Fig. 7. Infundibular abnormalities are first seen at E15.5 in Cx43-PCKO hearts. (A-C) Hematoxylin and Eosin stained sections from E15.5 control (A), Cx43-PCKO (B) and Cx43^fo/fo (C) hearts. Infundibular bulging is first apparent in the Cx43-PCKO and germline KO hearts at this stage (arrows in B and C). (D-F) Sections from control (D), Cx43-PCKO (E) and Cx43^fo/fo (F) E17.5 hearts. The RVOT of the Cx43-PCKO heart is markedly deformed, as is that of the Cx43^fo/fo heart (arrows in E and F, respectively). (G-I) Sections from control (G), Cx43-PCKO (H) and Cx43^fo/fo (I) E17.5 hearts at the level of the LVOT. The Cx43-PCKO LVOT, like that of the Cx43^fo/fo heart, appears similar to controls, although the RV-free walls of both the Cx43-PCKO and Cx43^fo/fo hearts are thinned in comparison with controls (asterisks in H and I, respectively). (J-L) Sections through the RVOT of neonatal control (J), Cx43-PCKO (K) and Cx43^fo/fo (L) hearts. The Cx43-PCKO RVOT is grossly dilated, heavily trabeculated (arrows) and bulges above the level of the pulmonic valve (arrowhead), unlike the control RVOT but similar to that of Cx43^fo/fo hearts. Neo, neonatal. Scale bar: 450 µm for A-C,N; 700 µm for D-M,O.