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Neuronal outgrowth is guided by both extrinsic and intrinsic factors, involving transcriptional regulation. The acetylation of histones and transcription factors, which facilitates promoter accessibility, ultimately promotes transcription, and depends on the balance between histone deacetylases (HDACs) and histone acetyltransferases (HATs) activities. However, a critical function for specific acetylation modifying enzymes in neuronal outgrowth has yet to be investigated. To address this issue, we have used an epigenetic approach to facilitate gene expression in neurons, by using specific HDAC inhibitors. Neurons treated with a combination of HDAC and transcription inhibitors display an acetylation and transcription-dependent increase in outgrowth and a reduction in growth cone collapse on both ‘permissive’ (poly-D-lysine, PDL) and ‘non-permissive’ substrates (myelin and chondroitin sulphate proteoglycans (CSPGs)). Next, we specifically show that the expression of the histone acetyltransferases CBP/p300 and P/CAF is repressed in neurons by inhibitory substrates, whereas it is triggered by HDAC inhibition on both permissive and inhibitory conditions. Gene silencing and gain of function experiments show that CBP/p300 and P/CAF are key players in neuronal outgrowth, acetylate histone H3 at K9-14 and the transcription factor p53, thereby initiating a pro-neuronal outgrowth transcriptional program. These findings contribute to the growing understanding of transcriptional regulation in neuronal outgrowth and may lay the molecular groundwork for the promotion of axonal regeneration after injury. [ABSTRACT FROM AUTHOR]

Transcription regulates axon outgrowth and regeneration. However, to date, no transcription complexes have been shown to control axon outgrowth and regeneration by regulating axon growth genes. Here, we report that the tumor suppressor p53 and its acetyltransferases CBP/p300 form a transcriptional complex that regulates the axonal growth-associated protein 43, a well-characterized pro-axon outgrowth and regeneration protein. Acetylated p53 at K372-3-82 drives axon outgrowth, GAP-43 expression, and binds specific elements on the neuronal GAP-43 promoter in a chromatin environment through CBP/p300 signaling. Importantly, in an axon regeneration model, both CBP and p53 K372-3-82 are induced following axotomy in facial motor neurons, where p53 K372-3-82 occupancy of GAP-43 promoter is enhanced as shown by in vivo chromatin immunoprecipitation. Finally, by comparing wild-type and p53 null mice, we demonstrate that the p53/GAP-43 transcriptional module is specifically switched on during axon regeneration in vivo. These data contribute to the understanding of gene regulation in axon outgrowth and may suggest new molecular targets for axon regeneration.Cell Death and Differentiation (2009) 16, 543–554; doi:10.1038/cdd.2008.175; published online 5 December 2008 [ABSTRACT FROM AUTHOR]

The aim of the present study was to investigate whether muscarinic receptor blockade with scopolamine modifies the excitability of specific cortical networks of the human motor cortex as tested with transcranial magnetic stimulation. The effects of scopolamine on the excitability of human motor cortex were investigated in four healthy subjects using transcranial magnetic stimulation before and after an intravenous dose of scopolamine (0.006 mg/kg). We measured the threshold for motor responses, amplitude of motor responses, the duration of the cortical silent period, intracortical inhibition and facilitation, and short-latency inhibition produced by somatosensory input from the hand. In addition, we evaluated the amplitude of motor responses evoked by electrical anodal stimulation, since these responses originate from direct activation of corticospinal axons in the white matter and are not sensitive to changes in cortical excitability. Scopolamine decreased the threshold to magnetic stimuli and increased the amplitude of motor responses evoked by magnetic stimulation. In contrast, motor responses evoked by electrical stimulation were unaffected by administration of scopolamine. Scopolamine also led to a highly significant reduction in the amount of short-latency inhibition produced by somatosensory input from the hand. In contrast, short-latency intracortical inhibition and facilitation were not modified by scopolamine. The differential effect of scopolamine on motor responses evoked by magnetic and electrical stimulation of the motor cortex and the selective effect on somatosensory inhibition demonstrate that muscarinic blockade modifies the excitability of specific cortical networks in the human motor cortex. [ABSTRACT FROM AUTHOR]

