Project description:Purpose: Spinal cord injury (SCI) is a devastating neurological disease without effective treatment. To generate a comprehensive view of the mechanisms involved in SCI pathology, we applied RNA-sequencing (RNA-seq) technology to characterize the temporal changes in global gene expression after contusive SCI in mice. Method Part1: A total of 27 female C57BI/6J mice (10-16 weeks of age; 20-25g; The Jackson Laboratory, Bar Harbor, ME) were used with 9 mice in each of following groups: shame control, 2 and 7 days after SCI. The surgical procedure for SCI were described previously [PMID:23289019]. Briefly, after anesthetization with a mixed solution of ketamine (80 mg/kg, ip) and xylazine (10 mg/kg, ip), mice received a dorsal laminectomy at the 9th thoracic vertebral (T9) level to expose the spinal cord and then a moderate T9 contusive injury using an Infinite Horizons impactor (PrecisionSystems and Instrumentation) at 60 kdyn with the spinestabilized using steel stabilizers inserted under the transverse processes one vertebra above and below the injury [PMID:19196178] . The shame control mice received only a dorsal laminectomy without contusive injury. Afterwards, the wound was sutured in layers, bacitracin ointment(Qualitest Pharmaceuticals,Huntsville, AL) was applied tothe wound area, 0.1mL of a 20 mg/ml stock of gentamicin(ButlerSchein, Dublin, OH) was injected subcutaneously, and the animals recovered on a water-circulating heating pad. Then mice received analgesic agent, buprenorphin(0.05 mg/kg, SQ; Reckitt Benckise, Hull, England)twice a day for two days. Bladders were manually expressed until automatic voiding returned spontaneously, which generally was within 7 days. At 2 or 7 days after SCI, the mice were anesthetized again with ketamine and xylazine and perfused briefly with normal physical saline. The injured spinal cords were then dissected and three 0.5 mm pieces of spinal cord were cut in the injured epicenter. All spinal cords were immediately frozen in liquid nitrogen and processed for RNA isolation. The spinal cords from three mice were combined into one biological replicate for RNA extraction. Three biological replicates were used. Method Part2: RNA-Seq was performed on the polyadenylated fraction of RNA isolated from tissue samples of acute (2D) and subacute phase (7D) and normal tissues (control, denoted as CTR hereafter). Three biological replicates were used for each phase.150-300 ng total RNAs were used for each sequencing library. RNA samples were polyA selected and paired-end sequencing libraries were constructed using TruSeq RNA Sample Prep Kit as described in the TruSeq RNA Sample Preparation V2 Guide (Illumina).The samples were then sequenced using the Illumina HiSeq sequencer. More than 30 million 100bp paired-end reads were generated from each biological replicate. Method Part3: Read mapping and Transcriptome construction were done by using optimized pipeline which integrate Tophat followed by Cufflinks. Result: We sequenced tissue samples from acute and subacute phases (2 days and 7 days after injury) and systematically characterized the transcriptomes with the goal of identifying pathways and genes critical in SCI pathology. The top enriched functional categories include ‘inflammation response’, ‘neurological disease’, ‘cell death and survival’ and ‘nervous system development’. The top enriched pathways include LXR/RXR Activation and Atherosclerosis Signaling etc. Furthermore, we developed a systems-based analysis framework in order to identify key determinants in the global gene networks of the acute and sub-acute phases. Some candidate genes that we identified have been shown to play important roles in SCI, which demonstrates the validity of our approach. There are also many genes whose functions in SCI have not been well studied and can be further investigated by future experiments. We have also incorporated pharmacogenomic information into our analyses. Among the genes identified, the ones with existing drug information can be readily tested in SCI animal models. Conclusion: in this study we have described an example of how global gene profiling can be translated to screening genes of interest and generating new hypotheses. Additionally, the RNA-seq enables splicing isoform identification and the estimation of expression levels, thus providing useful information for increasing the specificity of drug design and reducing potential side effect. In summary, these results provide a valuable reference data resource for a better understanding of the SCI process in the acute and sub-acute phases. mRNA profiles of Acute/subacute phase Spinal Cord Injury sample from mice were generated by RNA-sequencing using Illumina HiSeq.

