Project description:During brain wiring, mRNAs are trafficked into axons and growth cones where they are differentially translated in response to extrinsic signals. Differential control of local protein synthesis mediates neuronal compartment-specific behaviors that aid axon guidance. Yet little is understood about how specific mRNAs are selected for translation. Here we have investigated the local role of microRNAs (miRNAs) in mRNA-specific translation during axon pathfinding of Xenopus laevis retinal ganglion cell (RGC) axons. Profiling experiments revealed a rich repertoire of axonal miRNAs in developing RGC axons and identified miR-182 as one of the most abundant. Loss of miR182 impairs Slit2-induced growth cone repulsion and causes RGC axon targeting defects in vivo. To aid miRNA target prediction, we also profiled mRNA expression in RGC axons. Our results show that miR-182 targets cofilin1 mRNA in RGC growth cones and modulates its local translation in response to Slit2.
Project description:During neuronal wiring, extrinsic cues trigger the local translation of specific mRNAs in axons via cell surface receptors. The coupling of ribosomes to receptors has been proposed as a mechanism linking signals to local translation but it is not known how broadly this mechanism operates, nor whether it can selectively regulate mRNA translation. Here, we analyzed the interactome of endogenous DCC and Neuropilin-1 by analysing immunoprecipitated samples obtained from Xenopus Laevis brains with LC-MSMS. We find that DCC and Neuropilin-1 bind to ribosomal proteins and specific RNA-binding proteins confirming that multiple guidance cue receptors can bind to ribosomes and may use receptor-ribosome coupling to regulate cue-induced local translation in axons.
Project description:Pancreatic Ductal Adenocarcinoma (PDA) is a critical health issue in cancer field with little new therapeutic options. Several evidences support an implication of intra-tumoral microenvironment (stroma) on PDA progression. However, its contribution to the role of neuroplastic changes within pathophysiology and clinical course of PDA, mainly through tumor recurrence and neuropathic pain, remains unknown neglecting a putative therapeutic window. Here, we report that intra-tumoral microenvironment is a mediator of PDA Associated Neural Remodeling (PANR). With laser capture microdissection of stromal/tumoral compartment from human PDA followed by cDNA based microarray analyses we highlighted numerous factors expressed by stromal compartment that could impact on neuroplastic changes; among them, the Slit2/Robo axon guidance pathway. Using co-culture in vitro, we showed that stromal secreted Slit2 increases DRG neurite outgrowth and Schwann cells migration/proliferation by modulating N-Cadherin/β-Catenin signaling. Importantly, Slit2/Robo signaling inhibition disrupts this stromal/neural connection. Finally, we revealed in vivo that Slit2 expression is correlated with neural remodeling within Human and mouse PDA. These results demonstrate the implication of microenvironment, through secretion of axon guidance molecule, in PANR. Furthermore, it provides rationale to investigate the disruption of stromal/neural compartment dialogue by using Slit2/Robo pathway inhibitors for treatment of pancreatic cancer recurrence and associated pain. Freshly frozen tissue samples of PDACs were obtained from patients who underwent surgery. Patients underwent hemipancreaticoduodenectomy or distal pancreatectomy. No distant metastases were revealed at initial diagnosis. Histological examination confirmed diagnosis of PDAC in all cases. Prior to surgery all patients had signed an informed consent form that had been approved by the local ethics committee. Frozen sections were obtained from tissue samples of three tumors. After a brief staining sections were dehydrated and epithelial and stromal compartment has been microdissected using the PALM system. The microdissected material was immediately dissolute in a buffer containing β-mercaptoethanol and RNA carrier, and frozen before RNA extraction. Fifteen ug of total RNA was converted to biotinylated cRNA and hybridised to a human oligonucleotide array U133 Plus 2.0 (Genechip, Affymetrix, Santa Clara, CA).
Project description:Pancreatic Ductal Adenocarcinoma (PDA) is a critical health issue in cancer field with little new therapeutic options. Several evidences support an implication of intra-tumoral microenvironment (stroma) on PDA progression. However, its contribution to the role of neuroplastic changes within pathophysiology and clinical course of PDA, mainly through tumor recurrence and neuropathic pain, remains unknown neglecting a putative therapeutic window. Here, we report that intra-tumoral microenvironment is a mediator of PDA Associated Neural Remodeling (PANR). With laser capture microdissection of stromal/tumoral compartment from human PDA followed by cDNA based microarray analyses we highlighted numerous factors expressed by stromal compartment that could impact on neuroplastic changes; among them, the Slit2/Robo axon guidance pathway. Using co-culture in vitro, we showed that stromal secreted Slit2 increases DRG neurite outgrowth and Schwann cells migration/proliferation by modulating N-Cadherin/β-Catenin signaling. Importantly, Slit2/Robo signaling inhibition disrupts this stromal/neural connection. Finally, we revealed in vivo that Slit2 expression is correlated with neural remodeling within Human and mouse PDA. These results demonstrate the implication of microenvironment, through secretion of axon guidance molecule, in PANR. Furthermore, it provides rationale to investigate the disruption of stromal/neural compartment dialogue by using Slit2/Robo pathway inhibitors for treatment of pancreatic cancer recurrence and associated pain.
