KIT Is Required for Fetal Liver Hematopoiesis

In the mouse embryo, endothelial cell (EC) progenitors almost concomitantly give rise to the first blood vessels in the yolk sac and the large vessels of the embryo proper. Although the first blood cells form in the yolk sac before blood vessels have assembled, consecutive waves of hematopoietic progenitors subsequently bud from hemogenic endothelium located within the wall of yolk sac and large intraembryonic vessels in a process termed endothelial-to-hematopoietic transition (endoHT). The receptor tyrosine kinase KIT is required for late embryonic erythropoiesis, but KIT is also expressed in hematopoietic progenitors that arise via endoHT from yolk sac hemogenic endothelium to generate early, transient hematopoietic waves. However, it remains unclear whether KIT has essential roles in early hematopoiesis. Here, we have combined single-cell expression studies with the analysis of knockout mice to show that KIT is dispensable for yolk sac endoHT but required for transient definitive hematopoiesis in the fetal liver

VEGF189 binds NRP1 and is sufficient for VEGF/NRP1-dependent neuronal patterning in the developing brain

© 2015. Published by The Company of Biologists Ltd. This research was funded by a Wellcome Trust PhD fellowship to M.T. [092839/Z/10/Z] and a BBSRC project grant to C.R. and L.E. [BB/J00930X/1]. Deposited in PMC for immediate release.Peer reviewedPublisher PD

Erythro-myeloid progenitors contribute endothelial cells to blood vessels

The earliest blood vessels in mammalian embryos are formed when endothelial cells differentiate from angioblasts and coalesce into tubular networks. Thereafter, the endothelium is thought to expand solely by proliferation of pre-existing endothelial cells. Here we show that a complementary source of endothelial cells is recruited into pre-existing vasculature after differentiation from the earliest precursors of erythrocytes, megakaryocytes and macrophages, the erythro-myeloid progenitors (EMPs) that are born in the yolk sac. A first wave of EMPs contributes endothelial cells to the yolk sac endothelium, and a second wave of EMPs colonizes the embryo and contributes endothelial cells to intraembryonic endothelium in multiple organs, where they persist into adulthood. By demonstrating that EMPs constitute a hitherto unrecognized source of endothelial cells, we reveal that embryonic blood vascular endothelium expands in a dual mechanism that involves both the proliferation of pre-existing endothelial cells and the incorporation of endothelial cells derived from haematopoietic precursors

A Refined Single Cell Landscape of Haematopoiesis in the Mouse Foetal Liver

During prenatal life, the foetal liver is colonised by several waves of haematopoietic progenitors to act as the main haematopoietic organ. Single cell (sc) RNA-seq has been used to identify foetal liver cell types via their transcriptomic signature and to compare gene expression patterns as haematopoietic development proceeds. To obtain a refined single cell landscape of haematopoiesis in the foetal liver, we have generated a scRNA-seq dataset from a whole mouse E12.5 liver that includes a larger number of cells than prior datasets at this stage and was obtained without cell type preselection to include all liver cell populations. We combined mining of this dataset with that of previously published datasets at other developmental stages to follow transcriptional dynamics as well as the cell cycle state of developing haematopoietic lineages. Our findings corroborate several prior reports on the timing of liver colonisation by haematopoietic progenitors and the emergence of differentiated lineages and provide further molecular characterisation of each cell population. Extending these findings, we demonstrate the existence of a foetal intermediate haemoglobin profile in the mouse, similar to that previously identified in humans, and a previously unidentified population of primitive erythroid cells in the foetal liver

Imatinib inhibits VEGF-independent angiogenesis by targeting neuropilin 1-dependent ABL1 activation in endothelial cells.

To enable new blood vessel growth, endothelial cells (ECs) express neuropilin 1 (NRP1), and NRP1 associates with the receptor tyrosine kinase VEGFR2 after binding the vascular endothelial growth factor A (VEGF) to enhance arteriogenesis. We report that NRP1 contributes to angiogenesis through a novel mechanism. In human and mouse ECs, the integrin ligand fibronectin (FN) stimulated actin remodeling and phosphorylation of the focal adhesion component paxillin (PXN) in a VEGF/VEGFR2-independent but NRP1-dependent manner. NRP1 formed a complex with ABL1 that was responsible for FN-dependent PXN activation and actin remodeling. This complex promoted EC motility in vitro and during angiogenesis on FN substrates in vivo. Accordingly, both physiological and pathological angiogenesis in the retina were inhibited by treatment with Imatinib, a small molecule inhibitor of ABL1 which is widely used to prevent the proliferation of tumor cells that express BCR-ABL fusion proteins. The finding that NRP1 regulates angiogenesis in a VEGF- and VEGFR2-independent fashion via ABL1 suggests that ABL1 inhibition provides a novel opportunity for anti-angiogenic therapy to complement VEGF or VEGFR2 blockade in eye disease or solid tumor growth

Application of PestLCI model to site-specific soil and climate conditions: the case of maize production in Northern Italy

