Analyses of Avascular Mutants Reveal Unique Transcriptomic Signature of Non-conventional Endothelial Cells

Abstract

Endothelial cells appear to emerge from diverse progenitors. However, to which extent their developmental origin contributes to define their cellular and molecular characteristics remains largely unknown. Here, we report that a subset of endothelial cells that emerge from the tailbud possess unique molecular characteristics that set them apart from stereotypical lateral plate mesoderm (LPM)-derived endothelial cells. Lineage tracing shows that these tailbud-derived endothelial cells arise at mid-somitogenesis stages, and surprisingly do not require Npas4l or Etsrp function, indicating that they have distinct spatiotemporal origins and are regulated by distinct molecular mechanisms. Microarray and single cell RNA-seq analyses reveal that somitogenesis- and neurogenesis-associated transcripts are over-represented in these tailbud-derived endothelial cells, suggesting that they possess a unique transcriptomic signature. Taken together, our results further reveal the diversity of endothelial cells with respect to their developmental origin and molecular properties, and provide compelling evidence that the molecular characteristics of endothelial cells may reflect their distinct developmental history.

Endothelial versus pronephron fate decision is modulated by the transcription factors Cloche/Npas4l, Tal1, and Lmo2

“…It is not clear though how many of the pronephron cells once expressed npas4l . Furthermore, because both the LPM ( 2 , 9 ) and paraxial mesoderm ( 52 – 55 ) have been found to display high vasculogenic potential, it is not clear whether the mesoderm in general has high vasculogenic potential or whether there are specific progenitor cells for different types of mesoderm and endothelium. Specifically, it will be interesting to further investigate cells coexpressing endothelial and pronephron markers, or “renangioblasts,” in various developmental contexts.…”

“…The etsrp loss-of-function phenotypes that we observed are in line with those reported by Chestnut et al (25) who applied a reporterbased strategy to determine the fate of etsrp-expressing cells in etsrp mutants; in the absence of Npas4l or Etsrp function, endothelial progenitors become skeletal muscle cells. In mouse, chicken, and zebrafish, the paraxial mesoderm has been shown to be an additional source of endothelial cells (52)(53)(54)(55). In zebrafish, the paraxial mesoderm has also been reported to be a bipotent cell population that can give rise to hematopoietic stem and progenitor cells as well as muscle progenitors (53,56).…”

The Role of BMP Signaling in Endothelial Heterogeneity

“…Endothelial cells (ECs) exhibit great heterogeneity ( Aird, 2003 ), in their developmental origin ( Bautch and Caron, 2015 ; Pak et al, 2020 ), morphology ( Sailem and Al Haj Zen, 2020 ), as well as gene expression ( Chi et al, 2003 ). With technical advances, the concept of endothelial heterogeneity has been re-evaluated and extended at the single-cell level ( Nolan et al, 2013 ; Kalucka et al, 2020 ), which re-ignited the interest in signaling pathways essential for modulating endothelial heterogeneity in living organisms.…”

Transcriptional activity of Npas4l controls endothelial lineage specification and restriction in zebrafish

“…One effect that has been reported before is that npas4l mutants have more myocardium which sug-gests that endothelial progenitors in the cloche mutant may contribute to this cell type (Schoenebeck et al, 2007). Remaining endothelial cells in cloche mutants express genes associated with neurogenesis and somitogenesis, suggesting defects in their specification or a cellular origin distinct from conventional endothelial cells (Pak et al, 2020). Besides functional research on cloche mutants themselves, they were often used as an avascular and bloodless model system, to investigate the lack of endothelial and blood cells on developmental (Rasmussen et al, 2015;Fortuna et al, 2015;Posner et al, 2019) and regenerative (Hasegawa et al, 2015) processes.…”

“…The paraxial mesoderm has been suggested to be an additional source of endothelial cells (Couly et al, 1995;Wasteson et al, 2008;Stone and Stainier, 2019;Pak et al, 2020). In zebrafish, the paraxial mesoderm has been reported to be a source of a bipotent cell population that can give rise to hematopoietic stem and progenitor cells or muscle progenitors Sahai-Hernandez et al, 2020).…”