Molecular basis of individual locomotor function: Integrated understanding of gene expression regulation in the development and homeostasis of the musculoskeletal system.

This review examines the molecular mechanisms controlling the development and homeostasis of the musculoskeletal system through gene expression regulation. It introduces key discoveries from basic transcriptional control to advanced mechanotransduction pathways, focusing on our contributions including the EMBRYS database for transcription factor expression analysis and the identification of RP58 in muscle development and Mohawk (Mkx) in tendon formation. We also elucidated the role of miR-140 as a critical regulator in cartilage development and homeostasis. This microRNA is specifically expressed in cartilage, promotes chondrogenesis, and is involved in protective mechanisms against cartilage degenerative diseases such as osteoarthritis. Our discovery of the PIEZO1-Mkx pathway provides a molecular mechanism linking mechanical stimuli to gene expression in tendons, explaining tissue adaptation and differences in motor abilities. Understanding these pathways offers new therapeutic strategies for tendon and ligament injuries, age-related decline, and cartilage diseases. Currently, we are proposing the concept of "tenopenia" to complement sarcopenia, addressing the mechanisms of age-related tendon deterioration. This integrated approach to the musculoskeletal system as an environment-responsive entity advances both fundamental science and clinical applications aimed at maintaining mobility throughout life.