title: A novel alphaB-crystallin mutation associated with autosomal dominant congenital lamellar cataract.
abstract: OBJECTIVE
  To identify the mutation and the underlying mechanism of cataractogenesis in a five-generation autosomal dominant congenital lamellar cataract family.
  
  
  METHODS
  Nineteen mutation hot spots associated with autosomal dominant congenital cataract have been screened by PCR-based DNA sequencing. Recombinant wild-type and mutant human alphaB-crystallin were expressed in Escherichia coli and purified to homogeneity. The recombinant proteins were characterized by far UV circular dichroism, intrinsic tryptophan fluorescence, Bis-ANS fluorescence, multiangle light-scattering, and the measurement of chaperone activity.
  
  
  RESULTS
  A novel missense mutation in the third exon of the alphaB-crystallin gene (CRYAB) was found to cosegregate with the disease phenotype in a five-generation autosomal dominant congenital lamellar cataract family. The single-base substitution (G-->A) results in the replacement of the aspartic acid residue by asparagine at codon 140. Far UV circular dichroism spectra indicated that the mutation did not significantly alter the secondary structure. However, intrinsic tryptophan fluorescence spectra and Bis-ANS fluorescence spectra indicated that the mutation resulted in alterations in tertiary and/or quaternary structures and surface hydrophobicity of alphaB-crystallin. Multiangle light-scattering measurement showed that the mutant alphaB-crystallin tended to aggregate into a larger complex than did the wild-type. The mutant alphaB-crystallin was more susceptible than wild-type to thermal denaturation. Furthermore, the mutant alphaB-crystallin not only lost its chaperone-like activity, it also behaved as a dominant negative which inhibited the chaperone-like activity of wild-type alphaB-crystallin.
  
  
  CONCLUSIONS
  These data indicate that the altered tertiary and/or quaternary structures and the dominant negative effect of D140N mutant alphaB-crystallin underlie the molecular mechanism of cataractogenesis of this pedigree.
authors.affiliation: Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China.
authors.forename: Yizhi
authors.initials: Y
authors.lastname: Liu
authors.forename: Xinyu
authors.initials: X
authors.lastname: Zhang
authors.forename: Lixia
authors.initials: L
authors.lastname: Luo
authors.forename: Mingxing
authors.initials: M
authors.lastname: Wu
authors.forename: Ruiping
authors.initials: R
authors.lastname: Zeng
authors.forename: Gang
authors.initials: G
authors.lastname: Cheng
authors.forename: Bin
authors.initials: B
authors.lastname: Hu
authors.forename: Bingfen
authors.initials: B
authors.lastname: Liu
authors.forename: Jack J
authors.initials: JJ
authors.lastname: Liang
authors.forename: Fu
authors.initials: F
authors.lastname: Shang
mesh_terms: D000328:Adult; D017668:Age of Onset; D000368:Aged; D002386:Cataract / Q000151:congenital* / Q000235:genetics*; D002675:Child, Preschool; D002942:Circular Dichroism; D004252:DNA Mutational Analysis; D005260:Female; D015870:Gene Expression; D005799:Genes, Dominant; D006801:Humans; D007381:Intermediate Filament Proteins / Q000737:chemistry / Q000235:genetics*; D008297:Male; D008875:Middle Aged; D018832:Molecular Chaperones / Q000737:chemistry; D016297:Mutagenesis, Site-Directed; D020125:Mutation, Missense; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000235:genetics*; D010375:Pedigree; D016133:Polymerase Chain Reaction; D011494:Protein Kinases / Q000737:chemistry / Q000235:genetics*; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins; D013050:Spectrometry, Fluorescence; D038203:alpha-Crystallin B Chain / Q000737:chemistry / Q000235:genetics*
chemical_list: C059215:CRYAB protein, human; D007381:Intermediate Filament Proteins; D018832:Molecular Chaperones; D009419:Nerve Tissue Proteins; D011994:Recombinant Proteins; D038203:alpha-Crystallin B Chain; D011494:Protein Kinases