Tendons and ligaments are dense connective tissues of mesodermal origin, which connect muscles to bones or bone to bone, and transmit mechanical force. The extracellular matrix (ECM) consists mainly of collagen type 1, organized as triple-helix polypeptide chains, which unite into fibrils, fibers, fascicles, tertiary bundles, forming the tendon and ligament architecture. Damage to tendons and ligaments caused by overuse or injuries is not healed and rarely recovers completely. In addition, to injury, aging-related changes in cells and ECM of ligaments and tendons represent an important risk factor for the development of knee osteoarthritis or rotator cuff syndrome. Obstacles in the development of approaches to address tendon and ligament damage are partly due to the limited knowledge about mechanisms that regulate development, adult tissue homoeostasis and regenerative responses following injury. We recently identified Mohawk (Mkx) as a key regulator of tendon and ligament development. Mkx is a member of the Three Amino acid Loop Extension superclass of atypical homeobox genes. Mkx-/- mice had hypoplastic tendons throughout the body, clearly demonstrating an essential function of Mkx in tendon development. Importantly, Mkx is highly expressed in adult human and mouse tenocytes and ligament cells but its expression is decreased in aging or in arthritis-affected joints and in response to inflammatory stimuli such as interleukin-1. These observations support our hypothesis that Mkx is a central regulator of adult tendon and ligament homeostasis and that its suppression following injury or during aging and arthritis accounts for limited repair responses and leads to degenerative changes. To test this hypothesis and reveal the molecular mechanisms of Mkx to maintain and/or regenerate tendon/ligament, we will perform the following studies.
Aim 1 : Determine Mkx targets and functions in tendon/ligament cells during development and after birth.
Aim 2 : Analyze mechanisms controlling tendon/ligament specific expression of Mkx.
Aim 3 : Examine role of Mkx in tenogenic differentiation of mesenchymal stem cells and its potential to enhance repair or regeneration of tendon injuries. Feasibility of this project is based on availability of several genetically modified mouse lines, including conditional Mkx TG and KO mice;access to human ligament cells from a wide range of donors across the adult age spectrum and at various stages of ACL degeneration and multiple genome-wide screening systems. The findings from this study are expected to advance our current understanding of tendon and ligament biology and serve as a basis for the development of new therapeutic approaches for tendon and ligament injuries and diseases.

Public Health Relevance

We recently discovered MKX as a novel tendon/ligament specific transcription factor. This project will examine molecular mechanisms that control MKX expression, how MKX regulates development and homeostasis of adult tendon and ligament tissues and establish proof-of-principle whether increasing MKX expression can improve healing of tendon injuries. The findings from this study are expected to advance our current understanding of tendon and ligament biology and serve as a basis for the development of new therapeutic approaches for tendon and ligament injures and diseases.

National Institute of Health (NIH)
National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS)
Research Project (R01)
Project #
Application #
Study Section
Special Emphasis Panel (ZRG1-MOSS-C (03))
Program Officer
Tyree, Bernadette
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
Scripps Research Institute
La Jolla
United States
Zip Code
Nakamichi, Ryo; Ito, Yoshiaki; Inui, Masafumi et al. (2016) Mohawk promotes the maintenance and regeneration of the outer annulus fibrosus of intervertebral discs. Nat Commun 7:12503
Asahara, Hiroshi (2016) Current Status and Strategy of microRNA Research for Cartilage Development and Osteoarthritis Pathogenesis. J Bone Metab 23:121-7
Suzuki, Hidetsugu; Ito, Yoshiaki; Shinohara, Masahiro et al. (2016) Gene targeting of the transcription factor Mohawk in rats causes heterotopic ossification of Achilles tendon via failed tenogenesis. Proc Natl Acad Sci U S A 113:7840-5
Kayama, Tomohiro; Mori, Masaki; Ito, Yoshiaki et al. (2016) Gtf2ird1-Dependent Mohawk Expression Regulates Mechanosensing Properties of the Tendon. Mol Cell Biol 36:1297-309
Gernapudi, Ramkishore; Wolfson, Benjamin; Zhang, Yongshu et al. (2016) MicroRNA 140 Promotes Expression of Long Noncoding RNA NEAT1 in Adipogenesis. Mol Cell Biol 36:30-8
Matsubara, Yohei; Kato, Tomoko; Kashimada, Kenichi et al. (2015) TALEN-Mediated Gene Disruption on Y Chromosome Reveals Critical Role of EIF2S3Y in Mouse Spermatogenesis. Stem Cells Dev 24:1164-70
Otabe, Koji; Nakahara, Hiroyuki; Hasegawa, Akihiko et al. (2015) Transcription factor Mohawk controls tenogenic differentiation of bone marrow mesenchymal stem cells in vitro and in vivo. J Orthop Res 33:1-8
Miyata, Kohei; Miyata, Tomoko; Nakabayashi, Kazuhiko et al. (2015) DNA methylation analysis of human myoblasts during in vitro myogenic differentiation: de novo methylation of promoters of muscle-related genes and its involvement in transcriptional down-regulation. Hum Mol Genet 24:410-23
Miyaki, Shigeru; Sato, Tempei; Inoue, Atsushi et al. (2010) MicroRNA-140 plays dual roles in both cartilage development and homeostasis. Genes Dev 24:1173-85