Figure 6

Cx30.2-tdTomato mice permit morphological characterization of the AVN. (a) (i) The heart of a P0 Gjd3^{3′UTR-IRES-CreEGFP/+}; R26R^tdTomato/+ (Cx302-tdTomato) mouse was cleared by CUBIC (See Methods section) and imaged by whole-mount fluorescence microscopy. Confocal microscopy was used to image the AVN from the cleared heart and to provide a three-dimensional model, and selected snapshots (see Supplementary Video) are shown from the following views: (ii) top-down and (iii) end-on. A compact node with bilateral inferior nodal extensions and a single distal nodal extension can been observed in the Cx30.2⁺ AVN image. (b) The heart of a P42 Gjd3^{3′UTR-IRES-CreEGFP/+}; R26R^tdTomato/+ mouse was sectioned through the AVN and stained for Nppa (green) and α-actinin (magenta). See inset for visualization of tdTomato⁺/Nppa⁺ atrial-nodal transitional cells. (c) A more distal section containing an inferior nodal extension and the distal AVN was stained for Cx40 (green). (d) A consecutive section was stained for Myl2 (green) and α-actinin (magenta). (e) A distal section through the AV bundle (AVB) was stained for Cx40 (green). (f) AVN model based on 3D morphology observed in (a) with individual anatomical segments labeled with corresponding markers. Nuclei were counterstained with DAPI. A coordinate plane with labeled directions relative to the heart specimen are provided for orientation in (a) (ii,iii) and (f). Scale bars: as shown.