Project description:Depending on the severity of a CNS injury, in humans as well as in experimental animal models certain degrees of functional recovery are observed. Rodent studies have provided much evidence for underlying anatomical changes involving neurite outgrowth of both spared and axotomized fiber tracts, also referred to as sprouting. Following a thoracic spinal cord injury (SCI) in adult rats, axotomized fibers of the hindlimb corticospinal tract (CST) were found to sprout into the cervical spinal cord at different rostrocaudal levels. Anterograde tracings showed that these new collaterals of motor cortical hindlimb fibers project into the intermediate laminae of the cervical grey matter, particularly pronounced at the level of cervical segment three (C3). The molecular cues which induce the growth and guide these sprouts of hindlimb CST fibers are unknown. We hypothesize that sectreted factors and guidance and adhesion molecules are specifically expressed in the intermediate laminae of the cervical spinal cord to direct and target the ingrowth of the sprouting hindlimb CST fibers. To test our hypothesis the transcription profile of the target region of sprouts was investigated with RNA sequencing of total RNA extracted from the intermediate laminae (IV-VII) of the spinal gray matter at cervical level C3. Four major comparisons were performed, which were then again compared to each other. The first comparison was between samples of animals with an SCI sacrificed at four different time points after injury (1, 3, 6, 12 weeks after injury). The second and third comparison was between samples of rats with a SCI compared to their sham controls sacrificed at the same time point after surgery (1 week or 12 weeks respectively). The fourth comparison was between samples from animals of the two control groups, rats with a sham surgery which were either sacrificed at one or at twelve weeks after injury. We found that most changes in gene expression ocurred at one week after SCI and least changes occured at twelve weeks after SCI, suggesting that the largest effects on a global level of gene expression occur during early time points after injury. Interestingly, also we also found changes in gene expression when comparing the samples from the two control groups, which suggests that sham surgery consisting of a laminectomy is sufficient to induce transcriptional changes in the spinal cord. This is the first study to provide insight into transcriptional changes in the target region of sprouts investigating the role of the cervical spinal cord (target region) for sprouting of hindlimb CST fibers.

Project description:Purpose: Spinal cord injury (SCI) is a devastating neurological disease without effective treatment. To generate a comprehensive view of the mechanisms involved in SCI pathology, we applied RNA-sequencing (RNA-seq) technology to characterize the temporal changes in global gene expression after contusive SCI in mice. Method Part1: A total of 27 female C57BI/6J mice (10-16 weeks of age; 20-25g; The Jackson Laboratory, Bar Harbor, ME) were used with 9 mice in each of following groups: shame control, 2 and 7 days after SCI. The surgical procedure for SCI were described previously [PMID:23289019]. Briefly, after anesthetization with a mixed solution of ketamine (80 mg/kg, ip) and xylazine (10 mg/kg, ip), mice received a dorsal laminectomy at the 9th thoracic vertebral (T9) level to expose the spinal cord and then a moderate T9 contusive injury using an Infinite Horizons impactor (PrecisionSystems and Instrumentation) at 60 kdyn with the spinestabilized using steel stabilizers inserted under the transverse processes one vertebra above and below the injury [PMID:19196178] . The shame control mice received only a dorsal laminectomy without contusive injury. Afterwards, the wound was sutured in layers, bacitracin ointment(Qualitest Pharmaceuticals,Huntsville, AL) was applied tothe wound area, 0.1mL of a 20 mg/ml stock of gentamicin(ButlerSchein, Dublin, OH) was injected subcutaneously, and the animals recovered on a water-circulating heating pad. Then mice received analgesic agent, buprenorphin(0.05 mg/kg, SQ; Reckitt Benckise, Hull, England)twice a day for two days. Bladders were manually expressed until automatic voiding returned spontaneously, which generally was within 7 days. At 2 or 7 days after SCI, the mice were anesthetized again with ketamine and xylazine and perfused briefly with normal physical saline. The injured spinal cords were then dissected and three 0.5 mm pieces of spinal cord were cut in the injured epicenter. All spinal cords were immediately frozen in liquid nitrogen and processed for RNA isolation. The spinal cords from three mice were combined into one biological replicate for RNA extraction. Three biological replicates were used. Method Part2: RNA-Seq was performed on the polyadenylated fraction of RNA isolated from tissue samples of acute (2D) and subacute phase (7D) and normal tissues (control, denoted as CTR hereafter). Three biological replicates were used for each phase.150-300 ng total RNAs were used for each sequencing library. RNA samples were polyA selected and paired-end sequencing libraries were constructed using TruSeq RNA Sample Prep Kit as described in the TruSeq RNA Sample Preparation V2 Guide (Illumina).The samples were then sequenced using the Illumina HiSeq sequencer. More than 30 million 100bp paired-end reads were generated from each biological replicate. Method Part3: Read mapping and Transcriptome construction were done by using optimized pipeline which integrate Tophat followed by Cufflinks. Result: We sequenced tissue samples from acute and subacute phases (2 days and 7 days after injury) and systematically characterized the transcriptomes with the goal of identifying pathways and genes critical in SCI pathology. The top enriched functional categories include ‘inflammation response’, ‘neurological disease’, ‘cell death and survival’ and ‘nervous system development’. The top enriched pathways include LXR/RXR Activation and Atherosclerosis Signaling etc. Furthermore, we developed a systems-based analysis framework in order to identify key determinants in the global gene networks of the acute and sub-acute phases. Some candidate genes that we identified have been shown to play important roles in SCI, which demonstrates the validity of our approach. There are also many genes whose functions in SCI have not been well studied and can be further investigated by future experiments. We have also incorporated pharmacogenomic information into our analyses. Among the genes identified, the ones with existing drug information can be readily tested in SCI animal models. Conclusion: in this study we have described an example of how global gene profiling can be translated to screening genes of interest and generating new hypotheses. Additionally, the RNA-seq enables splicing isoform identification and the estimation of expression levels, thus providing useful information for increasing the specificity of drug design and reducing potential side effect. In summary, these results provide a valuable reference data resource for a better understanding of the SCI process in the acute and sub-acute phases.

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Identification of regulated genes associated with ketogenic diet treatment following SCI

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