Decorin gene expression in the differentiation of the skeletal connective tissues of the developing limb

• Decorin is co-expressed with TGFβ in joints and tendons of the developing autopod.
• Decorin modulates the early tendon and chondrogenic markers Scleraxis and Sox9.
• Decorin and Cadherin-11 are candidate genes to modulate TGFβ roles.

Tendons and cartilages are connective tissues of essential importance in the musculoskeletal system. During digit development, cartilage and tendon primordia develop from the undifferentiated mesenchymal cells originated in the lateral plate mesoderm. The specification of these tissues begins with the establishment of cellular aggregates, which prefigure the tendons and phalanges. Transforming growth factor beta proteins (TGFβs) are the inductive signals responsible not only for the initiation of chondrogenesis and tenogenesis during digit formation, but also for joint specification. An early role of this family of secreted proteins during these processes is to promote mesenchymal cell precursors condensation. Here we show that Decorin presents an overlapping pattern of expression with TGFβ2 in joint and tendon blastemas of the embryonic digits. Furthermore, Decorin expression is induced by TGFβ signaling, and DECORIN promotes aggregation of digit mesenchymal cell precursors. In addition, we provide gene expression studies suggesting that Cadherin-11 may function as an effector of Decorin in this experimental model.