Periodic Reporting for period 3 - AXONENDO (Endosomal control of local protein synthesis in axons)
Periodo di rendicontazione: 2023-09-01 al 2025-02-28
Neurons are morphologically complex and highly polarized cells that require tight spatiotemporal regulation of their proteome for proper development, function and survival. mRNA localization is essential in this process allowing precise control of where and when protein products are synthesized and execute their function. Moreover, mounting evidence suggests that neurodevelopmental and neurodegenerative disorders can arise when mRNA localization is impaired. However, the regulation of mRNA localization and local translation in neurons remains poorly understood.
The endosomal system is composed by a heterogeneous and interconnected population of vesicles that carry out the transport of specific cargos throughout the cytoplasm and thus coordinate how neurons integrate, process and transfer information within and between sub-compartments. It has been recently discovered that mRNAs and ribosomes can associate with endosomes in neuronal projections, opening the possibility that endosomal trafficking could also directly control the subcellular proteome by regulating the localization and/or translation of specific mRNAs.
The overall objectives of this project are to investigate the links between the endosomal pathway and subcellular control of protein synthesis in neurons and uncover the associated functions during axonal development. By achieving our research program, we plan to i) identify the mRNAs associated with endosomes and determine whether endosomal trafficking regulates their axonal localization, ii) decipher the roles of the endosomal pathway in the selective translation of axonal mRNAs, iii) determine the molecular mechanisms behind mRNA binding to endosomes and the effects of perturbing them during axon development, and iv) determine if dysregulations of endosomal control of protein synthesis could be directly linked to axonopathies.
The endosomal system is composed by a heterogeneous and interconnected population of vesicles that carry out the transport of specific cargos throughout the cytoplasm and thus coordinate how neurons integrate, process and transfer information within and between sub-compartments. It has been recently discovered that mRNAs and ribosomes can associate with endosomes in neuronal projections, opening the possibility that endosomal trafficking could also directly control the subcellular proteome by regulating the localization and/or translation of specific mRNAs.
The overall objectives of this project are to investigate the links between the endosomal pathway and subcellular control of protein synthesis in neurons and uncover the associated functions during axonal development. By achieving our research program, we plan to i) identify the mRNAs associated with endosomes and determine whether endosomal trafficking regulates their axonal localization, ii) decipher the roles of the endosomal pathway in the selective translation of axonal mRNAs, iii) determine the molecular mechanisms behind mRNA binding to endosomes and the effects of perturbing them during axon development, and iv) determine if dysregulations of endosomal control of protein synthesis could be directly linked to axonopathies.
During this initial phase of the project, we have successfully implemented most of the technical approaches required to achieve our experimental plan. By combining genome-wide analysis and imaging methods, we have been focusing on the characterization of endosome-mRNA association in the developing neuron. Notably, we have isolated and identified the transcripts associated with endosomes in different neuronal compartments and at different developmental stages. We have been able to characterize the spatiotemporal dynamics of mRNA binding to endosomal membranes and determined the changes in the axonal transcriptome when endosomal trafficking is impaired. We have also started to investigate the role of the endolysosomal system in controlling axonal protein synthesis. Moreover, we have been able to obtain new insights into late endosomal function in regulating RNA Binding protein trafficking in axons. Finally, we have generated a new mouse model for Charcot-Marie-Tooth type 2B axonopathy.
We have been able to obtain important new knowledge regarding the spatial and temporal dynamics of endosome-mRNA association in developing neurons. The results obtained so far already represent a significant advance for the research field that can further be relevant in various physiological and pathological contexts in neurons and other cell types. We are currently pursuing functional studies in axons using various models. Together, our findings are already pointing toward a key role for the endolysosomal system in regulating mRNA localization and translation in axons. By achieving our research program, we expect to obtain additional insights into the functional roles of endosomal-control of protein synthesis during axonal development as well as determining if impairments of this process could be linked to the pathophysiology behind specific neuropathies.