Age-related cataracts in alpha3Cx46-knockout mice are dependent on a calpain 3 isoform.
OBJECTIVE
Previous studies have demonstrated that in 129alpha3Cx46-/- mice, age-related nuclear cataract is formed. In the present study, a more in vivo-relevant model was generated to test the hypothesis that the calpain 3 gene is involved in age-related nuclear cataractogenesis in alpha3Cx46 knockout mice.


METHODS
To test the hypothesis that the calpain 3 gene is involved in age-related nuclear cataractogenesis in alpha3Cx46 knockout mice, 129alpha3Cx46-/- and CAPN3-/- mice were mated to generate homozygous double-knockout (dKO) mice. Lenses from the mice were examined by visual observation, laser scan analysis, and histologic and biochemical methods.


RESULTS
In the absence of the CAPN3 gene, the formation of a cataract was delayed, and its appearance was changed to a more diffuse, pulverulent type. Unlike in the 129alpha3Cx46-/- mouse, cleavage of gamma-crystallin was not detected in the dKO mouse. In both 129alpha3Cx46-/- and dKO mice, total Ca2+ increased.


CONCLUSIONS
The present study shows for the first time that calpain 3 is necessary for the formation of age-dependent nuclear cataracts in alpha3Cx46-/- mice. Evidence that the calpain 3 gene is directly involved in, or part of the pathway that leads to, gamma-crystallin cleavage is presented. These results are consistent with the hypothesis that the loss of alpha3Cx46 leads to increased levels of Ca2+ ions, and this increase activates the CAPN3 isoform, Lp82/85, which results in the formation of a nuclear cataract.
Tang
Yajun
Y
Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, Illinois 60612, USA.
Liu
Xiangyang
X
Zoltoski
Rebecca K
RK
Novak
Layne A
LA
Herrera
R Antonio
RA
Richard
Isabelle
I
Kuszak
Jer R
JR
Kumar
Nalin M
NM
D000375:Aging / Q000502:physiology*; D000818:Animals; D015153:Blotting, Western; D001834:Body Water / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002154:Calpain / Q000502:physiology*; D002386:Cataract / Q000378:metabolism* / Q000473:pathology; D017630:Connexins / Q000502:physiology*; D005260:Female; D005838:Genotype; D007908:Lens, Crystalline / Q000378:metabolism* / Q000473:pathology; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D008822:Mice, Transgenic; D009124:Muscle Proteins / Q000502:physiology*; D009924:Organ Culture Techniques; D009929:Organ Size; D020033:Protein Isoforms; D038222:gamma-Crystallins / Q000378:metabolism
D017630:Connexins; D009124:Muscle Proteins; D020033:Protein Isoforms; C082917:GJA3 protein, human; D038222:gamma-Crystallins; D002154:Calpain; C491373:Capn3 protein, mouse; D002118:Calcium