Fig 1: Notch signalling is found in the developing ICVS.All sections are frontal unless otherwise stated. Images are typical examples from a minimum of n = 3 at each stage. In E-AB, arrows point to the ICVS. (A–D) Sagittal sections show that Notch1ICD, Notch2 and Jag1 are abundant in the distal outflow wall (arrows) at E10.5. Jag2 is only found in the endothelium (arrow in D). (E–L) Notch1ICD, Notch2, Jag1 and Jag2 are found in the endocardium overlying the main cushions, but not within the cushions themselves at E10.5–11.5. All four localise to the ICVS at E10.5, with Notch1ICD, Notch2 and Jag1 maintained at E11.5. (M–P) Notch1ICD, Notch2 and Jag1 are found in the valve endothelium at E12.5, but none of these, nor Jag2, is found in the valve interstitial cells G-AB) Isl1 and Notch1ICD co-localise in the nuclei of only a few cells within the ICVS at E10.5, although Notch2, Jag1 and Jag2 are found in the membrane of Isl1 +nuclei containing cells in the core of the ICVS at this stage. Scale bar: A-D = 360 µm, E-H = 120 µm, I-L = 150 µm, M-P = 225 µm, Q-AB = 75 µm.