Endothelial ERK signaling controls lymphatic fate specification
Yong Deng, Deepak Atri, Anne Eichmann, Michael Simons
Yong Deng, Deepak Atri, Anne Eichmann, Michael Simons
View: Text | PDF
Research Article Vascular biology

Endothelial ERK signaling controls lymphatic fate specification

Abstract

Lymphatic vessels are thought to arise from PROX1-positive endothelial cells (ECs) in the cardinal vein in response to induction of SOX18 expression; however, the molecular event responsible for increased SOX18 expression has not been established. We generated mice with endothelial-specific, inducible expression of an RAF1 gene with a gain-of-function mutation (RAF1S259A) that is associated with Noonan syndrome. Expression of mutant RAF1S259A in ECs activated ERK and induced SOX18 and PROX1 expression, leading to increased commitment of venous ECs to the lymphatic fate. Excessive production of lymphatic ECs resulted in lymphangiectasia that was highly reminiscent of abnormal lymphatics seen in Noonan syndrome and similar “RASopathies.” Inhibition of ERK signaling during development abrogated the lymphatic differentiation program and rescued the lymphatic phenotypes induced by expression of RAF1S259A. These data suggest that ERK activation plays a key role in lymphatic EC fate specification and that excessive ERK activation is the basis of lymphatic abnormalities seen in Noonan syndrome and related diseases.

Authors

Yong Deng, Deepak Atri, Anne Eichmann, Michael Simons

×

Figure 2

Endothelial-specific expression of RAF1S259A induces enlarged lymphatic vessels.

Options: View larger image (or click on image) Download as PowerPoint
Endothelial-specific expression of RAF1S259A induces enlarged lymphatic ...
(A) S259A embryos show edema (arrowhead) at E14.5. Scale bars: 5 mm. (B) H&E staining of E14.5 embryo sections revealed extremely enlarged jugular lymph sacs (arrows) in S259A embryos. Scale bar: 100 μm. (C) H&E staining of E14.5 embryo sections revealed enlarged subcutaneous vessels (arrows). Scale bar: 150 μm. (D) Immunofluorescence staining of E14.5 embryo sections revealed enlarged subcutaneous lymphatic vessels (arrows). VEGFR3 (green); PROX1 (red); DAPI (blue). Scale bar: 200 μm. (E) Quantitative analysis of subcutaneous lymphatic vessel lumen area of E14.5 embryos based on VEGFR3/PROX1 double staining shown in (D). Lumen areas of subcutaneous lymphatic vessels. Data represent the mean ± SEM. (F) Distribution of subcutaneous lymphatic vessel lumen size. Subcutaneous lymphatic vessels shown in (D) were grouped based on different lumen sizes as indicated. Percentages of the number for each group out of the total number of vessels are shown. Data represent the mean of 4 embryos for each genotype. (G) VEGFR3 (red) whole-mount staining of E14.5 embryo dorsal skins. Scale bar: 200 μm. (H) Quantitative analysis of lymphatic vessel diameter based on VEGFR3 staining shown in (G). Control, n = 7 embryos; S259A, n = 6 embryos. Mean ± SEM. cv, cardinal vein; da, descending aorta; jls, jugular lymph sac.