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Authors & Affiliations
Veronica Murcia-Belmonte, M Teresa Lopez-Cascales, Angel Barco, Eloisa Herrera
Abstract
Axonal protein synthesis seems to play an important role in retinal ganglion cells (RGCs) axon guidance because axonal mRNAs could be locally translated “on demand” during axonal navigation. During embryonic development, RGC axons project to the brain and have to decide whether or not to cross the midline at the level of the optic chiasm. There are two types of RGCs, the contralateral ones (cRGCs) that respond to attractive cues; and the ipsilateral ones (iRGCs), that respond to repulsive cues. Although RGCs growth cones have a very fast dynamic behavior in response to environmental stimuli, knowledge if local translation is a mechanism involved in pass through the optic chiasm and in axon steering during this process is not known. With the purpose of identifying the translatome during RGC axon guidance steering, we have used a Cre-dependent riboTRAP with a specific cRGCs or iRGCs mouse lines. We have isolated ribosomes in the contralateral and ipsilateral RGC cell bodies and axons, and extracted the mRNA bound to these ribosomes to perform a RNAseq. As a result, the growth cone of the cRGC and iRGC axons showed different translational profile in each RGCs population. By fluorescence recovery after photobleaching visualization of Venus-3UTR constructs in axons navigating the optic chiasm, we confirmed axonal translation of the mRNAs identified in our screen. These findings confirm the existence of local protein synthesis in the cone of growing axons in vivo and provide a deeper understanding of the molecular machinery involved in axon guidance decisions.