Evolutionarily Conserved T-tubule-Mitochondria Contacts in Striated Muscle

The intricate architecture of skeletal muscle is essential for its contractile function, with the spatial organization of organelles such as T-tubules and mitochondria playing a crucial role in maintaining muscle performance and health 1,2 . T-tubules propagate electrical signals deep into muscle fibers to ensure synchronous contraction, while mitochondria provide the necessary energy for muscle contraction 3-5 . Previous studies have extensively documented the interactions between T-tubules and the sarcoplasmic reticulum (SR), which are essential for excitation-contraction coupling 6,7 . However, the detailed spatial relationship between T-tubules and mitochondria has remained relatively unexplored. In this study, we utilized zebrafish and mice as model organisms to investigate the contacts between T-tubules and mitochondria. Using array tomography, deep learning-based analysis, and advanced microscopy techniques, we discovered extensive membrane contact sites, termed T-tubule-Mitochondria (TTM) contacts. These contacts are evolutionarily conserved across vertebrates, including skeletal and cardiac muscles. Our findings reveal a previously unrecognized, intimate spatial coupling between T-tubules and mitochondria, with significant implications for muscle physiology and pathology. Understanding these TTM contacts could provide new insights into the mechanisms underlying muscle function and the development of muscle-related diseases.