Author response image 2. 3-D reconstruction of the entire mouse SAN preparations was used for immunofluorescent labeling of connexin 43 (Cx43, green) and HCN4 (red).

Mosaic images were created by superimposing of 3-D Z-stacks (averaged through 30-50 scanned layers; 50-200 μm thickness) of different regions throughout the SAN pacemaker complex. Pacemaker regions are shown to be characterized by HCN4-positive staining. From Glukhov et al. Eur Heart J. 2015 Mar 14;36(11):686-97.