Mutant Zebrafish Research Articles

Exome sequencing identifies a novel FBN1 variant in a Chinese family with Marfan syndrome that includes aberrant right subclavian artery

Abstract Background Marfan syndrome (MFS) is an inherited autosomal dominant disorder that affects connective tissue with an incidence of about 1 in 5,000 to 10,000 people. Ninety percent of MFS is caused by mutations in the fibrillin-1 (fbn1) gene. We recruited a family with MFS phenotype in South China and identified a novel variant in fbn1 by whole exome sequencing (WES). The zebrafish share high genetic similarity to humans. This study aimed to generate this novel mutation in the fbn1 gene of zebrafish using the CRISPR/Cas9 technology and researched whether this variant is pathogenic. Methods A three-generation consanguineous family was recruited in this study, which was visited and interviewed for the clinical data and family history. Peripheral blood samples were collected from family members for DNA isolation and WES. The 3D structure of the protein was predicted by Alphafold. CRISPR/Cas9 was applied to generate an fbn1 nonsense mutation (fbn1+/−) in zebrafish. Morphological abnormalities were assessed in F2 fbn1+/− zebrafish by comparing with the wild-type (WT) controls at different development stages. Results Our study recruited a family with MFS phenotype in South China and identified a novel variant [NM_000138.5; c.7764C>G: p.(Y2588*)] in fbn1. Through Sanger sequencing, we found that family members Ⅲ-1 (son) and Ⅲ-2 (daughter) had the fbn1 variant segregated with MFS in the family. The p.Y2588* mutation resulted in the absence of 283 amino acids, thereby leading to the deficiency of 17 β-folded structures, 4 α-helix structures, and various loop structures. Compared with WT zebrafish, F2 fbn1+/− zebrafish exhibited aortic arches bleeding, abnormal angiogenesis, decreased cardiac volume, cardiac function defects, curly tail, and cartilage malformations. Conclusion A novel variant [NM_000138.5; c.7764C>G: p.(Y2588*)] was identified in fbn1 gene, which has not been reported in previous literature. The variant caused loss of function through premature protein truncation or nonsense-mediated mRNA decay. In zebrafish, we identified functional evidence of the detected nonsense mutation, which aligns with the clinical significance, suggesting a pathogenic variant of fbn1. Zebrafish as a novel, efficient tool to allow for the quick classification of unknown variants in fbn1 and improve the clinical diagnosis and treatment of MFS. It has brought the implementation of personal and precision medicine in the clinic within reach and made it possible to find patient-specific treatments.Marfanoid symptoms of the patient.Phenotypic Spectrum of fbn1+/− Zebrafish

Galectin-3 zebrafish model: identification and pharmacological modulation of arrhythmogenic cardiomyopathy-related phenotypes

Abstract Background Arrhythmogenic Cardiomyopathy (ACM) is rare hereditary cardiac condition characterized by the substitution of ventricular myocardium with fibro-fatty tissue leading to high risk of life-threatening arrhythmias and sudden cardiac death, particularly among young individuals and athletes. Based on genotype-phenotype correlation, the spectrum of the ACM phenotype was shown to be broader than previously believed. Approximately 40% of ACM patients carry one or more putative pathogenic variants in genes encoding desmosomal proteins. Recently LGALS3 gene involvement in ACM early pathogenesis has been advocated. Aim To achieve a comprehensive understanding of LGALS3 role in the pathogenesis of AC. Methods This stable mutant line was generated by CRISPR/Cas9 strategy and then deeply characterized. Phenotyping included heart activity characterization using a recently published software specific for zebrafish, the pyHeart4Fish. Gene expression analysis was carried out by using RNAseq, Real Time PCR and signaling pathway reporter zebrafish lines. Immunofluorescence analysis were performed using and antibody against L-plastin, a leukocyte marker for the detection of inflammatory cells and Acridine Orange/Ethidium Bromide staining to check the possible presence of apoptotic and necrotic events. Results Morphological investigation revealed notable structural abnormalities such as pericardial effusion and/or hemopericardium. The heart activity analysis detected a diminished ventricle contractility and ejection fraction, with bradycardia and occurrence of arrhythmia events. Rna analysis highlighted the dysregulation of Wnt/β-catenin signaling pathway. Moreover, the L-plastin inflammatory marker revealed a significant infiltration of inflammatory cells in the heart as well as an elevated number of apoptotic and necrotic cells (figure 1). The pharmacological treatment, partially rescued a subset of AC-related cardiac phenotypes observed, including heart contractility, bradycardia and arrhythmia. Conclusion Our findings strongly validate our lgals3a zebrafish mutant as an effective model to elucidate its role in ACM related phenotype. This model accurately replicates the cardiac abnormalities and dysregulation in cell signaling that are characteristic of ACM. Further, observed cell death and inflammation and the partial recovery of cardiac phenotypes through pharmacological intervention, underscores the potential of targeting the Wnt/β-catenin signaling pathway as future perspective for ACM.Figure 1

