VEGFR3 is required for button junction formation in lymphatic vessels.

Lymphatic capillaries develop discontinuous cell-cell junctions that permit the absorption of large macromolecules, chylomicrons, and fluid from the interstitium. While excessive vascular endothelial growth factor 2 (VEGFR2) signaling can remodel and seal these junctions, whether and how VEGFR3 can alter lymphatic junctions remains incompletely understood. Here, we use lymphatic-specific Flt4 knockout mice to investigate VEGFR3 signaling in lymphatic junctions. We show that loss of Flt4 prevents specialized button junction formation in multiple tissues and impairs interstitial absorption. Knockdown of FLT4 in human lymphatic endothelial cells results in impaired NOTCH1 expression and activation, and overexpression of the NOTCH1 intracellular domain in Flt4 knockout vessels rescues the formation of button junctions and absorption of interstitial molecules. Together, our data reveal a requirement for VEGFR3 and NOTCH1 signaling in the development of button junctions during postnatal development and may hold clinical relevance to lymphatic diseases with impaired VEGFR3 signaling. [Display omitted] • VEGFR3 is required for the development of lymphatic capillary button junctions • VEGFR3 is not required for maintaining button junctions after their formation • Failure to form buttons impedes the absorption of interstitial molecules • NOTCH1 signaling can rescue button formation and function in the absence of VEGFR3 Lymphatic capillaries form discontinuous junctions called buttons to enable absorption of interstitial contents. Jannaway et al. show that vascular endothelial growth factor receptor 3 (VEGFR3) expression is required for the formation of button junctions and that NOTCH1 signaling can fully rescue button formation in the absence of VEGFR3. [ABSTRACT FROM AUTHOR]