title: Functional studies reveal new mechanisms for deafness caused by connexin mutations.
abstract: OBJECTIVE
  Connexin26 (Cx26) and Cx30 are the major protein subunits forming gap junction (GJ) intercellular channels in the cochlea. Mutations in these 2 Cxs are the major cause of nonsyndromic early childhood deafness in humans. The underlying mechanism for cochlear abnormality is unclear. Here, we used targeted Cx30 gene deletion (Cx30-/-) mice to investigate molecular mechanisms responsible for Cx mutation-linked deafness. Our hypothesis is that specific loss of GJ-mediated biochemical coupling in the cochlea is sufficient to cause deafness.
  
  
  METHODS
  We compared: (1) expression of major cochlear GJ protein subunits, Cx26 and Cx30; and (2) biochemical coupling among cochlear supporting cells in the cochleae of wild type and Cx30-/- mice.
  
  
  METHODS
  Immunolabeling was used to examine the expression of the remaining Cx protein expression in the cochlea of Cx30-/- mice. We also used a fluorescent dye diffusion assay performed on a novel flattened cochlear preparation to examine GJ-mediated metabolite transfer among cochlear supporting cells.
  
  
  RESULTS
  Estimation of the residual ionic conductance indicated that considerable intercellular ionic coupling remained in the cochlea of Cx30-/- mice. Direct measurement of GJ-mediated biochemical coupling showed that the transfer of metabolites among cochlear supporting cells in Cx30-/- mice was severely reduced.
  
  
  CONCLUSIONS
  Our data support that deficiency in GJ-mediated biochemical coupling is sufficient to cause Cx mutation-linked deafness.
authors.affiliation: Department of Otolaryngology, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
authors.forename: Qing
authors.initials: Q
authors.lastname: Chang
authors.forename: Wenxue
authors.initials: W
authors.lastname: Tang
authors.forename: Shoeb
authors.initials: S
authors.lastname: Ahmad
authors.forename: Benjamin
authors.initials: B
authors.lastname: Stong
authors.forename: Grace
authors.initials: G
authors.lastname: Leu
authors.forename: Xi
authors.initials: X
authors.lastname: Lin
mesh_terms: D000818:Animals; D003051:Cochlea / Q000033:anatomy & histology / Q000502:physiology; D000072259:Connexin 26; D000075302:Connexin 30; D017630:Connexins / Q000235:genetics*; D003638:Deafness / Q000235:genetics* / Q000473:pathology*; D004058:Diffusion; D004848:Epithelium / Q000473:pathology; D005456:Fluorescent Dyes; D017629:Gap Junctions / Q000235:genetics; D005947:Glucose / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D009154:Mutation / Q000235:genetics* / Q000502:physiology*
chemical_list: D000075302:Connexin 30; D017630:Connexins; D005456:Fluorescent Dyes; C000607042:GJB2 protein, human; C100629:Gjb6 protein, mouse; D000072259:Connexin 26; D005947:Glucose