Defects in exosome biogenesis are associated with sensorimotor defects in zebrafish vps4a mutants.

Mutations in human VPS4A are associated with neurodevelopmental defects, including motor delays and defective muscle tone. VPS4A encodes a AAA-ATPase required for membrane scission, but how mutations in VPS4A lead to impaired control of motor function is not known. Here we identified a mutation in zebrafish vps4a, T248I, that affects sensorimotor transformation. Biochemical analyses indicate that the T248I mutation reduces the ATPase activity of Vps4a and disassembly of ESCRT filaments, which mediate membrane scission. Consistent with the role for Vps4a in exosome biogenesis, vps4aT248I larvae have enlarged endosomal compartments in the CNS and decreased numbers of circulating exosomes in brain ventricles. Resembling the central form of hypotonia in VPS4A patients, motor neurons and muscle cells are functional in mutant zebrafish. Both somatosensory and vestibular inputs robustly evoke tail and eye movements, respectively. In contrast, optomotor responses, vestibulospinal, and acoustic startle reflexes are absent or strongly impaired in vps4aT248I larvae, indicating a greater sensitivity of these circuits to the T248I mutation. ERG recordings revealed intensity-dependent deficits in the retina, and in vivo calcium imaging of the auditory pathway identified a moderate reduction in afferent neuron activity, partially accounting for the severe motor impairments in mutant larvae. Further investigation of central pathways in vps4aT248I mutants showed that activation of descending vestibulospinal and midbrain motor command neurons by sensory cues is strongly reduced. Our results suggest that defects in sensorimotor transformation underly the profound yet selective effects on motor reflexes resulting from the loss of membrane scission mediated by Vps4a.Significance Statement Here we present a T248I mutation in vps4a, which causes sensorimotor defects in zebrafish larvae. Vps4a plays a key role in membrane scission. Spanning biochemical to systems level analyses, our study indicates that a reduction in Vps4a enzymatic activity leads to abnormalities in membrane-scission dependent processes such as endosomal protein trafficking and exosome biogenesis, resulting in pronounced deficits in sensorimotor transformation of visual, auditory, and vestibular cues. We suggest that the mechanisms underlying this type of dysfunction in zebrafish may also contribute to the condition seen in human patients with de novo mutations in the human VPS4A orthologue.

Shared and unique consequences of Joubert Syndrome gene dysfunction on the zebrafish central nervous system.

Joubert Syndrome (JBTS) is a neurodevelopmental ciliopathy defined by a highly specific midbrain-hindbrain malformation, variably associated with additional neurological features. JBTS displays prominent genetic heterogeneity with >40 causative genes that encode proteins localising to the primary cilium, a sensory organelle that is essential for transduction of signalling pathways during neurodevelopment, among other vital functions. JBTS proteins localise to distinct ciliary subcompartments, suggesting diverse functions in cilium biology. Currently, there is no unifying pathomechanism to explain how dysfunction of such diverse primary cilia-related proteins results in such a highly specific brain abnormality. In order to identify the shared consequence of JBTS gene dysfunction, we carried out transcriptomic analysis using zebrafish mutants for the JBTS-causative genes cc2d2aw38, cep290fh297, inpp5ezh506, talpid3i264 and togaram1zh510and the Bardet-Biedl syndrome-causative gene bbs1k742. We identified no commonly dysregulated signalling pathways in these mutants and yet all mutants displayed an enrichment of altered gene sets related to central nervous system function. We found that JBTS mutants have altered primary cilia throughout the brain, however do not display abnormal brain morphology. Nonetheless, behavioural analyses revealed reduced locomotion and loss of postural control which, together with the transcriptomic results, hint at underlying abnormalities in neuronal activity and/or neuronal circuit function. These zebrafish models therefore offer the unique opportunity to study the role of primary cilia in neuronal function beyond early patterning, proliferation and differentiation.

