The maternal control in the embryonic development of zebrafish

Parental exposure to antidepressants has lasting effects on offspring? A case study with zebrafish

Fish have common neurotransmitter pathways with humans, exhibiting a significant degree of conservation and homology. Thus, exposure to fluoxetine makes fish potentially susceptible to biochemical and physiological changes, similarly to what is observed in humans. Over the years, several studies demonstrated the potential effects of fluoxetine on different fish species and at different levels of biological organization. However, the effects of parental exposure to unexposed offspring remain largely unknown. The consequences of 15-day parental exposure to relevant concentrations of fluoxetine (100 and 1000 ng/L) were assessed on offspring using zebrafish as a model organism. Parental exposure resulted in offspring early hatching, non-inflation of the swimming bladder, increased malformation frequency, decreased heart rate and blood flow, and reduced growth. Additionally, a significant behavioral impairment was also found (reduced startle response, basal locomotor activity, and altered non-associative learning during early stages and a negative geotaxis and scototaxis, reduced thigmotaxis, and anti-social behavior at later life stages). These behavior alterations are consistent with decreased anxiety, a significant increase in the expression of the monoaminergic genes slc6a4a (sert), slc6a3 (dat), slc18a2 (vmat2), mao, tph1a, and th2, and altered levels of monoaminergic neurotransmitters. Alterations in behavior, expression of monoaminergic genes, and neurotransmitter levels persisted until offspring adulthood. Given the high conservation of neuronal pathways between fish and humans, data show the possibility of potential transgenerational and multigenerational effects of pharmaceuticals' exposure. These results reinforce the need for transgenerational and multigenerational studies in fish, under realistic scenarios, to provide realistic insights into the impact of these pharmaceuticals.

Developmental cardiotoxicity of 4,5-dichloro-2-n-octyl-4-isothiazolin-3-one (DCOIT) in marine medaka (Oryzias melastigma)

The application of 4,5-dichloro-2-n-octyl-4-isothiazolin-3-one (DCOIT) as an antifouling biocide causes high toxicity to non-target marine organisms. To examine the developmental cardiotoxicity and mechanisms of DCOIT, we concurrently performed sub-chronic exposure and life-cycle exposure experiments using marine medaka embryos. After sub-chronic exposure to DCOIT at 1, 3, 10, and 33 μg/L, cardiac defects were caused by upregulation of cardiac gene transcriptions, decreasing heart size, and accelerating heartbeat. Hyperthyroidism in medaka larvae was identified as the cause of developmental cardiotoxicity of DCOIT sub-chronic exposure. In addition, parental life-cycle exposure to 1, 3, and 10 μg/L DCOIT led to transgenerational impairment of cardiogenesis in offspring medaka. A crossbreeding strategy discriminated a concentration-dependent mechanism of transgenerational cardiotoxicity. At 1 μg/L, the DCOIT-exposed female parent transferred a significantly higher amount of triiodothyronine (T3) hormone to offspring, corresponding to an accelerated heart rate. However, DCOIT at higher exposure concentrations modified the methylome imprinting in larval offspring, which was associated with cardiac dysfunction. Overall, the findings provide novel insights into the developmental cardiotoxicity of DCOIT. The high risks of DCOIT-even at environmentally realistic concentrations-raise concerns about its applicability as an antifoulant in a marine environment.

Bifidobacterium mediate gut microbiota-remedied intestinal barrier damage caused by cyproconazole in zebrafish (Danio rerio)

The widespread use of cyproconazole (CPZ) enhances food security but may pose potential risks to non-target organisms. Therefore, we applied Multi-omics techniques to reveal the response of the intestinal barrier to CPZ exposure and explore whether the Bifidobacterium intervention experiment can repair the damage. First, we found that exposure to CPZ at environmentally relevant concentrations led to intestinal injury phenotype, significantly down-regulated intestinal protein gene expression, and up-regulated pro-inflammatory gene expression, further causing intestinal dysbacteriosis and metabolic disorders. In particular, by combining analysis of gut microbiota and metabolites, we noticed acetate, a key metabolite, which decreased sharply after exposure to high concentration of CPZ. Expectedly, after supplementing with Bifidobacterium (a core bacterium that produces acetate), we noticed that the acetate content was quickly restored. Further, we also verified that the increase in acetate content after Bifidobacterium supplementation at least partially promoted IL-22 secretion, which in turn stimulated the secretion of β-defensins (zfbd-1, zfbd-2, zfbd-3), thereby repairing the intestinal damage. In conclusion, our work confirms the potential of Bifidobacterium to improve intestinal damage and metabolic dysbiosis caused by CPZ exposure. It provides directional recommendations for the application of probiotics to repair the toxicological risk of pesticide exposure.

