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

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SUMMARY

The discussion centers on the role of ADAMTS4 and ADAMTS5 in aggrecan cleavage within the growth plates of mice. Immunostaining with the GI-TEGE antibody revealed significant staining in wild-type mice, negligible staining in ADAMTS4 -/- mice, and similar staining in ADAMTS5 -/- mice compared to wild-type. The conclusion drawn is that ADAMTS4 is the primary aggrecanase responsible for aggrecan cleavage at this anatomical site. The lack of staining in ADAMTS4 -/- mice is attributed to their inability to generate GI-TEGE due to the knockout of both copies of the ADAMTS4 gene.

PREREQUISITES
  • Understanding of aggrecan and its role in cartilage structure
  • Knowledge of aggrecanases, specifically ADAMTS4 and ADAMTS5
  • Familiarity with immunostaining techniques and neo-epitope detection
  • Basic genetics related to gene knockout models in mice
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  • Research the mechanisms of aggrecan cleavage by ADAMTS4 and ADAMTS5
  • Explore the implications of GI-TEGE as a biomarker in cartilage studies
  • Investigate the role of ADAMTS4 in osteoarthritis and related conditions
  • Learn about advanced immunostaining techniques for cartilage analysis
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This discussion is beneficial for researchers in cartilage biology, molecular biologists studying aggrecanases, and professionals investigating osteoarthritis mechanisms.

amanda.ka
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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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thank you!