View Program - 63rd Annual Drosophila Research Conference

Mutations in the fragile X mental retardation 1 (FMR1) gene result in fragile X syndrome (FXS) and fragile X primary ovarian insufficiency (FXPOI) - leading causes of intellectual disability (ID), autism spectrum disorder (ASD) and premature ovarian failure. FMR1 encodes the RNA-binding protein FMRP, which binds to dozens of mRNAs associated with various ASDs. Both neurons and oocytes translationally regulate stored mRNAs that are associated with FMRP. Mature oocytes are large, transcriptionally silent cells which depend entirely on the translation of stored mRNAs, making them a useful model to study FMRP-dependent gene regulation. Our lab previously demonstrated that Drosophila Fmr1 functions in oocytes primarily as a translational activator, and promotes the production of many large proteins essential for neurodevelopment.

We developed a single molecule fluorescent in situ hybridization (smFISH)-based assay to identify novel regulators of Fmr1 during Drosophila oogenesis. The mRNA of the Fmr1 target, Poe, is localized to RNP particles in an Fmr1 and translation-dependent manner. The loss of the RNA binding protein Rasputin (Rin), led to the dispersal of these ‘Poe-particles,’ which we hypothesize is due to reduced Poe translation. We performed co-immunoprecipitation of endogenously tagged Fmr1 from ovarian extracts followed by mass spectrometry. Our results showed an enrichment of Rin in Fmr1-tagged extracts relative to controls. We also identified several other RNA binding proteins as novel Fmr1 interactors, including CG5726, an ortholog of the mammalian non-canonical translation initiation factor CTIF. Previous studies have led to a proposed role for Rin in the stabilization and translational upregulation of its target mRNAs. We hypothesize that Rin interacts with Fmr1 and CG5726 to facilitate translational activation of Fmr1 targets in oocytes and neurons.

Rasputin – A mediator of translational activation for essential proteins in neurodevelopment