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 10

Discontinuous ECM in developing LV valve leaflets of induced RASA1-deficient embryos.

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Discontinuous ECM in developing LV valve leaflets of induced RASA1-defic...
Rasa1fl/fl and Rasa1fl/fl Ubert2cre embryos were administered tamoxifen at E15.5. (A) Mesenteries were harvested at E17.5 and stained with antibodies against PROX1 and collagen IV. Shown are representative confocal microscopic images of individual and merged antibody staining. Note the discontinuous collagen IV staining in the developing leaflet of the valve in the Rasa1fl/fl Ubert2cre LVs (arrowheads). See also Supplemental Figure 8, which highlights apoptotic LECs in the same leaflet of the Rasa1fl/fl Ubert2cre vessel. (B) Mesenteries were harvested at E19.5 and stained with antibodies against PROX1, collagen IV, and smooth muscle actin (SMA). Shown are confocal images of merged PROX1 and collagen IV staining and merged PROX1 and SMA staining of representative valve regions and expected valve regions in Rasa1fl/fl and Rasa1fl/fl Ubert2cre LVs, respectively. Note the absence of collagen IV intraluminal projections in the Rasa1fl/fl Ubert2cre LVs and normal lymphatic muscle coverage.