Figure 3
From: Irx3 is required for postnatal maturation of the mouse ventricular conduction system
Irx3 is required for postnatal formation of the VCS.
(a) Representative images of right bundle branch (RBB) in Irx3+/+;Cx40+/EGFP and Irx3−/−;Cx40+/EGFP mice at postnatal day 4 (P4). Note that RBB is absent in many cases when Irx3 is lost. (b) Representative images of the VCS in left ventricle of Irx3+/+;Cx40+/EGFP and Irx3−/−;Cx40+/EGFP mice at P4 and P0. Irx3−/−;Cx40+/EGFP mouse heart exhibit progressive deterioration of the VCS, characterized by reduced fiber density and thickness, compared to P0 heart which show only a mild structural defect. (c) A schematic diagram illustrates three different levels of the VCS (i.e. base, mid and apex) for analyzing VCS morphology by counting the number of fiber fraction. (d) Quantification of fiber fraction at three levels of the VCS (i.e. base, mid and apex) in three different developmental stages (i.e. P0, P4 and adult). (P0, Irx3+/+/Irx3−/−, n = 5/3; P4, Irx3+/+/Irx3−/−, n = 3/4; and adult, Irx3+/+/Irx3−/−, n = 6/4) *P < 0.05 vs. Irx3+/+;Cx40+/EGFP. (e) Representative phospho-histone H3 (PH3) immunofluorescence in the left ventricle of P4 Irx3 mutant mouse heart expressing Cx40-EGFP that marks the VCS cells. (f) Quantification of PH3-positive cells revealed significantly higher number of proliferating cells in Irx3−/−;Cx40+/EGFP hearts, mainly in EGFP-negative myocardium, compared to Irx3+/+;Cx40+/EGFP hearts. n = 4. *P < 0.05 vs. Irx3+/+;Cx40+/EGFP hearts.