Differential roles of NR4A2 (NURR1) paralogs in the brain and behavior of zebrafish.

Dopaminergic (DAnergic) dysfunction and imbalanced dopamine (DA) levels are known contributors to the pathogenesis of numerous psychiatric and neurodegenerative disorders. Of the many identified risk factors for DA-associated disorders, nuclear receptor subfamily 4 group A2 (NR4A2; or nuclear receptor related-1 protein (NURR1)), a transcription factor involved in DAnergic differentiation, has been associated with Parkinson's disease and attention deficit hyperactive disorder (ADHD). In zebrafish, transient loss of nr4a2 was previously shown to decrease tyrosine hydroxylase (TH) expression and impair locomotion. To further characterize the roles of the two zebrafish nr4a2 paralogs, nr4a2a, and nr4a2b, we produced targeted loss-of-function mutants and examined DAnergic neuron regeneration, oxidative respiration, and behavioral traits. The loss of nr4a2a function more closely recapitulated Parkinsonian phenotypes and affected neurotrophic factor gene expression. Conversely, nr4a2b mutants displayed behavioral symptoms reminiscent of mice deficient in Nr4a2 with increased neurotrophic output. In contrast, nr4a2b mutants also displayed increased metabolic input from non-mitochondrial sources indicative of high cytosolic reactive oxygen species and perturbed mitochondrial function. The nr4a2a mutants also showed increased maximal respiration, which may suggest a compensatory mechanism to meet the metabolic requirements of DAnergic neuron health. Overall, the zebrafish mutants generated in this study helped uncover molecular mechanisms involved in DA-related disease pathologies, and in the regeneration of DAnergic neurons.

Astrogliosis and neuroinflammation underlie scoliosis upon cilia dysfunction.

Cilia defects lead to scoliosis in zebrafish, but the underlying pathogenic mechanisms are poorly understood and may diverge depending on the mutated gene. Here, we dissected the mechanisms of scoliosis onset in a zebrafish mutant for the rpgrip1l gene encoding a ciliary transition zone protein. rpgrip1l mutant fish developed scoliosis with near-total penetrance but asynchronous onset in juveniles. Taking advantage of this asynchrony, we found that curvature onset was preceded by ventricle dilations and was concomitant to the perturbation of Reissner fiber polymerization and to the loss of multiciliated tufts around the subcommissural organ. Rescue experiments showed that Rpgrip1l was exclusively required in foxj1a-expressing cells to prevent axis curvature. Genetic interactions investigations ruled out Urp1/2 levels as a main driver of scoliosis in rpgrip1 mutants. Transcriptomic and proteomic studies identified neuroinflammation associated with increased Annexin levels as a potential mechanism of scoliosis development in rpgrip1l juveniles. Investigating the cell types associated with annexin2 over-expression, we uncovered astrogliosis, arising in glial cells surrounding the diencephalic and rhombencephalic ventricles just before scoliosis onset and increasing with time in severity. Anti-inflammatory drug treatment reduced scoliosis penetrance and severity and this correlated with reduced astrogliosis and macrophage/microglia enrichment around the diencephalic ventricle. Mutation of the cep290 gene encoding another transition zone protein also associated astrogliosis with scoliosis. Thus, we propose astrogliosis induced by perturbed ventricular homeostasis and associated with immune cell activation as a novel pathogenic mechanism of zebrafish scoliosis caused by cilia dysfunction.

