Recruitment and maintenance of tendon progenitors by TGFbeta signaling are essential for tendon formation.
Tendons and ligaments mediate the attachment of muscle to bone and of bone to bone to provide connectivity and structural integrity in the musculoskeletal system. We show that TGFbeta signaling plays a major role in the formation of these tissues. TGFbeta signaling is a potent inducer of the tendon progenitor (TNP) marker scleraxis both in organ culture and in cultured cells, and disruption of TGFbeta signaling in Tgfb2(-/-);Tgfb3(-/-) double mutant embryos or through inactivation of the type II TGFbeta receptor (TGFBR2; also known as TbetaRII) results in the loss of most tendons and ligaments in the limbs, trunk, tail and head. The induction of scleraxis-expressing TNPs is not affected in mutant embryos and the tendon phenotype is first manifested at E12.5, a developmental stage in which TNPs are positioned between the differentiating muscles and cartilage, and in which Tgfb2 or Tgfb3 is expressed both in TNPs and in the differentiating muscles and cartilage. TGFbeta signaling is thus essential for maintenance of TNPs, and we propose that it also mediates the recruitment of new tendon cells by differentiating muscles and cartilage to establish the connections between tendon primordia and their respective musculoskeletal counterparts, leading to the formation of an interconnected and functionally integrated musculoskeletal system.
Pryce
Brian A
BA
Shriners Hospital for Children, Research Division, Portland, OR 97239, USA.
Watson
Spencer S
SS
Murchison
Nicholas D
ND
Staverosky
Julia A
JA
Dünker
Nicole
N
Schweitzer
Ronen
R
D000483:Alleles; D000818:Animals; D015415:Biomarkers; D002356:Cartilage / Q000196:embryology / Q000378:metabolism; D002478:Cells, Cultured; D005121:Extremities / Q000196:embryology; D051379:Mice; D009132:Muscles / Q000196:embryology / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D015398:Signal Transduction; D013234:Stem Cells / Q000378:metabolism; D013710:Tendons / Q000196:embryology* / Q000378:metabolism*; D013997:Time Factors; D046509:Tissue Culture Techniques; D053781:Transforming Growth Factor beta2 / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D053782:Transforming Growth Factor beta3 / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*
D015415:Biomarkers; C509042:Tgfb2 protein, mouse; C509045:Tgfb3 protein, mouse; D053781:Transforming Growth Factor beta2; D053782:Transforming Growth Factor beta3