Neurofilament proteins form an annular superstructure in guinea-pig type I vestibular hair cells.
Neurofilaments, the neuron-specific intermediate filaments, are composed of three immunochemically distinct subunits: NF-L, NF-M and NF-H that can be either phosphorylated or unphosphorylated. In mammals, the distribution of these subunits has been described in vestibular ganglion neurons, but there are no reports on the presence of neurofilaments in vestibular hair cells. We investigated, by immunocytochemistry, neurofilaments in vestibular hair cells from rat and guinea-pig using antibodies against the three subunits and to dephosphorylated NF-H (clone SMI 32, recognizes also NF-M on immunoblots), on Vibratome sections of the vestibular end-organs and on isolated hair cells. Various immunostaining protocols were used, as appropriate for the method of observation: laser scanning confocal microscopy (immunofluorescence) and transmission electron microscopy (immunoperoxidase, pre-embedding technique). In rat and guinea-pig cristae and utricles, neurofilament immunoreactivity was observed in axons inside and below the sensory epithelia. In guinea-pig, in addition to this staining, intensely immunoreactive annular structures were found in the basal regions of hair cells. These rings were detected with anti-NF-L, -NF-M and -dephosphorylated NF-H/M antibodies, but not with anti-phosphorylation-independent NF-H. Ring-containing hair cells were present in all regions of the sensory epithelia but were more abundant in the peripheral areas. All levels of observation (Vibratome and thin sections, and isolated hair cells) showed that only the guinea-pig type I hair cells contained a neurofilament ring. High-resolution observations showed that the ring was located below the nucleus, often close to smooth endoplasmic reticulum and the cell membrane.
Laboratoire de Neurophysiologie Sensorielle, Unité INSERM 254, Montpellier, France.
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Dechesne
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Scarfone
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Atger
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Desmadryl
D000818:Animals; D000906:Antibodies; D000911:Antibodies, Monoclonal; D006168:Guinea Pigs; D006198:Hair Cells, Auditory / Q000166:cytology* / Q000648:ultrastructure; D007150:Immunohistochemistry; D046911:Macromolecular Substances; D008322:Mammals; D018613:Microscopy, Confocal; D016253:Microscopy, Immunoelectron; D016900:Neurofilament Proteins / Q000032:analysis* / Q000648:ultrastructure; D051381:Rats; D017207:Rats, Sprague-Dawley; D014722:Vestibule, Labyrinth / Q000166:cytology* / Q000648:ultrastructure
D000906:Antibodies; D000911:Antibodies, Monoclonal; D046911:Macromolecular Substances; D016900:Neurofilament Proteins