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 7

RAF1S259A induces Sox18 expression.

Options: View larger image (or click on image) Download as PowerPoint
RAF1S259A induces Sox18 expression. (A) qPCR of SOX18, SOX17, and SOX...
(A) qPCR of SOX18, SOX17, and SOX7 in HUVECs transduced with null (control), wild-type RAF1 (WT), or RAF1S259A (S259A) lentiviruses. Mean ± SEM; n = 3. (B) qPCR analysis of SOX18 expression of HDLECs infected with adenoviruses expressing GFP, wild-type RAF1 (WT), or RAF1S259A (S259A) constructs. Mean ± SEM; n = 3. (C) qPCR analysis of Sox18 and Pecam1 expression in primary ECs isolated from E12.5 embryos. Mean ± SEM; n = 5 embryos. (D) H&E staining of E14.5 embryos demonstrating larger jugular lymphatic sacs, smaller jugular veins, and normal-sized carotid arteries in S259A compared with control embryos. Scale bar: 28 μm. (E and F) Quantification of lumen sizes of the jugular vein (E) and the carotid artery (F) at the indicated positions (heart level) as shown in (D). The values were then normalized to that of carotid arteries and averaged to represent the mean number for each embryo. The average carotid artery lumen size in control embryos was designated as 1. Control, n = 5 embryos; S259A, n = 3 embryos. Mean ± SEM. ca, carotid artery.