Eur J Anat, 4 (2): 111-120 (2000)

Pattern of neurofilament expression in the developing cochleovestibular ganglia in vivo, and modulation by neurotrophin 3 in vitro

Cabo R., San Jose I., Carreres A., Vega J.A., Represa J.

Departamento de Anatomia Humana, Facultad de Medicina, Universidad de Valladolid, C/ Ramón y Cajal 7, 47005-Valladolid, Spain

ABSTRACT Neurofilaments are the cytoskeletal intermediate filaments in neurons. They consist of three proteins (NFPs) with estimated molecular masses of 68, 160 and 200 kDa. The expression of NFPs by cells is regarded as a hallmark of neuronal differentiation and evolution. In the present study we analyzed the pattern of NFP expression in the neurons of the chicken cochleo-vestibular ganglion (CVG) during development and early post-hatching stages. We also investigated the expression of NFPs "in vitro" and their regulation by the neurotrophic factor NT3 to assess the participation of NFPs in neurotrophin-induced effects. The occurrence of NFP immunoreactivity (IR) "in vivo" and "in vitro" was studied using both Western-blot and immunohistochemistry on whole mount embryos, tissue sections and primary cultures. The 68 kDa NFP subunit was expressed as from stage E4 to E10, while the 160 kDa NFP subunit was found in all developmental stages and on the early post-hatching days (P10). The 200 kDa NFP subunit was observed at later developmental stages from E10 to P30. The immunoreactivity for each NFP subunit detected in inner ear sections was consistent with the data obtained by immunoblotting. NFPs were localized in the neuronal perikarya and their processes, allowing us to establish the temporal pattern of innervation of the sensory neuroepithelia located in the inner ear. Primary cultures with NT3 reproduced the "in vivo" pattern of NFP expression. The present results demonstrate that NFP subunits are developmentally regulated, suggesting that they may be specifically involved in the maturation of CVG neurons. Furthermore, the findings obtained in cultured neurons point to a regulation of NFP expression by neurotrophin-3.

Keywords: neurofilament protein, neurotrophin 3, animal experiment, animal tissue, article, chicken, embryo, ganglion, immunohistochemistry, immunomodulation, nerve cell differentiation, neurofilament, nonhuman, protein expression, vestibulocochlear nerve, Western blotting