title: Connexin50D47A decreases levels of fiber cell connexins and impairs lens fiber cell differentiation.
abstract: OBJECTIVE
  Substitutions of aspartate-47 (D47) of Connexin50 (Cx50) have been linked to autosomal dominant congenital cataracts in several human pedigrees. To elucidate the lens abnormalities caused by a substitution at this position, we studied No2 mice, which carry the Cx50D47A mutation and parallel the human pathology.
  
  
  METHODS
  Lenses from mice of different ages (neonatal to 4 months) were examined by dark-field and immunofluorescence microscopy. Protein levels were determined by immunoblotting using primary antibodies directed against connexins, other membrane proteins, crystallins, and proteins residing in different organelles.
  
  
  RESULTS
  Lenses of both heterozygous and homozygous Cx50D47A mice had cataracts and were smaller than those of wild-type littermates. Levels of Cx50 were severely reduced in mutant animals as compared with those in wild-type mice (<20% in heterozygotes and ≤3% in homozygotes). Levels of Cx46 and aquaporin0 were also decreased, but to a lesser extent. The immunostaining pattern of lens connexins was altered in mutant animals. The lenses of Cx50D47A mice showed persistence of nuclear remnants in deep regions of the lens and elevated levels of H3 histone and the mitochondrial protein, Tom20. γ-Crystallin levels were decreased in lenses of all mutant mice, and β-crystallins were reduced in homozygotes.
  
  
  CONCLUSIONS
  These data suggest that mice expressing Cx50D47A develop cataracts due to a severe decrease in the abundance of functional connexin channels. They also implicate Cx50 in fiber cell differentiation, since mutant lenses showed impaired degradation of organelles and decreased levels of some crystallins.
authors.affiliation: Department of Pediatrics, University of Chicago, Chicago, Illinois.
authors.forename: Viviana M
authors.initials: VM
authors.lastname: Berthoud
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Minogue
authors.forename: Helena
authors.initials: H
authors.lastname: Yu
authors.forename: Richard
authors.initials: R
authors.lastname: Schroeder
authors.forename: Joseph I
authors.initials: JI
authors.lastname: Snabb
authors.forename: Eric C
authors.initials: EC
authors.lastname: Beyer
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D020346:Aquaporins / Q000378:metabolism*; D002386:Cataract / Q000235:genetics* / Q000378:metabolism; D002454:Cell Differentiation / Q000502:physiology*; D002467:Cell Nucleus / Q000378:metabolism; D017630:Connexins / Q000235:genetics* / Q000378:metabolism*; D003459:Crystallins / Q000378:metabolism; D004847:Epithelial Cells / Q000378:metabolism; D005136:Eye Proteins / Q000235:genetics* / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000502:physiology; D006657:Histones; D015151:Immunoblotting; D007908:Lens, Crystalline / Q000166:cytology* / Q000378:metabolism; D051379:Mice; D008809:Mice, Inbred C3H; D008817:Mice, Mutant Strains; D008856:Microscopy, Fluorescence; D017354:Point Mutation; D000099264:Connexin 50
chemical_list: D020346:Aquaporins; D017630:Connexins; D003459:Crystallins; D005136:Eye Proteins; D006657:Histones; D000099264:Connexin 50; C030328:aquaporin 0; C082917:GJA3 protein, human
keywords: congenital cataract; connexin; crystallins; gap junction; organelle degradation