ID: 117: Defining the intrinsic determinants of leukaemia inhibitory factor-induced myelin gene expression in CG4 oligodendrocytes

Leukaemia inhibitory factor (LIF) and erythropoietin (EPO) are functionally related, neuroprotective cytokines. Previously we found that, in rat CG4 oligodendrocyte precursor cells modified to overexpress the EPOR, EPO induces myelin oligodendrocyte glycoprotein (MOG) and myelin basic protein (MBP) expression in a dose-dependent fashion (0.4–400 ng/ml), as measured by qPCR. In contrast, LIF demonstrates a bell-shaped induction of MOG; a low dose (0.2 ng/ml) increases MOG whereas a high dose (10 ng/ml) is inhibitory. In this study, we sought to define the key intrinsic determinants of LIF-induced myelin gene expression. Inhibition of LIF-induced phospho-STAT3 with stattic downregulated MOG expression. Inhibition of LIF-induced phospho-ERK1/2 with PD184352 as confirmed by western blot, led to a 2-fold increase in MOG at low and high doses of LIF. This was associated with inhibition of LIF-induced early growth response gene 2 (Egr2), a transcription factor which inhibits myelination in this model. In the absence of LIF, differentiation induced basal levels of phospho-ERK1/2 and consequent inhibition increased MBP expression by over 4-fold. High dose LIF also induced 8-fold more suppressor of cytokine signalling 3 (SOCS3) which inversely correlates with the dose-dependent reduction of MOG. In fitting with its linear dose–response, EPO induced comparatively little phospho-STAT3 and SOCS3. These data suggest that the activation of ERK1/2 and the induction of SOCS3 inhibit myelination downstream of the LIF receptor. Overall, the balance of positive and negative intracellular signals determines the myelinogenic capacity of CG4 oligodendrocytes. Pharmacological inhibition of negative signalling pathways could potentiate remyelination in a host of demyelinating diseases.