CYTOLOGICAL STUDIES OF DEVELOPING AND MATURE NEURONS

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Our goal is to utilize advanced tissue culture systems to improve our understanding of Schwann cell function; our longer term goal is to apply this understanding to foster neuronal regeneration in the experimental animal and in the human patient. We will study extracellular matrix production by Schwann cells and the role of this Schwann cell function in peripheral nerve organization and in regenerative nerve growth. Detailed studies of the mechanism of basal lamina assembly by Schwann cells are proposed (in collaboration with Dr. J. Heuser) using both morphological and immunostaining techniques. Studies on the axonal regulation of type IV collagen deposition by Schwann cells will be emphasized inasmuch as basal lamina formation sppears critically dependent on this component. Relative rates of synthesis during specific funcitonal states of Schwann cells will be assessed by the use of a cDNA probe for the type IV collagen message. We will attempt to identify specific Schwann cell products providing support for neuronal survival and neurite growth. We will study axonal, Schwann cell and extracellular matrix contributions to the process of axonal ensheathment. We will seek to determine to what extent the connective tissue environment influences ensheathment of an unmyelinated axons by Schwann cells. We will seek to identify membrane components uniquely expressed on axons capable of inducing myelination and on Schwann cells responding to these axonal signals. We will study the process of Schwann cell myelination in the presence of antibodies to known antigens such as L1 (in collaboration with Dr. M. Schachner) and galactocerebroside. In order to facilitate identification of unique surface components expressed in the most highly differentiated state of Schwann cells and myelinated axons, we propose (in collaboration with Dr. J. Milbrandt to prepare mRNA and recombinant DNA from Schwann cells and neurons and to screen these libraries for molecules characterizing the Schwann cell undertaking myelination and the neuron inducing myelination. Finally we propose detailed tissue culture studies of human Schwann cells to determine if the regulation of their function occurs according to the same rules that apply to rodent Schwann cells. We propose studying these cell in co-culture with sensory neurons (rather than as isolated populations) because this method of investigating Schwann cells is more relevant to Schwann cell function in the animal.