FLT4 and infection: Infection of adult mice with M. pulmonis or vaccinia virus can transform buttons back into zippers in tracheal lymphatics and skin lymphatics, respectively, suggesting that the button junction phenotype is not permanent.4,8 To test whether VEGFR3 signaling maintains button junctions, we induced Flt4 deletion at P21 and analyzed junction types in diaphragm lymphatic capillaries 2 weeks later at P35 (Figure 2A).