A research team has uncovered fundamental molecular mechanisms governing the formation of tendons and ligaments, which are essential for musculoskeletal integration. Understanding these mechanisms could pave the way for the regeneration of tendons, ligaments, and their attachment sites, known as entheses, which have limited capacity for functional repair after injury because of their poor vascularization.
The research was published in the journal Development on June 1, 2026. Development also published an interview with the paper’s authors .
The international team has identified a novel enhancer that controls the tissue-specific expression of Scleraxis (Scx), a key transcription factor for the formation and maturation of tendons, ligaments, and entheses. Enhancers are DNA sequences that function as genetic switches, controlling when and where genes are activated. The newly identified Scx enhancer directs Scx gene expression specifically in tendons, ligaments, and their attachment sites during development.
Scleraxis, a basic helix-loop-helix transcription factor, is also reactivated in adults during tissue repair and adaptation to mechanical loading. Scientists have long known that tendons, ligaments, and entheses fail to develop properly when Scx gene function is lost. Entheses are also vulnerable to injury and mechanical stress, leading to pain and functional impairment known as enthesopathy.
For their study, the team used transgenic reporter mice, a powerful tool that allows researchers to visualize when and where DNA sequences activate gene expression in living tissues. Using this approach, the team identified a 5.3 kb downstream Scleraxis enhancer (dSE) that drove robust, stable, and faithful reporter activity (Figure 1). Within the dSE, the team further identified a 343 bp conserved Scleraxis enhancer (CSE). Remarkably, this CSE is highly conserved from lobe-finned fishes to tetrapods and is capable of recapitulating Scx gene expression in the developing limbs.
Mice lacking the CSE showed a marked reduction in endogenous Scx gene expression during limb development and failed to form the deltoid tuberosity (DT), a prominent bone ridge where the deltoid muscle attaches to the humerus and supports shoulder movement (Figure 2). Thus, precise activation of the CSE during a critical developmental window is essential for proper DT formation (Figure 3). Despite the early reduction in Scx gene expression, its expression gradually recovered at later stages. The team suggests that this recovery is mediated by additional elements within the dSE. These findings demonstrate that the CSE acts as a key enhancer required for the timely activation of Scx during early limb development for proper DT formation.
“Through in vivo analysis using transgenic mice, we identified a regulatory region containing a tendon- and ligament-specific enhancer and discovered within it an evolutionarily important sequence that has been conserved from coelacanths to humans,” said Professor Chisa Shukunami , from the Graduate School of Biomedical and Health Sciences , Hiroshima University. The team’s research also demonstrated through genome editing-mediated deletion that this region plays a critical role in DT formation.
With this study, the team’s goal was to elucidate the tissue-specific regulatory mechanisms of Scx, a transcription factor essential for musculoskeletal integration. “Since tendons, ligaments, and entheses are avascular and have limited regenerative capacity,” said Shukunami, “understanding how Scx gene expression is controlled is crucial for understanding the molecular basis of tendon and ligament formation and for establishing the foundation of regenerative medicine.” Regenerative medicine aims to repair, replace, or regenerate damaged cells, tissues, and organs in the body to restore their normal function.
The team has made significant progress toward understanding the molecular mechanisms that regulate Scx gene expression. “This study provides an important foothold for uncovering the fundamental molecular mechanisms that control tendon and ligament formation,” said Shukunami. Looking ahead, the team plans to further expand this line of research. “Moving forward, we aim to elucidate the full picture of the upstream regulatory network governing Scx gene expression and ultimately identify, ahead of the rest of the world, the central regulatory factors that orchestrate musculoskeletal integration,” said Shukunami.
The research team includes Shinsei Yambe and Chisa Shukunami of Hiroshima University, Japan; Kenta Sumiyama of Nagoya University, Japan; Hitomi Watanabe, Gen Kondoh, and Aki Takimoto of Kyoto University, Japan; Takako Sasaki of Oita University, Japan; and Denitsa Docheva of the University of Wuerzburg, Germany.
The research is funded by the Japan Society for the Promotion of Science Grants-in-Aid for Scientific Research; the Frontier Development Program for Genome Editing funded by the Doctoral Program for World-leading Innovative and Smart Education, JST SPRING; and the Cooperative Research Program of the Institute for Frontier Life and Medical Sciences, Kyoto University, Japan.
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About Hiroshima University
Since its foundation in 1949, Hiroshima University has striven to become one of the most prominent and comprehensive universities in Japan for the promotion and development of scholarship and education. Consisting of 12 schools for undergraduate level and 5 graduate schools, ranging from natural sciences to humanities and social sciences, the university has grown into one of the most distinguished comprehensive research universities in Japan. English website: https://www.hiroshima-u.ac.jp/en
Development
Divergent temporal control of deltoid tuberosity and limb tendon development by an evolutionarily conserved scleraxis enhancer
1-Jun-2026