Why Does ADAMTS4 Knockout Show Least Staining If It Cleaves Aggrecan in Mice?

[amanda.ka]

-Aggrecan is an abundant component of cartilage within the growth plate as well as the articular cartilage of joints
-ADAMTS4 and ADAMTS5 are aggrecanases that cleave aggrecan
-Analysis of the growth plates of mice were performed by immunostaining the growth plates with an antibody against neo-epitope of aggrecan (GI-TEGE) which is generated following cleavage by aggrecanases
The results showed:

a) Wild-type mice: significant staining

b) ADAMTS4 -/- mice: negligible staining

c) ADAMTS5 -/- mice: similar staining to that of wild-type mice

Conclusion: ADAMTS4 is the sole aggrecanase responsible for aggrecan cleavage at this anatomical location

My question is that if GI-TEGE is generated following cleavage shouldn't ADAMTS4 be showing the most staining since it is responsible for cleaving at this site? Why is there the least staining at ADAMTS4 ? Am I missing something?
Thank you in advanced!
*image and data are taken from paper titled: deletion of active ADAMTS5 prevents cartilage degradation in a murine model of osteoarthritis by Glasson et al. 2005

 

[Ygggdrasil]

ADAMTS4 -/- mice have both copies of the ADAMTS4 gene knocked out. Because these mice lack ADAMTS4, they are unable to generate GI-TEGE and show no staining in the figure. When ADAMTS5 is knocked out (in the ADAMTS5 -/- mice), there is no change to the staining. Because mice lacking ADAMTS5 are capable of producing wild-type levels of GI-TEGE, they conclude that ADAMTS5 is not required for aggrecan cleavage at the location they stained.

 

[amanda.ka]

thank you!