Probiotic Lactobacillus rhamnosus alleviates the neurotoxicity of microcystin-LR in zebrafish (Danio rerio) through the gut-brain axis

Microcystin-LR (MCLR) is one of the most toxic cyanobacterial toxins and is harmful to the central nervous system of fish. Probiotic additives can improve neuroendocrine function in fish. Although both MCLR and probiotics aim at the nervous system, whether they interact with each other and the mechanisms remain unexplored. In the present study, 4-month-old zebrafish were exposed to 0, 2.2, and 22 μg/L of MCLR for 28 days with or without the probiotic L. rhamnosus. We found that MCLR exposure could inhibit the swimming speed of zebrafish, while the presence of L. rhamnosus mitigated this abnormality. To elucidate the mechanism of how L. rhamnosus alleviates MCLR-induced neurotoxicity, we examined the bioaccumulation of MCLR, changes in neurotransmitters, immune biochemical indicators, and hormone content of the hypothalamic-pituitary-interrenal (HPI) axis in zebrafish along the gut-brain axis. Our results showed L. rhamnosus could reverse the abnormal swimming behavior and eventually alleviate neurotoxicity in zebrafish by modulating intestinal and brain neural signaling, neuroinflammation, and HPI axis responses. This study provides implications for the application of probiotics in the aquaculture industry.

The splicing factor DHX38 enables retinal development through safeguarding genome integrity

DEAH-Box Helicase 38 (DHX38) is a pre-mRNA splicing factor and also a disease-causing gene of autosomal recessive retinitis pigmentosa (arRP). The role of DHX38 in the development and maintenance of the retina remains largely unknown. In this study, by using the dhx38 knockout zebrafish model, we demonstrated that Dhx38 deficiency causes severe differentiation defects and apoptosis of retinal progenitor cells (RPCs) through disrupted mitosis and increased DNA damage. Furthermore, we found a significant accumulation of R-loops in the dhx38-deficient RPCs and human cell lines. Finally, we found that DNA replication stress is the prerequisite for R-loop-induced DNA damage in the DHX38 knockdown cells. Taken together, our study demonstrates a necessary role of DHX38 in the development of retina and reveals a DHX38/R-loop/replication stress/DNA damage regulatory axis that is relatively independent of the known functions of DHX38 in mitosis control.

Evaluation and Mechanistic Study of Transgenerational Neurotoxicity in Zebrafish upon Life Cycle Exposure to Decabromodiphenyl Ethane (DBDPE)

The novel brominated flame retardant decabromodiphenyl ethane (DBDPE) has become a ubiquitous emerging pollutant in the environment, which may evoke imperceptible effects in humans or wild animals. Hence in this study, zebrafish embryos were exposed to DBDPE (0, 0.1, 1, and 10 nM) until sexual maturity (F0), and F1 and F2 generations were cultured without further exposure to study the multi- and transgenerational toxicity and underlying mechanism. The growth showed sex-different changing profiles across three generations, and the social behavior confirmed transgenerational neurotoxicity in adult zebrafish upon life cycle exposure to DBDPE. Furthermore, maternal transfer of DBDPE was not detected, whereas parental transfer of neurotransmitters to zygotes was specifically disturbed in F1 and F2 offspring. A lack of changes in the F1 generation and opposite changing trends in the F0 and F2 generations were observed in a series of indicators for DNA damage, DNA methylation, and gene transcription. Taken together, life cycle exposure to DBDPE at environmentally relevant concentrations could induce transgenerational neurotoxicity in zebrafish. Our findings also highlighted potential impacts on wild gregarious fish, which would face higher risks from predators.

Altered ovarian transcriptome is linked to early mortality and abnormalities in zebrafish embryos after maternal exposure to gamma irradiation

Recent laboratory studies focusing on multigenerational approach demonstrated drastic phenotypic effects after chronic fish irradiation exposure. No irradiation effect at phenotypic scale was observed for F0 (reproductive performances) while early mortality and malformations were observed in F1 offspring whether they were irradiated or not. The objective was to study molecular mechanisms likely to be involved in these phenotypic effects induced by parental irradiation. Thus, F0 adult zebrafish were irradiated for ten days until reproduction and maternal involvement in offspring development was assessed. Levels of maternal provided cortisol and vitellogenin, needed for embryo development, were not impacted by irradiation. However, maternal transcriptome highlighted irradiation effect on processes involved in oocyte development, as well as on essential maternal factors needed for offspring development. Therefore, this study highlighted the importance of parental exposure on offspring fate and of the importance of multigenerational exposure in risk assessment.