The calculation of emissions from the use of pesticides is a critical issue in LCA studies of agrifood products and only occasionally discussed in details in literature studies. The objective of this study is to assess the results of the application of PestLCI 2.0 model to the production of maize in Northern Italy using site-specific soil and climate data, which were added for this purpose in PestLCI database. In this way, the application of the tool and its database were tailored to that area. Moreover, the results were compared with those obtained assuming maize cultivation on other soil typologies in the surrounding areas. Results show that soil variation scarcely affects the emissions to air and surface water are whereas it affects significantly the emissions to groundwater. Finally, some features of PestLCI were highlighted and comments for a further improvement of the model were provided

Diagnose e manejo da ferrugem da folha, do oídio e do mosaico comum na cultura do trigo

Wheat (Triticum aestivum L.) is the most important winter cereal in Brazil, and it is cultivated mainly in the states of Paraná, Santa Catarina and Rio Grande do Sul. Among the diseases of greatest importance to the crop leaf rust, powdery mildew and soil-borne wheat mosaic virus (SBWMV) stand out. As control measures are: the use of resistant cultivars, seed treatment with fungicides, balanced fertilization and spraying fungicides.O trigo (Tritcum aestvum L.) é o cereal de inverno de maior importância no Brasil, sendo cultivado principalmente nos estados do Paraná, de Santa Catarina e do Rio Grande do Sul. Entre as doenças de maior importância para a cultura do trigo destacam-se a ferrugem da folha, o oídio e o mosaico comum do trigo. Como medidas de controle estão: a utlização de cultivares resistentes, o tratamento de sementes com fungicidas, a adubação equilibrada e a pulverização de fungicidas

The cytoplasmic domain of neuropilin-1 regulates focal adhesion turnover

AbstractThough the vascular endothelial growth factor coreceptor neuropilin-1 (Nrp1) plays a critical role in vascular development, its precise function is not fully understood. We identified a group of novel binding partners of the cytoplasmic domain of Nrp1 that includes the focal adhesion regulator, Filamin A (FlnA). Endothelial cells (ECs) expressing a Nrp1 mutant devoid of the cytoplasmic domain (nrp1cytoΔ/Δ) migrated significantly slower in response to VEGF relative to the cells expressing wild-type Nrp1 (nrp1+/+ cells). The rate of FA turnover in VEGF-treated nrp1cytoΔ/Δ ECs was an order of magnitude lower in comparison to nrp1+/+ ECs, thus accounting for the slower migration rate of the nrp1cytoΔ/Δ ECs

KIT is dispensable for physiological organ vascularisation in the embryo

Blood vessels form vast networks in all vertebrate organs to sustain tissue growth, repair and homeostatic metabolism, but they also contribute to a range of diseases with neovascularisation. It is, therefore, important to define the molecular mechanisms that underpin blood vessel growth. The receptor tyrosine kinase KIT is required for the normal expansion of hematopoietic progenitors that arise during embryogenesis from hemogenic endothelium in the yolk sac and dorsal aorta. Additionally, KIT has been reported to be expressed in endothelial cells during embryonic brain vascularisation and has been implicated in pathological angiogenesis. However, it is neither known whether KIT expression is widespread in normal organ endothelium nor whether it promotes blood vessel growth in developing organs. Here, we have used single-cell analyses to show that KIT is expressed in endothelial cell subsets of several organs, both in the adult and in the developing embryo. Knockout mouse analyses revealed that KIT is dispensable for vascularisation of growing organs in the midgestation embryo, including the lung, liver and brain. By contrast, vascular changes emerged during late-stage embryogenesis in these organs from KIT-deficient embryos, concurrent with severe erythrocyte deficiency and growth retardation. These findings suggest that KIT is not required for developmental tissue vascularisation in physiological conditions, but that KIT deficiency causes foetal anaemia at late gestation and thereby pathological vascular remodelling

VEGF165-induced vascular permeability requires NRP1 for ABL-mediated SRC family kinase activation.

The vascular endothelial growth factor (VEGF) isoform VEGF165 stimulates vascular growth and hyperpermeability. Whereas blood vessel growth is essential to sustain organ health, chronic hyperpermeability causes damaging tissue edema. By combining in vivo and tissue culture models, we show here that VEGF165-induced vascular leakage requires both VEGFR2 and NRP1, including the VEGF164-binding site of NRP1 and the NRP1 cytoplasmic domain (NCD), but not the known NCD interactor GIPC1. In the VEGF165-bound receptor complex, the NCD promotes ABL kinase activation, which in turn is required to activate VEGFR2-recruited SRC family kinases (SFKs). These results elucidate the receptor complex and signaling hierarchy of downstream kinases that transduce the permeability response to VEGF165. In a mouse model with choroidal neovascularisation akin to age-related macular degeneration, NCD loss attenuated vessel leakage without affecting neovascularisation. These findings raise the possibility that targeting NRP1 or its NCD interactors may be a useful therapeutic strategy in neovascular disease to reduce VEGF165-induced edema without compromising vessel growth