Project description:During the development of the Drosophila central nervous system the process of midline crossing is orchestrated by a number of guidance receptors and ligands. Many key axon guidance molecules have been identified in both invertebrates and vertebrates, but the transcriptional regulation of growth cone guidance remains largely unknown. One open question is whether transcriptional regulation plays a role in midline crossing, or if local translation can account for the necessary fine tuning of protein levels. To investigate this issue, we conducted a genome wide analysis of transcription in Drosophila embryos using wild type and a number of well-characterized Drosophila guidance mutants and transgenics. We also analyzed a publicly available microarray time course of Drosophila embryonic development with an axon guidance focus. Using hopach, a novel clustering method which is well suited to microarray data analysis, we identified groups of genes with similar expression patterns across guidance mutants and transgenics. We then systematically characterized the resulting clusters with respect to their relevance to axon guidance using two complementary controlled vocabularies: the Gene Ontology (GO) and anatomical annotations of the Atlas of Pattern of Gene Expression (APoGE) in situ hybridization database. The analysis indicates that regulation of gene expression does play a role in the process of axon guidance in Drosophila. We also find a strong link between axon guidance and hemocyte migration, a result that agrees with mounting evidence that axon guidance molecules are co-opted in vertebrate vascularization. Cell cyclin activity in the context of axon guidance is also suggested from our array data. RNA and protein patterns of cell cyclin in axon guidance mutants and transgenics support this possible link. This study provides important insights into the regulation of axon guidance in vivo and suggests that transcription does play a role in control of axon guidance. Experiment Overall Design: Several mutants and transgenics were analyzed, totalizing 17 distinct conditions. Individual descriptions are included in each microarray. For each condition there are 3 or 4 replicates. The file's name indicates the replicates, e.g., comm.a reflects the replicate a of mutant commissureless. The experiment design covers a range of mutants and transgenics of key axon guidance mutans, in different dosages. The protocol was the standard Affymetrix protocol.
Project description:During the development of the Drosophila central nervous system the process of midline crossing is orchestrated by a number of guidance receptors and ligands. Many key axon guidance molecules have been identified in both invertebrates and vertebrates, but the transcriptional regulation of growth cone guidance remains largely unknown. One open question is whether transcriptional regulation plays a role in midline crossing, or if local translation can account for the necessary fine tuning of protein levels. To investigate this issue, we conducted a genome wide analysis of transcription in Drosophila embryos using wild type and a number of well-characterized Drosophila guidance mutants and transgenics. We also analyzed a publicly available microarray time course of Drosophila embryonic development with an axon guidance focus. Using hopach, a novel clustering method which is well suited to microarray data analysis, we identified groups of genes with similar expression patterns across guidance mutants and transgenics. We then systematically characterized the resulting clusters with respect to their relevance to axon guidance using two complementary controlled vocabularies: the Gene Ontology (GO) and anatomical annotations of the Atlas of Pattern of Gene Expression (APoGE) in situ hybridization database. The analysis indicates that regulation of gene expression does play a role in the process of axon guidance in Drosophila. We also find a strong link between axon guidance and hemocyte migration, a result that agrees with mounting evidence that axon guidance molecules are co-opted in vertebrate vascularization. Cell cyclin activity in the context of axon guidance is also suggested from our array data. RNA and protein patterns of cell cyclin in axon guidance mutants and transgenics support this possible link. This study provides important insights into the regulation of axon guidance in vivo and suggests that transcription does play a role in control of axon guidance. Keywords: Mutant Analysis
Project description:The neuronal RNA-binding protein Ptbp2 regulates neuronal differentiation by modulating alternative splicing programs in the nucleus. Such programs contribute to axonogenesis by adjusting the levels of protein isoforms involved in axon growth and branching. While its functions in alternative splicing have been described in detail, cytosolic roles of Ptbp2 for axon growth have remained elusive. Here, we show that Ptbp2 is located in the cytosol and in axons of motoneurons, and that depletion of Ptbp2 affects axon growth. We identified Ptbp2 as a major interactor of the 3' UTR of Hnrnpr mRNA. Axonal localization of Hnrnpr mRNA and local synthesis of hnRNP R protein are strongly reduced when Ptbp2 is depleted, leading to defective axon growth. Ptbp2 regulates hnRNP R translation by mediating the association of Hnrnpr with ribosomes in a manner dependent on the translation factor eIF5A2. Our data thus, suggest a mechanism whereby Ptbp2 modulates axon growth by fine-tuning the mRNA transport and local synthesis of an RNA-binding protein.
Project description:Cue-directed axon guidance depends partly on local translation in growth cones. Many mRNA transcripts are known to reside in developing axons yet little is known about their subcellular distribution or, specifically, which transcripts are in growth cones. Laser capture microdissection (LCM) was used to isolate the growth cones of retinal ganglion cell (RGC) axons of two vertebrate species, mouse and Xenopus, coupled with unbiased genome-wide microarray profiling. Localized mRNA from the isolated growth cones of Xenopus laevis and Mus musculus retinal ganglion cells were subjected to microarray analysis
Project description:Cue-directed axon guidance depends partly on local translation in growth cones. Many mRNA transcripts are known to reside in developing axons yet little is known about their subcellular distribution or, specifically, which transcripts are in growth cones. Laser capture microdissection (LCM) was used to isolate the growth cones of retinal ganglion cell (RGC) axons of two vertebrate species, mouse and Xenopus, coupled with unbiased genome-wide microarray profiling.