A Col22a1-EGFP reporter reveals dynamic three-dimensional organization of the myotendinous junction
- 1Laboratory of Animal Regeneration Systemology, Department of Life Sciences, School of Agriculture, Meiji University
Abstract
The myotendinous junction (MTJ) is a specialized extracellular matrix-rich interface that transmits contractile force generated by skeletal muscle to tendon, but its three-dimensional organization and dynamics remain poorly characterized. Here, we generate a Col22a1-EGFP knock-in mouse that enables direct visualization and quantitative analysis of MTJs from embryonic development to adulthood. Tissue-clearing and three-dimensional imaging reveal extensive variation in MTJ morphology and spatial distribution among skeletal muscles and between myofiber types. During embryonic MTJ formation, COL22A1-EGFP undergoes a striking transition from intracellular puncta within developing myofibers to extracellular accumulation at myofiber tips, associated with polarized Golgi organization. We further identify complex tendon protrusions that emerge during postnatal growth and connect tendon bodies with subsets of MTJs. These interfaces contain morphologically distinct Scx-lineage cells that express Col22a1, identifying a specialized tendon-associated population at the MTJ. Finally, muscle unloading and overload differentially alter COL22A1-EGFP signal intensity and area, respectively, demonstrating that the reporter provides a quantitative readout of MTJ responses to altered mechanical conditions. Thus, Col22a1-EGFP reveals previously unrecognized spatial, developmental, and adaptive features of the muscle-tendon interface and provides an experimental platform for investigating MTJ biology in vivo.
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BibTeX
@misc{yamasaki2026col22a1egfp,
title = {{A Col22a1-EGFP reporter reveals dynamic three-dimensional organization of the myotendinous junction}},
author = {Y. Yamasaki and Y. Kawa and R. Sagasaki and S. Yashiro and J. Shin and M. Mishima and K. Arakawa and H. Suzuki and S. Mizuno and K. Otsuka and T. Hayata and C. Shukunami and M. Inui},
howpublished = {bioRxiv},
year = {2026},
month = oct,
doi = {10.64898/2026.10.08.757742},
url = {https://www.biorxiv.org/content/10.64898/2026.10.08.757742v1},
note = {CC BY},
}
RIS
TY - UNPB
TI - A Col22a1-EGFP reporter reveals dynamic three-dimensional organization of the myotendinous junction
AU - Y. Yamasaki
AU - Y. Kawa
AU - R. Sagasaki
AU - S. Yashiro
AU - J. Shin
AU - M. Mishima
AU - K. Arakawa
AU - H. Suzuki
AU - S. Mizuno
AU - K. Otsuka
AU - T. Hayata
AU - C. Shukunami
AU - M. Inui
PY - 2026
DA - 2026/10/08
PB - bioRxiv
DO - 10.64898/2026.10.08.757742
UR - https://www.biorxiv.org/content/10.64898/2026.10.08.757742v1
AB - The myotendinous junction (MTJ) is a specialized extracellular matrix-rich interface that transmits contractile force generated by skeletal muscle to tendon, but its three-dimensional organization and dynamics remain poorly characterized. Here, we generate a Col22a1-EGFP knock-in mouse that enables direct visualization and quantitative analysis of MTJs from embryonic development to adulthood. Tissue-clearing and three-dimensional imaging reveal extensive variation in MTJ morphology and spatial distribution among skeletal muscles and between myofiber types. During embryonic MTJ formation, COL22A1-EGFP undergoes a striking transition from intracellular puncta within developing myofibers to extracellular accumulation at myofiber tips, associated with polarized Golgi organization. We further identify complex tendon protrusions that emerge during postnatal growth and connect tendon bodies with subsets of MTJs. These interfaces contain morphologically distinct Scx-lineage cells that express Col22a1, identifying a specialized tendon-associated population at the MTJ. Finally, muscle unloading and overload differentially alter COL22A1-EGFP signal intensity and area, respectively, demonstrating that the reporter provides a quantitative readout of MTJ responses to altered mechanical conditions. Thus, Col22a1-EGFP reveals previously unrecognized spatial, developmental, and adaptive features of the muscle-tendon interface and provides an experimental platform for investigating MTJ biology in vivo.
ER -