Mechanism of cataract formation in alphaA-crystallin Y118D mutation.
OBJECTIVE
The aim of this study was to elucidate the molecular mechanisms that lead to a dominant nuclear cataract in a mouse harboring the Y118D mutation in the alphaA-crystallin gene.


METHODS
The physicochemical properties of alpha-crystallin obtained from mouse lenses with the Y118D mutation as well as a recombinant Y118D alphaA-crystallin were studied using gel filtration, two-dimensional (2D) gel electrophoresis, multi-angle light scattering, circular dichroism, fluorescence, and chaperone activities.


RESULTS
Both native alpha-crystallin from mutant lens and recombinant alphaA-Y118D displayed higher molecular mass distribution than the wild-type. Circular dichroism spectra indicated changes in the secondary structures of alphaA-Y118D. The alphaA-Y118D protein prevented nonspecific protein aggregation more effectively than wild-type alphaA-crystallin. The gel filtration and 2D gel electrophoresis analysis showed a significant reduction of Y118D mutant protein in comparison with wild-type alphaA protein of heterozygous mutant lenses. Quantitative RT-PCR results confirmed a decrease in alphaA and alphaB transcripts in the homozygous mutant alpha A(Y118D/Y118D) lenses.


CONCLUSIONS
The alphaA-Y118D mutant protein itself displays an increased chaperone-like activity. However, the dominant nuclear cataract is associated with a significant decrease in the amount of alphaA-crystallin, leading to a reduction in total chaperone capacity needed for maintaining lens transparency.
Huang
Qingling
Q
Jules Stein Eye Institute, University of California Los Angeles, Los Angeles, California 90095, USA.
Ding
Linlin
L
Phan
Kim B
KB
Cheng
Catherine
C
Xia
Chun-hong
CH
Gong
Xiaohua
X
Horwitz
Joseph
J
D000818:Animals; D002386:Cataract / Q000235:genetics*; D002850:Chromatography, Gel; D002942:Circular Dichroism; D015180:Electrophoresis, Gel, Two-Dimensional; D007908:Lens, Crystalline; D008027:Light; D051379:Mice; D017354:Point Mutation; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012542:Scattering, Radiation; D038202:alpha-Crystallin A Chain / Q000235:genetics*
D038202:alpha-Crystallin A Chain