RASA1 regulates the function of lymphatic vessel valves in mice
Philip E. Lapinski, … , Michael J. Davis, Philip D. King
Philip E. Lapinski, … , Michael J. Davis, Philip D. King
Published May 22, 2017
Citation Information: J Clin Invest. 2017;127(7):2569-2585. https://doi.org/10.1172/JCI89607.
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Research Article Vascular biology

RASA1 regulates the function of lymphatic vessel valves in mice

Abstract

Capillary malformation–arteriovenous malformation (CM-AVM) is a blood and lymphatic vessel (LV) disorder that is caused by inherited inactivating mutations of the RASA1 gene, which encodes p120 RasGAP (RASA1), a negative regulator of the Ras small GTP-binding protein. How RASA1 mutations lead to the LV leakage defects that occur in CM-AVM is not understood. Here, we report that disruption of the Rasa1 gene in adult mice resulted in loss of LV endothelial cells (LECs) specifically from the leaflets of intraluminal valves in collecting LVs. As a result, valves were unable to prevent fluid backflow and the vessels were ineffective pumps. Furthermore, disruption of Rasa1 in midgestation resulted in LEC apoptosis in developing LV valves and consequently failed LV valvulogenesis. Similar phenotypes were observed in induced RASA1-deficient adult mice and embryos expressing a catalytically inactive RASA1R780Q mutation. Thus, RASA1 catalytic activity is essential for the function and development of LV valves. These data provide a partial explanation for LV leakage defects and potentially other LV abnormalities observed in CM-AVM.

Authors

Philip E. Lapinski, Beth A. Lubeck, Di Chen, Abbas Doosti, Scott D. Zawieja, Michael J. Davis, Philip D. King

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Figure 4

Specific induced loss of RASA1 within LECs results in dysfunction of popliteal and mesenteric LV valves.

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Specific induced loss of RASA1 within LECs results in dysfunction of pop...
LV valve function tests were conducted with popliteal LV valves from Rasa1fl/fl Prox1ert2cre mice administered tamoxifen 11 weeks previously (A–C) (n = 7) or mesenteric LV valves from littermate Rasa1fl/fl and Rasa1fl/fl Prox1ert2cre mice administered tamoxifen 20 weeks previously (D–F) (n = 8 and 10, respectively). (A and D) Valve-closure tests. Graphs show adverse pressure required for valve closure versus D/Dmax. Each valve is represented by a different colored symbol. (B and E) Graphs show Psn as a function of Pout in low-pressure back-leak tests. (C and F) Graphs show Psn as a function of Pout in high-pressure back-leak tests. The same colored symbols are used for the same valves in graphs A–C and D–F. See also the following: Supplemental Video 3, which shows a low-pressure back-leak test of a Rasa1fl/fl Prox1ert2cre popliteal LV valve that failed to close and leaked (gray circles in A–C); Supplemental Video 4, which shows a high-pressure back-leak test of a control Rasa1fl/fl popliteal LV valve; Supplemental Video 5, which shows a high-pressure back-leak test of a Rasa1fl/fl Prox1ert2cre popliteal LV valve that closed at a Pout of 50 cm H2O and prevented further back-leak thereafter (red triangles in A–C); Supplemental Video 6, which shows a low-pressure back leak test of a Rasa1fl/fl mesenteric LV valve; Supplemental Video 7, which shows a low-pressure back-leak test of a Rasa1fl/fl Prox1ert2cre mesenteric LV valve (blue circles in D–F).