Endothelio-Mesenchymal Interaction Controls runx1 Expression and Modulates the notch Pathway to Initiate Aortic Hematopoiesis

SummaryHematopoietic stem cells (HSCs) are produced by a small cohort of hemogenic endothelial cells (ECs) during development through the formation of intra-aortic hematopoietic cell (HC) clusters. The Runx1 transcription factor plays a key role in the EC-to-HC and -HSC transition. We show that Runx1 expression in hemogenic ECs and the subsequent initiation of HC formation are tightly controlled by the subaortic mesenchyme, although the mesenchyme is not a source of HCs. Runx1 and Notch signaling are involved in this process, with Notch signaling decreasing with time in HCs. Inhibiting Notch signaling readily increases HC production in mouse and chicken embryos. In the mouse, however, this increase is transient. Collectively, we show complementary roles of hemogenic ECs and mesenchymal compartments in triggering aortic hematopoiesis. The subaortic mesenchyme induces Runx1 expression in hemogenic-primed ECs and collaborates with Notch dynamics to control aortic hematopoiesis

The quail genome:insights into social behaviour, seasonal biology and infectious disease response

Background: The Japanese quail (Coturnix japonica) is a popular domestic poultry species and an increasingly significant model species in avian developmental, behavioural and disease research. Results: We have produced a high-quality quail genome sequence, spanning 0.93 Gb assigned to 33 chromosomes. In terms of contiguity, assembly statistics, gene content and chromosomal organisation, the quail genome shows high similarity to the chicken genome. We demonstrate the utility of this genome through three diverse applications. First, we identify selection signatures and candidate genes associated with social behaviour in the quail genome, an important agricultural and domestication trait. Second, we investigate the effects and interaction of photoperiod and temperature on the transcriptome of the quail medial basal hypothalamus, revealing key mechanisms of photoperiodism. Finally, we investigate the response of quail to H5N1 influenza infection. In quail lung, many critical immune genes and pathways were downregulated after H5N1 infection, and this may be key to the susceptibility of quail to H5N1. Conclusions: We have produced a high-quality genome of the quail which will facilitate further studies into diverse research questions using the quail as a model avian species

The EHA Research Roadmap: Normal Hematopoiesis.

International audienceIn 2016, the European Hematology Association (EHA) published the EHA Roadmap for European Hematology Research1 aiming to highlight achievements in the diagnostics and treatment of blood disorders, and to better inform European policy makers and other stakeholders about the urgent clinical and scientific needs and priorities in the field of hematology. Each section was coordinated by 1–2 section editors who were leading international experts in the field. In the 5 years that have followed, advances in the field of hematology have been plentiful. As such, EHA is pleased to present an updated Research Roadmap, now including 11 sections, each of which will be published separately. The updated EHA Research Roadmap identifies the most urgent priorities in hematology research and clinical science, therefore supporting a more informed, focused, and ideally a more funded future for European hematology research. The 11 EHA Research Roadmap sections include Normal Hematopoiesis; Malignant Lymphoid Diseases; Malignant Myeloid Diseases; Anemias and Related Diseases; Platelet Disorders; Blood Coagulation and Hemostatic Disorders; Transfusion Medicine; Infections in Hematology; Hematopoietic Stem Cell Transplantation; CAR-T and Other Cell-based Immune Therapies; and Gene Therapy

Applications de sondes moleculaires a l'etude de la migration et de la diversification cellulaires chez l'embryon d'oiseau in ovo

SIGLECNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

L'endothélium aortique chez l'embryon : genèse et rôle dans l'hématopoïèse

L'hématopoïèse aortique se caractérise par la production de Cellules Souches Hématopoïétiques (CSH) qui naissent à partir de l'endothélium ventral du vaisseau à la suite de modifications phénotypiques des Cellules Endothéliales (CE). Ces CSH colonisent alors les organes hématopoïétiques définitifs. A l'aide du modèle de greffe interspécifique caille/poule, nous avons étudié la formation de l'aorte avant, pendant et après l'hématopoïèse. Nous avons pu montrer que 1) avant l'hématopoïèse, le toit de l'aorte, initialement d'origine splanchnopleurale, est entièrement colonisé par des CE provenant des somites. Ce vaisseau subit donc un premier remodelage qui aboutit à la formation d'un nouveau toit et de nouveaux côtés constitués de CE d'origine somatopleurale alors que le cadran ventral reste formé par des CE d'origine splanchnopleurale. 2) Pendant l'hématopoïèse, les CE somitiques commencent à coloniser la partie ventrale du vaisseau. Cette colonisation s'effectue par intercalation de ces CE sous les bourgeonnements de CSH. 3) Après l'hématopoïèse, les hémangioblastes aortiques ont disparu du plancher de l'aorte et sont remplacés par les CE somitiques. L'aorte subit donc un deuxième remodelage, à la suite duquel la totalité des CE du vaisseau est d'origine somitique. 4) Nous avons également identifié une contribution du somite à l'élaboration de la tunique musculaire lisse de l'aorte. 5) En greffant soit le dermomyotome, soit le sclérotome entre la caille et le poulet, nous avons montré que les CE proviennent du dermomyotome alors que les cellules musculaires lisses vasculaires sont originaires du sclérotome. Ces résultats apportent un éclairage nouveau sur la production hématopoïétique de l'aorte et le devenir de l'endothélium hémogénique. Ils expliquent aussi la nature transitoire de l'hématopoïèse aortique, observée dans toutes les classes de vertébrés