AlphaA-crystallin R49Cneo mutation influences the architecture of lens fiber cell membranes and causes posterior and nuclear cataracts in mice.
BACKGROUND
AlphaA-crystallin (CRYAA/HSPB4), a major component of all vertebrate eye lenses, is a small heat shock protein responsible for maintaining lens transparency. The R49C mutation in the alphaA-crystallin protein is linked with non-syndromic, hereditary human cataracts in a four-generation Caucasian family.


METHODS
This study describes a mouse cataract model generated by insertion of a neomycin-resistant (neor) gene into an intron of the gene encoding mutant R49C alphaA-crystallin. Mice carrying the neor gene and wild-type Cryaa were also generated as controls. Heterozygous knock-in mice containing one wild type gene and one mutated gene for alphaA-crystallin (WT/R49Cneo) and homozygous knock-in mice containing two mutated genes (R49Cneo/R49Cneo) were compared.


RESULTS
By 3 weeks, WT/R49Cneo mice exhibited large vacuoles in the cortical region 100 mum from the lens surface, and by 3 months posterior and nuclear cataracts had developed. WT/R49Cneo mice demonstrated severe posterior cataracts at 9 months of age, with considerable posterior nuclear migration evident in histological sections. R49Cneo/R49Cneo mice demonstrated nearly complete lens opacities by 5 months of age. In contrast, R49C mice in which the neor gene was deleted by breeding with CreEIIa mice developed lens abnormalities at birth, suggesting that the neor gene may suppress expression of mutant R49C alphaA-crystallin protein.


CONCLUSIONS
It is apparent that modification of membrane and cell-cell interactions occurs in the presence of the alphaA-crystallin mutation and rapidly leads to lens cell pathology in vivo.
Andley
Usha P
UP
Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, St Louis, Missouri, USA. andley@vision.wustl.edu
D019943:Amino Acid Substitution; D000818:Animals; D002386:Cataract / Q000235:genetics* / Q000378:metabolism / Q000473:pathology*; D002462:Cell Membrane / Q000473:pathology / Q000648:ultrastructure; D004847:Epithelial Cells / Q000378:metabolism / Q000473:pathology / Q000648:ultrastructure; D018628:Gene Dosage; D055879:Gene Knock-In Techniques; D007903:Lens Capsule, Crystalline / Q000378:metabolism / Q000473:pathology / Q000648:ultrastructure; D007904:Lens Cortex, Crystalline / Q000378:metabolism / Q000473:pathology* / Q000648:ultrastructure*; D007907:Lens Nucleus, Crystalline / Q000378:metabolism / Q000473:pathology* / Q000648:ultrastructure; D051379:Mice; D023421:Models, Animal; D009154:Mutation; D038202:alpha-Crystallin A Chain / Q000235:genetics* / Q000378:metabolism
D038202:alpha-Crystallin A Chain