Fig. 3. Cardiac phenotype of Gja1^Jrt/+ mutants. Histopathology revealed very few, tiny `gap junctions' in the longitudinal muscle fibers of the myocardium of mutants following immunofluorescence for Cx43 (green) (arrow) compared with wild-type controls (+/+) in which intense Cx43 staining is seen in the gap junctions at the intercalated disks (arrows) (A,B). Histopathology also revealed patent foramen ovale in some mutants (arrows in C,D). The body weight (BW) of Gja1^Jrt/+ mutants was markedly reduced relative to controls both when young (8-14 weeks) and when old (50-67 weeks) (E). The left ventricular inner chamber dimension in diastole (LV IDd) was large relative to the body weight^0.33 and the ventricular wall thickness in diastole (WTd) was reduced relative to the LV IDd in Gja1^Jrt/+ mutants (E). In older mutants, there was a prolongation of the LV pre-ejection time (PET) and ejection time (ET) when compared with controls (E). Old mutants evaluated by echocardiography exhibited reduced right ventricular (RV) fractional shortening (FS) and reduced RV WTd, suggesting the development of RV failure with aging (E). LV FS did not change (not shown). ^*P<0.05, ^**P0.005. Scale bars: 20 µm in A,B; 500 µm in C,D. la, left atrium; ra, right atrium; lvw, left ventricular wall; ivs, interventricular septum.