Mechanisms of oligodendroglial ciliary function in white matter injury repair

PROJECT ABSTRACT After damage to white matter tracts (WMI) in CNS diseases such as multiple sclerosis (MS) in adults and newborn brain injuries that cause cerebral palsy (CP), myelin sheaths can be regenerated by activated oligodendrocyte precursor cells (OPCs). Failure of this remyelination program often occurs due to the improper recruitment of OPCs into injury sites, contributing significantly to ongoing neurological dysfunction and disease progression. Understanding the mechanisms controlling OPC biology during remyelination will provide insights as to why myelin repair fails in human cases. Importantly, OPCs dynamically produce primary cilia, microtubule- based organelles that transduce intercellular cues in a specialized signaling compartment. The role of primary cilia in regulating developmental pathways in OPCs remains poorly understood. Here, we show that OPCs require primary cilia to respond properly to WMI. First, this grant will demonstrate that genetically removing primary cilia from OPCs results in inadequate WMI repair, identifying the primary cilium as a critical effector of biological change in OPCs necessary for the WMI response. Furthermore, as there remains little mechanistic understanding of ciliary signaling pathways in OPCs, we will use a combination of approaches that ultimately define a GPCR/cAMP/CREB signaling axis beginning at the primary cilium as a crucial regulator of OPC biology. Finally, with recent advances in proximity-labeling, we can now catalogue the proteins that survey OPC primary cilia using a technique termed cilia-APEX. This grant will utilize cilia-APEX to identify signaling molecules that localize to OPC primary cilia in vitro and during remyelination in vivo. This will demonstrate dynamic changes in the protein content of OPC primary cilia during different stages of remyelination, while also adding significant insight into the extent of ciliary functions in OPCs. Together, these studies will show that primary cilia are a critical signaling module in OPCs for the regulation of remyelination, and will reveal potential therapeutic target for conditions such as MS and CP, where the OPC response to injury can be dysfunctional. 1