Project description:Local protein synthesis has not been believed to occur in adult forebrain axons. We have used translating ribosome affinity purification (TRAP) to capture mRNA from the distal amygdaloid projections of auditory cortical axons. An eYFP-tagged ribosomal protein (rpL10a) was expressed in the adult rat auditory cortex via a lentiviral vector, and rats were given Pavlovian fear conditioning or control training two hours before collection of auditory cortex and amygdala. The eYFP tag alone was used as an IP control. Polysome extraction and eYFP immunoprecipitation were performed according to published protocols (Heiman et al., 2008 Cell 135:78; Kratz et al. 2014 Genome Res. 24:1396).
Project description:Local mRNA translation mediates the adaptive responses of axons to extrinsic signals but direct evidence that it occurs in mammalian CNS axons in vivo is scant. We developed an axon-TRAP-RiboTag approach in mouse that allows deep-sequencing analysis of ribosome-bound mRNAs in the retinal ganglion cell axons of the developing and adult retinotectal projection in vivo. The embryonic-to-postnatal axonal translatome comprises an evolving subset of enriched genes with axon-specific roles suggesting distinct steps in axon wiring, such as elongation, pruning and synaptogenesis. Adult axons, remarkably, have a complex translatome with strong links to axon survival, neurotransmission and neurodegenerative disease. Translationally co-regulated mRNA subsets share common upstream regulators, and novel sequence elements generated by alternative splicing that promote axonal mRNA translation. Our results indicate that intricate regulation of compartment-specific mRNA translation in mammalian CNS axons supports the formation and maintenance of neural circuits in vivo. The profiling of ribosome-bound mRNAs in mouse retinal ganglion cell axons at 4 different developmental stages
Project description:We have conducted quantitative proteomic analyses of the axons of cultured rat cortical neurons. Axons are isolated by using glass chips that enable the axons and their cell bodies of neurons to grow in separated regions on the chip surface. Proteins extracted from the isolated axons, as well as those extracted from whole cortical neurons are subjected to two-dimensional liquid chromatography (2D-LC)-mass spectrometry (MS)-MS analyses. The abundances of proteins in the axon are found to be strongly correlated with their average abundances in whole neurons. Based upon these data, a quantitative description of the protein distribution among various subcellular structures in the axon has been generated. The proteins extracted from the axons and whole neurons are also subjected to stable isotope dimethyl labeling reaction and then to 2D-LC-MS/MS analysis. Proteins enriched in the axon compartment of rat cortical neurons are thus identified.
Project description:Efficient growth cone regeneration requires protein synthesis in the adult mammalian brain and spinal cord. Recent evidence suggests that the local availability of protein synthesis machinery in adult mammalian axons may be an indicator of their regenerative capacity. Here we investigated the local protein synthesis capacity in matured cortical axons, which have poor regenerative capacity, yet are critical for recovery following injury due to traumatic brain injury and stroke. This work is the first to biochemically isolate and identify mRNA from mammalian cortical axons, making use of a unique microfluidic platform to isolate axons free of other cellular debris. We first sought to identify mRNA in naïve axons that makes up the pool of mRNA available for translation initiated following axotomy. Next, we investigated changes in the mRNA population localized to axons 2 days following axotomy and growth cone regeneration. Experiment Overall Design: Cortical axons were harvested using the compartmentalized microfluidic platform after 13 days in culture at a time when they express mature synaptic proteins. A total of 7 Genechips were used for the uninjured cortical axons from 3 different culture batches. 3 Genechips were used for neurons isolated from the neuronal compartment of the microfluidic platfrom. The neuronal Genechip were used to compare mRNA populations with axonal Genechips and for quality control purposes. 3 Genechips were used for regenerating axons; for these, axons were axotomized at 11 days in culture, then allowed to regrow for 2 days before harvesting.
Project description:Local mRNA translation mediates the adaptive responses of axons to extrinsic signals but direct evidence that it occurs in mammalian CNS axons in vivo is scant. We developed an axon-TRAP-RiboTag approach in mouse that allows deep-sequencing analysis of ribosome-bound mRNAs in the retinal ganglion cell axons of the developing and adult retinotectal projection in vivo. The embryonic-to-postnatal axonal translatome comprises an evolving subset of enriched genes with axon-specific roles suggesting distinct steps in axon wiring, such as elongation, pruning and synaptogenesis. Adult axons, remarkably, have a complex translatome with strong links to axon survival, neurotransmission and neurodegenerative disease. Translationally co-regulated mRNA subsets share common upstream regulators, and novel sequence elements generated by alternative splicing that promote axonal mRNA translation. Our results indicate that intricate regulation of compartment-specific mRNA translation in mammalian CNS axons supports the formation and maintenance of neural circuits in vivo.
Project description:Efficient growth cone regeneration requires protein synthesis in the adult mammalian brain and spinal cord. Recent evidence suggests that the local availability of protein synthesis machinery in adult mammalian axons may be an indicator of their regenerative capacity. Here we investigated the local protein synthesis capacity in matured cortical axons, which have poor regenerative capacity, yet are critical for recovery following injury due to traumatic brain injury and stroke. This work is the first to biochemically isolate and identify mRNA from mammalian cortical axons, making use of a unique microfluidic platform to isolate axons free of other cellular debris. We first sought to identify mRNA in naïve axons that makes up the pool of mRNA available for translation initiated following axotomy. Next, we investigated changes in the mRNA population localized to axons 2 days following axotomy and growth cone regeneration. Keywords: axonal expression analysis; injury state analysis
Project description:Employing translating ribosome affinity purification with RNA sequencing (TRAPseq) on cortical tissue to isolate astroglial-specific translatome from Aldh1l1-L10-GFP mice and examine sex (male + female) and age (postnatal days 1, 4, 7, 14, 35; adults (9 weeks)) dependent changes in the astroglial translatome.