In ribosomopathies, perturbed expression of ribosome components leads to tissue-specific phenotypes, such as limb and craniofacial defects as well as bone marrow failure. A key example of a ribosomopathy is Diamond Blackfan Anemia (DBA) which results in an erythroid-specific disease manifestation. What accounts for such tissue-selective manifestations as a result of mutations in the ribosome, a ubiquitous cellular machine, has remained a mystery. Our preliminary data strongly support that translational dysfunction may contribute to disease pathogenesis. In particular, our findings show that translational specificity to gene expression upon ribosomal protein (RP) haploinsufficiency may arise from an intermediary pathway, the p53-4E-BP1-eIF4E axis, which becomes activated and links RP haploinsufficiency to selective changes in cap-dependent translation, namely mRNAs with structured 5’UTRs that require eIF4A helicase activity or that have a specific sequence element. This preliminary data strongly supports the rationale to examine translational control and protein synthesis within the hematopoietic compartment, which has been previously unattainable to resolve and has limited our understanding of DBA pathogenesis. Strikingly, while it has been known for over 20 years that RP mutations lead to bone marrow failure associated with ribosomopathies, there has not been any genome-wide studies to pinpoint specific translation impairments underlying hematological abnormalities in- vivo. This is at least in part due to a technical limitation in being able to employ technologies such as ribosome profiling analysis for small numbers of cells. In Aim 1, we will utilize a new technology optimized for small cell numbers to characterize the translational landscape of gene expression for the first time within the early erythroid lineage of the hematopoietic compartment of a faithful DBA mouse model. This will enable characterization of the global translation landscape of gene expression underlying hematopoietic dysfunction in vivo in DBA for the first time. In Aim 2, we will test the hypothesis that the translation factor 4EBP1 play a causative role in alterations in transcript-specific translational control underlying DBA disease pathogenesis and address the fundamental question of whether shared structural features are present in the 5’UTRs of selective mRNAs that account for specificity to gene expression changes underlying ribosomopathies. In Aim 3, we will undertake a state-of-the-art chemical screen to, for the first time, identify translational activators that have the potential to transform the treatment of DBA. In particular, by leveraging over 130,000 diverse compounds available at the High Throughput Screening Knowledge Center (HTSKC), the chemical space will allow for mechanistically novel hits to emerge, including those that directly target the protein synthesis machinery. Together, this proposal holds the potential to transform our understanding and t...