Biology subjects

Harvey, N. L.

Publications and source records attributed to Harvey, N. L..

4 recordsLinked to original sources

bioRxiv2023

Multiple cis-regulatory elements control prox1a expression in distinct lymphatic vascular beds

Lymphatic vessels play a role in several physiological and pathological processes including tissue fluid homeostasis, dietary fat absorption, immunosurveillance, and immunomodulation. During embryonic development, lymphatic endothelial cell (LEC) precursors are distinguished from blood endothelial cells by the expression of the transcription factor Prospero-related homeobox 1 (PROX1). PROX1 is essential for lymphatic vascular network formation in mouse and zebrafish. The initiation of PROX1 expression precedes LEC sprouting and migration, serving as the definitive marker of specified LECs. Despite its crucial role in lymphatic development, the upstream regulation of PROX1 in LECs remains to be uncovered. SOX18 and COUP-TFII are thought to regulate Prox1 expression in mice by binding to its promoter region. However, how the specificity of Prox1 expression to LECs is achieved remains to be studied in detail. In this study, we analysed evolutionary conservation and chromatin accessibility to identify enhancer sequences located in the proximity of zebrafish prox1a active in developing LECs. We confirmed the functional role of the identified sequences through CRISPR/Cas9 mutagenesis of a lymphatic valve enhancer. The deletion of this genomic region results in impaired valve morphology and function. Overall, our results reveal the intricate control of prox1a expression through a collection of enhancers. Ray-finned fish-specific distal enhancers drive pan-lymphatic expression, while vertebrate-conserved proximal enhancers refine expression in functionally distinct subsets of lymphatic vessels. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=89 SRC="FIGDIR/small/550483v1_ufig1.gif" ALT="Figure 1"> View larger version (28K): org.highwire.dtl.DTLVardef@fed780org.highwire.dtl.DTLVardef@f62a8dorg.highwire.dtl.DTLVardef@163b04corg.highwire.dtl.DTLVardef@1cb7f87_HPS_FORMAT_FIGEXP M_FIG C_FIG

developmental biology↗

bioRxiv2021

Self-renewing tissue-resident endothelial-macrophage progenitor cells originate from yolk sac and are a local source of inflammation and neovascularization in postnatal aorta

Converging evidence indicates that extra-embryonic yolk sac is the source of both macrophages and endothelial cells in adult mouse tissues. Prevailing views are that these embryonically derived cells are maintained after birth by proliferative self-renewal in their differentiated states. Here we identify clonogenic endothelial-macrophage (EndoMac) progenitor cells in the adventitia of embryonic and postnatal mouse aorta, that are independent of Flt3-mediated bone marrow hematopoiesis and derive from an early embryonic CX3CR1+ and CSF1R+ source. These bipotent progenitors are proliferative and vasculogenic, contributing to adventitial neovascularization and forming perfused blood vessels after transfer into ischemic tissue. We establish a regulatory role for angiotensin II, which enhances their clonogenic and differentiation properties and rapidly stimulates their proliferative expansion in vivo. Our findings demonstrate that embryonically derived EndoMac progenitors participate in local vasculogenic responses in the aortic wall by contributing to the expansion of endothelial cells and macrophages postnatally.

cell biology↗

bioRxiv2021

The blood vasculature instructs lymphatics patterning in a SOX7-dependent manner

Despite a growing catalogue of secreted factors critical for lymphatic network assembly, little is known about the mechanisms that modulate the expression level of these molecular cues in blood vascular endothelial cells (BECs). Here, we show that a BEC-specific transcription factor, SOX7, plays a crucial role in lymphatic vessel patterning by modulating the transcription of lymphangiocrine signals. While SOX7 is not expressed in lymphatic endothelial cells (LECs), loss of SOX7 function in mouse embryos causes a dysmorphic dermal lymphatic phenotype. We identify novel distant regulatory regions in mice and humans that contribute to directly repressing the transcription of a major lymphangiogenic growth factor (Vegfc) in a SOX7-dependent manner. Further, we show that SOX7 directly binds HEY1, a canonical repressor of the Notch pathway, suggesting that transcriptional repression may also be modulated by the recruitment of this protein partner at Vegfc genomic regulatory regions. Our work unveils a role for SOX7 in modulating downstream signalling events crucial for lymphatic patterning, at least in part via the transcriptional repression of VEGFC levels in the blood vascular endothelium.

developmental biology↗

bioRxiv2021

Pkd1 and Wnt5a genetically interact to control lymphatic vascular morphogenesis in mice

Lymphatic vascular development is regulated by well-characterised signalling and transcriptional pathways. These pathways regulate lymphatic endothelial cell (LEC) migration, motility, polarity and and morphogenesis. Canonical and non-canonical WNT signalling pathways are known to control LEC polarity and development of lymphatic vessels and valves. PKD1, encoding Polycystin-1, is the most commonly mutated gene in polycystic kidney disease but has also been shown to be essential in lymphatic vascular morphogenesis. The mechanism by which Pkd1 acts during lymphangiogenesis remains unclear. Here we find that loss of non-canonical WNT signalling components Wnt5a and Ryk phenocopy lymphatic defects seen in Pkd1 knockout mice. To investigate genetic interaction, we generated Pkd1/Wnt5a double knockout mice. Loss of Wnt5a suppressed phenotypes seen in the lymphatic vasculature of Pkd1-/- mice and Pkd1 deletion suppressed phenotypes observed in Wnt5a-/- mice. Thus, we report mutually suppressive roles for Pkd1 and Wnt5a, with developing lymphatic networks restored to a more wild-type state in double mutant mice. This genetic interaction between Pkd1 and the non-canonical WNT signalling pathway ultimately controls LEC polarity and the morphogenesis of developing vessel networks. Our work suggests that Pkd1 acts at least in part by regulating non-canonical WNT signalling during the formation of lymphatic vascular networks.

developmental biology↗