Poly(A)-Specific Ribonuclease Deficiency Leads to Deregulated Expression of Genes Involved in Sex Determination and Gonadal Maturation in Zebrafish

Abstract Background Deadenylation, the process of removal of poly (A) tail of messenger ribonucleic acids (mRNAs), is a rate-limiting step in mRNA stability, and poly(A)-specific ribonuclease (PARN) is the most important exonuclease involved in this process. Besides mRNA stability, PARN is also involved in several other processes including telomere maintenance, noncoding RNA maturation, ribosome biogenesis, and TP53 function. Previously, we have shown that zebrafish PARN null mutants are viable and fertile but turn out to only develop into males, indicating a role in oogenesis. The present study was focused on analyzing the expression of genes involved in sex determination and gonadal development in PARN mutant zebrafish. Materials and Methods Total RNA was extracted and quantitative real-time polymerase chain reaction was performed to determine the expression level of genes involved in gonad development in PARN mutant embryos (4 days postfertilization [dpf]) and adults (120 dpf) in comparison to their wild-type siblings. The expression levels were estimated by the ΔΔCT relative quantification method. Results At 4 dpf, the expression of germ cell-specific genes did not show any significant difference in the null mutants compared to the heterozygous and their wild-type siblings, suggesting no effect on germ cell differentiation due to the loss of PARN. However, the majority of the ovary-associated genes analyzed showed an increased expression in PARN null and heterozygous mutants compared to the wild-type siblings. Intriguingly, the expression of testis-associated genes showed decreased expression in the mutants compared to their wild-type siblings at 4 dpf. In adult stages, as expected, the expression of genes that jointly regulate the proper formation and function of ovaries and testes showed decreased expression in PARN null mutants. Interestingly, the expression of genes involved in the differentiation of testes, despite showing a decreased expression in the mutants, was comparable between the null and heterozygous mutants. Conclusion Taken together, these results suggest that the loss of PARN does not affect germ cell differentiation but affects the sexual differentiation that happens at later stages of development, particularly the process of oogenesis, in zebrafish.

8415 Rapid Generation Of An In Vivo Loss-Of-Function Genetic Model Of sdhb Zebrafish: Functional And Metabolic Characterization

Abstract Disclosure: S. Parisien-La Salle: None. F. Nobilleau: None. J. Lamontagne: None. S. Éric: None. I. Bourdeau: None. Introduction: Animal research has been limited in pheochromocytomas and paragangliomas (PPGLs). Recently, Dona et al., described a sdhb mutated zebrafish model by introducing a 13 bp frameshift mutation at the sdhb exon1—intron1 boundary into the zebrafish sdhb gene that recapitulated features of PPGLs. Objective: To generate a new model of mutated sdhb zebrafish to further investigate the underlying metabolic and biochemical perturbations in vivo. Methods: We took advantage of the genetic accessibility of zebrafish embryo to generate loss-of-function model for sdhb using CRISPR/Cas9 technology. Three guide RNAs were designed and microinjected in one-cell stage zebrafish embryos to target the coding sequence of zebrafish sdhb gene. In order to control for the stress brought on by injections, we injected a group of zebrafish with Cas9 endonuclease as a control. At five days post fertilization, mutant and control zebrafish were flash frozen and sent for liquid chromatography mass spectrometry measurements of Krebs cycle metabolites and normetanephrines/metanephrines. All results were normalized to the control groups consisting of wild-type or Cas9 injected larvae. Sdhb expression was analyzed by RT-qPCR in sdhb mutants and wild-type zebrafish larvae. We also monitored survival and heart rate in sdhb mutant zebrafish, compared to wild-type and Cas9. Results: Firstly, we confirmed the significant reduction of sdhb expression in CRISPR-injected larvae compared to wild-type larvae at 5 dpf (0.0613 vs 1.000 p<0.0001). Our metabolic panel showed that succinate was up to 26 times more elevated in sdhb mutants than in wild-type fish extracts (sdhb: 26.51 p<0.0001). Lactate (sdhb: 5.27 p<0.0001), leucine (sdhb: 2.88 p<0.0001), arginine (sdhb: 1.50 p=0.0034) and HMG-CoA (sdhb: 1.36 p=0.0033) were also higher in sdhb mutants. Whereas aspartate (sdhb: 0.244 p<0.0001) and oxidized gluthiatone (sdhb: 0.64 p=0.0011) were significantly lower in sdhb mutants than in wild-types. In regards to functionality, normetanephrine and metanephrine levels were at least four folds higher in sdhb mutants than in Cas9 injected larvaes (4.06 p<0.0001 and 3.42 p<0.0001 respectively). Interestingly, this difference was more noticeable in the fish bathing medium than in larvae tissue extracts, suggesting an increased hormonal excretion (normetanephrines: 4.81 p<0.0001 and metanephrines: 9.40 p<0.0001). Finally, sdhb mutated zebrafish presented with a higher heart rate (148 vs 133 p<0.0001) and reduced lifespan (p<0.0001) when compared to the wild-type/Cas9 group. Conclusion: These findings confirm that the zebrafish is an ideal model for studying PPGLs and their associated genetic defects. Our approach allows the in vivo assessment of a large metabolic panel, opening avenues on new potential clinical metabolic biomarkers in a loss-of-function of the SDHB gene. Ref: Dona M, et al. Endocr Relat Cancer. 2021 Presentation: 6/1/2024

