title: Arginine 54 and Tyrosine 118 residues of {alpha}A-crystallin are crucial for lens formation and transparency.
abstract: OBJECTIVE
  To identify new mouse models for studying roles of alphaAlpha-crystallin in vivo and to investigate why and how different mutations of the alphaAlpha-crystallin gene lead to dominant or recessive cataracts.
  
  
  METHODS
  Using mouse genetic approaches and slit lamp screening, we identified two mouse cataractous mutant lines. Causative genes were mapped by a genome-wide linkage analysis. DNA sequencing verified missense mutations of alphaA-crystallin gene in both mutant lines. Histology, imaging of green fluorescent protein (GFP)-positive lenses, and protein 2-DE gel were used to determine the morphologic and biochemical properties of mutant lenses.
  
  
  RESULTS
  Two new alphaA-crystallin gene mutations were identified, alphaA-R54C (alphaA-Cys) and alphaA-Y118D, which cause recessive whole cataracts and dominant nuclear cataracts, respectively. In homozygous alphaA-Cys mutant mice, lens epithelial and fiber cells lost their characteristic cellular features and developed disrupted subcellular structures, such as actin filaments and mitochondria. The nuclear cataract caused by alphaA-Y118D mutation was associated with increased water-insoluble crystallins (alpha, beta, and gamma classes). These results suggest that the Arg54 residue in the N-terminal region is crucial for alphaA-crystallin to perform its roles in lens epithelial and fiber cells during development, whereas the Y118D mutation in the central alpha-crystallin domain impairs alphaA-crystallin's ability to maintain the solubility of crystallin proteins in the lens.
  
  
  CONCLUSIONS
  This work demonstrates that different regions of alphaA-crystallin mediate distinct functions in vivo. These two mutant mouse lines provide useful animal models for further investigating the multiple roles of alphaA-crystallin in the lens.
authors.affiliation: School of Optometry and Vision Science Program, University of California, Berkeley, Berkeley, California 94720-2020, USA.
authors.forename: Chun-hong
authors.initials: CH
authors.lastname: Xia
authors.forename: Haiquan
authors.initials: H
authors.lastname: Liu
authors.forename: Bo
authors.initials: B
authors.lastname: Chang
authors.forename: Catherine
authors.initials: C
authors.lastname: Cheng
authors.forename: Debra
authors.initials: D
authors.lastname: Cheung
authors.forename: Meng
authors.initials: M
authors.lastname: Wang
authors.forename: Qingling
authors.initials: Q
authors.lastname: Huang
authors.forename: Joseph
authors.initials: J
authors.lastname: Horwitz
authors.forename: Xiaohua
authors.initials: X
authors.lastname: Gong
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D001120:Arginine / Q000502:physiology*; D002386:Cataract / Q000235:genetics* / Q000473:pathology; D002874:Chromosome Mapping; D004195:Disease Models, Animal; D015180:Electrophoresis, Gel, Two-Dimensional; D004847:Epithelial Cells / Q000502:physiology; D005260:Female; D005799:Genes, Dominant; D005808:Genes, Recessive; D008040:Genetic Linkage; D049452:Green Fluorescent Proteins; D007908:Lens, Crystalline / Q000502:physiology*; D008297:Male; D051379:Mice; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D008928:Mitochondria / Q000473:pathology; D010641:Phenotype; D017354:Point Mutation; D014443:Tyrosine / Q000502:physiology*; D038202:alpha-Crystallin A Chain / Q000235:genetics*
chemical_list: D000199:Actins; D038202:alpha-Crystallin A Chain; D049452:Green Fluorescent Proteins; D014443:Tyrosine; D001120:Arginine