Modulation of Oligodendrocyte Development by Voltage-Operated Calcium Channels

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PROJECT SUMMARY/ABSTRACT Accumulating evidence implicate Cav1.2 voltage-gated Ca++ channels in regulating dendritic spine morphology and thereby postsynaptic stability in neurons. Cav1.2 channels form signaling complexes in postsynaptic dendrites and dendritic spines, and functionally interact with several synaptic proteins. We have recently established that the activity of these Ca++ channels is crucial for the adequate migration, proliferation and maturation of oligodendrocyte progenitor cells (OPCs). Furthermore, our preliminary data suggest that Cav1.2 activity is associated with the expression of synaptic proteins in OPCs and is essential for the normal interaction of OPCs with neurons. Thus, we hypothesize that Cav1.2 channels that function in synaptic communication between neurons also mediate synaptic signaling between neurons and OPCs. In this research plan, we will employ imaging and electrophysiological techniques to study how Cav1.2 channels modulate the formation of synaptic connections between OPCs and neurons. We will determine whether increase Cav1.2 activity is sufficient to stimulate OPC synaptic connectivity and we will study how the activity of these channels modulates the expression of genes associated with OPC development. Three specific Aims are proposed: in the first Aim, we will employ the pseudopod subcellular fractionation system in combination with proteomics and RNA-Seq to investigate how the activity of Cav1.2 channels affect the expression of genes associated with OPC synaptic connections. Then, we will examine by electrophysiology and Ca++ imaging the synaptic connectivity of cortical OPCs in which Cav1.2 channels and specific synaptic proteins will be knock-down. In the second Aim, we will use a mouse model in which overactive Cav1.2 channels will be expressed in OPC at different postnatal time-points. The development and synaptic connectivity of these OPCs will be studied by a combination of techniques such as electrophysiology and RNA-Seq. Finally, we propose to use chemo-genetic technologies to influence the electrical properties of OPCs and thus OPC synaptic communications during brain development. Via Cre-mediated recombination we will express two G-protein-coupled receptors in OPCs, hM3Dq and hM4Di. We will evaluate how plasma membrane hyperexcitability (hM3Dq) and hyperpolarization (hM4Di) modify the establishment of synapses between OPCs and neurons and how these electrical changes affect the development of OPCs in the postnatal as well as in the adult brain. Decoding how OPCs can integrate and process synaptic input is of fundamental importance for understanding brain development and for improving remyelination of damaged white matter. We hypothesize that Cav1.2 channels are central components of OPC- neuronal synapses and are the principal ion channels mediating activity-dependent myelination.