Fig. 1.
Notch4* expression in adult mouse lung endothelium. A–C: immunostaining with anti-β-gal demonstrates colocalization with the endothelial marker CD31 (scale bars, 50 μm). D: when the tetracycline transactivator (tTA) was coupled to the lacZ transgene, β-gal reporter of tTA activity was diffusely detected by frozen section X-gal staining (scale bar, 100 μm). E: quantitative PCR analysis of RNA extracted from whole lung shows increased expression of Notch4* (int3) in mutants (Tie2-tTA/TRE-int3) relative to controls or Dox-treated mutants. Reinstitution of doxycycline results in prompt reversal of tTA activity and repression of Notch4* expression. *ΔΔCt = (Ct,int3 − Ct,HPRT)mouse x - (Ct,int3 − Ct,HPRT)TRE-int3Ave.