Maternal body condition and season influence RNA deposition in the oocytes of alfalfa leafcutting bees (Megachile rotundata)

Maternal effects are an important source of phenotypic variance, whereby females influence offspring developmental trajectory beyond direct genetic contributions, often in response to changing environmental conditions. However, relatively little is known about the mechanisms by which maternal experience is translated into molecular signals that shape offspring development. One such signal may be maternal RNA transcripts (mRNAs and miRNAs) deposited into maturing oocytes. These regulate the earliest stages of development of all animals, but are understudied in most insects. Here we investigated the effects of female internal (body condition) and external (time of season) environmental conditions on maternal RNA in the maturing oocytes and 24-h-old eggs (24-h eggs) of alfalfa leafcutting bees. Using gene expression and WGCNA analysis, we found that females adjust the quantity of mRNAs related to protein phosphorylation, transcriptional regulation, and nuclease activity deposited into maturing oocytes in response to both poor body condition and shorter day lengths that accompany the late season. However, the magnitude of these changes was higher for time of season. Females also adjusted miRNA deposition in response to seasonal changes, but not body condition. We did not observe significant changes in maternal RNAs in response to either body condition or time of season in 24-h eggs, which were past the maternal-to-zygotic transition. Our results suggest that females adjust the RNA transcripts they provide for offspring to regulate development in response to both internal and external environmental cues. Variation in maternal RNAs may, therefore, be important for regulating offspring phenotype in response to environmental change.

Probiotic supplementation mitigates the developmental toxicity of perfluorobutanesulfonate in zebrafish larvae

Perfluorobutanesulfonate (PFBS) is an emerging pollutant of international concern, which is found to impair the early embryonic development of fishes. In the context of ubiquitous and persistent pollution, it is necessary to explore mitigatory strategies against the developmental toxicity of PFBS. In this study, zebrafish larvae were acutely exposed to 0, 1, 3.3 and 10 mg/L of PFBS till 168 h post-fertilization (hpf), during which probiotic Lactobacillus rhamnosus bacteria were administered via the exposure media. After the singular or combined exposure, interaction between PFBS and probiotics on the growth of zebrafish larvae was measured. PFBS exposure significantly decreased the larval body weight, weight gain and specific growth rate, while probiotic supplementation efficiently inhibited the growth retardation caused by PFBS. Furthermore, PFBS and probiotic combinations remarkably activated the antioxidant capacity to timely scavenge the reactive oxidative species and protect the larvae from lipid peroxidation. Biochemical assay and fluorescent staining verified that PFBS exposure significantly promoted the production of bile acids, which were further enhanced by the probiotics. In coexposed zebrafish larvae, up-regulation of peroxisome proliferator-activated receptor (PPARb) would enhance the β-oxidation of fatty acids to meet the energy demand from larval growth, subsequently decreasing fatty acid concentrations. In addition, probiotic supplements masked the dysbiosis of PFBS and potently shaped the gut microbiota, which closely modulated the production of bile acids. Overall, the present findings underline the beneficial effects of probiotics to protect the developing larvae from the aquatic toxicities of PFBS, thus highlighting the potential application values of probiotic recipe in aquaculture and ecological reservation.

Probiotic intervention mitigates the metabolic disturbances of perfluorobutanesulfonate along the gut-liver axis of zebrafish

Probiotic supplementation is effective to modulate the metabolic disorders caused by perfluorobutanesulfonate (PFBS). However, the underlying mechanisms remain unclear. To this end, the present study exposed adult zebrafish to PFBS (0 and 10 μg/L), probiotics, or their binary combinations for 40 days. After the exposure, the nutritional stores, intestinal organization, and metabolic activities along the gut-liver axis were investigated. The results showed that PFBS exposure decreased the nutrient reserves significantly, especially the lipid content, which was alleviated by the probiotic administration. Intestinal mucus secretion was promoted remarkably in the presence of the probiotic, which enhanced epithelial protection against PFBS damage. Metagenomic analysis showed that PFBS alone induced gut microbial dysbiosis, which was efficiently antagonized by the probiotic bacteria. Intestinal metabolomic profiling revealed that ferroptosis occurred because of the unrestricted lipid peroxidation following PFBS exposure. However, probiotic administration prevented the ferroptotic symptoms induced by PFBS, further highlighting the beneficial effects of the probiotic on the host. In PFBS-exposed livers, high levels of bile acid metabolites (e.g., taurochenodeoxycholic acid) accumulated, implying the induction of cholestasis. Notably, probiotic addition recovered the metabolomic homeostasis under PFBS stress, probably resulting from the activation of detoxification pathways based on the pentose and glucuronate interconversion. Overall, the present study provides systematic evidence of the antagonistic interaction between PFBS and the probiotic regarding the metabolic activities along the microbe, gut and liver axis, highlighting the application values of probiotic recipe in aquaculture industry and ecological reservation.