We report an Italian family with autosomal recessive quadriceps-sparing inclusion-body myopathy (ARQS-IBM). The patients (two second cousins) developed a slowly progressive distal and proximal myopathy with complete sparing of the quadriceps. Muscle biopsy showed rimmed vacuoles in numerous muscle fibers, and electron microscopy documented accumulation of 15-21 nm filaments. DNA analysis established linkage to 9p1 and haplotype analysis revealed that the patients shared a recombined common haplotype. The gene locus of ARQS-IBM was initially mapped to chromosome 9p1-q1 in families of Iranian-Jewish origin and later confirmed in a few other ethnic groups. This is the first report of Italian patients with ARQS-IBM showing positive linkage to chromosome 9p1. Our data suggest that patients having distal and proximal myopathy with rimmed vacuoles and possible recessive inheritance, often classified as distal myopathies, should be thoroughly investigated according to the diagnostic criteria of h-IBM and, when positive, studied for linkage to chromosome 9p1. [ABSTRACT FROM AUTHOR]

Spinal cord injury (SCI) results in delayed biochemical changes that contribute to secondary tissue damage and dysfunction. The microglial-induced inflammatory response, long implicated in secondary tissue damage after SCI, includes release of various factors known to be toxic to neurons. However, the response of microglia and their subsequent role remains controversial and poorly understood. The present study evaluated the acute and chronic gene expression profiles in rats after traumatic SCI. Using anchor genes selected from the literature because of their relationship to microglial-induced inflammation, high density microarray expression profiles were examined after contusion. Two temporally correlated clusters were identified: one was expressed immediately after injury, peaking between 4 and 24 hours and declining to baseline or below baseline levels; the second was expressed chronically after injury, and remained elevated up to 6 months after injury. Expression profiles for genes of each group were confirmed using real-time quantitative PCR, immunoblotting, and immunohistochemistry. One of the genes chronically expressed from 24 hours to 6 months postinjury was p22phox, a component of the NADPH oxidase enzyme. To investigate the role of this chronically expressed gene after SCI and the effect of modification of its activity, the NADPH oxidase inhibitor apocynin was added to purified microglia cultures and microglial activation after LPS stimulation was investigated. Inhibition of p22phox/NADPH oxidase resulted in significant suppression of microglial proliferation, nitric oxide production, and microglial-induced neurotoxicity. This study demonstrates the potential utility of microarray technology in identifying possible targets for future therapeutics. Additionally, it identifies p22phox and NADPH as potential components of microglial-induced neurotoxicity, with implications for neuroprotective therapy. [Copyright &y& Elsevier]

Regeneration after injury occurs in axons that lie in the peripheral nervous system but fails in the central nervous system, thereby limiting functional recovery. Differences in axonal signalling in response to injury that might underpin this differential regenerative ability are poorly characterized. Combining axoplasmic proteomics from peripheral sciatic or central projecting dorsal root ganglion (DRG) axons with cell body RNA-seq, we uncover injury-dependent signalling pathways that are uniquely represented in peripheral versus central projecting sciatic DRG axons. We identify AMPK as a crucial regulator of axonal regenerative signalling that is specifically downregulated in injured peripheral, but not central, axons. We find that AMPK in DRG interacts with the 26S proteasome and its CaMKIIα-dependent regulatory subunit PSMC5 to promote AMPKα proteasomal degradation following sciatic axotomy. Conditional deletion of AMPKα1 promotes multiple regenerative signalling pathways after central axonal injury and stimulates robust axonal growth across the spinal cord injury site, suggesting inhibition of AMPK as a therapeutic strategy to enhance regeneration following spinal cord injury.