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We evaluated the immunogenicity and protective ability of a chimpanzee replication-deficient adenovirus vectored COVID-19 vaccine (BV-AdCoV-1) expressing a stabilized pre-fusion SARS-CoV-2 spike glycoprotein in golden Syrian hamsters. Intranasal administration of BV-AdCoV-1 elicited strong humoral and cellular immunity in the animals. Furthermore, vaccination prevented weight loss, reduced SARS-CoV-2 infectious virus titers in the lungs as well as lung pathology and provided protection against SARS-CoV-2 live challenge. In addition, there was no vaccine-induced enhanced disease nor immunopathological exacerbation in BV-AdCoV-1-vaccinated animals. Furthermore, the vaccine induced cross-neutralizing antibody responses against the ancestral strain and the B.1.617.2, Omicron(BA.1), Omicron(BA.2.75) and Omicron(BA.4/5) variants of concern. These results demonstrate that BV-AdCoV-1 is potentially a promising candidate vaccine to prevent SARS-CoV-2 infection, and to curtail pandemic spread in humans.

A cis-regulatory genetic element which targets gene expression to stem cells, termed stem cell enhancer, serves as a molecular handle for stem cell-specific genetic engineering. Here we show the generation and characterization of a tamoxifen-inducible CreER

SummaryThe RUNX genes encode transcription factors involved in development and human disease. RUNX1 and RUNX3 are frequently associated with leukemias, yet the basis for their involvement in leukemogenesis is not fully understood. Here, we show that Runx1;Runx3 double-knockout (DKO) mice exhibited lethal phenotypes due to bone marrow failure and myeloproliferative disorder. These contradictory clinical manifestations are reminiscent of human inherited bone marrow failure syndromes such as Fanconi anemia (FA), caused by defective DNA repair. Indeed, Runx1;Runx3 DKO cells showed mitomycin C hypersensitivity, due to impairment of monoubiquitinated-FANCD2 recruitment to DNA damage foci, although FANCD2 monoubiquitination in the FA pathway was unaffected. RUNX1 and RUNX3 interact with FANCD2 independently of CBFβ, suggesting a nontranscriptional role for RUNX in DNA repair. These findings suggest that RUNX dysfunction causes DNA repair defect, besides transcriptional misregulation, and promotes the development of leukemias and other cancers.

The hallmark of vertebrate definitive hematopoiesis is the establishment of the hematopoietic stem/progenitor cell (HSPC) pool during embryogenesis. This process involves a defined ontogenic switching of HSPCs in successive hematopoietic compartments and is evolutionarily conserved from teleost fish to human. In zebrafish, HSPCs originate from the ventral wall of the dorsal aorta (VDA), from which they subsequently mobilize to an intermediate hematopoietic site known as the caudal hematopoietic tissue (CHT) and finally colonize the kidney for adult hematopoiesis. Despite substantial understanding of the ontogeny of HSPCs, the molecular basis governing migration, colonization and maintenance of HSPCs remains to be explored fully. Here, we report the isolation and characterization of two zebrafish mutants, rumbahkz1 and sambahkz2, that are defective in generating definitive hematopoiesis. We find that HSPC initiation in the VDA and subsequent homing to the CHT are not affected in these two mutants. However, the further development of HSPCs in the CHT is compromised in both mutants. Positional cloning reveals that Rumba is a novel nuclear C2H2 zinc-finger factor with unknown function and samba encodes an evolutionarily conserved protein that is homologous to human augmin complex subunit 3 (HAUS3). Furthermore, we show that these two factors independently regulate cell cycle progression of HSPCs and are cell autonomously required for HPSC development in the CHT. Our study identifies Rumba and Haus3 as two essential regulators of HSPC maintenance during zebrafish fetal hematopoiesis.

RUNX1/AML1 is among the most commonly mutated genes in human leukemia. Haploinsufficiency of RUNX1 causes familial platelet disorder with predisposition to myeloid malignancies (FPD/MM). However, the molecular mechanism of FPD/MM remains unknown. Here we show that murine Runx1+/− hematopoietic cells are hypersensitive to granulocyte colony-stimulating factor (G-CSF), leading to enhanced expansion and mobilization of stem/progenitor cells and myeloid differentiation block. Upon G-CSF stimulation, Runx1+/− cells exhibited a more pronounced phosphorylation of STAT3 as compared with Runx1+/+ cells, which may be due to reduced expression of Pias3, a key negative regulator of STAT3 signaling, and reduced physical sequestration of STAT3 by RUNX1. Most importantly, blood cells from a FPD patient with RUNX1 mutation exhibited similar G-CSF hypersensitivity. Taken together, Runx1 haploinsufficiency appears to predispose FPD patients to MM by expanding the pool of stem/progenitor cells and blocking myeloid differentiation in response to G-CSF.

Myelopoiesis is the process of producing all types of myeloid cells including monocytes/macrophages and granulocytes. Myeloid cells are known to manifest a wide spectrum of activities such as immune surveillance and tissue remodeling. Irregularities in myeloid cell development and their function are known to associate with the onset and the progression of a variety of human disorders such as leukemia. In the past decades, extensive studies have been carried out in various model organisms to elucidate the molecular mechanisms underlying myelopoiesis with the hope that these efforts will yield knowledge translatable into therapies for related diseases. Zebrafish has recently emerged as a prominent animal model for studying myelopoiesis, especially during early embryogenesis, largely owing to its unique properties such as transparent embryonic body and external development. This review introduces the methodologies used in zebrafish research and focuses on the recent research progresses of zebrafish myelopoiesis.

Hematopoiesis is a complex process which gives rise to all blood lineages in the course of an organism's lifespan. However, the underlying molecular mechanism governing this process is not fully understood. Here we report the isolation and detailed study of a newly identified zebrafish ugly duckling (Udu) mutant allele, Udusq1. We show that loss-of-function mutation in the udu gene disrupts primitive erythroid cell proliferation and differentiation in a cell-autonomous manner, resulting in red blood cell (RBC) hypoplasia. Positional cloning reveals that the Udu gene encodes a novel factor that contains 2 paired amphipathic α-helix–like (PAH-L) repeats and a putative SANT-L (SW13, ADA2, N-Cor, and TFIIIB–like) domain. We further show that the Udu protein is predominantly localized in the nucleus and deletion of the putative SANT-L domain abolishes its function. Our study indicates that the Udu protein is very likely to function as a transcription modulator essential for the proliferation and differentiation of erythroid lineage.

The stem cell leukemia (SCL) gene encodes a basic helix-loop-helix transcription factor and is essential for embryonic angiogenesis, hematopoietic stem cell specification, and erythrocyte maturation. Here, we report the isolation and characterization of the zebrafish scl promoter. We show that a 5-kilobase (kb) genomic fragment immediately upstream of the translation start site is capable of targeting the enhanced green fluorescence protein (EGFP) expression to the anterior and posterior lateral mesoderm where the endogenous scl normally expresses. Detailed analysis of the stable transgenic fish reveals that this 5-kb upstream sequence is sufficient to direct the EGFP transcription to the brain, spinal cord, and hematopoietic-endothelial progenitors, possibly the hemangioblast, but not primitive erythrocyte, suggesting that the zebrafish scl transcription in hematopoietic-endothelial progenitors and erythrocyte is regulated by distinct cis element(s). Our study has defined the cis regulatory element(s) for zebrafish scl expression in the brain, spinal cord, and hematopoietic-endothelial progenitors and established a valuable transgenic line Tg(5'5kbscl:EGFP) for studying hematopoietic lineage development.