Abstract
The axonal migration of nucleic acids and their precursors has been studied following injection of radioactive uridine or thymidine into a single eye of newhatched chicks. After monocular injection of tritiated uridine, a progressive increase was observed in the specific activity of RNA of the optic lobe contralateral to the injected eye. This accumulation was first apparent 18 hours after injection and increased for at least 6 days. There was also a lesser accumulation of trichloracetic acid soluble radioactivity in this contralateral lobe relative to the ipsilateral lobe. RNA was prepared from morphological fractions of optic lobes after differential centrifugation. Radioactive analysis of these RNA fractions suggested that mitochondrial, ribosomal and transfer RNA all migrated axonally to a considerable degree. At neither 4 hours or 4 days after monocular injection of tritiated thymidine, was there any excess of radioactivity in DNA of lobes contralateral to the injected eye relative to DNA of ipsilateral lobes. Thus there was no evidence for the flow of DNA along the axon. The data suggest that a wide variety of RNA species synthesised in the nerve cell body migrate distally and appear at nerve endings.
Highlights
At one and at 6 hours after monocular injection of 10 μC 3H-uridine, there was no significant difference in the specific activity of RNA within paired optic lobes (Table 1)
A large part of the RNA migrating along the axon has been reported as being within the mitochondrion (Edstrom et al, 1969) which may have its origin in the nerve cell body (Barondes, 1966)
We have evidence for mitochondrial RNA transport distally along the axon, we have not detected any such movement of DNA
Summary
The axonal migration of nucleic acids and their precursors has been studied following injection of radioactive uridine or thymidine into a single eye of newhatched chicks. After monocular injection of tritiated uridine, a progressive increase was observed in the specific activity of RNA of the optic lobe contralateral to the injected eye. This accumulation was first apparent 18 hours after injection and increased for at least 6 days. RNA was prepared from morphological fractions of optic lobes after differential centrifugation Radioactive analysis of these RNA fractions suggested that mitochondrial, ribosomal and transfer RNA all migrated axonally to a considerable degree. The specific activity of RNA or DNA and the level of unincorporated radioactivity was determined in these brain regions
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