Biology subjects

Rufin Florat, D.

Publications and source records attributed to Rufin Florat, D..

2 recordsLinked to original sources

bioRxiv2025

Jam2 Signaling Functions Downstream of Hand2 To Initiate The Formation Of Organ-Specific Vascular Progenitors In Zebrafish

The mechanisms regulating the formation of organ-specific vasculature are still poorly understood. We have previously identified a population of late-forming endothelial progenitor cells in zebrafish embryos (termed secondary vascular field, SVF), which emerge from the lateral plate mesoderm after 24 hpf stage, when blood circulation has already been initiated. Here, we investigate the functional role of SVF cells and the molecular mechanisms that govern the emergence of these SVF cells and their contribution to vasculature. We found that the bHLH transcription factor Hand2 and junctional adhesion molecule Jam2b are expressed in the SVF-forming region and are required for the emergence of SVF cells in zebrafish embryos. Time-lapse imaging and jam2b:Cre-based lineage tracing showed that SVF cells serve as the major source of the intestinal vasculature, including the supraintestinal artery (SIA) and subintestinal vein (SIV), which are subsequently remodeled to provide blood flow to many internal organs. To analyze the functional role of jam2b and the related jam2a gene in vascular development, we generated double maternal-zygotic jam2a; jam2b mutants, which display a greatly reduced number of SVF cells and show defects in the development of the intestinal vasculature. Further analysis showed that hand2 functions in the SVF-forming region upstream of jam2b and is required to induce expression of the transcription factor etv2/etsrp, a known master regulator of vasculogenesis. In summary, our results identify new roles for Jam2 signaling and Hand2 function in the emergence of organ-specific vascular progenitors. The presence of similar progenitors in mammalian embryos suggests that this mechanism is evolutionarily conserved.

developmental biology↗

bioRxiv2023

SH2 domain protein E (SHE) and ABL signaling regulate blood vessel size

Blood vessels in different vascular beds vary in lumen diameter, which is essential for their function and fluid flow along the vascular network. Molecular mechanisms involved in the formation of a vascular lumen of appropriate size, or tubulogenesis, are still only partially understood. Src homology 2 domain containing E (She) protein was previously identified in a screen for proteins that interact with Abelson (Abl)-kinase. However, its biological role has remained unknown. Here we demonstrate that She and Abl signaling regulate vascular lumen size in zebrafish embryos and human endothelial cell culture. Zebrafish she mutants displayed increased endothelial cell number and enlarged lumen size of the dorsal aorta (DA) and defects in blood flow. Vascular endothelial specific overexpression of she resulted in a reduced diameter of the DA lumen, which correlated with the reduced arterial cell number and lower endothelial cell proliferation. Chemical inhibition of Abl signaling in zebrafish embryos caused a similar reduction in the DA diameter and alleviated the she mutant phenotype, suggesting that She acts as a negative regulator of Abl signaling. Enlargement of the DA lumen in she mutants correlated with an increased endothelial expression of claudin 5a and 5b (cldn5a / cldn5b), which encode proteins enriched in tight junctions. Inhibition of cldn5a expression partially rescued the enlarged DA in she mutants, suggesting that She regulates DA lumen size, in part, by promoting cldn5a expression. SHE knockdown in human endothelial umbilical vein cells resulted in a similar increase in the diameter of vascular tubes, and also increased phosphorylation of a known ABL downstream effector CRKL. These results argue that SHE functions as an evolutionarily conserved inhibitor of ABL signaling and regulates lumen size during vascular tubulogenesis.

developmental biology↗