and mechanisms of action of neurotrophins and their receptors in diverse fish tissues. Enhanced efforts are needed to include a broader range of fish species in these studies to advance our understanding of these agents in complex vertebrates, thereby shedding light on tissue development, regeneration, and maintenance, with potential implications for addressing organ-related issues. [ABSTRACT FROM AUTHOR]

NLRP3 inflammasome activation is pivotal for cytokine secretion and pyroptosis in response to diverse stimuli, playing a crucial role in innate immunity. While extensively studied in mammals, the regulatory mechanisms governing NLRP3 activation in non-mammalian vertebrates remain largely unexplored. Teleosts, as basal vertebrates, represent an ideal model for exploring the evolutionary trajectory of inflammasome regulation. In this study, ABE assays, confocal microscopy, and biochemical analyses were applied to systematically characterize the mechanisms underlying NLRP3 inflammasome in teleosts, using large yellow croakers (Larimichthys crocea, Lc) and zebrafish (Danio rerio, Dr) as representative models. Our findings revealed a previously unrecognized palmitoylation-dependent regulatory mechanism essential for teleost NLRP3 activation. Specifically, zDHHC18- mediated palmitoylation at a teleost-specific cysteine residue (C946 in LcNLRP3, C1037 in DrNLRP3) was required for the translocation of NLRP3 to the dispersed trans-Golgi network, facilitating its subsequent recruitment to the microtubule-organizing center. This membrane trafficking was crucial for inflammasome assembly and downstream inflammatory responses. These findings provide new insights into the distinct regulatory mechanisms of NLRP3 activation in teleosts, highlighting an evolutionary divergence that contributes to innate immunity adaptation in early vertebrates. [ABSTRACT FROM AUTHOR]

Intermuscular bone（IB）is one of three morphological characters of teleosts, and is becoming an obstacle for fish processing. Recently, some cyprinid fish without IB have been generated by Crispr/Cas9 technology, will be very helpful for our fresh fish culture in China. So far bmp6 and runx2b have been determined as key genes for the development of IBs, however, upstream signal pathway to regulate the development is not sure, and the complex evolution of IBs in teleost is in lack of understanding. This review first gives us a basic introduction on the IB types, distribution, and the role in swimming, then focuses on the research advance on IB developmental model, cellular origin, and upstream regulation factors. Finally, a preliminary hypothesis is proposed in this review to explain IB evolution in teleosts, indicating IB evolution potential associations between axial muscle diversification and locomotion adaptive radiations that generated modern teleost lineages. [ABSTRACT FROM AUTHOR]

Histopathological studies of parasitic infections in fish from the natural environment of Brazilian Amazon, are quite scarce. In this study, we investigated the histopathological changes of the proximal intestine of specimens of the Amazonian fish Hoplias malabaricus infected by the hematophagous nematode Procamallanus (Spirocamallanus) paraensis. The prevalence of the infection was 60%, with an average abundance of 1.46 and an average intensity of 2.43 parasites/fish. No significant difference was observed in the prevalence of infection and fish size or sex, but larger fish showed greater infection intensity, which was also significantly higher in male hosts. Histological sections of the proximal intestine showed reduction and loss of the epithelial lining, exposure of the lamina propria where the nematode interacts with the intestine wall, through the insertion of the buccal capsule and fish cellular debris in the intestinal lumen. In addition, areas with bleeding and inflammatory infiltrate were observed, but no changes or presence of parasite structures were observed in the other tunics of the intestinal wall. [ABSTRACT FROM AUTHOR]

Hydrostatic pressure is a global sensory cue exploited by fish to navigate in the vertical dimension. Unlike other navigational cues in the horizontal plane that usually require learning and memory to determine location, hydrostatic pressure signals the absolute position along the vertical axis. Recently, it was shown that fish can use hydrostatic signals to navigate. It remains unclear, however, which brain regions are involved in processing this signal. Here, we tested whether the dorsomedial and lateral parts of the pallium, two regions that were found to be critical in horizontal navigation, are also critical for hydrostatic cue detection in goldfish. The results show that lesions to both these regions cause fish performance to deteriorate to chance values, indicating that both regions play an important role in processing hydrostatic pressure cues. These findings thus contribute to the rapidly growing body of knowledge on teleost navigation in space.

