The mRNA decay factor CAR-1 regulates axon regeneration via mitochondrial calcium dynamics
Ontology highlight
ABSTRACT: mRNA decay factors regulate mRNA turnover by recruiting non-translating mRNAs and targeting them for degradation, yet it remains poorly understood how mRNA decay factors function in vivo to regulate specific cellular processes. Here we show that mRNA decay factors form cytoplasmic puncta in C. elegans neurons and have opposing roles in axon maintenance and regrowth. While the decapping enzymes DCAP-1/DCP1 and DCAP-2/DCP2 regulate developmental axon guidance and promote axon regrowth upon injury, the translational repressors CAR-1/LSM14 and CGH-1/DDX6 regulate axon maintenance and inhibit axon regrowth in adult animals. We identified mRNA targets of CAR-1 in neurons and found that the mitochondrial calcium uptake regulator micu-1 is repressed by CAR-1. We show that axon injury triggers a transient mitochondrial calcium influx via the MCU-1 uniporter that is more sustained in car-1 loss of function mutants. The enhanced axon regrowth and defective axon maintenance of car-1 mutants are dependent on MICU-1 function. Our results uncover specific roles for mRNA decay regulators in neurons and reveal a novel pathway that controls axon regrowth through mitochondrial calcium uptake.
Project description:Animal development is dictated by the selective and timely decay of mRNAs in developmental transitions, but the impact of mRNA decapping scaffold proteins in development is unknown. This study unveils the roles and interactions of the DCAP-2 decapping scaffolds EDC-3 and EDC-4 in the embryonic development of C. elegans. EDC-3 facilitates the timely removal of specific embryonic mRNAs, including cgh-1, car-1, and ifet-1 by reducing their expression, and preventing excessive accumulation of DCAP-2 condensates in somatic cells. We further uncover a novel role for EDC-3 in defining the boundaries between P-bodies, germ granules, and stress granules. Lastly, we show that EDC-4 counteracts EDC-3 and engenders the assembly of DCAP-2 with the GID (CTLH) complex, a ubiquitin ligase involved in maternal-to-zygotic transition (MZT). Our findings support a model wherein multiple RNA decay mechanisms temporally partake in the clearance of maternal and zygotic mRNAs throughout embryonic development.
Project description:Animal development is dictated by the selective and timely decay of mRNAs in developmental transitions. The implication of mRNA decapping scaffold proteins in these processes was unknown. This study delineates the roles and interactions of the DCAP-2 decapping scaffolds EDC-3 and EDC-4 in the embryonic development of C. elegans. EDC-3 facilitates the timely removal of specific embryonic mRNAs, including ifet-1, car-1, and cgh-1, reducing their expression, and preventing excessive accumulation of DCAP-2 condensates in somatic cells. We further uncover a novel role for EDC-3 in defining the biochemical boundaries between P-bodies, P-granules, and stress granules. Lastly, we show that EDC-4 counteracts EDC-3 and mediates the assembly of DCAP-2 with the GID (CTLH) complex, a ubiquitin ligase involved in maternal-to-zygotic transition (MZT). Our findings refine a model wherein multiple RNA decay mechanisms temporally partake in the clearance of maternal and zygotic mRNAs throughout embryonic development.
Project description:The Puf family of RNA-binding proteins regulate gene expression by controlling protein synthesis or stimulating RNA decay. Puf3p is one of six related proteins in Saccharomyces cerevisiae characterised as targeting and regulating decay of nuclear-encoded mRNAs specifying mitochondrial proteins. Much prior work has examined how Puf3p regulates COX17 mRNA. We undertook a genome-wide approach to quantitatively assess the impact of loss of PUF3 on gene expression. Comparing transcript levels in wild-type and puf3∆ cells revealed that that only a small fraction of mRNA levels alter, suggesting Puf3p determines mRNA stability for only some target mRNAs.
Project description:Localized mRNA translation regulates synapse function and axon maintenance, but how compartment-specific mRNA repertoires are regulated is largely unknown. We developed an axonal transcriptome capture method that allows deep sequencing of metabolically-labeled mRNAs from retinal ganglion cell axon terminals in mouse. Comparing axonal-to-somal transcriptomes and axonal translatome-to-transcriptome enables genome-wide visualization of mRNA transport and translation and unveils potential regulators tuned to each process. FMRP and TDP-43 stand out as key regulators of transport, and experiments in Fmr1 knock-out mice validate FMRP’s role in the axonal transportation of synapse-related mRNAs. Pulse-and-chase experiments enable genome-wide assessment of mRNA stability in axons and reveal a strong coupling between mRNA translation and decay. Measuring the absolute mRNA abundance per axon terminal shows that the axonal transcriptome is stably maintained in adulthood by persistent transport. Our datasets provide a rich resource for unique insights into RNA-based mechanisms in maintaining presynaptic structure and function in vivo.
