PTEN mediates Notch-dependent stalk cell arrest in angiogenesis

Coordinated activity of VEGF and Notch signals guides the endothelial cell (EC) specification into tip and stalk cells during angiogenesis. Notch activation in stalk cells leads to proliferation arrest via an unknown mechanism. By using gain- and loss-of-function gene-targeting approaches, here we show that PTEN is crucial for blocking stalk cell proliferation downstream of Notch, and this is critical for mouse vessel development. Endothelial deletion of PTEN results in vascular hyperplasia due to a failure to mediate Notch-induced proliferation arrest. Conversely, overexpression of PTEN reduces vascular density and abrogates the increase in EC proliferation induced by Notch blockade. PTEN is a lipid/protein phosphatase that also has nuclear phosphatase-independent functions. We show that both the catalytic and non-catalytic APC/C-Fzr1/Cdh1-mediated activities of PTEN are required for stalk cells' proliferative arrest. These findings define a Notch-PTEN signalling axis as an orchestrator of vessel density and implicate the PTEN-APC/C-Fzr1/Cdh1 hub in angiogenesis.We thank Ramon Parsons (The Mount Sinai Hospital, NY, US) for pGL3 PTEN HindIII-NotI construct and Lluis Espinosa (IMIM, Barcelona), Alba Martinez (Research Laboratory, Catalan Institute of Oncology, IDIBELL, Barcelona) and Magali Castells (Vascular Signalling laboratory, IDIBELL) for support with experiments. This work was supported by research grants SAF2010-15661 and SAF2013-46542-P from MICINN (Spain), 2014-SGR-725 from the Catalan Government, from the People Programme (Marie Curie Actions) of the European Union's Seventh Framework Programme FP7/2007-2013/(REA grant agreement 317250) and Ajuts Joves Investigadors from IDIBELL to M.G., and SAF2013-40922 and RD12/0036/0054 to A.B. Personal support was from FPI of the Spanish Ministry of Education (A.S.), IDIBELL (H.S.) and Ramon y Cajal fellow of the Spanish Ministry of Education (M.G. and O.C.). The work of A.C. is supported by the Ramon y Cajal award, the Basque Department of Industry, Tourism and Trade (Etortek), health (2012111086) and education (PI2012-03), Marie Curie (277043), Movember, ISCIII (PI10/01484, PI13/00031) and ERC (336343). The work of M.P. is supported by the Max Planck Society, the Deutsche Forschungsgemeinschaft (SFB 834) and an ERC Starting Grant (ANGIOMET). H.G. is supported by Cancer Research UK, the Lister Institute of Preventive Medicine, the Leducq Network Grant ARTEMIS, BIRAX and an ERC starting grant Reshape 311719.S