Edwardsiella piscicida is a Gram-negative intracellular pathogen. Currently, the immune evasion strategies of E. piscicida are not yet fully understood. In this study, we revealed that E. piscicida exploited mitophagy to enhance its intracellular survival in grass carp (Ctenopharyngodon idella) monocytes/macrophages. The results showed that in E. piscicida -infected cells, there was a significant loss of mitochondrial membrane potential and a marked increase in the production of mitochondrial reactive oxygen species (mtROS), indicating the damage to the mitochondria in the infected cells. Furthermore, fluorescence confocal images presented that E. piscicida infection elicited the colocalization of mitochondria with microtubule-associated protein 1 light chain 3 (LC3, a key marker molecule of autophagy) and lysosomes, suggesting the occurrence of mitophagy. This notion was supported by the findings that E. piscicida significantly stimulated LC3-II protein and damped Tom20 (a marker molecule of mitochondria) protein levels. Subsequently, a mitophagy inducer carbonyl cyanide m -chlorophenyl hydrazine (CCCP) and a mitophagy inhibitor mitochondrial division inhibitor 1 (Mdivi-1) were used to evaluate the role of mitophagy in modulating the intracellular survival of E. piscicida. The results revealed that CCCP significantly promoted intracellular survival of E. piscicida , whereas Mdivi-1 hindered the bacterial growth. Moreover, Mdivi-1 further increased the production of bacteria-induced mitochondrial ROS in an additive manner. In particular, CCCP suppressed and Mdivi-1 promoted the colocalization of LC3-II with E. piscicida , implying that E. piscicida -triggered mitophagy to facilitate its growth probably by subverting the autophagy targeting this bacterium, a previously known clearance pathway of E. piscicida. Overall, our findings suggest a new survival strategy employed by E. piscicida within fish monocytes/macrophages. • Edwardsiella piscicida infection results in mitochondrial damage. • Inducible mitophagy enhances the intracellular survival of Edwardsiella piscicida. • Edwardsiella piscicida employs mitophagy to mitigate mitochondrial ROS production. • Mitophagy facilitates E. piscicida growth probably by subverting autophagy-mediated defense. [ABSTRACT FROM AUTHOR]

It is known that the insulin-like growth factor (Igf) system is involved in gonadal development and, in turn, reproduction in vertebrates. In this study, the circulating levels of Igf-1 and follicle-stimulating hormone (Fsh) were assessed as physiological signals related to gonadal maturation stage in juvenile male European sea bass at 1 year of age. The seasonal profiles of Igf-1 and Fsh were analyzed in non-precocious (NP) and precocious (PR) fish during the early onset of puberty. Subsequently, gonadal expression patterns of the three igf genes and their two receptors, igf-1r and igf-2r , were studied during their first year of life. The analysis was continued to evaluate the mRNA expression profiles of three genes (sox17 , scf , nf2) mediating spermatogenesis progression. Collectively, these results demonstrated that PR males have higher circulating levels of Igf-1 as compared to NP fish before and during the putative gonadal development period (PGD). Plasma Fsh levels were significantly higher in PR males as compared to NP fish before the start of the PGD period, although this was followed by a decrease in Fsh levels and a subsequent recovery, coinciding with the reproductive season (February). Results showed that the total variance associated with the appearance of precocity may be explained by the contribution of factors such as body size and plasma levels of Igf-1, Fsh and sex steroids in male sea bass. Expression of igfs was high during stage I, and this was significantly correlated with the expression of genes related to cell cycle progression, including sox17 , scf and nf2. Finally, the decreased expression of all these gonadal factors in precocious animals suggests their potential involvement in regulating the proliferative growth of spermatogonia and supporting cells during the early stages of spermatogenesis, thus evoking the onset of puberty in male sea bass. • Igf-1 and Fsh plasma levels are indicators of early puberty in juvenile male sea bass. • The igf/igfr system shows differential gene expression, depending on the testicular stage. • Gonadal expression of igfs is positively correlated with proliferation-related genes. • igfs , sox17 , scf and nf2 are involved in spermatogenesis progression in sea bass. [ABSTRACT FROM AUTHOR]