Project description:The Puf family of RNA-binding proteins regulate gene expression by controlling protein synthesis or stimulating RNA decay. Puf3p is one of six related proteins in Saccharomyces cerevisiae characterised as targeting and regulating decay of nuclear-encoded mRNAs specifying mitochondrial proteins. Much prior work has examined how Puf3p regulates COX17 mRNA. We undertook genome-wide approaches to define an expanded set of Puf3p target mRNAs. In agreement with prior studies, our sequencing of affinity-purified Puf3p-TAP associated mRNAs (RIP-seq) identified mRNAs encoding mitochondrially-targeted proteins. We also found an additional 720 mRNA targets that predominantly encode proteins that enter the nucleus.
Project description:The Puf family of RNA-binding proteins regulate the expression of genes by controlling protein synthesis or stimulating RNA decay. Puf3p is one of six Puf-family members in Saccharomyces cerevisiae. Puf3p has been characterised previously as regulating mRNA decay of nuclear mRNAs that encode for mitochondrial proteins. We undertook a series of genome wide approaches to identify an expanded set of Puf3p target mRNAs and to quantitatively assess the impact of loss of PUF3 on the expression control in actively growing wild type and puf3Δ strains. Here we report our quantifications of relative protein levels. The data suggest that loss of Puf3p only impacts on a small proportion of the proteins encoded by its mRNA targets.
Project description:Axon regeneration of dorsal root ganglia (DRG) neurons after peripheral axotomy involves epigenetic reconfigurations that rewire gene regulatory circuits to establish regenerative gene program. However, the mechanisms and transcriptional regulators remain poorly understood. Here, we conducted an unbiased survey of DNA differentially hydroxymethylated regions (DhMRs) in DRG after peripheral lesion, which identified enriched binding motif for Bmal1, a transcription factor and a central regulator of the circadian clock. Through applying conditional deletion of Bmal1, in vitro and in vivo models of axon regrowth, and transcriptomic profiling, we showed that Bmal1 inhibits axon regeneration in part through Tet3-dependent manner. Mechanistically, Bmal1 functions as a gatekeeper of neuroepigenetic injury responses by limiting Tet3 expression and restricting 5hmC modifications. Notably, Bmal1-regulated genes after axotomy not only concern axon guidance and axon regrowth, but also stress responses, energy homeostasis, and neuroinflammation. Furthermore, we uncovered diurnal oscillation of Tet3 and 5hmC in DRG neurons, and this epigenetic rhythm corresponded to time-of-day effect on axon growth potential. Collectively, our studies showed that Bmal1 deletion mimics the conditioning lesion in lifting epigenetic barriers to enhance axon regeneration.
Project description:Removal of the 5’ cap of mRNAs (decapping) is mainly catalyzed by a conserved holoenzyme, composed of the catalytic subunit DCP2 and its essential cofactor DCP1. Studies in C. elegans have shown that ageing is characterized by the accumulation of decapping factors in P-Bodies, and loss of DCAP-1/DCP1 or DCAP-2/DCP2 significantly shortens lifespan. However, the relationship between mRNA decapping and ageing remains elusive. Here we present a comparative microarray study that aims to uncover this link by identifying differentially expressed genes between wild type mid-aged worms (9 days old) and age-matched animals with reduced function of DCAP-1/DCP1.
Project description:Salamanders have the remarkable ability to functionally regenerate after spinal cord transection. In response to injury, GFAP+ glial cells in the axolotl spinal cord proliferate and migrate to replace the missing neural tube and create a permissive environment for axon regeneration. Molecular pathways that regulate the pro-regenerative axolotl glial cell response are poorly understood. Here we show axolotl glial cells up-regulate AP-1cFos/JunB after injury, which promotes a pro-regenerative glial cell response. Axolotl glial cells directly repress c-Jun expression via up-regulation of miR-200a. Inhibition of miR-200a during regeneration causes defects in axonal regrowth and transcriptomic analysis revealed that miR-200a inhibition leads to differential regulation of genes involved with reactive gliosis, the glial scar, ECM remodeling and axon guidance. This work identifies a novel role for miR-200a in inhibiting reactive gliosis in glial cell in axolotl during spinal cord regeneration