The Role of m6A-RNA Methylation in Memory Formation and Recall and Its Modulation and Influence on Long-Term Outcomes as a Consequence of Early Life Lead Exposure

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Regulation of transcription is central to proper nervous system development and functioning. Dysregulation of transcriptional and post-transcriptional regulatory pathways are associated with various neurodevelopmental diseases and disorders including developmental lead (Pb) exposure, which often results in significant and persistent cognitive and behavioral deficits. We have previously reported Pb-induced methylation changes at gene promoter regions and effects of Pb on various post-translational histone modifications (PTHMs) in hippo- campus (HIPP) and medial prefrontal cortex (mPFC) in animals with Pb-induced cognitive dysfunction, with sex, amount of Pb exposure, and developmental window of exposure as effect modifiers. While prior work has focused on effects of Pb on DNA-related mechanisms, an additional molecular transcriptional control mechanism that has not been studied in this regard is RNA modification. Preliminary data from our lab support the hypothesis that direct RNA methylation via N6-methyladenosine (m6A/m), may be an important mechanism contributing to the functionally altered transcriptome after developmental Pb exposure. Direct modifications of RNA appear to provide an additional layer of control over RNA function for the fine-tuning of transcriptomic responses to the environment, critical for normal plasticity and memory function. Considering the negative impact that Pb exposure has on neural plasticity and memory, we suggest that there is a potentially important role of m6A/m in post-transcriptional regulation of gene-specific responses associated with Pb-induced plasticity/ memory impairments. Our hypothesis is that this abundant epitranscriptomic mark, m6A/m, not only plays an important role in modulating memory processes under normal circumstances but is altered by early Pb exposure with an adverse influence on transcriptional and behavioral responses to Pb. We will test this hypothesis in the following aims: Aim1: Examine the extent to which transcriptome-wide m6A/m profiles in mPFC and HIPP CA1 and are altered by developmental Pb exposure in males and females and associated with expression of memory deficits. Hypothesis: There will be brain region-distinct transcriptome-wide enrichment profiles of m6A/m (detected by m6A-eCLIP (enhanced UV-crosslinking and immunoprecipitation), particularly associated with memory/plasticity-related genes and pathways, that are aberrantly modulated in Pb-exposed, memory-impaired animals; Aim2: Examine the functional significance of m6A/m modification in mPFC and CA1 in Pb-exposed animals through manipulation of m6A/m levels. As preliminary data indicate decreased m6A levels and increased FTO expression in Pb-exposed rats with memory deficits, we will explore the potential efficacy of viral-mediated targeted knockdown of FTO on Pb-induced memory impairments and m6A/m levels and memory/plasticity-related gene expression in mPFC and CA1. We hypothesize that by increasing m6A/m levels we will at least partially ameliorate the Pb-induced memory impairment.