RNA AND PROTEIN SYNTHESIS IN MAUTHNER NERVE FIBER COMPONENTS OF FISH

Abstract

The presence of RNA is not in itself conclusive but is a prerequisite condition for protein synthesis. In the Mauthner axon and in its myelin sheath, the majority of the RNA is likely to be outside mitochondria. It is also reasonable to ascribe a functional role to this RNA, because there are strong suggestions that the major portion of the local protein synthesis in this system is linked to components other than mitochondria. There are also indications that the local supply is quantitatively significant in the axon of the Mauthner neuron. This chapter reviews the properties of RNA in the axon and myelin sheath of the Mauthner neuron. One of the obvious difficulties in evaluating the results of biochemical experiments with whole nerve is to differentiate between contributions from the different compartments, among which are satellite cells, axoplasm, blood vessels, endoneural fluid, and connective tissue. The Mauthner neuron from fish provides a system that can be used to eliminate this difficulty. The myelinated Mauthner axon can be isolated at different levels from its cellular origin and can be dissected into its axonal and myelin sheath compartment, which then can be analyzed separately with microchemical methods. The chapter further discusses RNA content and distribution in the Mauthner neuron, the base composition of RNA from the different compartments of the Mauthner neuron, RNA synthesis in the Mauthner fiber, and protein synthesis in the Mauthner fiber components.