DISTRIBUTION OF CYTOSKELETAL PROTEINS (NEUROFILAMENTS, PERIPHERIN ANDMAP-TAU) IN THE COCHLEA OF THE HUMAN FETUS

We report here an immunohistochemical study of the distribution of int ermediate filaments (neurofilament, peripherin) and a microtubules-ass ociated protein, tau, in the human fetal cochlea at 27 weeks of gestat ion. Neurofilament immunoreactivity (160 and 200 KDa) was localized in afferent and efferent fibers of the cochlear innervation and restrict ed to a few small spiral ganglion neurons. Peripherin immunoreactivity was specifically distributed in some small ganglion neurons and in th eir central and peripheral extensions, particularly in fibers reaching the lower part of the outer hair cells. Double immune-labelling studi es with these neurofilaments and peripherin antibodies show that only small neuron cell bodies were stained. Morpholometrical data indicate that immunostained neurons could be related to the Type II neuron popu lation in the spiral ganglion. Tau protein was localized in intragangl ionic spiral bundle fibers and in fibers that reach the lower part of hair cells. These observations suggest that neurofilament and peripher in antibodies slain a particular population of human spiral ganglion n eurons with Type II characteristics. Moreover, the specificity of peri pherin labelling in Type II cells and their processes suggest that per ipherin could be used as a probe for the developmental study of this s ystem in the human cochlea. On the other hand, tau antibody appeared a s a marker for efferent fibers during development and could give infor mation on the ontogenesis of efferent innervation