The mechanosensory channel Piezo1 Triggers Angiopoietin-Tie Signaling in the Lymphatics
Angiopoietin-Tie1 signaling is required for lymphatic vascular integrity and both ANGPT2 and TIE1 genetic variants have been associated with lymphedema in patients.  Concurrent with growth-factor signaling, mechanical forces sensed by lymphatic endothelial cells (LECs) are also needed to regulate lymphatics3, 4.  How these two pathways might interact in the lymphatic system is unknown.  Here, we identified a regulatory network in LECs linking activation of the mechanosensory channel, PIEZO1 to Angiopoietin-Tie signaling and repression of a downstream FOXO1 transcriptional response. RNAseq analysis of dermal LECs fromTie1-deficient embryos showed persistent FOXO1 activity with downregulation of LEC-associated genes including Ccl21a, Foxc2, Gata2 and Gja4, as well as increased expression of the mechanosensory channel, Piezo1.  Activation of PIEZO1 in human dermal LECs (HDLECs) by the small molecule agonist, Yoda1, triggered exocytosis of the Tie ligand, Angiopoietin-2 (ANGPT2), activation of Tie/AKT/PI3K signaling and export of FOXO1 out of the nucleus.Our data identify a novel molecular pathway linking mechano-transduction to ANGPT2-Tie1 activity and dynamic modulation of FOXO1 activity needed for patterning and function of the lymphatic system Overall design: Tie1_WT and Tie1_KO cells were FACS sorted from fresh E18.5 embryonic skin samples