Cul4a promotes zebrafish primitive erythropoiesis via upregulating scl and gata1 expression

Tango6 regulates HSPC proliferation and definitive haematopoiesis via Ikzf1 and Cmyb in caudal haematopoietic tissue

Haematopoietic stem and progenitor cells (HSPCs) arise from the aorta-gonad-mesonephros and migrate to the caudal haematopoietic tissue (CHT) in zebrafish, where nascent HSPCs undergo tightly controlled proliferation and differentiation to promote definitive haematopoiesis. Effective expansion of HSPCs requires the coordination of well-established vesicle trafficking systems and appropriate transcription factors. However, the underlying molecules are yet to be identified. Using large-scale genetic screening of zebrafish larvae, Tango6 of the coat protein complex I (COPI) vesicle trafficking system was found to be indispensable for HSPC proliferation and definitive haematopoiesis. Homozygous tango6cq72 mutants display defective expansion of HSPCs in the CHT and compromised haematopoiesis. However, haematopoietic overexpression of Tango6 promoted haematopoietic expansion. tango6 deficiency caused a decline in RNA polymerase II subunit B and accumulation of DNA damage, which suppressed cell expansion in a P53-dependent manner. ikzf1 and cmyb (myb), two indispensable haematopoietic transcription factors, are targets of P53 and are used by tango6 in haematopoiesis. The haematopoietic phenotype was partially recovered by compensating for loss of ikzf1 and cmyb in tango6cq72 mutants. This study reveals a vesicle trafficking-mediated Tango6-P53-Ikzf1/Cmyb axis in zebrafish definitive haematopoiesis.

Zebrafish ELL-associated factors Eaf1/2 modulate erythropoiesis via regulating gata1a expression and WNT signaling to facilitate hypoxia tolerance

EAF1 and EAF2, the eleven-nineteen lysine-rich leukemia (ELL)-associated factors which can assemble to the super elongation complex (AFF1/4, AF9/ENL, ELL, and P-TEFb), are reported to participate in RNA polymerase II to actively regulate a variety of biological processes, including leukemia and embryogenesis, but whether and how EAF1/2 function in hematopoietic system related hypoxia tolerance during embryogenesis remains unclear. Here, we unveiled that deletion of EAF1/2 (eaf1^-/- and eaf2^-/-) caused reduction in hypoxia tolerance in zebrafish, leading to reduced erythropoiesis during hematopoietic processes. Meanwhile, eaf1^-/- and eaf2^-/- mutants showed significant reduction in the expression of key transcriptional regulators scl, lmo2, and gata1a in erythropoiesis at both 24 h post fertilization (hpf) and 72 hpf, with gata1a downregulated while scl and lmo2 upregulated at 14 hpf. Mechanistically, eaf1^-/- and eaf2^-/- mutants exhibited significant changes in the expression of epigenetic modified histones, with a significant increase in the binding enrichment of modified histone H3K27me3 in gata1a promoter rather than scl and lmo2 promoters. Additionally, eaf1^-/- and eaf2^-/- mutants exhibited a dynamic expression of canonical WNT/β-catenin signaling during erythropoiesis, with significant reduction in p-β-Catenin level and in the binding enrichment of both scl and lmo2 promoters with the WNT transcriptional factor TCF4 at 24 hpf. These findings demonstrate an important role of Eaf1/2 in erythropoiesis in zebrafish and may have shed some light on regeneration medicine for anemia and related diseases and on molecular basis for fish economic or productive traits, such as growth, disease resistance, hypoxia tolerance, and so on.

Stress-induced reduction of Na+/H+ exchanger isoform 1 promotes maladaptation of neuroplasticity and exacerbates depressive behaviors

Major depression disorder (MDD) is a neuropsychiatric disorder characterized by abnormal neuronal activity in specific brain regions. A factor that is crucial in maintaining normal neuronal functioning is intracellular pH (pHi) homeostasis. In this study, we show that chronic stress, which induces depression-like behaviors in animal models, down-regulates the expression of the hippocampal Na⁺/H⁺ exchanger isoform 1, NHE1, a major determinant of pHi in neurons. Knockdown of NHE1 in CA1 hippocampal pyramidal neurons leads to intracellular acidification, promotes dendritic spine loss, lowers excitatory synaptic transmission, and enhances the susceptibility to stress exposure in rats. Moreover, E3 ubiquitin ligase cullin4A may promote ubiquitination and degradation of NHE1 to induce these effects of an unbalanced pHi on synaptic processes. Electrophysiological data further suggest that the abnormal excitability of hippocampal neurons caused by maladaptation of neuroplasticity may be involved in the pathogenesis of this disease. These findings elucidate a mechanism for pHi homeostasis alteration as related to MDD.

