KSEF RDE: GSK3 and Regulation of Alternative Splicing in Oligodendrocytes:A Target to Enhance Remyelination in Human Disease

Multiple Sclerosis (MS) is an inflammatory demyelinating disorder of unknown etiology, which affects >1 million people worldwide 2. Failure of oligodendrocytes (OL), the myelin producing cells of the central nervous system (CNS), to remyelinate is a major cause of disability in MS 3. The myelin protein, PLP is neuroprotective and its abundance is regulated by alternative splicing of the primary transcript at the time of OL differentiation 4-5. We have discovered that the Glycogen Synthase Kinase (GSK) 3b regulates PLP alternative splicing in OL. We show that a splicing factor,polypyrimidine tract binding protein-associated factor (PSF), is a downstream target of GSK3bmediated regulation of PLP splicing and ultimately PLP abundance. GSK3b is a target of the PI3K (phosphatydil-inositol-3-kinase)-Akt pathway, which plays pivotal roles in oligodendrocyte survival and differentiation 6-8, thus linking alternative splicing with this vital signaling pathway. In this proposal, we will determine the function of the GSK3-PSF pathway in regulating PLP splicing, myelination and remyelination in vivo. We are currently making a conditional knockout (cko) by inactivating GSK3b in OL. In Aim 1, we will examine the effect that ablation of GSK3b has on myelination by measuring alternative splicing of PLP and the other myelin proteins in the postnatal brain, characterizing oligodendrocyte lineage progression and myelin formation. Mice will be examined with cage behavior and motor testing. In Aim 2, we will test the role of oligodendrocytic GSK3b in remyelination in the acute cuprizone model. This is a toxic model of de-myelination, characterized by spontaneous re-myelination after withdrawal of cuprizone from the diet, hence demyelination and re-myelination can be examined individually 9. Oligodendrocyte recruitment and differentiation, alternative splicing of PLP and myelin proteins and myelination will be characterized in the GSK3b cko and compared to control littermates at the end of the cuprizone-treatment and in the recovery stage. Together, these studies will establish the role of GSK3b in alternative splicing and myelin formation in myelination and re-myelination in vivo.