Antagonistic interaction between perfluorobutanesulfonate and probiotic on lipid and glucose metabolisms in the liver of zebrafish

Perfluorobutanesulfonate (PFBS) and probiotic bacteria can interact to induce hepatic hypertrophy. However, the molecular events occurring in the hypertrophic liver are still unknown. Therefore, we performed this follow-up study using adult zebrafish that were exposed for 40 days to 0 and 10 μg/L PFBS, with or without dietary supplementation of probiotic Lactobacillus rhamnosus. After PFBS or/and probiotic exposures, proteome perturbation, histological pathogenesis and glucose metabolism were investigated in the livers. Proteomic analysis showed potent intervention of PFBS or/and probiotic with hepatic functions. PFBS single exposure caused marked disturbances in lipid metabolisms, which may underlie the severe vacuolization in male liver. The addition of probiotic alleviated the lipid metabolic disorders of PFBS. Furthermore, probiotic supplementation enhanced ATP energy production using glucose in mitochondrial respiratory chain of male fish. However, PFBS alone caused remarkable increase in blood glucose level (by 2.5-fold relative to the control), underlining the onset of hyperglycemia symptom. In contrast, the liver of male fish from the coexposure group functioned appropriately, which immediately increased insulin levels by 2.2-fold to reduce the glucose accumulation in blood. In female liver, PFBS alone significantly decreased the blood glucagon concentration by 2.9-fold. The deficiency of glucagon hormone consequently contributed to the accumulation of glycogen (3.2-fold) therein. Vigorous antagonistic interaction between PFBS and probiotic was noted with respect to glucose metabolism, which restored ATP, glucose, glycogen and glucagon to the control levels. Overall, the present study finds that probiotic L. rhamnosus is efficient to mitigate the metabolic disorders of PFBS on lipid and glucose, highlighting the potential values of probiotic bacteria to protect the aquatic ecosystem.

Probiotic Lactobacillus rhamnosus modulates the impacts of perfluorobutanesulfonate on oocyte developmental rhythm of zebrafish

Potent interaction between probiotic bacteria and perfluorobutanesulfonate (PFBS), an aquatic pollutant of emerging concern, was previously reported on reproduction of zebrafish. However, the underlying mechanism is largely unexplored. In this regard, the present study continued to focus on the interactive modes between probiotics and PFBS. Adult zebrafish were exposed for 28 days to 0 and 10 μg/L PFBS with or without dietary supplementation of probiotic Lactobacillus rhamnosus. With the relevance to fecundity outcome, a suite of reproductive indices at transcriptional, hormonal, proteomic and histological levels of biological organization were measured herein. The fecundity monitoring results showed that probiotic additive shifted the impacts of PFBS on egg spawn, gradually approaching the control level. Based on ovary histological observation, oocyte growth was significantly promoted by probiotics or/and PFBS exposures, while the presence of probiotic bacteria partially antagonized the effects of PFBS on oocyte growth. The combination of probiotics and PFBS increased the concentration of maturation inducing hormones in ovary. Despite the enhanced hormonal signals, gene transcriptions of ovarian local auto/paracrine factors were consistently decreased in all exposure groups, suggesting the blocked transition from oocyte growth phase toward oocyte maturation phase. Ovary proteomic analysis found that PFBS exposure with or without probiotic bacteria mainly affected the RNA metabolic processes, although the addition of probiotics exerted extra influences on amino acid metabolism. Overall, the present study provided more mechanistic evidence about the interactive behavior between probiotic bacteria and PFBS pollutant. Feed additive of probiotic bacteria modulated the impacts of PFBS on egg production rhythm through oocyte growth and maturation phases.

Shift in skin microbiota and immune functions of zebrafish after combined exposure to perfluorobutanesulfonate and probiotic Lactobacillus rhamnosus

Dysbiosis of fish skin microbiome and immunity by environmental pollutants are rarely studied in toxicological research in spite of their importance for fish health. In the present study, adult zebrafish were exposed to 0 and 10 μg/L of perfluorobutanesulfonate (PFBS) for 40 days, with or without the supplementation of probiotic Lactobacillus rhamnosus, with objectives to explore the interaction between PFBS pollutant and probiotic bacteria on skin mucosal microbiota and immune response. Amplicon sequencing analysis found that PFBS alone significantly disturbed the microbial community composition and abundance on the skin, favoring the growth of stress-tolerant bacteria (e.g., Deinococcus and Enhydrobacter genera). However, the administration of probiotic inhibited the dysbiosis of PFBS and shaped the skin microbiome in the combined exposure group. PFBS single exposure also promoted the production of mucus on the skin of male zebrafish, which may be related to the growth of Limnobacter bacteria. In contrast, probiotic supplements remarkably improved the immune functions in male skin mucus from the combined group, as evidenced by the consistent increases in lysozyme activity, immunoglobulin concentrations and peroxidase activity. Overall, the present study provides the first clue about the singular and combined effects of PFBS and probiotic on skin microbiota and immunity, highlighting the beneficial action of probiotic L. rhamnosus against PFBS stress.