There are numerous fish diseases that affect the central nervous system. However, few studies have investigated the immune cells and immunological responses of fish brains. Meanwhile, microglial cells, as the brain's first line of defense, play a vital role in neuroimmunology. Furthermore, CD83 is a co-stimulatory protein that regulates immunological responses and the activation of dendritic cells and macrophages. Although CD83 expression has been linked to the initial activation of microglia in various disease scenarios in mammals, its role in teleost microglial biology remains unclear. In a recent investigation, we discovered that Ginbuna crucian carp (Gb) contains two CD83 homologs (GbCD83 and GbCD83-L). In this study, we used modified procedures of mouse-based macrophage culture from the brain and kidney to identify that GbCD83-L is highly expressed by the brain microglia-like cells and kidney-resident macrophages (KRMs) at both the protein and gene levels. Interestingly, GbCD83-L was considerably elevated in the microglia-like cells and KRMs after 24 h of lipopolysaccharide stimulation. These findings provide the first evidence of CD83 as a potential marker for active microglia and KRMs in teleosts, thus making it a crucial regulator in fish neuroimmunology and a candidate for future immunomodulatory applications in aquaculture. • Brain and kidney macrophages exhibit differences in morphology and cell behavior. • GbCD83-L is highly expressed in both microglia-like cells and kidney-resident macrophages. • GbCD83-L expression is upregulated in microglia-like cells and KRMs post-LPS stimulation. • Expression profiles suggest the potential of CD38 as an immune stimulator. [ABSTRACT FROM AUTHOR]

Transcriptome analysis has become a central tool in evolutionary and functional genomics. However, variation among biological samples and analysis techniques can greatly influence results, potentially compromising insights into the phenomenon under study. Here, we evaluate differences in the brain transcriptome between female and male Gulf pipefish (Syngnathus scovelli). We perform comparisons between results from entire pipelines for brain transcriptome assembly, quantification, and analysis. We also offer a unique biological comparison between two sampling instances (Redfish Bay: n = 15, Port Lavaca: n = 7). Our results demonstrate crucial shortcomings with current experimental approaches. We found high variation within our results that was driven by both technical differences between pipelines and biological differences between pipefish samples. In our analysis of highly expressed genes, we found that the choice of methods influenced the degree of contamination or noise included in the identified genes. Notably, genes identified within the same pipeline were more similar than any other comparison. Our differential expression analysis revealed that both methodology and sampling location influenced the quantity and consistency of statistically significant transcripts. In the context of these results, we offer modifications to current practices that may increase the robustness of transcriptome-based conclusions. In particular, the use of a reference-guided assembly and an increase in sample sizes are likely to improve resistance to noise or error., (© The American Genetic Association. 2024.)

Understanding the immune response in fish through transcriptomic and microRNA (miRNA) profiling may unlock critical insights into disease resistance mechanisms. The objective of the present study was to examine the immune modulation of the European seabass (Dicentrarchus labrax) following bacterial infection and vaccination. Therefore, sequencing of circulating miRNA isolated from blood serum and 3'UTR transcriptome sequencing of head kidney was conducted. In the infected fish 19 miRNAs were found to be differentially expressed. This included two novel miRNAs exhibiting high levels in the infected fish. Regarding circulating miRNAs following vaccination, three specific miRNAs have been identified that demonstrated a substantial increase in expression. Two of them, miR-216b and miR-30a-5p, have been documented to possess the capacity to delay the progression of viral infections. 3'UTR sequencing analysis of the infected fish revealed no significant enrichment of down-regulated transcripts. However, there was a significant enrichment of up-regulated transcripts related to ribosome biogenesis and protein processing. In vaccinated fish up-regulated transcripts did not demonstrate substantial enrichment. Down-regulated genes on the other hand were involved in cytoskeleton organization and apoptosis, indicating that cellular disruption might be a potential hindrance to effective immunity. Overall, these results provide first insights into the progression and regulation of host immune responses to pathogen infection and vaccination. Moreover, the detection of in total 13 differential expressed circulating miRNAs, including regulators of critical innate immunity-related genes such as Toll-like receptor 18, suggests a potential for circulating miRNAs to play a significant role in the post-transcriptional control of fish immune defenses., (Copyright © 2025 The Authors. Published by Elsevier Ltd.. All rights reserved.)

