Abstract
The atrioventricular node (AVN) coordinates the timing of atrial and ventricular contraction to optimize cardiac performance. To study this critical function using mouse genetics, however, new reagents are needed that allow AVN-specific manipulation. Here we describe a novel Gjd3-CreEGFP mouse line that successfully recombines floxed alleles within the AVN beginning at E12.5. These mice have been engineered to express CreEGFP under the control of endogenous Gjd3 regulatory elements without perturbing native protein expression. Detailed histological analysis of Gjd3-CreEGFP mice reveals specific labeling of AVN cardiomyocytes and a subset of cardiac endothelial cells. Importantly, we show that Gjd3-CreEGFP mice have preserved cardiac mechanical and electrical function. In one application of our newly described mouse line, we provide a three-dimensional (3D) view of the AVN using tissue clearing combined with confocal microscopy. With this 3D model as a reference, we identify specific AVN sub-structures based on marker staining characteristics. In addition, we use our Gjd3-CreEGFP mice to guide microdissection of the AVN and construction of a single-cell atlas. Thus, our results establish a new transgenic tool for AVN-specific recombination, provide an updated model of AVN morphology, and describe a roadmap for exploring AVN cellular heterogeneity.
Highlights
The atrioventricular node (AVN) coordinates the timing of atrial and ventricular contraction to optimize cardiac performance
We found that tdTomato co-localizes with both GFP and Cx30.2 (Figs 2b, iii and S5) and that the subset of AVC cells marked by tdTomato at E12.5 was stable across multiple mouse hearts
We show that gap junction delta 3 (Gjd3)-CreEGFP mice precisely label the AVN beginning at E12.5 and a population of cardiac endothelial cells in adult mice
Summary
The atrioventricular node (AVN) coordinates the timing of atrial and ventricular contraction to optimize cardiac performance. In one application of our newly described mouse line, we provide a three-dimensional (3D) view of the AVN using tissue clearing combined with confocal microscopy. With this 3D model as a reference, we identify specific AVN sub-structures based on marker staining characteristics. Newly described approaches for single-cell RNA sequencing[13] and tissue clearing[14] have improved the resolution of cellular and imaging studies, respectively Application of these contemporary methods may shed new light on the structural and functional complexity inherent to the AVN. Based on the studies described, we anticipate that Gjd33′UTR-IRES-CreEGFP/+ mice will enable important mechanistic studies to unravel AVN development and function, and we provide a starting point for the exploration of AVN cellular heterogeneity
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