Changing Serotonin Receptor 2C Splice Variants to Combat Spasticity After Spinal Cord Injury

Spinal cord injury (SCI) in the chronic phase is complicated bymuscle spasms, which is to a large degree caused by hyperactivation of receptors caudal of the injury. The G-protein coupled serotonin receptor 2C (5HT2C) generates at least 25 isoforms with different regulatory properties and plays a major part in the maladaptation. The ratio of these isoforms, generated through alternative pre-mRNA splicing and editing control the system’s response to serotonin. For example, an alternative splice variant (5HT2C-RNA1) sequesters the other receptor isoforms (collectively called RNA2) inside the cell, effectively switching off the system. 5HT2C’s isoforms change after SCI, for example an isoform that is active without serotonin is up-regulated. Our preliminary data showed in addition to a change in RNA editing, spinal cord T4-transections change the ratios of RNA1 to RNA2 isoforms. To intervene with the isoform ratios, we developed a series of oligonucleotides that either increase or decrease the RNA1/RNA2 ratio, as well as an antiserum that is specific for the RNA1-endcoded protein. Using these tools, we will test the hypothesis that spinal cord injury leads to a change of RNA1 to RNA2 ratios, deregulating spinal cord neuronal activity leading to spasms, which can be combatted using our oligonucleotides that changes splicing isoforms. Using an established T12-transversion rat model, we will test this hypothesis in two Specific Aims: In Specific Aim#1, we will map the spatial and temporal changes in receptor isoforms; In Specific Aim#2, we will test the influence of splicing-changing oligonucleotides on the development of tail spasms.