Understanding the Molecular Basis of Memory Defects in Fragile X Syndrome

Abstract

Fragile X Syndrome (FXS) is the most common genetic cause of Intellectual Disability, affecting 1 in 4000 boys and 1 in 6000 girls. Work in our lab using Drosophila melanogaster and since replicated in the mouse model has shown that excess protein synthesis is a major mechanism connecting the observed learning and memory problems and the mutation in the fragile x gene. My masters thesis project aims at understanding further the molecular mechanisms leading to dysregulation in protein synthesis in Fragile X. Previous research has found a major protein synthesis regulation pathway, the AKT-mTOR pathway to be disrupted in Fragile X mice (Sharma et al., 2010). I initially carried out an analysis of potential target proteins within the AKT-mTOR axis of the Insulin Receptor pathway in a Drosophila melanogaster (fruit fly) model of Fragile X syndrome. This identified multiple targets that are dysregulated in Fragile X. We show that decreasing Insulin signaling in neurons throughout the brain results in impairments of both learning and protein synthesis dependent memory specifically. The final phase of this project was to identify treatment methods for Fragile X syndrome. We selected drugs targeting key candidate proteins misregulated in Fragile X mutant flies. Acute administration of Metformin, a hypoglycemiant, and Rolipram, an inhibitor of phosphodiesterase, led to significant rescuing of the learning and memory defects seen in Fragile X. Taken together the data may offer new insights into the molecular mechanisms underlying the learning and memory defects seen in Fragile X syndrome and identify potential treatment methods to improve learning and memory defects.