Modeling hematopoietic disorders in zebrafish

Zebrafish offer a powerful vertebrate model for studies of development and disease. The major advantages of this model include the possibilities of conducting reverse and forward genetic screens and of observing cellular processes by; in vivo; imaging of single cells. Moreover, pathways regulating blood development are highly conserved between zebrafish and mammals, and several discoveries made in fish were later translated to murine and human models. This review and accompanying poster provide an overview of zebrafish hematopoiesis and discuss the existing zebrafish models of blood disorders, such as myeloid and lymphoid malignancies, bone marrow failure syndromes and immunodeficiencies, with a focus on how these models were generated and how they can be applied for translational research

SRP54 mutations induce Congenital Neutropenia via dominant-negative effects on XBP1 splicing

Heterozygous de novo missense variants of SRP54 were recently identified in patients with congenital neutropenia (CN), displaying symptoms overlapping with Shwachman-Diamond-Syndrome (SDS).1 Here, we investigate srp54 KO zebrafish as the first in vivo model of SRP54 deficiency. srp54-/- zebrafish are embryonically lethal and display, next to severe neutropenia, multi-systemic developmental defects. In contrast, srp54+/- zebrafish are viable, fertile and only show mild neutropenia. Interestingly, injection of human SRP54 mRNAs carrying mutations observed in patients (T115A, T117Δ and G226E) aggravated neutropenia and induced pancreatic defects in srp54+/- fish, mimicking the corresponding human clinical phenotypes. These data suggest that the variable phenotypes observed in patients may be due to mutation-specific dominant negative effects on the functionality of the residual wildtype SRP54 protein. Consistently, overexpression of mutated SRP54 also induced neutropenia in wildtype fish and impaired granulocytic maturation of human promyelocytic HL-60 cells as well as of healthy cord-blood derived CD34+ HSPCs. Mechanistically, srp54 mutant fish and human cells show impaired unconventional splicing of the transcription factor X-box binding protein 1 (Xbp1). Vice-versa, xbp1 morphants recapitulate phenotypes observed in srp54 deficiency and, importantly, injection of spliced, but not unspliced xbp1 mRNA rescues neutropenia in srp54+/- zebrafish. Together, these data indicate that SRP54 is critical for the development of various tissues, with neutrophils reacting most sensitively to SRP54 loss. The heterogenic phenotypes observed in patients, ranging from mild CN to SDS-like disease, may be due to different dominant negative effects of mutated SRP54 proteins on downstream XBP1 splicing, which represents a potential therapeutic target

Evi1 regulates Notch activation to induce zebrafish hematopoietic stem cell emergence

During development, hematopoietic stem cells (HSCs) emerge from aortic endothelial cells (ECs) through an intermediate stage called hemogenic endothelium by a process known as endothelial-to-hematopoietic transition (EHT). While Notch signaling, including its upstream regulator Vegf, is known to regulate this process, the precise molecular control and temporal specificity of Notch activity remain unclear. Here, we identify the zebrafish transcriptional regulator evi1 as critically required for Notch-mediated EHT In vivo live imaging studies indicate that evi1 suppression impairs EC progression to hematopoietic fate and therefore HSC emergence. evi1 is expressed in ECs and induces these effects cell autonomously by activating Notch via pAKT Global or endothelial-specific induction of notch, vegf, or pAKT can restore endothelial Notch and HSC formations in evi1 morphants. Significantly, evi1 overexpression induces Notch independently of Vegf and rescues HSC numbers in embryos treated with a Vegf inhibitor. In sum, our results unravel evi1-pAKT as a novel molecular pathway that, in conjunction with the shh-vegf axis, is essential for activation of Notch signaling in VDA endothelial cells and their subsequent conversion to HSCs

Mutations In Signal Recognition Particle Srp54 Cause Syndromic Neutropenia With Shwachman-Diamond-Like Features

Shwachman-Diamond syndrome (SDS) (OMIM # 260400) is a rare inherited bone marrow failure syndrome (IBMFS) that is primarily characterized by neutropenia and exocrine pancreatic insufficiency. Seventy-five to ninety percent of patients have compound heterozygous loss-of-function mutations in the Shwachman-Bodian-Diamond syndrome (SBDS) gene. Using trio whole-exome sequencing (WES) in an SBDS-negative SDS family and candidate gene sequencing in additional SBDS-negative SDS cases or molecularly undiagnosed IBMFS cases, we identified 3 independent patients, each of whom carried a de novo missense variant in SRP54 (encoding signal recognition particle 54 kDa). These 3 patients shared congenital neutropenia linked with various other SDS phenotypes. 3D protein modeling revealed that the 3 variants affect highly conserved amino acids within the GTPase domain of the protein that are critical for GTP and receptor binding. Indeed, we observed that the GTPase activity of the mutated proteins was impaired. The level of SRP54 mRNA in the bone marrow was 3.6-fold lower in patients with SRP54-mutations than in healthy controls. Profound reductions in neutrophil counts and chemotaxis as well as a diminished exocrine pancreas size in a SRP54-knockdown zebrafish model faithfully recapitulated the human phenotype. In conclusion, autosomal dominant mutations in SRP54, a key member of the cotranslation protein-targeting pathway, lead to syndromic neutropenia with a Shwachman-Diamond-like phenotype.WoSScopu

Des sources du savoir aux médicaments du futur

L'origine des pharmacopées traditionnelles L'élaboration des pharmacopées Les médicaments du XXIe siècle Comment les connaissances des savoirs thérapeutiques se sont-elles transmises au travers des différentes cultures ? Cet ouvrage innovant, qui réunit les travaux présentés au 4e Congrès européen d'ethnopharmacologie, fait remonter à la préhistoire les sources des connaissances thérapeutiques. Si les pharmacopées écrites jalonnent l'histoire des grandes médecines savantes, d'autres modes d'accès à la connaissance semblent exister dans l'univers chamanique des sociétés de tradition orale ainsi que dans la façon dont les animaux malades se soignent par les plantes. L'évaluation des propriétés pharmaco-toxicologiques et chimiques des plantes d'usage traditionnel devrait par ailleurs favoriser le développement futur des médicaments à base de plantes, l'un des thèmes porteurs abordés dans cet ouvrage. Mais l'objectif de ce livre est aussi de susciter, partout dans le monde, de nouvelles thématiques de recherche dans le domaine de la préhistoire du médicament et de la compréhension de l'acquisition et de la transmission du savoir. Le développement du phytomédicament non toxique destiné à l'homme et à l'animal figure également parmi les enjeux majeurs de demain.The origin of traditional pharmacopoeias The development of pharmacopoeias The medicines of the XXIth century How have the traditional Therapeutical knowledges been transmited to the différent cultures? This innovating book containing the proceedings of the 4th European Congress of Ethnopharmacology return to prehistory the sources of fherapeutical knowledge and asks how the animals cure themselves with plants. If the printing pharmacopoeias ponctuate the history of learning medicines other way of accessibility to the knowledge seems exist in the world of shaman in society with oral tradition. Ethnopharmacological evaluation of traditional médicinal plant should favour the development of phytomedicine. The purpose of this publication is also to provide dues to scientists in the whole world and help them identify new avenues for research in the field of the prehistory of drugs, for a better understanding of the way knowledge is acquired and then transmitted, and for the development of non-toxic herbal medicines for administration to human and animal beings