Rnf111 has a pivotal role in regulating development of definitive hematopoietic stem and progenitor cells through the Smad2/3-Gcsfr/NO axis in zebrafish.

The ubiquitination or SUMOylation of hematopoietic related factors plays pivotal roles in hematopoiesis. RNF111, known as a ubiquitin ligase (Ubl), is a newly discovered SUMO-targeted ubiquitin ligase (STUbl) involved in multiple signaling pathways mediated by TGF-β family members. However, its role in hematopoiesis remains unclear. Herein, a heritable Rnf111 mutant zebrafish line was generated by CRISPR/Cas9-mediated genome editing. Impaired hematopoietic stem and progenitor cells (HSPC) of definitive hematopoiesis was found in Rnf111 deficient mutants. Ablation of Rnf111 resulted in decreased phosphorylation of Smad2/3 in HSPC. Definitive endoderm 2 inducer (IDE2), which specifically activates TGF-β signaling and downstream Smad2 phosphorylation, can restore the definitive hematopoiesis in Rnf111-deficient embryos. Further molecular mechanism studies revealed that Gcsfr/NO signaling was an important target pathway of Smad2/3 involved in Rnf111-mediated HSPC development. In conclusion, our study demonstrated that Rnf111 contributes to the development of HSPC by maintaining Smad2/3 phosphorylation and the Gcsfr/NO signaling pathway activation. Keywords: Rnf111, Ubiquitin ligase (UbL), HSPC, Smad2/3, Gcsfr/NO.

Foxe1 mutant zebrafish show indications of a hypothyroid phenotype and increased sensitivity to ethanol for craniofacial malformations.

FOXE1 mutations in humans are associated with cleft palate and hypothyroidism. We previously developed a foxe1 mutant zebrafish demonstrating mineralization defects in larvae. In the present study, we investigate the thyroid status and skeletal phenotype of adult foxe1 mutants. Mutant fish have increased expression of tshβ in the pituitary, and of hepatic dio1 and dio2. In plasma, we found higher Mg levels. Together these findings are indicative of hypothyroidism. We further observed mineralization defects in scales due to enhanced osteoclast activity as measured by increased expression levels of tracp, ctsk, and rankl. Gene-environment interactions in the etiology of FOXE1-related craniofacial abnormalities remain elusive, which prompts the need for models to investigate genotype-phenotype associations. We here investigated whether ethanol exposure increases the risk of developing craniofacial malformations in foxe1 mutant larvae that we compared to wild types. We found in ethanol-exposed mutants an increased incidence of developmental malformations and marked changes in gene expression patterns of cartilage markers (sox9a), apoptotic markers (casp3b), retinoic acid metabolism (cyp26c1), and tissue hypoxia markers (hifaa, hifab). Taken together, this study shows that the foxe1 mutant zebrafish recapitulates phenotypes associated with FOXE1 mutations in human patients and a clear foxe1-ethanol interaction.

