Unknown,Transcriptomics,Genomics,Proteomics

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Dynamic membrane depolarization is an early regulator of ependymoglial cell response to spinal cord injury in axolotl

ABSTRACT: Salamanders, such as the Mexican axolotl, are some of the few vertebrates fortunate in their ability to regenerate diverse structures after injury. Unlike mammals they are able to regenerate a fully functional spinal cord after injury. However, the early signals required to initiate a pro-regenerative response after spinal cord injury is not well understood. To address this question we developed a spinal cord injury model in axolotls and used in vivo imaging of ion sensitive dyes and determined that spinal cord injury induces a rapid and dynamic change in the resting membrane potential of ependymoglial cells. Prolonged depolarization of ependymoglial cells after injury inhibits glial cell proliferation and subsequent axon regeneration. Using transcriptional profiling we identified c-Fos as a key voltage sensitive early response gene that is expressed specifically in the ependymoglial cells after injury. This data establishes that dynamic changes in the membrane potential after injury are essential for regulating the specific spatiotemporal expression of c-Fos that is critical for promoting faithful spinal cord regeneration in axolotl. All axolotls used in these experiments were bred in the axolotl facility at the University of Minnesota under the IACUC protocol #1201A08381. Axolotls of 2â3 cm were used for all in vivo experiments, and animals were kept in separate containers and fed daily with artemia; water was changed daily. Animals were anesthetized in 0.01% p-amino benzocaine (Sigma) before microinjection was performed. Experimental Design: Ivermectin injection Ivermectin or vehicle only (water) was pressure injected into the central canal of the spinal cord, and this was visualized by the addition of Fast Green into the solution. Directly after injection, a portion of the spinal cord was surgically removed and the animals were placed back into water in individual containers. One day post injury (1dpi) animals were anesthetized again and the area of the injury was removed. Tissue from 10 animals were pooled for each microarray replicate.

ORGANISM(S): Ambystoma mexicanum

SUBMITTER: Karen Echeverri

PROVIDER: E-GEOD-71934 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Endogenous bioelectric signaling via changes in cellular resting potential (Vmem) is a key regulator of patterning during regeneration and embryogenesis in numerous model systems. Depolarization of Vmem has been functionally implicated in de-differentiation, tumorigenesis, anatomical re-specification, and appendage regeneration. However, no unbiased analyses have been performed to understand genome-wide transcriptional responses to Vmem change in vivo. Moreover, it is unknown which genes or gene networks represent conserved targets of bioelectrical signaling across different patterning contexts and species. Here, we use microarray analysis to comparatively analyze transcriptional responses to specific Vmem depolarization. We compare the response of the transcriptome during embryogenesis (Xenopus development), regeneration (Axolotl regeneration), and stem cell differentiation (human mesenchymal stem cells in culture) to identify common networks across model species that are associated with depolarization. Both sub-network enrichment and PANTHER analyses identified a number of key genetic modules as targets of Vmem change, and also revealed important (well-conserved) commonalities in bioelectric signal transduction, despite highly diverse experimental contexts and species. Depolarization regulates specific transcriptional networks across all three germ layers (ectoderm, mesoderm and endoderm) such as cell differentiation and apoptosis, and this information will be used for developing mechanistic models of bioelectric regulation of patterning. Moreover, our analysis reveals that Vmem change regulates transcripts related to important disease pathways such as cancer and neurodegeneration, which may represent novel targets for emerging electroceutical therapies. All axolotls used in these experiments were bred in the axolotl facility at the University of Minnesota under the IACUC protocol #1201A08381. Axolotls of 2â3 cm were used for all in vivo experiments, and animals were kept in separate containers and fed daily with artemia; water was changed daily. Animals were anesthetized in 0.01% p-amino benzocaine (Sigma) before microinjection was performed. There were 9 microarrays conducted, and these were ivermectin-treated (n=3). Experimental Design: Ivermectin injection Ivermectin or vehicle only (water) was pressure injected into the central canal of the spinal cord, and this was visualized by the addition of Fast Green into the solution. Directly after injection, a portion of the spinal cord was surgically removed and the animals were placed back into water in individual containers. One day post injury (1dpi) animals were anesthetized again and the area of the injury was removed. Tissue from 10 animals were pooled for each microarray replicate. Mature - Uninjured spinal cord tissue Sc Crush- spinal cord tissue 1 day after injury Ivermectin - Ivermectin injected spinal cord tissue 1 day after injury.

Project description:Purpose: The goal of this study was to determine the gene expression changes that occur over 7 days in parralyzed muscle in response to isometric contraction elicited by electrical stimulation initiated 4 months after spinal cord injury and to compare such changes to those observed in a normal muscle subjected to overload. Methods: Electrical stimulation of the soleus and plantaris muscle was stimulated in female rats with complete transection of the spinal cord at the interspace between the 9th and 10th thoracic vertebrae. Stimulation was begun 16 weeks after spinal cord transection and produced near-isometric contraction of soleus, plantaris and tibialis anterior. Muscle was analyzed at 1, 2 and 7 days after starting exercise with electrical stimulation. To provide a baseline reference for gene expression at 16 weeks after spinal cord injury, muscle was also analysed from an additional group of spinal cord transected animals. One additional group of animals with a sham-spinal cord injury was included to provide information about gene expression in neurologically intact animals of similar age. In parallel studies, rats underwent bilateral gastrocnemius ablation to overload soleus and plantaris, or a sham ablation as a control. Muscle was analyzed at 1, 3 and 7 days after gastrocnemius ablation or sham-ablation. Gene expression was determined using Affymetrix Rat Exon microarrays. For each group of animals, microarray analysis was performed for soleus muscle for each of 3 separate animals, using one array per animal. Control sammples for the spinal cord injured groups included a group of animals with a Sham-spinal cord injury, and a group of spinal cord injured animals that did not get electrical stimulation. The comparator for determining fold-change expression values was the spinal cord injured group that did not receive electrical stimulation. For each day after gastrocnemius ablation, a control was included that received all procedures needed for this ablation except cutting the distal insertion of the gastrocnemius into the Achilles tendon to control for effects of the surgery on gene expression.

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Dynamic membrane depolarization is an early regulator of ependymoglial cell response to spinal cord injury in axolotl

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