Differential expression of otoferlin in brain, vestibular system, immature and mature cochlea of the rat.
Mutations of the human otoferlin gene lead to an autosomal recessive nonsyndromic form of prelingual, sensorineural deafness (deafness autosomal recessive 9, DFNB9). Several studies have demonstrated expression of otoferlin in the inner ear and brain, and suggested a role of otoferlin in Ca(2+)-triggered exocytosis. So far, otoferlin expression profiles were solely based on the detection of mRNA. Here, we analysed the expression of otoferlin protein and mRNA using immunohistochemistry, in situ hybridization and RT-PCR in neonatal and mature Wistar rat tissue. In agreement with previous studies, otoferlin expression was found in the brain and in inner and vestibular hair cells. Otoferlin mRNA and protein was, however, also detected in mature outer hair cells of low-frequency processing cochlear turns and in auditory nerve fibres. In outer, inner and vestibular hair cells, otoferlin was subcellularly localized at a considerable distance from the presumed active release sites. Double-staining with the synaptic ribbon marker, C-terminal binding protein 2 (CtBP2), or the presynaptic Ca(2+)-channel, Ca(v)1.3, both assumed to mark the sites of vesicle fusion and transmitter release, did not colocalize with otoferlin expression and thus do not necessarily support a selected role of otoferlin in Ca(2+)-triggered exocytosis. The widespread distribution of otoferlin in neurons, nerve fibres and hair cells, and its subcellular distribution extending beyond the regions of synaptic vesicle fusion, i.e. coenrichment with the cytosolic Golgi matrix protein 130 (GM130) in inner hair cells or the early endosomal autoantigen 1 (EEA1) in outer hair cells support instead the idea of a more ubiquitous role of otoferlin in early/recycling endosome trans-Golgi network dynamics.
Schug
Nicola
N
University of Tübingen, Institute of Human Genetics, Wilhelmstr. 27, 72074 Tübingen, Germany.
Braig
Claudia
C
Zimmermann
Ulrike
U
Engel
Jutta
J
Winter
Harald
H
Ruth
Peter
P
Blin
Nikolaus
N
Pfister
Markus
M
Kalbacher
Hubert
H
Knipper
Marlies
M
D000367:Age Factors; D000818:Animals; D000831:Animals, Newborn; D001324:Autoantigens / Q000378:metabolism; D015153:Blotting, Western / Q000379:methods; D001921:Brain / Q000254:growth & development / Q000378:metabolism*; D020746:Calcium Channels, L-Type / Q000378:metabolism; D003051:Cochlea / Q000254:growth & development / Q000378:metabolism*; D005136:Eye Proteins / Q000378:metabolism; D005455:Fluorescent Antibody Technique / Q000379:methods; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D008565:Membrane Proteins / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D014722:Vestibule, Labyrinth / Q000254:growth & development / Q000378:metabolism*
D001324:Autoantigens; D020746:Calcium Channels, L-Type; C486016:Ctbp2 protein, rat; D005136:Eye Proteins; D008565:Membrane Proteins; D012333:RNA, Messenger; C516233:otoferlin protein, mouse