A prioritization tool for cilia-associated genes and their in vivo resources unveils new avenues for ciliopathy research.

Defects in ciliary signaling or mutations in proteins that localize to primary cilia lead to a class of human diseases known as ciliopathies. Approximately 10% of mammalian genes encode cilia-associated proteins, and a major gap in the cilia research field is knowing which genes to prioritize to study and finding the in vivo vertebrate mutant alleles and reagents available for their study. Here, we present a unified resource listing the cilia-associated human genes cross referenced to available mouse and zebrafish mutant alleles, and their associated phenotypes, as well as expression data in the kidney and functional data for vertebrate Hedgehog signaling. This resource empowers researchers to easily sort and filter genes based on their own expertise and priorities, cross reference with newly generated -omics datasets, and quickly find in vivo resources and phenotypes associated with a gene of interest.

Gα13 controls pharyngeal endoderm convergence by regulating E-cadherin expression and RhoA activation.

Pharyngeal endoderm cells undergo convergence and extension (C&E), which is essential for endoderm pouch formation and craniofacial development. Our previous work implicates Gα13/RhoA-mediated signaling in regulating this process, but the underlying mechanisms remain unclear. Here, we have used endoderm-specific transgenic and Gα13 mutant zebrafish to demonstrate that Gα13 plays a crucial role in pharyngeal endoderm C&E by regulating RhoA activation and E-cadherin expression. We showed that during C&E, endodermal cells gradually establish stable cell-cell contacts, acquire apical-basal polarity and undergo actomyosin-driven apical constriction, which are processes that require Gα13. Additionally, we found that Gα13-deficient embryos exhibit reduced E-cadherin expression, partially contributing to endoderm C&E defects. Notably, interfering with RhoA function disrupts spatial actomyosin activation without affecting E-cadherin expression. Collectively, our findings identify crucial cellular processes for pharyngeal endoderm C&E and reveal that Gα13 controls this through two independent pathways - modulating RhoA activation and regulating E-cadherin expression - thus unveiling intricate mechanisms governing pharyngeal endoderm morphogenesis.

Knockout of rbm24a and rbm24b genes in zebrafish impairs skeletal and cardiac muscle integrity and function during development.

Skeletal and cardiac muscles are contractile tissues whose development and function are dependent on genetic programs that must be precisely orchestrated in time and space. In addition to transcription factors, RNA-binding proteins tightly regulate gene expression by controlling the fate of RNA transcripts, thus specific proteins levels within the cell. Rbm24 has been identified as a key player of myogenesis and cardiomyogenesis in several vertebrates, by controlling various aspects of post-transcriptional regulation, including pre-mRNA alternative splicing and mRNA stabilization. In zebrafish, knockdown of rbm24a or rbm24b also causes skeletal and cardiac muscle phenotypes, but how their combined loss affects muscle integrity and function remains elusive. By genome editing, we have generated rbm24a and rbm24b single mutants as well as double mutants. Structural analyses indicate that homozygous rbm24a and rbm24b double mutants exhibit severe somitic muscle and cardiac phenotypes, although rbm24b single mutants are obviously normal. We further show that the loss of rbm24a and rbm24b disrupts sarcomere organization, impairing functional contractility and motility of skeletal and cardiac muscles. The rbm24 mutant zebrafish represents a new genetic tool for in-depth studies of Rbm24-mediated post-transcriptional regulation of skeletal and cardiac muscle development, disease and regeneration.

Identification of a neuropeptide in suppressing food intake in zebrafish

Neuropeptides play crucial roles in regulating various physiological processes in vertebrates. In this study, we identified a novel neuropeptide-encoding gene, nwk, in the genomes of some vertebrate species. The nwk cDNA was subsequently cloned from the brain of zebrafish. The Nwk precursor comprises 88 amino acids, with a putative mature peptide (Nwk-22) of 22 amino acids. Sequence analysis revealed that Nwk-22 is relatively conserved across vertebrate species. Nwk is predominantly expressed in the brain, with positive mRNA cells identified in the TPp and preoptic area. Intraperitoneal injection of Nwk-22 suppressed food intake and downregulated the mRNA expression of the orexigenic factor agouti-related peptide (agrp) in zebrafish. Additionally, a CRISPR/Cas9 approach was used to generate nwk mutant zebrafish. The nwk−/− zebrafish exhibited increased food consumption compared to wild-type controls. Furthermore, Nwk-22a injection in nwk−/− fish also suppressed agrp expression while stimulating the expression of the anorexigenic gene pomca, further supporting the anorexigenic role of Nwk. Taken together, these findings suggest that Nwk functions as an anorexigenic factor, reducing food intake by downregulating orexigenic genes like agrp and upregulating anorexigenic genes like pomc in zebrafish.

