Deformation of the Outer Hair Cells and the Accumulation of Caveolin-2 in Connexin 26 Deficient Mice.
BACKGROUND
Mutations in GJB2, which encodes connexin 26 (Cx26), a cochlear gap junction protein, represent a major cause of pre-lingual, non-syndromic deafness. The degeneration of the organ of Corti observed in Cx26 mutant-associated deafness is thought to be a secondary pathology of hearing loss. Here we focused on abnormal development of the organ of Corti followed by degeneration including outer hair cell (OHC) loss.


METHODS
We investigated the crucial factors involved in late-onset degeneration and loss of OHC by ultrastructural observation, immunohistochemistry and protein analysis in our Cx26-deficient mice (Cx26f/fP0Cre).


RESULTS
In ultrastructural observations of Cx26f/fP0Cre mice, OHCs changed shape irregularly, and several folds or notches were observed in the plasma membrane. Furthermore, the mutant OHCs had a flat surface compared with the characteristic wavy surface structure of OHCs of normal mice. Protein analysis revealed an increased protein level of caveolin-2 (CAV2) in Cx26f/fP0Cre mouse cochlea. In immunohistochemistry, a remarkable accumulation of CAV2 was observed in Cx26f/fP0Cre mice. In particular, this accumulation of CAV2 was mainly observed around OHCs, and furthermore this accumulation was observed around the shrunken site of OHCs with an abnormal hourglass-like shape.


CONCLUSIONS
The deformation of OHCs and the accumulation of CAV2 in the organ of Corti may play a crucial role in the progression of, or secondary OHC loss in, GJB2-associated deafness. Investigation of these molecular pathways, including those involving CAV2, may contribute to the elucidation of a new pathogenic mechanism of GJB2-associated deafness and identify effective targets for new therapies.
Department of Otorhinolaryngology, Juntendo University Faculty of Medicine, Tokyo 113-8421, Japan.
Takashi
T
Anzai
Department of Otorhinolaryngology, Juntendo University Faculty of Medicine, Tokyo 113-8421, Japan.
Ichiro
I
Fukunaga
Department of Otorhinolaryngology, Juntendo University Faculty of Medicine, Tokyo 113-8421, Japan.
Kaori
K
Hatakeyama
Department of Otorhinolaryngology, Juntendo University Faculty of Medicine, Tokyo 113-8421, Japan.
Ayumi
A
Fujimoto
Department of Otorhinolaryngology, Juntendo University Faculty of Medicine, Tokyo 113-8421, Japan.
Kazuma
K
Kobayashi
Department of Otorhinolaryngology, Juntendo University Faculty of Medicine, Tokyo 113-8421, Japan.
Atena
A
Nishikawa
Department of Otorhinolaryngology, Juntendo University Faculty of Medicine, Tokyo 113-8421, Japan.
Toru
T
Aoki
Department of Cell Biology, Japanese Foundation for Cancer Research, Cancer Institute, Tokyo 135-8550, Japan; Team for Advanced Development and Evaluation of Human Disease Models, RIKEN BioResource Center, Tsukuba 305-0074, Japan.
Tetsuo
T
Noda
Team for Advanced Development and Evaluation of Human Disease Models, RIKEN BioResource Center, Tsukuba 305-0074, Japan.
Osamu
O
Minowa
Department of Otorhinolaryngology, Juntendo University Faculty of Medicine, Tokyo 113-8421, Japan.
Katsuhisa
K
Ikeda
Department of Otorhinolaryngology, Juntendo University Faculty of Medicine, Tokyo 113-8421, Japan.
Kazusaku
K
Kamiya
D000818:Animals; D015153:Blotting, Western; D051243:Caveolin 2 / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism*; D000072259:Connexin 26; D017630:Connexins / Q000502:physiology*; D005260:Female; D005455:Fluorescent Antibody Technique; D018072:Hair Cells, Auditory, Outer / Q000378:metabolism / Q000473:pathology*; D034381:Hearing Loss / Q000378:metabolism / Q000473:pathology*; D007091:Image Processing, Computer-Assisted / Q000379:methods; D007124:Immunoenzyme Techniques; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D046529:Microscopy, Electron, Transmission
D051243:Caveolin 2; D017630:Connexins; C000607042:GJB2 protein, human; C000607043:Gjb2 protein, mouse; D000072259:Connexin 26