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

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Aggrecan is a key component of cartilage, and ADAMTS4 and ADAMTS5 are enzymes that cleave it. In a study analyzing mouse growth plates, wild-type mice showed significant staining for the neo-epitope GI-TEGE, while ADAMTS4 knockout mice exhibited negligible staining, indicating a lack of cleaved aggrecan. Conversely, ADAMTS5 knockout mice displayed similar staining levels to wild-type, suggesting that ADAMTS5 is not essential for cleavage at this site. The findings conclude that ADAMTS4 is the primary aggrecanase responsible for cleavage in this anatomical region. The lack of staining in ADAMTS4 knockout mice is due to their inability to produce GI-TEGE, confirming the enzyme's critical role.
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-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
 

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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.
 
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