The precise control of jaw movements during vertebrate predatory behaviour is crucial for successful prey capture. In mammals, the movement patterns associated with orofacial movements, have been investigated via long-lasting intracortical microstimulation, and revealed a cortical contribution of integrated jaw movements to prey capture. However, little is known regarding the role of the pallium, a homologue of the mammalian cortex, in the control of jaw movements in anamniotes, such as fish and amphibians. Here, we therefore investigated the pallial involvement in the orobranchial movements using Odontobutis obscura, a bottom-dwelling fish, as a case study. Electrical microstimulation of the pallial surface elicited an integrated feeding motor program with a jaw opening‒closure sequence combined with a closure of the operculums (gills). We could also evoke a sustained jaw closure. Furthermore, the effective stimulation sites for the two kinematic patterns were found to be primarily distributed in the caudomedial part of the dorsal pallium. We also observed associations between opercular movements and the two kinematic patterns, and recorded the prey capture composed of several distinct phases, approach, fixation, snapping and withdrawing backwards. In the snapping, jaw opening and closure was combined with gill movements. These findings suggest evolutionary continuity in the neural mechanisms underlying predatory behaviours across vertebrates, from teleosts to mammals., (© 2025. Published by The Company of Biologists.)

NLRP3 inflammasome activation is pivotal for cytokine secretion and pyroptosis in response to diverse stimuli, playing a crucial role in innate immunity. While extensively studied in mammals, the regulatory mechanisms governing NLRP3 activation in non-mammalian vertebrates remain largely unexplored. Teleosts, as basal vertebrates, represent an ideal model for exploring the evolutionary trajectory of inflammasome regulation. In this study, ABE assays, confocal microscopy, and biochemical analyses were applied to systematically characterize the mechanisms underlying NLRP3 inflammasome in teleosts, using large yellow croakers ( Larimichthys crocea , Lc ) and zebrafish ( Danio rerio , Dr ) as representative models. Our findings revealed a previously unrecognized palmitoylation-dependent regulatory mechanism essential for teleost NLRP3 activation. Specifically, zDHHC18-mediated palmitoylation at a teleost-specific cysteine residue (C946 in Lc NLRP3, C1037 in Dr NLRP3) was required for the translocation of NLRP3 to the dispersed trans-Golgi network, facilitating its subsequent recruitment to the microtubule-organizing center. This membrane trafficking was crucial for inflammasome assembly and downstream inflammatory responses. These findings provide new insights into the distinct regulatory mechanisms of NLRP3 activation in teleosts, highlighting an evolutionary divergence that contributes to innate immunity adaptation in early vertebrates.

The paraphyletic group referred to as fishes represents several extant and extinct classes that demonstrate the greatest diversity and abundance of any of the vertebrates on the Earth. Anatomically and physiologically, the systems of fish are comparable to those of other vertebrates and the thyroid and hypothalamic-pituitary-thyroid (HPT) axis are no exceptions. This article reviews the current literature on thyroid endocrinology of elasmobranch and teleost fishes with an emphasis on relevance to clinical management and highlights some of the anatomic and physiologic differences of the HPT axis in fishes., Competing Interests: Disclosure The authors have nothing to disclose., (Copyright © 2024 Elsevier Inc. All rights reserved.)