Project description:During central nervous system (CNS) development, proper and timely induction of axon elongation is critical for generating functional, mature neurons and neuronal networks. Despite the wealth of information on the action of extracellular cues, little is known about the intrinsic gene regulatory factors that control this developmental decision. Here we report the identification of Prox1, a homeobox transcription factor, as a key player in inhibiting axon elongation. Although Prox1 promotes acquisition of early neuronal identity and is expressed in nascent post-mitotic neurons, it is heavily down-regulated in the majority of terminally differentiated neurons, indicating a regulatory role in delaying axon outgrowth in newly formed neurons. Consistently, we show that Prox1 is sufficient to inhibit neurite extension in neuroblastoma cell lines. Furthermore, shRNA-mediated knock-down of Prox1 in Neuro2A cells induces the extension of neurites. More importantly, Prox1 overexpression suppresses axon elongation in primary neuronal cultures as well as in the developing mouse brain, while Prox1 knock-down promotes axon outgrowth. Mechanistically, RNA-Seq analysis reveals that Prox1 affects critical pathways for neuronal maturation and neurite extension. Interestingly, Prox1 strongly inhibits many components of Ca2+ signaling pathway, an important mediator of axon extension and neuronal maturation. In accordance, Prox1 represses Ca2+ entry upon KCl-mediated depolarization and reduce CREB phosphorylation. These observations suggest that Prox1 acts as a potent suppressor of axon elongation by inhibiting Ca2+ signaling pathway. This action may provide the appropriate time window for nascent neurons to find the correct position in the CNS prior to initiation of axon elongation.
Project description:N6-methyladenosine (m6A) affects multiple aspects of mRNA metabolism and regulates developmental transitions by promoting mRNA decay. Little is known about the role of m6A in the adult mammalian nervous system. Here we report that sciatic nerve lesion elevates levels of m6A-tagged transcripts encoding many regeneration-associated genes and protein translation machinery components in the adult mouse dorsal root ganglion (DRG). Single base resolution m6A-CLIP mapping further reveals a dynamic m6A landscape in the adult DRG upon injury. Loss of either m6A methyltransferase complex component Mettl14 or m6A-binding protein Ythdf1 globally attenuates injury induced protein translation in adult DRGs and reduces functional axon regeneration in the peripheral nervous system in vivo. Furthermore, Pten deletion-induced axon regeneration of retinal ganglion neurons in the adult central nervous system is attenuated upon Mettl14 knockdown. Our study reveals a critical epitranscriptomic mechanism in promoting injury-induced protein synthesis and axon regeneration in the adult mammalian nervous system.
Project description:After injury to the central nervous system (CNS), both neuron-intrinsic limitations on regenerative responses and inhibitory factors in the injured CNS environment restrict regenerative axon growth. Instances of successful axon regrowth offer opportunities to identify features that differentiate these situations from that of the normal adult CNS. One such opportunity is provided by the kinase inhibitor RO48, which dramatically enhances neurite outgrowth of neurons in vitro and substantially increased contralateral sprouting of corticospinal tract neurons when infused intraventricularly following unilateral pyramidotomy. The authors present here a transcriptomic deconvolution of RO48-associated axon growth, with the goal of identifying transcriptional regulators associated with axon growth in the CNS. Through the use of RNA sequencing (RNA-seq) and transcription factor binding site enrichment analysis, the authors identified a list of transcription factors putatively driving differential gene expression during RO48-induced neurite outgrowth of rat hippocampal neurons in vitro. The 82 transcription factor motifs identified in this way included some with known association to axon growth regulation, such as Jun, Klf4, Myc, Atf4, Stat3, and Nfatc2, and many with no known association to axon growth. A phenotypic loss-of-function screen was carried out to evaluate these transcription factors for their roles in neurite outgrowth; this screen identified several potential outgrowth regulators. Subsequent validation suggests that the Forkhead box (Fox) family transcription factor Foxp2 restricts neurite outgrowth, while FoxO subfamily members Foxo1 and Foxo3a promote neurite outgrowth. The authors’ combined transcriptomic-phenotypic screening strategy therefore allowed identification of novel transcriptional regulators of neurite outgrowth downstream of a multitarget kinase inhibitor.
Project description:In our study, we found that reprogrammed glia by activating PI3K and EGFR pathways promotes axon regeneration in the central nervous systems of Drosophila larvae. Thus, we analysized the transcriptome of the CNS collected from flies with or without repromgrammed glia by RNA-seq.
Project description:The adult central nervous system (CNS) has a limited capacity for self-repair. Severed CNS axons typically do not regrow. There is an unmet need for treatments specifically designed to enhance neuronal viability, facilitate CNS axon regeneration, and ultimately restore lost neurological functions to individuals with traumatic CNS injury, multiple sclerosis, and stroke, among other disorders. Here we demonstrate that both mouse and human bone marrow (BM) neutrophils upregulate markers of alternative activation, and acquire the ability to promote neurite outgrowth, following polarization with a combination of recombinant interleukin-4 (IL-4) and granulocyte-colony stimulating factor (G-CSF). Moreover, adoptively transferring IL-4/G-CSF polarized BM neutrophils into experimental models of CNS injury resulted in significant axon regeneration within the optic nerve and spinal cord. The findings reported in this paper hold significant implications for the future development of autologous myeloid cell-based therapies that may bring us closer to effective solutions for reversing CNS damage.
Project description:RATIONALE: Radiolabeled monoclonal antibodies, such as iodine I 131 monoclonal antibody 3F8, can find tumor cells and carry tumor-killing substances to them without harming normal cells. This may be an effective treatment for central nervous system cancer or leptomeningeal metastases.
PURPOSE: This phase II trial is studying the side effects and how well iodine I 131 monoclonal antibody 3F8 works in treating patients with central nervous system cancer or leptomeningeal cancer.
Project description:Accumulation of excess nutrients hampers proper liver function and is linked to non-alcoholic fatty liver disease (NAFLD) in obesity. However, the signals responsible for an impaired adaptation of hepatocytes to obesogenic dietary cues remain still largely unknown. Post-translational modification by the Small Ubiquitin-like Modifier (SUMO), allows for adynamic regulation of numerous processes including transcriptional reprograming. We demonstrate that specific SUMOylation of transcription factor Prox1 represents a nutrient-sensitive determinant of hepatic fasting metabolism. Prox1 was highly SUMOylated on lysine 556 in the liver of ad libitum and re-fed mice, while this modification was abolished upon fasting. In the context of diet-induced obesity, Prox1 SUMOylation became less sensitive to fasting cues. The hepatocyte-selective knock-in of a SUMOylation-deficient Prox1 mutant into mice fed a high-fat/high-fructose diet led to a reduction of systemic cholesterol levels, associated with the induction of liver bile acid detoxifying pathways during fasting. The generation of tools to maintain the nutrient-sensitive SUMO-switch on Prox1 may thus contribute to the development of “fasting-based” approaches for the preservation of metabolic health.