Biology relies on quickly adapting to environmental and developmental cues. Large cells such as oocytes and neurons can rapidly alter their proteomes by activating translation when needed. A number of reproductive and neuronal disorders are caused by misregulated translation. By understanding how disease factors control translation at the molecular level, we aim to open a path towards therapeutics for autism and ovarian disorders.
We have developed a model system for studying translational control in its “purest” state in vivo using mature Drosophila oocytes. Mature oocytes are giant cells which are transcriptionally inactive and rely entirely on the translation of stored mRNAs. We study how oocytes control the translation of their stored mRNAs by (1) characterizing translation genome-wide using ribosome profiling and RNA sequencing in wild type and mutant backgrounds (2) identifying novel factors using genetic screens and cell-type specific perturbations, and (3) discovering roles for translation factors in development and aging by studying effects on oogenesis and early embryonic development.
- We found that Fmr1, a gene mutated in the most common autism and ovarian disorders, is part of a system that translates many of the largest proteins encoded in the genome (Greenblatt and Spradling 2018). We are interested in understanding how this system works, and whether restoring the normal balance between translational activators such as Fmr1 and translational repressors can ameliorate molecular defects underlying ovarian and autism spectrum disorders.
- Oocytes contain large pools of mRNAs, which are preserved for several weeks. While mRNA levels are stable, translation declines substantially during aging (>50%), and this reduction is associated with meiotic failure and infertility (Greenblatt et al. 2019). During development human oocytes also cease transcription (~10 weeks prior to maturation). We will test the hypothesis that the inability to maintain sufficient translation from long-lived mRNAs leads to age-associated meiotic errors and follicle loss that limits human reproductive lifespan.
- While the vast majority of genes are translationally repressed in oocytes, 6% of genes are translationally upregulated specifically during the oocyte’s prolonged developmental arrest (Greenblatt et al. 2019). Some of these genes – such as Fmr1, Hsp26 and Hsp27 act as “pilot lights,” prolonging oocyte function during extended periods of developmental arrest. We aim to understand the role of pilot light genes in oocytes preservation and whether these genes play important roles in other tissues such as the nervous system.
Current Lab Members
Kayla Judson: Research Technician
Xueling Kong: Undergraduate Researcher
Lucy Chi: Undergraduate Researcher
1. Fmr1 translationally activates stress-sensitive mRNAs encoding large proteins in oocytes and neurons. Greenblatt EJ, Spradling AC. bioRxiv. 2020 June 27.
2. Prolonged ovarian storage of mature Drosophila oocytes dramatically increases meiotic instability. Greenblatt EJ, Obniski R, Mical C, Spradling AC. eLife. 2019 Nov 22; 8:e49455.
3. Fragile X mental retardation 1 gene enhances the translation of large autism-related proteins. Greenblatt EJ, Spradling AC. Science. 2018 Aug 17;361(6403):709-712.
4. Unassembled CD147 is an endogenous endoplasmic reticulum-associated degradation substrate. Tyler RE, Pearce MM, Shaler TA, Olzmann JA, Greenblatt EJ, Kopito RR. Molecular Biology of the Cell. 2012 Dec;23(24):4668-78.
5. Making the cut: intramembrane cleavage by a rhomboid protease promotes ERAD. Greenblatt EJ, Olzmann JA, Kopito RR. Nature Structural and Molecular Biology. 2012 Oct;19(10):979-81.
6. Defining human ERAD networks through an integrative mapping strategy. Christianson JC, Olzmann JA, Shaler TA, Sowa ME, Bennett EJ, Richter CM, Tyler RE, Greenblatt EJ, Harper JW, Kopito RR. Nature Cell Biology. 2011 Nov 27;14(1):93-105.
7. Derlin-1 is a rhomboid pseudoprotease required for the dislocation of mutant α-1 antitrypsin from the endoplasmic reticulum. Greenblatt EJ, Olzmann JA, Kopito RR. Nature Structural and Molecular Biology. 2011 Sep 11;18(10):1147-52.
8. A two-hybrid assay to study protein interactions within the secretory pathway. Dube DH, Li B, Greenblatt EJ, Nimer S, Raymond AK, Kohler JJ. PLoS One. 2010 Dec 28;5(12):e15648.