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Architecture of the cardiac transverse–axial tubular system across different mammalian species

Greiner J, Sonak F, Jones WD, Morais Costa P, Madl J, Ryeng KA, Efimov IR, Iqbal Z, Seidel T, Kohl P, Rog-Zielinska EA (2026)

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Publication Type: Journal article

Publication year: 2026

Journal

DOI: 10.1113/JP291136

Abstract

Abstract: Cardiac excitation–contraction coupling relies on a pancellular network of regular cardiomyocyte surface membrane invaginations, termed the transverse–axial tubular system (TATS). The TATS is ubiquitously present in adult mammalian cardiomyocytes, enabling efficient structural and functional coupling of sarcolemma and intracellular Ca²⁺ stores. However TATS ultrastructural characteristics across species, and their relation to cardiomyocyte morphology and physiological parameters such as heart rate, remain largely unexplored. Here we quantified TATS and cardiomyocyte features in a confocal microscopy dataset (91 three-dimensional image volumes) obtained from tissue slices across eight species (mouse, rat, rabbit, pig, horse, elephant, whale, and humans). We applied a semi-automated image analysis pipeline to quantify mean cytosolic distances to the nearest TATS element (Cyto-TATSmin), transverse tubule fraction, and cardiomyocyte dimensions. Cyto-TATSmin and transverse tubule fraction differed substantially between species, with the lowest Cyto-TATSmin in mouse and highest in humans. No significant within-species associations between Cyto-TATSmin and cardiomyocyte size were detected in six of eight species. Associations were limited to pig (cross-sectional area and width) and elephant (area, depth, and width), although elephant was represented by a single subject. Across all species, Cyto-TATSmin positively correlated with species’ lifespan and body mass, and was inversely correlated with resting heart rate. Our findings reveal structural scaling principles in cardiac cellular ultrastructure and provide a resource for studying TATS organisation in health and disease. As TATS remodelling is a common hallmark of cardiac pathology, awareness of species differences in reference states and remodelling dynamics is needed to guide the design and interpretation of translational research. (Figure presented.). Key points: The transverse–axial tubular system (TATS) is essential for efficient excitation–contraction coupling in cardiomyocytes and, consequently, normal cardiac function. However systematic comparisons of TATS architecture across mammalian species remain limited. We analysed 91 three-dimensional (3D) image volumes, obtained using confocal microscopy, from eight mammalian species (mouse, rat, rabbit, pig, horse, humans, elephant, whale) using a unified image analysis pipeline. We quantified mean cytosolic distance to the nearest TATS element (Cyto-TATSmin), transverse tubule percentage, and 3D cardiomyocyte morphology. Cyto-TATSmin and transverse tubule percentage showed species-dependent patterns, with Cyto-TATSmin being lowest in mouse and highest in human. Across species, Cyto-TATSmin covaries with organismal physiology (lifespan, body mass, and resting heart rate). Our quantitative data provide a cross-species reference framework for interpreting physiological adaptations and pathological remodelling of the cardiac TATS.

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APA:

Greiner, J., Sonak, F., Jones, W.D., Morais Costa, P., Madl, J., Ryeng, K.A.,... Rog-Zielinska, E.A. (2026). Architecture of the cardiac transverse–axial tubular system across different mammalian species. The Journal of Physiology. https://doi.org/10.1113/JP291136

MLA:

Greiner, Joachim, et al. "Architecture of the cardiac transverse–axial tubular system across different mammalian species." The Journal of Physiology (2026).

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