Vestibular ganglion neurons survive hair cell defects in jerker, shaker, and Varitint-waddler mutants and downregulate calretinin expression.
Bipolar neurons (BNs) in the vestibular ganglion (VG) connect vestibular hair cells with the central nervous system (CNS). Disturbed function and cell loss in central vestibular target areas or in the vestibular periphery involve BNs either retro- or anterogradely. However, the impact of central vestibular disturbances or hair cell defects on the maintenance of BNs is poorly understood. In the present study the volume of the VG, the size and total number of BNs, and the number of BNs expressing the calcium-binding protein calretinin (Calr) were quantified stereologically in the cerebellar mutants purkinje cell degeneration (pcd/pcd), weaver (wv/wv), and Lurcher (Lc/+), and in the vestibular mutants jerker (je/je), shaker-1 (sh/sh), and Varitint-waddler (Va/+). In all the different mutant mice investigated the total number of BNs did not differ from that of wildtypes. In contrast, the number of Calr-positive BNs was significantly reduced in je/je (23%) and sh/sh (33%) mutants. Reduced cell size was apparent in sh/sh mutants and the volume of the VG significantly decreased in je/je mice. Calr was virtually absent from calyx endings in the vestibular periphery of je/je, sh/sh, and Va/+ mutants, whereas in wildtypes and cerebellar mutants many calyces displayed intense Calr labeling. These results imply that the survival of BNs is apparently unaffected by the peripheral and central target defects found in the mutants investigated. Whether the decrease in Calr expression may reflect biochemical adaptations in response to input disturbances or a specific loss of large BNs is discussed.
Department of Physiology, Charité, Universitätsmedizin Berlin, Campus Benjamin Franklin, D-14195 Berlin, Germany.
Mario
M
Cabraja
Jörg
J
Bäurle
D000818:Animals; D064032:Calbindin 2; D002452:Cell Count; D002531:Cerebellum / Q000166:cytology / Q000378:metabolism*; D017950:Ganglia, Sensory / Q000166:cytology / Q000378:metabolism*; D006198:Hair Cells, Auditory / Q000166:cytology; D007150:Immunohistochemistry; D007395:Interneurons / Q000378:metabolism*; D051379:Mice; D008818:Mice, Neurologic Mutants; D009475:Neurons, Afferent / Q000166:cytology / Q000378:metabolism; D009929:Organ Size; D064030:S100 Calcium Binding Protein G / Q000235:genetics / Q000378:metabolism*; D013045:Species Specificity; D014725:Vestibular Nerve / Q000166:cytology / Q000378:metabolism*
C576511:Calb2 protein, mouse; D064032:Calbindin 2; D064030:S100 Calcium Binding Protein G