A few axonal proteins distinguish ventral spinal cord neurons from dorsal root ganglion neurons.

Abstract

A series of proteins putatively involved in the generation of axonal diversity was identified. Neurons from ventral spinal cord and dorsal root ganglia were grown in a compartmented cell-culture system which offers separate access to cell somas and axons. The proteins synthesized in the neuronal cell somas and subsequently transported into the axons were selectively analyzed by 2-dimensional gel electrophoresis. The patterns of axonal proteins were substantially less complex than those derived from the proteins of neuronal cell bodies. The structural and functional similarity of axons from different neurons was reflected in a high degree of similarity of the gel pattern of the axonal proteins from sensory ganglia and spinal cord neurons. Each axonal type, however, had several proteins that were markedly less abundant or absent in the other. These neuron-population enriched proteins may be involved in the implementation of neuronal diversity. One of the proteins enriched in dorsal root ganglia axons had previously been found to be expressed with decreased abundance when dorsal root ganglia axons were co-cultured with ventral spinal cord cells under conditions in which synapse formation occurs (P. Sonderegger, M. C. Fishman, M. Bokoum, H. C. Bauer, and P.G. Nelson, 1983, Science [Wash. DC], 221:1294-1297). This protein may be a candidate for a role in growth cone functions, specific for neuronal subsets, such as pathfinding and selective axon fasciculation or the initiation of specific synapses. The methodology presented is thus capable of demonstrating patterns of protein synthesis that distinguish different neuronal subsets. The accessibility of these proteins for structural and functional studies may contribute to the elucidation of neuron-specific functions at the molecular level.

Protein expression patterns of identified neurons and of sprouting cells from the leech central nervous system

“…The striking differences between the gels from ganglia versus those of cell bodies indicate that the major proteins expressed in neuronal cell bodies partially differ from those expressed in neurites and synapses and/or satellite cells. In accordance with these results differences in the protein pattern of axons and the corresponding cell bodies have been found in retina (von Boxberg et al, 1990) and dorsal root ganglion (Sonderegger et al, 1984). In addition differences in protein composition of different parts of the CNS have been reported (Geschwind et al, 1996).…”

Identification of proteins secreted from axons of embryonic dorsal‐root‐ganglia neurons

“…Under the conditions employed here, which have been elaborated previously for the selective metabolic labeling of cell-bound proteins of axons [24], local incorporation of radioactive amino acid into secretory proteins synthesized by cells of the side compartment did not occur.…”

“…After exposure to fluorodeoxyuridine from day two to day five after plating, only isolated nonneuronal cells survive in the side compartment (for details cf. [24]). …”

“…Especially in the proximal half of the barrier, where lsoelectric point (B) indicate the coordinates of the expected location of these proteins the supply of radioactive amino acid may be virtually unlimited (for an illustration cf. [24], Fig. 2), the extremely narrow extracellular space available for the secreted proteins might lead to a local protein concentration which is considerably higher than that of the medium of the center Compartment.…”

“…Ventral and dorsal halves of spinal cords were dissected from 6-day-old embryos as described by Masuko et al [28]. Culture conditions were as given by Sonderegger et al [24]. Retinas were obtained from 7-dayold embryos and cultured according to Brackenbury et al [29].…”