Endothelial expression of constitutively active Notch4 elicits reversible arteriovenous malformations in adult mice

doi:10.1073/pnas.0504391102

Endothelial expression of constitutively active Notch4 elicits reversible arteriovenous malformations in adult mice

^*Pacific Vascular Research Laboratory, Division of Vascular Surgery, Department of Surgery and ^†Department of Anatomy, University of California, San Francisco, CA 94143; and ^§The Wistar Institute, University of Pennsylvania, Philadelphia, PA 19104

Communicated by Henry R. Bourne, University of California, San Francisco, CA, May 26, 2005 (received for review March 23, 2005)

Abstract

Direct communication between arteries and veins without intervening capillary beds is the primary pathology of arteriovenous malformations (AVMs). Although Notch signaling is implicated in embryonic arteriovenous (AV) differentiation, its function in the adult mammalian vasculature has not been established due to the embryonic lethality that often occurs in both gain- and loss-of-function mutants. We expressed a constitutively active Notch4, int3, in the adult mouse endothelium by using the tetracycline-repressible system to suppress int3 during embryogenesis. int3 caused profound blood vessel enlargement and AV shunting, which are hallmarks of AVM, and led to lethality within weeks of its expression. Vessel enlargement, a manifestation of AVM, occurred in an apparently tissue-specific fashion; the liver, uterus, and skin were affected. int3-mediated vascular defects were accompanied by arterialization, including ectopic venous expression of ephrinB2, increased smooth muscle cells, and up-regulation of endogenous Notch signaling. Remarkably, the defective vessels and illness were reversed upon repression of int3 expression. Finally, endothelial expression of a constitutively active Notch1 induced similar hepatic vascular lesions. Our results provide gain-of-function evidence that Notch signaling in the adult endothelium is sufficient to render arterial characteristics and lead to AVMs.

Footnotes

↵ ¶ To whom correspondence should be addressed at: University of California, HSW 1618, P.O. Box 0507, 513 Parnassus Avenue, San Francisco, CA 94143-0507. E-mail: rongw{at}itsa.ucsf.edu.
↵ ‡ Present address: Portola Pharmaceuticals, South San Francisco, CA 94080.
Author contributions: T.R.C., Y.Y., X.W., M.T.L., G.L.T., and R.W. designed research; T.R.C., Y.Y., X.W., M.T.L., G.L.T., and R.W. performed research; Y.Y., L.J.B., A.J.C., Z.W., and R.W. contributed new reagents/analytic tools; T.R.C., X.W., M.T.L., G.L.T., L.M.M., Z.W., and R.W. analyzed data; and T.R.C. and R.W. wrote the paper.
Abbreviations: AV, arteriovenous; AVM, arteriovenous malformation; EC, endothelial cell; SMC, smooth muscle cell; Dox, doxycycline; tTA, tetracycline transactivator; TRE, tetracycline response element; α-SMA, SMC-α-actin.