Deletion of the foxO1 gene reduces hypoxia tolerance in zebrafish embryos by influencing erythropoiesis

FoxO1 (Forkhead box O1) belongs to the evolutionarily conserved FoxO subfamily and is involved in diverse physiologic processes, including apoptosis, cell cycle, DNA damage repair, oxidative stress and cell differentiation. FoxO1 plays an important role in regulating the hypoxia microenvironment such as cancers, but its role in hypoxia adaptation remains unclear in animals. To understand the function of foxO1 in hypoxia response, we constructed foxO1a and foxO1b mutant zebrafish using CRISPR/Cas9 technology. It was found that foxO1a and foxO1b destruction affected the hematopoietic system in the early zebrafish embryos. Specifically, FoxO1a and FoxO1b were found to affect the transcriptional activity of runx1, a marker gene for hematopoietic stem cells (HSCs). Moreover, foxO1a and foxO1b had complementary features in hypoxia response, and foxO1a or/and foxO1b destruction resulted in tolerance of zebrafish becoming weakened in hypoxia due to insufficient hemoglobin supply. Additionally, the transcriptional activity of these two genes was demonstrated to be regulated by Hif1α. In conclusion, foxO1a and foxO1b respond to Hif1α-mediated hypoxia response by participating in zebrafish erythropoiesis. These results will provide a theoretical basis for further exploring the function of FoxO1 in hematopoiesis and hypoxia response.

Contributions of mirror-image hair cell orientation to mouse otolith organ and zebrafish neuromast function.

Otolith organs in the inner ear and neuromasts in the fish lateral-line harbor two populations of hair cells oriented to detect stimuli in opposing directions. The underlying mechanism is highly conserved: the transcription factor EMX2 is regionally expressed in just one hair cell population and acts through the receptor GPR156 to reverse cell orientation relative to the other population. In mouse and zebrafish, loss of Emx2 results in sensory organs that harbor only one hair cell orientation and are not innervated properly. In zebrafish, Emx2 also confers hair cells with reduced mechanosensory properties. Here, we leverage mouse and zebrafish models lacking GPR156 to determine how detecting stimuli of opposing directions serves vestibular function, and whether GPR156 has other roles besides orienting hair cells. We find that otolith organs in Gpr156 mouse mutants have normal zonal organization and normal type I-II hair cell distribution and mechano-electrical transduction properties. In contrast, gpr156 zebrafish mutants lack the smaller mechanically-evoked signals that characterize Emx2-positive hair cells. Loss of GPR156 does not affect orientation-selectivity of afferents in mouse utricle or zebrafish neuromasts. Consistent with normal otolith organ anatomy and afferent selectivity, Gpr156 mutant mice do not show overt vestibular dysfunction. Instead, performance on two tests that engage otolith organs is significantly altered - swimming and off-vertical-axis rotation. We conclude that GPR156 relays hair cell orientation and transduction information downstream of EMX2, but not selectivity for direction-specific afferents. These results clarify how molecular mechanisms that confer bi-directionality to sensory organs contribute to function, from single hair cell physiology to animal behavior.

Instantaneous visual genotyping and facile site-specific transgenesis via CRISPR-Cas9 and phiC31 integrase.