Probiotic modulation of perfluorobutanesulfonate toxicity in zebrafish: Disturbances in retinoid metabolism and visual physiology

Perfluorobutanesulfonate (PFBS), an aquatic pollutant of emerging concern, is found to disturb gut microbiota, retinoid metabolism and visual signaling in teleosts, while probiotic supplementation can shape gut microbial community to improve retinoid absorption. However, it remains unknown whether probiotic bacteria can modulate the toxicities of PFBS on retinoid metabolism and visual physiology. In the present study, adult zebrafish were exposed for 28 days to 0, 10 and 100 μg/L PFBS, with or without dietary administration of probiotic Lactobacillus rhamnosus. Interaction between PFBS and probiotic was examined regarding retinoid dynamics (intestine, liver and eye) and visual stimuli transmission. PFBS single exposures remarkably inhibited the absorption of retinyl ester in female intestines, which were, however, restored by probiotic to normal status. Although coexposure scenarios markedly increased the hepatic storage of retinyl ester in females, mobilization of retinol was reduced in livers by single or combined exposures regardless of sex. In the eyes, transport and catalytic conversion of retinol to retinal and retinoic acid were interrupted by PFBS alone, which were efficiently antagonized by probiotic presumably through an indirect action. In response to the availability of retinal chromophore, transcriptions of opsins and arrestin genes were altered adaptively to control visual perception and termination. Neurotransmission across retina circuitry was changed accordingly, centering on epinephrine and norepinephrine. In summary, the present study found the efficient modulation of probiotic on retinoid metabolic disorders of PFBS pollution, which subsequently impacted visual signaling. A future work is warranted to provide mechanistic clues in retinoid interaction.

Dietary administration of probiotic Lactobacillus rhamnosus modulates the neurological toxicities of perfluorobutanesulfonate in zebrafish

Perfluorobutanesulfonate (PFBS), an aquatic pollutant of emerging concern, is found to disturb the neural signaling along gut-brain axis, whereas probiotic additives have been applied to improve neuroendocrine function of teleosts. Both PFBS and probiotics can commonly target nervous system. However, whether and how probiotic bacteria can modulate the neurotoxicities of PFBS remain not explored. It is thus necessary to elucidate the probiotic modulation of PFBS neurotoxicity, which can provide implications to the application of probiotic bacteria in aquaculture industry. In the present study, adult zebrafish were exposed to 0, 10 and 100 μg/L PFBS with or without dietary administration of probiotic Lactobacillus rhamnosus. Interaction between PFBS and probiotic along gut-brain axis was examined, covering three dominant pathways (i.e., neurotransmission, immune response and hypothalamic-pituitary-adrenal (HPA) axis). The results showed that, compared to the single effects, PFBS and probiotic coexposure significantly altered the acetylcholinesterase activity and neurotransmitter profiles in gut and brain of zebrafish, with mild effects on neuronal integrity. Neurotransmitters closely correlated reciprocally in intestines, which, however, was distinct from the correlation profile in brains. In addition, PFBS and probiotic were combined to impact brain health through absorption of bacterial lipopolysaccharides and production of inflammatory cytokines. Relative to neurotransmission and immune signaling, HPA axis was not involved in the neurotoxicological interaction between PFBS and probiotic. Furthermore, it needs to point out that interactive modes between PFBS and probiotic varied a lot, depending on exposure concentrations, sex and toxic indices. Overall, the present study provided the first evidence that probiotic supplement could dynamically modulate the neurotoxicities of PFBS in teleost.

Parental exposure to perfluorobutane sulfonate disturbs the transfer of maternal transcripts and offspring embryonic development in zebrafish

Parental exposure to perfluorobutane sulfonate (PFBS), an aquatic pollutant of emerging concern, is previously found to impair the embryonic development of offspring. However, the impairing mechanisms remain to clarify. In the present study, adult zebrafish were exposed to 0, 10 and 100 μg/L PFBS for 28 d, after which disturbances in maternal transcript transfer and offspring embryogenesis were investigated. Prior to zygotic genome activation, high-throughput transcriptomic sequencing revealed that parental PFBS exposure significantly altered the transcript profile of maternal origin in offspring eggs, while toxic actions varied as a function of PFBS concentrations. In offspring eggs derived from 10 μg/L exposure group, differential transcripts were mainly associated with the histone-DNA interaction of nucleosome, which would modify the compacted chromatin configuration and accessibility of transcriptional factors to DNA sequences. In this regard, the timing of zygotic genome activation was presumably disrupted. Parental exposure to 100 μg/L PFBS primarily interrupted the maternal transfer of adherens junction transcripts, which was supposed to dysregulate the cell-cell adhesion during early embryo formation. Development and growth of offspring embryos were significantly compromised by parental PFBS exposure, as exemplified by higher mortality, delayed hatching, slower heart rate, reduced body weight and neurobehavioral disorders. Overall, the present study presented the first toxicological evidence about the disturbances of PFBS in maternal transcript transfer, although the inherent linkage between maternal transcript modifications and offspring development defects still needs future works to construct.

