Alterations to proteins in the lens of hereditary Crygs-mutated cataractous mice

Purpose: To investigate the altered expression of proteins in the lens of mice with inherited cataracts. Methods: Mice with inherited cataracts caused by a spontaneous mutation of the gene gamma S-crystallin (Crygs) were used as the subjects. Lens proteins were extracted and separated by two-dimensional electrophoresis (2-DE). The spots representing differential proteins were first identified by image analysis, and then further analyzed by matrix assisted laser desorption/ionization-time of flight-tandem mass spectrometry (MALDI-TOF-MS/MS). Results: 2-DE were conducted under high (882 mu g) and low dosage (190 mu g) of sample. Under each condition, the numbers of protein spots found in cataract lenses were similar to those in normal lenses (p>0.05). Seventeen proteins were identified in normal lenses, including alpha A-to alpha B-, beta A1- to beta A4-, beta B1- to beta B3-, gamma A- to gamma F-, and gamma S-crystallin, and bead-filament structure protein (BFSP/filensin). Seven differential ones were consistently identified. In the cataract lenses BFSP and gamma S-crystallin were absent; gamma F-crystallin was downregulated; and beta A1-, beta B1-, beta B2-, and alpha B-crystallin were upregulated. Those abnormally upregulated crystallins, when compared to normal ones, had smaller molecular weight, suggesting possible truncation. Conclusions: The mutant Crygs gene can lead to changes of BFSP/filensin and other crystallins. The changes to these crystallins, together, may secondarily lead to cataract formation.