Here, we introduce 'TICIT', targeted integration by CRISPR-Cas9 and integrase technologies, which utilizes the site-specific DNA recombinase - phiC31 integrase - to insert large DNA fragments into CRISPR-Cas9 target loci. This technique, which relies on first knocking in a 39-basepair phiC31 landing site via CRISPR-Cas9, enables researchers to repeatedly perform site-specific transgenesis at the exact genomic location with high precision and efficiency. We applied this approach to devise a method for the instantaneous determination of a zebrafish's genotype simply by examining its color. When a zebrafish mutant line must be propagated as heterozygotes due to homozygous lethality, employing this method allows facile identification of a population of homozygous mutant embryos even before the mutant phenotypes manifest. Thus, it should facilitate various downstream applications, such as large-scale chemical screens. We demonstrated that TICIT could also create reporter fish driven by an endogenous promoter. Further, we identified a landing site in the tyrosinase gene that could support transgene expression in a broad spectrum of tissue and cell types. In sum, TICIT enables site-specific DNA integration without requiring complex donor DNA construction. It can yield consistent transgene expression, facilitate diverse applications in zebrafish, and may be applicable to cells in culture and other model organisms.

Prox1a promotes liver growth and differentiation by repressing cdx1b expression and intestinal fate transition in zebrafish

The liver is a key endoderm-derived multifunctional organ within the digestive system. Prospero homeobox 1 (Prox1) is an essential transcription factor for liver development, but its specific function is not well understood. Here, we show that hepatic development, including the formation of intrahepatic biliary and vascular networks, is severely disrupted in prox1a mutant zebrafish. We find that Prox1a is essential for liver growth and proper differentiation but not required for early hepatic cell fate specification. Intriguingly, prox1a depletion leads to ectopic initiation of a Cdx1b-mediated intestinal program and the formation of intestinal lumen-like structures within the liver. Morpholino knockdown of cdx1b alleviates liver defects in the prox1a mutant zebrafish. Finally, chromatin immunoprecipitation analysis reveals that Prox1a binds directly to the promoter region of cdx1b, thereby repressing its expression. Overall, our findings indicate that Prox1a is required to promote and protect hepatic development by repression of Cdx1b-mediated intestinal cell fate in zebrafish.

The people behind the papers - Joey Ghersi and Stefania Nicoli.

Akt is believed to be important for vascular development, but complex tissue-specific loss-of-function studies have been difficult in mice because of embryonic lethality. In a new study, Wenping Zhou, Joey Ghersi, Stefania Nicoli and colleagues report the phenotype of a complete Akt mutant zebrafish and its role in arterial specification via Notch signaling. To learn more about their work, we spoke with corresponding authors Joey Ghersi, Assistant Professor at Centre Hospitalier Universitaire (CHU) Sainte-Justine, Canada, and Stefania Nicoli, Associate Professor Tenure at Yale University, USA.

Genetic and Environmental Factors Co-Contributing to Behavioral Abnormalities in adnp/adnp2 Mutant Zebrafish.

Human mutations of ADNP and ADNP2 are known to be associated with neural developmental disorders (NDDs), including autism spectrum disorders (ASDs) and schizophrenia (SZ). However, the underlying mechanisms remain elusive. In this study, using CRISPR/Cas9 gene editing technology, we generated adnp and adnp2 mutant zebrafish models, which exhibited developmental delays, brain deficits, and core behavioral features of NDDs. RNA sequencing analysis of adnpa-/-; adnpb-/- and adnp2a-/-; adnp2b-/- larval brains revealed altered gene expression profiles affecting synaptic transmission, autophagy, apoptosis, microtubule dynamics, hormone signaling, and circadian rhythm regulation. Validation using whole-mount in situ hybridization (WISH) and real-time quantitative PCR (qRT-PCR) corroborated these findings, supporting the RNA-seq results. Additionally, loss of adnp and adnp2 resulted in significant downregulation of pan-neuronal HuC and neuronal fiber network α-Tubulin signals. Importantly, prolonged low-dose exposure to environmental endocrine disruptors (EEDs) aggravated behavioral abnormalities in adnp and adnp2 mutants. This comprehensive approach enhances our understanding of the complex interplay between genetic mutations and environmental factors in NDDs. Our findings provide novel insights and experimental foundations into the roles of adnp and adnp2 in neurodevelopment and behavioral regulation, offering a framework for future preclinical drug screening aimed at elucidating the pathogenesis of NDDs and related conditions.