Hussmann, M. | Search bioRxiv

bioRxiv2023

Angpt1 binding to Tie1 regulates the signaling required for lymphatic vessel development in zebrafish

Development of the vascular system is regulated by multiple signaling pathways mediated by receptor tyrosine kinases (RTKs). Among them, Angiopoietin (Ang)/Tie signaling regulates lymphatic and blood vessel development in mammals. Of the two Tie receptors, Tie2 is well known as a key mediator of Ang/Tie signaling, but unexpectedly, recent studies reveal that the Tie2 locus has been lost in many vertebrate species, while the Tie1 gene is more commonly present. However, Tie1-driven signaling pathways, including ligands and cellular functions, are not well understood. Here, we performed comprehensive mutant analyses of Angiopoietins and Tie receptors in zebrafish and found that only angpt1 and tie1 mutants show defects in trunk lymphatic vessel development. Among zebrafish Angiopoietins, only Angpt1 binds to Tie1 as a ligand. We indirectly monitored Ang1/Tie1 signaling and detected Tie1 activation in sprouting endothelial cells (ECs), where Tie1 inhibits nuclear import of EGFP-Foxo1a. Angpt1/Tie1 signaling functions in EC migration, proliferation, and lymphatic specification during early lymphangiogenesis, at least in part by modulating Vegfc/Vegfr3 signaling. Thus, we show Angpt1/Tie1 signaling to constitute an essential signaling pathway for lymphatic development in zebrafish. Brief Summary StatementZebrafish Angpt1/Tie1 signaling is characterized as an essential signaling pathway for trunk lymphatic development, with Tie1 regulating Foxo1 localization and modulating Vegfc/Vegfr3 signaling.

developmental biology↗

bioRxiv2022

svep1 and tie1 genetically interact and affect aspects of facial lymphatic development in a Vegfc-independent manner

Multiple factors are required to form functional lymphatic vessels. Here, we uncover an essential role for the secreted protein Svep1 and the transmembrane receptor Tie1 during the development of subpopulations of the zebrafish facial lymphatic network. This specific aspect of the facial network forms independently of Vegfc signalling, which otherwise is the most prominent signalling axis in all other lymphatic beds. Additionally, we find that multiple specific and newly uncovered phenotypic hallmarks of svep1 mutants are also present in tie1, but not in tie2 or vegfc mutants. These phenotypes are observed in the lymphatic vasculature of both head and trunk, as well as in the development of the dorsal longitudinal anastomotic vessel (DLAV) under reduced flow conditions. Furthermore, we show genetic interaction between svep1 and tie1 during the migration of parachordal lymphangioblasts (PLs). Therefore, our study demonstrates an important function for Tie1 signalling during lymphangiogenesis as well as blood vessel development in zebrafish and provides the first in vivo evidence for zebrafish Svep1 and Tie1 interaction. Since compound heterozygous mutations for SVEP1 and TIE2 have recently been reported in human glaucoma patients, our data have clinical relevance in demonstrating a role for Svep1 in Tie signalling in an in vivo setting.

developmental biology↗