Probiotic Modulation of Lipid Metabolism Disorders Caused by Perfluorobutanesulfonate Pollution in Zebrafish

To determine whether and how probiotic supplement can alter gut microbiota dysbiosis and lipid metabolism disorders caused by perfluorobutanesulfonate (PFBS), the present study exposed adult zebrafish to 0, 10, and 100 μg/L PFBS for 28 days, with or without dietary administration of probiotic Lactobacillus rhamnosus. Regarding intestinal health and gut microbiota, probiotic supplement altered the innate toxicities of PFBS, depending on exposure concentration and the sex of the fish. Lactobacillus genus correlated positively (P < 0.001; r > 0.5) with other beneficial bacteria in the gut microbiota, thereby indirectly regulating host metabolic activities. In female fish, the PFBS and probiotic combination enhanced fatty acid synthesis and β-oxidation, but mitigated the accumulation of cholesterol in the blood compared with PFBS single exposure, highlighting the benefits of the probiotic to host health. In male zebrafish, probiotic administration antagonized the PFBS-induced disturbances of bile acid metabolism, presumably via farnesoid X receptor signaling. However, coexposure to PFBS and probiotic caused significant accumulation of triglyceride in male livers (2.6-fold relative to the control), implying the induction of hepatic steatosis. Overall, the present study underlined the potential of probiotics to modulate gut microbial dysbiosis and lipid metabolism disorders caused by PFBS exposure, which could provide implications to the application of probiotics in aquaculture.

Glycogen storage in a zebrafish Pompe disease model is reduced by 3-BrPA treatment

Pompe disease (PD) is an autosomal recessive muscular disorder caused by deficiency of the glycogen hydrolytic enzyme acid α-glucosidase (GAA). The enzyme replacement therapy, currently the only available therapy for PD patients, is efficacious in improving cardiomyopathy in the infantile form, but not equally effective in the late onset cases with involvement of skeletal muscle. Correction of the skeletal muscle phenotype has indeed been challenging, probably due to concomitant dysfunctional autophagy. The increasing attention to the pathogenic mechanisms of PD and the search of new therapeutic strategies prompted us to generate and characterize a novel transient PD model, using zebrafish. Our model presented increased glycogen content, markedly altered motor behavior and increased lysosome content, in addition to altered expression of the autophagy-related transcripts and proteins Beclin1, p62 and Lc3b. Furthermore, the model was used to assess the beneficial effects of 3-bromopyruvic acid (3-BrPA). Treatment with 3-BrPA induced amelioration of the model phenotypes regarding glycogen storage, motility behavior and autophagy-related transcripts and proteins. Our zebrafish PD model recapitulates most of the defects observed in human patients, proving to be a powerful translational model. Moreover, 3-BrPA unveiled to be a promising compound for treatment of conditions with glycogen accumulation.

Fundc1 is necessary for proper body axis formation during embryogenesis in zebrafish

FUN14 domain-containing protein 1 (FUNDC1) is a mitochondrial outer membrane protein which is responsible for hypoxia-induced mitophagy in mammalian cells. Knockdown of fundc1 is known to cause severe defects in the body axis of a rare minnow. To understand the role of Fundc1 in embryogenesis, we used zebrafish in this study. We used bioimaging to locate zebrafish Fundc1 (DrFundc1) with MitoTracker, a marker of mitochondria, and/or CellLight Lysosomes-GFP, a label of lysosomes, in the transfected ovary cells of grass carp. The use of Western blotting detected DrFundc1 as a component of mitochondrial proteins with endogenous COX IV, LC3B, and FUNDC1 in transgenic human embryonic kidney 293 T cells. DrFundc1 induced LC3B activation. The ectopic expression of Drfundc1 caused cell death and apoptosis as well as impairing cell proliferation in the 293 T cell line, as detected by Trypan blue, terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) and incorporation of BrdU. DrFundc1 up-regulated expression of both autophagy- and apoptosis-related genes, including ATG5, ATG7, LC3B, BECLIN1, and BAX in transgenic 293 T cells. A knockdown of Drfundc1 using short hairpin RNA (shRNA) led to midline bifurcation with two notochords and two spinal cords in zebrafish embryos. Co-injection of Drfundc1 mRNA repaired defects resulting from shRNA. Knockdown of Drfundc1 resulted in up- or down-regulation of genes related to autophagy and apoptosis, as well as decreased expression of neural genes such as cyclinD1, pax2a, opl, and neuroD1. In summary, DrFundc1 is a mitochondrial protein which is involved in mitophagy and is critical for typical body axis development in zebrafish.

