Fig. 6.

Fig. 6.

Model for role of muscle contraction in enthesis development. (A) Mechanical force from muscle contraction regulates the balance of sox9a and scxa expression resulting in a higher ratio of scxa to sox9a expression in the tenocytes further away from the cartilage/bone. Balanced co-expression of scxa and sox9a regulates composition of enthesis ECM. (B) Lack of mechanical force in paralyzed embryos leads to higher levels of sox9a and no change in scxa expression at the enthesis, leading to a lower ratio of scxa to sox9a in the tenocytes, which causes changes in the enthesis ECM making it less elastic and more predominantly fibrocartilage.