Using the Zebrafish as a Genetic Model to Study Erythropoiesis

Vertebrates generate mature red blood cells (RBCs) via a highly regulated, multistep process called erythropoiesis. Erythropoiesis involves synthesis of heme and hemoglobin, clearance of the nuclei and other organelles, and remodeling of the plasma membrane, and these processes are exquisitely coordinated by specific regulatory factors including transcriptional factors and signaling molecules. Defects in erythropoiesis can lead to blood disorders such as congenital dyserythropoietic anemias, Diamond–Blackfan anemias, sideroblastic anemias, myelodysplastic syndrome, and porphyria. The molecular mechanisms of erythropoiesis are highly conserved between fish and mammals, and the zebrafish (Danio rerio) has provided a powerful genetic model for studying erythropoiesis. Studies in zebrafish have yielded important insights into RBC development and established a number of models for human blood diseases. Here, we focus on latest discoveries of the molecular processes and mechanisms regulating zebrafish erythropoiesis and summarize newly established zebrafish models of human anemias.

Tipping the Scales With Zebrafish to Understand Adaptive Tumor Immunity

The future of improved immunotherapy against cancer depends on an in-depth understanding of the dynamic interactions between the immune system and tumors. Over the past two decades, the zebrafish has served as a valuable model system to provide fresh insights into both the development of the immune system and the etiologies of many different cancers. This well-established foundation of knowledge combined with the imaging and genetic capacities of the zebrafish provides a new frontier in cancer immunology research. In this review, we provide an overview of the development of the zebrafish immune system along with a side-by-side comparison of its human counterpart. We then introduce components of the adaptive immune system with a focus on their roles in the tumor microenvironment (TME) of teleosts. In addition, we summarize zebrafish models developed for the study of cancer and adaptive immunity along with other available tools and technology afforded by this experimental system. Finally, we discuss some recent research conducted using the zebrafish to investigate adaptive immune cell-tumor interactions. Without a doubt, the zebrafish will arise as one of the driving forces to help expand the knowledge of tumor immunity and facilitate the development of improved anti-cancer immunotherapy in the foreseeable future.

ADP receptor P2y12 prevents excessive primitive hematopoiesis in zebrafish by inhibiting Gata1

In the past two decades, purinergic signaling has emerged as a key regulator of hematopoiesis in physiological and pathological conditions. ADP receptor P2y12 is a crucial component of this signaling, but whether it is involved in primitive hematopoiesis remains unknown. To elucidate the function of P2y12 and provide new insights for drug development, we established a zebrafish P2y12 mutant by CRISPR/Cas 9-based genetic modification system, and investigated whether P2y12 acted as an important regulator for primitive hematopoiesis. By using mass spectrometry (MS) combined with RNA sequencing, we showed that absence of P2y12 induced excessive erythropoiesis, evidenced by significantly increased expression of mature erythrocytes marker α-globin (Hbae1 and Hbae3), β-globin (Hbbe1 and Hbbe3). Expression pattern analysis showed that P2y12 was mainly expressed in red blood cells and endothelial cells of early zebrafish embryos. Further studies revealed that primitive erythroid progenitor marker Gata1 was markedly up-regulated. Remarkably, inhibition of Gata1 by injection of Gata1 morpholino could rescue the erythroid abnormality in P2y12 mutants. The present study demonstrates the essential role of purinergic signaling in differentiation of proerythrocytes during primitive hematopoiesis, and provides potential targets for treatment of blood-related disease and drug development.

iTRAQ-based quantitative proteomic analysis of the therapeutic effects of 2% hydrogen gas inhalation on brain injury in septic mice

Sepsis encephalopathy (SAE) has a high incidence and mortality rate in patients with sepsis; however, there is currently no effective treatment. Our previous studies have reported that 2% hydrogen (H₂) gas inhalation had a protective effect on sepsis and SAE; however, the specific mechanism have not been fully elucidated. In the current study, male Institute of Cancer Research mice were either used to create the cecal ligation and puncture (CLP) model or for sham surgery, followed by 2% H₂ gas inhalation for 60 min beginning at 1 and 6 h following sham or CLP surgeries. The isobaric tags for relative and absolute quantitation (iTRAQ)-based quantitative proteomics combined with liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis, hematoxylin and eosin (H&E) staining, Nissl staining, and western blot analysis were used to investigate the effects of H₂ on brain injury in mice with sepsis. The results of the H&E, and Nissl staining indicated that the CLP mice had a significant brain injury, which was characterized by aggravated pathological damage and was alleviated by 2% H₂ inhalation. Quantitative proteomics based on iTRAQ combined with LC-MS/MS analysis quantified a total of 5317 proteins, of which 39 were connected with the protective mechanism of H₂. In addition, H₂ could regulate the immune and the coagulation systems. Furthermore, western blot analysis revealed that H₂ decreased SAE in septic mice by downregulating the protein expression levels of SMAD4, DPYS, PTGDS and upregulating the expression level of CUL4A. These results provide insights into the mechanism of the positive effect of H₂ on SAE and contribute to the clinical application of H₂ in patients with sepsis.