ZFP24 Control of the myelination program of oligodendrocytes

Thezincfingerprotein24(ZFP24)isrequiredforoligodendrocyte maturation and CNS myelination. ZFP24 binds to a consensus DNA sequence in proximity to genes important for oligodendrocyte differentiation, and this binding enhances target gene expression. ZFP24 contains four C2H2 zinc-finger domains that are interspersed by three conserved linkers. ZFP24 DNA binding is controlled byphosphorylation of the conserved linkers: phosphorylated ZFP24, which does not bind DNA, is the predominant form in oligodendrocyte progenitor cells (OPCs). As these cells mature into oligodendrocytes, the non-phosphorylated, DNA-binding form accumulates. Our findings indicatethat changes to ZFP24 phosphorylation control its binding to regulatory regions of genes important for oligodendrocyte maturation, controls their expression, and thereby regulates oligodendrocyte differentiation and CNS myelination. Therefore, it is critical to identify the kinase(s) and phosphatase(s) responsible for controlling the functionalstatus of ZFP24. In the first aim we propose two distinct unbiased screening approaches toward the identification of the ZFP24 kinase(s). Wewill also examinethe effect of inhibition of the identified kinase(s) on ZFP24 phosphorylation, ZFP24 activity, oligodendrocyte maturation and myelin related gene expression. The second aim focuses on identifying the phosphatase(s) that de-phosphorylates ZFP24to generate the functional transcriptional factor. We will use a candidate phosphatase screen, as well as an unbiased screento identify these ZFP24 phosphatases. Wewill also examine the effect of inhibition of the identified phosphatase(s) on ZFP24 activity, ZFP24 phosphorylation, oligodendrocyte maturation and myelin related gene expression. In thethird aim we willcharacterize phosphorylation intermediateisoforms of ZFP24.We have identified ZFP24 isoformsin which one, two or all three potential phosphorylation sitesin the conserved ZFP24 linker domainsare phosphorylated in cultured oligodendrocyte lineage cells. Currently it is unclear whether these are non-functional, transitionalZFP24 isoforms, or if these forms are important intermediates with unique functionsin oligodendrocyte development. Therefore, in the thirdaim we will study the half-lifeof the intermediate forms and determine if the distinct isoforms have unique functionsin oligodendrocyte development. Aim four is devoted to the elucidation of the potential role that ZFP24 plays in the CNS of adult animals, including myelin maintenance and remyelination. We also propose to generate a new mouse model that will allow for the inducible expression of the active, non-phosphorylated, form of ZFP24 in OPCs. This model will be used to test the potential ability of the active form of ZFP24 to enhance remyelination. Overall, the studies described here will provide a more detailed understanding of the role that ZFP24 phosphorylation plays in oligodendrocyte maturation, CNS myelination, and remyelination. This understanding may allow for the therapeutic modulation of ZFP24 activity to enhancethe myelinating and remyelinating potential of OPCs.