Extracellular Matrix Regulation of Myelination

Myelination is essential for brain development and function but the precise mechanisms that control the development of myelinating oligodendrocytes are not known. In demyelinating diseases such as multiple sclerosis, the loss of myelin is also thought to contribute to neurodegeneration. Myelin abnormalities of unknown origin are also found in autism, schizophrenia, and Alzheimer's disease. Candidates to regulate myelination include extrinsic factors such as extracellular matrix (ECM) molecules found in the developing brain. In contrast to neurons, little is known about the oligodendrocyte receptors and signaling mechanisms that regulate interactions with ECM. The long term goal of our research is to understand to what degree ECM regulates myelination and to determine how ECM signals lead to phenotypic changes in myelinating cells. In the current proposal we will test the hypothesis that the ECM molecule laminin enhances the survival and differentiation of oligodendrocytes by acting through specific transmembrane receptors and signaling effector molecules. We will first determine the oligodendrocyte receptor requirements for laminins using several approaches to disrupt or addback individual receptor interactions in oligodendrocytes alone or in coculture with neurons. Fyn kinase is required for laminin to enhance oligodendrocyte survival and differentiation, but the molecular mechanisms underlying this requirement are not known. We will test the hypothesis that laminins modulate Fyn regulatory mechanisms using experiments designed to disrupt Fyn regulatory molecules as well as to monitor Fyn regulatory mechansims that are activated by laminins. Finally, we will test whether Fyn regulatory mechanisms are modulated by laminins in vivo using a model for laminin deficiency that causes CMSdysmyelination. These studies are designed to uncover key mechanisms in the reciprocal axonal-glial signaling events that trigger and regulate the processes of oligodendrocyte survival, differentiation, and myelination. We hope to discover signals that stimulate myelination, a process where specialized brain cells produce an insulation, termed myelin, that is necessary for the survival and function of neurons. In doing so, we may learn which of these signals are missing or scrambled in diseases such as Multiple Sclerosis where myelin is destroyed, and, may learn how to protect neurons in neurodegenerative diseases such as Alzheimer's.