Parental Exposure to Perfluorobutanesulfonate Impairs Offspring Development through Inheritance of Paternal Methylome

Perfluorobutanesulfonate (PFBS), an environmental pollutant of emerging concern, significantly impairs offspring development and overall health after parental exposure. However, the true inducer of offspring developmental defects among the complexity of parental influences remains unknown. In the present study, marine medaka (Oryzias melastigma) were exposed to environmentally realistic concentrations of PFBS (0, 1, 3, and 10 μg/L) for an entire life cycle. By mixing and mating control and exposed medaka (male or female), a crossbreeding strategy was employed to produce offspring eggs from various crossbreeds, with the aim of differentiating the maternal and paternal influences. Measurements of swimming performance in larval offspring showed that larvae of exposed male parents swam hyperactively in comparison to the control larvae. Contrasting trends in PFBS transfer and maternal factor transfer (e.g., proteins and lipids) to that of swimming behavior eliminated these two factors as major inducers of offspring developmental impairment. Inheritance of the exposed paternal methylome marks in offspring may be partially responsible for abnormal swimming behavior, although different toxic mechanisms may be involved depending on the exposure concentration. Overall, these findings suggest that inheritance of epigenetic modifications implicates a long-lasting threat of PFBS to the fitness and sustainability of fish populations.

Perfluorobutanesulfonate Exposure Skews Sex Ratio in Fish and Transgenerationally Impairs Reproduction

Perfluorobutanesulfonate (PFBS) is increasingly polluting aquatic environments due to worldwide manufacturing and application. However, toxicological knowledge regarding PFBS exposure remains scarce. Here, we showed that PFBS life-cycle exposure at environmentally realistic concentrations (0, 1.0, 2.9, and 9.5 μg/L) skewed the sex ratio in fish toward male dominance, while reproductive functions of female fish were greatly impaired, as characterized by extremely small ovaries, blocked oocyte development, and decreased egg production. Endocrine disruption through the hypothalamus-pituitary-gonad axis was induced by PFBS exposure, showing antiestrogenic activity in females but estrogenic activity in males. PFBS was found to gradually accumulate in F0 adults during continuous exposure but can be rapidly eliminated when depurated in clean water. Parental exposure also transferred PFBS pollutant to F1 offspring eggs. Although no trace of PFBS was detected in F1 adults and F2 eggs, adverse effects from parental exposure persisted in F1 and F2 offspring. These transgenerational effects implicate PFBS as an ongoing threat to the fitness and sustainability of fish populations. The dramatic impairment of fish reproduction highlights the urgency of re-evaluations of the ecological and evolutionary consequences of PFBS exposure.

TiO2 nanoparticles and BPA are combined to impair the development of offspring zebrafish after parental coexposure

Titanium dioxide (TiO₂) nanoparticles and bisphenol A (BPA) in aquatic environments interact reciprocally to enhance the maternal transfer of pollutants to offspring, thus varying the innate toxicities during early embryonic development. However, it remains unexplored regarding the molecular mechanisms of developmental toxicity in offspring after parental coexposure. In the present study, adult zebrafish were exposed to TiO₂ nanoparticles (100 μg/L), BPA (20 μg/L) or their binary mixture for four months. Then, eggs of F1 generation were collected and reared in clean water until 5 days post-fertilization. In characteristic of larval survival and growth, parental coexposure to TiO₂ particles and BPA caused a severer inhibition of F1 offspring larvae compared with single exposure. Mechanistic investigation by shotgun proteomics found that development of larval offspring from coexposed parents was impaired through a distinct mode of toxicity, that is, specifically altering the activity of phagosome and lysosome. Single exposure of adult zebrafish to TiO₂ mainly affected insulin-responsive compartment; and BPA parental exposure mainly affected carbohydrate metabolism and calcium signaling of larval offspring. Furthermore, considering the tight regulation of sex hormones in the expression of vitellogenin (VTG), addition of nanoparticles during parental exposure led to inconsistencies between VTG induction and endogenous levels of sex hormones (estradiol and testosterone) in F1 offspring fish. This implied that transfer of nanoparticles to offspring larvae may change the availability of hormonal molecules and BPA at target tissues. Overall, current results provided mechanistic clues into the multigenerational developmental toxicity by parental coexposure to TiO₂ particles and BPA.

Therapeutic applications of zebrafish (Danio rerio) miRNAs linked with human diseases: A prospective review

MicroRNAs (miRNAs) are the class of small, non-coding RNAs that are produced from precursor transcripts by subsequent processing steps mediated by members of the RNaseIII family, Dicer and Drosha protein within cell. The importance of zebrafish miRNAs in regulation of normal cellular development and support to various kinds of metabolism process. Although the zebrafish model provides a fundamental platform for the study of developmental biology but recent work with zebrafish model has expanded its appliance to a broad range of experimental studies relevant to different kind of human diseases. Presently, the zebrafish model is used for the study of cardiovascular disease, schizophrenia, bipolar I disorder in eyes, psoriasis, spinal cord injury, cancer and diabetes that showing in some selected miRNAs are regulate these diseases in molecular levels. Here, a superior drive performed to depict the fundamental utilization of the zebrafish miRNAs that targeted to several clinical diseases connected to human. This review aims to provide a summary of understanding of the cellular mechanism which is responsible for selected diseases and suggests some therapeutic application for inhibition of miRNA functions.

