Figure 2.

Sections through a mouse heart at embryonic day (E) 15.5. A Confocal micrograph showing a section double labelled for connexin45 (Cx45) (green) and connexin40 (Cx40) (red). The insert shows a low power view of the section with the area shown at high power indicated by the box. Bar marker = 500 μm. The crest of the interventricular septum (IVS) labelled positively for Cx45 only (common atrioventricular bundle). Cx40 label is present in the left bundle branch (LBB) where it colocalizes, in part, with Cx45 to give yellow spots. The remnant of the conus myocardium is also labelled only for Cx45 (*). The tissue of the atrial appendage (At) is clearly positive for Cx40. More posterior sections through the E15.5 heart double labelled for Cx45 and Cx40 (B) or Cx43 (C) show that the atrioventricular bundle continues to express Cx45 only. Bar markers = 50 μm