RNA methylation in synaptic plasticity and drug-seeking

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Abstract Aberrant synaptic plasticity is a key underlying biological mechanism of drug addiction. The long-lasting synaptic changes are dependent on changes in gene expression and evidence support the involvement of epigenetic mechanisms. However, histone modifications, DNA methylation or DNA hydroxymethylation affects gene expression at transcriptional level, which is not only slow in affecting protein synthesis but also lacks synaptic specificity. RNA N6-methyladenosine (m6A) modification has been found to significantly affect RNA splicing, export, localization, translation efficiency and stability. All there are key factors in regulating translation and potentially localized translation in synapses. Both our preliminary data and published studies suggest that deficiency in m6A dependent pathways significantly impairs neuronal function including dopamine signaling and dopamine dependent learning. Therefore we propose to focus on the role of m6A modification of mRNAs in synaptic plasticity and in drug addiction models. We will use mice with the m6A methyltransferase METTL14 deleted in D1 positive striatal neurons in the nucleus accumbens. In Aim 1, we will test the hypothesis that mutant mice have impaired appetitive Pavlovian learning and impaired cue-induced reinstatement of cocaine self-administration. In Aim 2, we will record from brain slices and test if mutant mice have impaired corticostriatal plasticity and diminished changes in corticostriatal synaptic strengths caused by cocaine exposure. In Aim 3, we will determine how m6A RNA methylation regulates synaptic protein translation in responses to drug challenges and other changes on neuronal activity. We will first examine if cocaine exposure in vivo affects level of m6A RNA methylation and identify downstream targets. The rest of the proposed experiments will examine the degree to which m6A RNA methylation affects protein translation in the soma vs. dendrites where local translation is under control of synapses. We will use dissociated neuronal cortical-striatal co-cultures from METTL14 knockout and control mice.