Effects of Parental Aging During Embryo Development and Adult Life: The Case of Nothobranchius furzeri

Studies on parental aging are a very attractive field, although it is poorly understood how parental age affects embryonic development and adult traits of the offspring. In this study, we used the turquoise killifish Nothobranchius furzeri, as is the vertebrate with shortest captive lifespan and an interesting model. The embryos of N. furzeri can follow two distinct developmental pathways either entering diapause or proceeding through direct development. Thus, this embryonic plasticity allows this model to be used to study different factors that could affect their embryonic development, including parental age. The first goal of the present study was to investigate whether parental aging could affect the embryo development. To do this, we collected F1 embryos from two breeder groups (old parents and young parents). We monitored the duration of embryonic development and analyzed genes involved in dorsalization process. The second goal was to investigate if embryonic developmental plasticity could be modulated by an epigenetic process. To this end, the expression of DNMTs genes was examined. Our data support the hypothesis that diapause, occurring more frequently in embryos from old parents, is associated with increased expression of DNMT3A and DNMT3B suggesting an epigenetic control. Finally, we analyzed whether parental age could affect metabolism and growth during adult life. Morphometric results and qPCR analysis of genes from IGF system showed a slower growth in adults from old breeders. Moreover, a gender-specificity effect on growth emerged. In conclusion, these results may contribute to the better understanding of the complex mechanism of aging.

Relative transcription of autophagy-related genes in Amblyomma sculptum and Rhipicephalus microplus ticks

Ticks endure stressful off-host periods and perform as vectors of a diversity of infectious agents, thus engaging pathways that expectedly demand for autophagy. Little is known of ticks' autophagy, a conserved eukaryotic machinery assisting in homeostasis processes that also participates in tissue-dependent metabolic functions. Here, the autophagy-related ATG4 (autophagin-1), ATG6 (beclin-1) and ATG8 (LC3) mRNAs from the human diseases vector Amblyomma sculptum and the cattle-tick Rhipicephalus microplus were identified. Comparative qPCR quantifications evidenced different transcriptional status for the ATG genes in the salivary glands (SG), ovaries and intestines of actively feeding ticks. These ATGs had increased relative transcription under nutrient-deprivation, as determined by validation tests with R. microplus embryo-derivative cells BME26 and A. sculptum SG explants incubations in HBSS. Starvation lead to 4-31.8× and ~ 60-500× increments on the ATGs mRNA loads in BME26 and A. sculptum SG explants, respectively. PI3K inhibitor 3MA treatment also affected ATGs expression in BME26. Some ATGs were more transcribed in the SGs than in the ovaries of cattle-ticks. Amblyomma sculptum/R. microplus interspecific comparisons showed that ATG4 and ATG6 were 0.18× less expressed in A. sculptum SGs, but ~ 10-100× more expressed in their ovaries when compared to R. microplus organs. ATG4 and ATG8a transcript loads were ~ 120× and ~ 40× higher, respectively, in A. sculptum intestines when compared to cattle-ticks of similar weight category. ATGs expression in A. sculptum intestines increased with tick weight, indicating Atgs contribution to intracellular blood digestion. Possible roles of the autophagy machinery and their organ-specific expression profile on vector biology are discussed.

In silico predicted reproductive endocrine transcriptional regulatory networks during zebrafish (Danio rerio) development

The interconnected topology of transcriptional regulatory networks (TRNs) readily lends to mathematical (or in silico) representation and analysis as a stoichiometric matrix. Such a matrix can be 'solved' using the mathematical method of extreme pathway (ExPa) analysis, which identifies uniquely activated genes subject to transcription factor (TF) availability. In this manuscript, in silico multi-tissue TRN models of brain, liver and gonad were used to study reproductive endocrine developmental programming in zebrafish (Danio rerio) from 0.25h post fertilization (hpf; zygote) to 90 days post fertilization (dpf; adult life stage). First, properties of TRN models were studied by sequentially activating all genes in multi-tissue models. This analysis showed the brain to exhibit lowest proportion of co-regulated genes (19%) relative to liver (23%) and gonad (32%). This was surprising given that the brain comprised 75% and 25% more TFs than liver and gonad respectively. Such 'hierarchy' of co-regulatory capability (brain<liver<gonad) indicated presence of highly gene-specific TRNs in the brain, alluding to its role as 'master controller' of endocrine function. Second, TRN models were constrained with varying TF availabilities during zebrafish development. Normalized numbers of genes active during development showed concomitant activations between brain and gonad from 10 to 12 hpf (embryonic life stage) up to 30-90 dpf (adult life stage). This indicated a putative 'syncing' between the brain and gonad, and initiation of an early reproductive endocrine developmental program. Finally, comparison of in vivo active genes with those predicted in silico showed relatively good agreement for brain (49%), liver (27%) and gonad (32%). The multi-tissue TRN models presented can lend diagnostic insights into the effects of changing environmental and/or genetic constraints on reproductive endocrine function.