PROJECT SUMMARY Intellectual disability (ID), which affects approximately 1-3% of the human population, is characterized by neurological deficiencies. Genetic forms of ID are often associated with an increased risk of obesity compared to the general population and often individuals diagnosed with ID have various forms of metabolic defects. Common metabolic defects include an increase in body fat, high triglyceride levels, and high blood sugar. The underlying link(s) between neuronal dysfunction and metabolism are not yet clear. The Corbett and Moberg labs co-discovered a non-syndromic autosomal recessive form of ID caused by mutations in the gene encoding an evolutionarily conserved and ubiquitously expressed zinc-finger, polyadenosine RNA-binding protein (RBP), ZC3H14. A Drosophila model has been invaluable to study the function of ZC3H14. Initial work revealed that Nab2, the Drosophila orthologue of ZC3H14, while ubiquitously expressed, is required specifically in neurons to support proper axon guidance, locomotion, and olfactory memory. Further studies identified a robust genetic interaction between Nab2 and Mettl3, the catalytic component of the m6A methyltransferase complex, which deposits the most abundant post-transcriptional modification on RNA. An unbiased RNA Seq analysis comparing control and nab2 mutant flies identified a set of metabolic transcripts that are altered when Nab2 is lost. My preliminary data reveal that loss of Nab2 causes increases both in lipid droplet size in the Drosophila fat body (human adipose tissue equivalent) and the steady state levels of two metabolic transcripts: dilp2 and dilp5. Drosophila insulin like peptides (Dilp), Dilp2 and Dilp5, are released from the insulin-producing cells in the brain into the hemolymph where they travel to the fat body to regulate lipid storage and larval metabolism. As many patients with ID also have various metabolic defects, my project investigates how loss of ZC3H14/Nab2 results in metabolic dysfunction. Thus, I will test the hypothesis that the evolutionarily conserved RNA binding protein Nab2 regulates lipid storage and mRNA transcripts critical for proper metabolic function. I will test this hypothesis through the following complementary but independent specific aims: 1) Use lipidomics coupled with a cell-type specific RNAi to define the effect of Nab2 loss on lipids in larvae; 2) Test the effect of Nab2 loss on dilp2/dilp5 mRNA levels and Pi3K/insulin signaling; and 3) Define cell-type specific requirement for Mettl3 in regulating lipid droplet size and examine levels of m6A modifications on dilp2 and dilp5 in Nab2null larvae. Successful completion of the proposed Aims will provide insights into novel molecular mechanisms of ZC3H14/Nab2 in regulating fat storage and target RNAs critical for proper metabolic function. This proposal supports our long-term goal of exploiting a Drosophila model of ID to understand how loss of an RBP in brain neurons can elicit physiological ch...