Unknown,Transcriptomics,Genomics,Proteomics

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Transcriptional changes in sensory ganglion associated with primary afferent collateral sprouting in spared dermatome model

ABSTRACT: Primary afferent collateral sprouting (PACS) is a process whereby non-injured primary afferent neurons respond to some stimulus by extending new branches from existing axons. In the model used here (spared dermatome), the intact sensory neurons respond to the denervation of adjacent areas of skin by sprouting new axon branches into that adjacent denervated territory. Neurons of both the central and peripheral nervous systems undergo this process, which contributes to both adaptive and maladaptive plasticity. Investigations of gene expression changes associated with PACS can provide a better understanding of the molecular mechanisms controlling this process. Consequently, it can be used to develop treatment for spinal cord injury to promote functional recovery. In this study, we sought to identify gene expression changes in PACS using 20 Affymetrix Rat Genome 230 2.0 microarrays. The experiments were designed to discover global gene expression changes in non-injured DRG neurons undergoing PACS. T11 DRG neurons remained intact and undergo PACS after the cutaneous nerves of the adjacent segments (T9, T10, T12, and T13) were injured and regeneration of those injured nerves prevented by ligation. Thus, the T9, T10, T12, and T13 dermatomes were denervated, but the T11 dermatome remained intact. Axons of the T11dermatome (and thus housed in the T11 dorsal root ganglion (DRG)), extended new branches to innervate the T9, T10, T12, and T13 dermatomes. N.B.: This is NOT a spared root experiment. ALL spinal roots were non-injured. Peripheral nerves were used. A total of 20 Affymetrix Rat Genome 230 2.0 microarrays were analyzed: six naÃ¯ve controls, seven replicates at day 7 post-surgery (presumed to represent an â??initiation phaseâ??), and seven replicates at day 14 post-surgery (presumed to represent a â??maintenance phaseâ??). DRGs were NOT pooled onto microarrays. Each animal had its own microarray with T11 DRG sample which underwent 2-round amplification. After quality control analysis, one of the naÃ¯ve control microarrays was removed from further analysis.

ORGANISM(S): Rattus norvegicus

SUBMITTER: Eric Rouchka

PROVIDER: E-GEOD-72551 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:This study aimed to quantify the regulation of transcripts in the hairy skin of the back of adult rats in the condition of loss of sensory and autonomic (sympathetic) innervation (i.e., denervated). Denervated skin has reduced wound healing capacity, reduced proliferation of epidermal progenitor cells, and also expresses factors that regulate ingrowth of sensory and sympathetic axons from neighboring regions of innervated skin. It was expected that this quantification f transcript regulation would offer insight into the general and specific mechanisms that may contribute to these important biological processes. All animals were adult (200-250g) Sprague-Dawley female rats. Three conditions were examined. Groups were naive (n=6), 7-day denervated skin (n=5), and 14-day (n=5) denervated skin. Denervation preparations: Full-thickness incision along long-axis of the body 1cm to right of midline (to avoid injuring skin to be sampled). Incision was centered rostro-caudally on the T13 (thoracic 13) costo-vertebral angle so as to allow access to the T9-L2 (lumbar 2) cutaneous nerves. Skin was reflected to the left and the left T9, T10, L1, and L2 dorsal and lateral cutaneous nerves were isolated, ligated with 7-0 monofilament suture close to their exit from the body wall, and transected. Approximately 5mm of the distal portion of the nerve was resected. The T11 nerves were left unperturbed and were not isolated from the surrounding fascia. This generated two strips of skin that were devoid of sensory and autonomic innervation (those strips served by the T9 and T10 nerves, and by the L1 and L2 nerves). Between these denervated strips of skin was a strip of skin that retained the sensory and autonomic axons supplied by T11 nerves. The denervated zones were identified by mapping the cutaneous trunk muscle (CTM) reflex (see Petruska-JC et al. (2013) Journal of Comparative Neurology; Diamond-J et al., (1992) J Neuroscience), and the border marked with pen and remarked every few days. The samples were taken from the rostral (T9/10) denervated zone. Samples from naive animals (no denervation) were taken from the same region, using the dorsal cutaneous nerves as registration landmarks. Animals displayed no signs of overgrooming of the denervated skin. Because the CTM inserts onto the dermis of this region of skin, samples necessarily include both skin and underlying CTM (which is innervated from another source so was not denervated in the experiment).

Project description:Vagal afferent neurons are thought to convey primarily physiological information, whereas spinal afferents transmit noxious signals from the viscera to the central nervous system. In order to elucidate molecular identities for these different properties, we compared gene expression profiles of neurons located in nodose ganglia (NG) and dorsal root ganglia (DRG) in mice. Intraperitoneal administration of Alexa Fluor-488 conjugated Cholera toxin B allowed identification of neurons projecting to the viscera. Fluorescent neurons in DRG (from T10 to T13) and NG were isolated using laser capture microdissection. Gene expression profiles of visceral afferent neurons, obtained by microarray hybridization, were analysed using multivariate spectral map analysis, SAM algorithm (Significance Analysis of Microarray data) and fold-difference filtering. A total of 1996 genes were found to be differentially expressed in DRG versus NG, including 41 G-protein coupled receptors and 60 ion channels. Expression profiles obtained on laser-captured neurons were contrasted to those obtained on whole ganglia demonstrating striking differences and the need for microdissection when studying visceral sensory neurons because of dilution of the signal by somatic sensory neurons. Furthermore, a detailed catalogue of all adrenergic and cholinergic, GABA, glutamate, serotonin and dopamine receptors, voltage-gated potassium, sodium and calcium channels and transient receptor potential cation channels present in visceral afferents is provided. Our genome-wide expression profiling data provide novel insight into molecular signatures that underlie both functional differences and similarities between NG and DRG visceral sensory neurons. Moreover, these findings will offer novel insight into mode of action of pharmacologic agents modulating visceral sensation. Experiment Overall Design: Three separate experiments were performed. First, 5 whole dorsal root ganglia were compared to 7 whole nodose ganglia. Second, Laser captured visceral neurons derived from 5 dorsal root ganglia and 5 nodose ganglia were compared on MG-U74Av2. Third, Laser captured visceral neurons derived from 9 dorsal root ganglia and 11 nodose ganglia were compared on Mouse430_2.

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Transcriptional changes in sensory ganglion associated with primary afferent collateral sprouting in spared dermatome model

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