Ribosome Heterogeneity and Preferential Translation in Proneural Protein-Mediated Neurogenesis in Drosophila

Selective production of cell-type specific proteins is at the core of cell differentiation. During the past forty years, studies of cell-type specific gene expression were dominated by the regulation of mRNA production. Recent results are beginning to unravel the regulatory roles of ribosomes in protein production. Specialized ribosomes, the ribosomes with specific composition, could produce cell-type specific proteins by preferential translation of selective transcripts. In the preliminary results, we showed that one specific ribosomal protein, RpL10A, is up-regulated in the sensory organ precursors (SOPs) and their lineage cells. SOPs actively synthesize new rRNA and proteins in the nucleolus. We also discover that the export of RpL10A from nucleolus to cytoplasm requires Actin-related protein 6 (Arp6), which is a novel proneural protein-interacting protein and is required for timely SOP specification. RpL10A preferentially associates with mRNA of senseless that encodes a neural specific protein for SOP development, and overexpreesion of senseless rescues the delay of SOP specification in Arp6 mutants. Together, these results are consistent with the model that the neural precursors produce specific proteins by preferential translation (sens) and ribosome heterogeneity (RpL10A). Based on the results, we propose to further study the functional roles of RpL10A in external sensory organ development, and investigate the in-vivo function of RpL10A to the untranslated regions (UTRs) of sens mRNAs. Furthermore, we would like to identify additional, preferential RpL10A target substrates in SOP development by co-IP of RpL10A-associated mRNAs (Translating Ribosome Affinity purification, TRAP assay) in the SOPs. To analyze the functions of the candidate genes more efficiently, we will also develop the reagents to test the applicability of tissue-specific CRISPR (tsCRISPR) to generate mutants specifically in SOPs and the developing external sensory organs. bHLH proneural proteins are highly conserved transcriptional activators in neurogenesis. By polysome profiling assay, we found that proneural proteins might elevate translation of a few SOP-specific transcripts. Thus, we propose to study the role of Myc in proneural protein-mediated ribosome biogenesis, and to identify the translatome and the potential ribosome heterogeneity in proneural protein-mediated neurogenesis by polysome profiling followed by RNA-seq and mass spectrometry. We believe our finding will illuminate a new layer of regulation on tissue-specific protein production by ribosome, and suggest mechanisms to test for ribosome-related disorders in higher organisms.

Project ID:PA10907-1081
External Project ID:MOST109-2311-B182-002-MY3