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For many decades, the inability of lesioned central neurons to regrow was accepted almost as a "law of nature", and on the clinical level, spinal cord and brain lesions were seen as being irreversible. Today we are starting to understand the mechanisms of neuronal regeneration in the central nervous system and its presence in the periphery. There is now a rapid expansion in this field of neuroscience. Developmental neurobiology has produced tools and concepts that start to show their impact on regeneration research. This is particularly true for the availability of antibodies and factors and for the rapidly growing cellular and molecular understanding of crucial aspects of neurite growth, guidance, target finding, and synapse stabilization. New cell biological concepts on the mechanisms of neuron survival and death and on the interaction of inflammatory cells with the central nervous system also find their way into the field of spinal cord and brain lesions and have, indeed, led already to new therapeutic approaches. This review briefly summarizes the current knowledge on the mechanisms involved in degeneration and tissue loss and in axonal regeneration subsequent to spinal cord lesions, particularly in mammals and humans.

N-myristoylation is a common form of co-translational protein fatty acylation resulting from the attachment of myristate to a required N-terminal glycine residue.1,2 We show that aberrantly acquired N-myristoylation of SHOC2, a leucine-rich repeat-containing protein that positively modulates RAS-MAPK signal flow,3–6 underlies a clinically distinctive condition of the neuro-cardio-facial-cutaneous disorders family. Twenty-five subjects with a relatively consistent phenotype previously termed Noonan-like syndrome with loose anagen hair [OMIM 607721]7 shared the 4A>G missense change (Ser2Gly) in SHOC2 that introduces an N-myristoylation site, resulting in aberrant targeting of SHOC2 to the plasma membrane and impaired translocation to the nucleus upon growth factor stimulation. Expression of SHOC2S2G in vitro enhanced MAPK activation in a cell type-specific fashion. Induction of SHOC2S2G in Caenorhabditis elegans engendered protruding vulva, a neomorphic phenotype previously associated with aberrant signaling. These results document the first example of an acquired N-terminal lipid modification of a protein causing human disease.

CREB-binding protein and p300 function as transcriptional coactivators in the regulation of gene expression through various signal-transduction pathways. Both are potent histone acetyl transferases. A certain level of CREB-binding protein is essential for normal development, since inactivation of one allele causes Rubinstein-Taybi syndrome (RSTS). There is a direct link between loss of acetyl transferase activity and RSTS, which indicates that the disorder is caused by aberrant chromatin regulation. We screened the entire CREB-binding protein gene (CBP) for mutations in patients with RSTS by using methods that find point mutations and larger rearrangements. In 92 patients, we were able to identify a total of 36 mutations in CBP. By using multiple ligation-dependent probe amplification, we found not only several deletions but also the first reported intragenic duplication in a patient with RSTS. We extended the search for mutations to the EP300 gene and showed that mutations in EP300 also cause this disorder. These are the first mutations identified in EP300 for a congenital disorder.

Bohring-Opitz syndrome is characterized by severe intellectual disability, distinctive facial features and multiple congenital malformations. We sequenced the exomes of three individuals with Bohring-Opitz syndrome and in each identified heterozygous de novo nonsense mutations in ASXL1, which is required for maintenance of both activation and silencing of Hox genes. In total, 7 out of 13 subjects with a Bohring-Opitz phenotype had de novo ASXL1 mutations, suggesting that the syndrome is genetically heterogeneous.

Injury to the spinal cord induces a complex cascade of cellular reactions at the local lesion area: secondary cell death and inflammatory reactions as well as scar and cavity formation take place. In order to investigate the molecular features underlying this local wounding response and to determine their pathophysiological implications, we studied the expression pattern of pro-inflammatory and chemoattractant cytokines in an experimental spinal cord injury model in mouse. We show by in situ hybridization that transcripts for the pro-inflammatory cytokines TNF alpha and IL-1 as well as the chemokines MIP-1alpha and MIP-1beta are upregulated within the first hour following injury. In this early phase, the expression of the pro-inflammatory cytokines is restricted to cells in the surroundings of the lesion area probably resident CNS cells. While TNF alpha is expressed in a very narrow time window, IL-1 can be detected in a second phase in a subset of polymorphonuclear granulocytes which immigrate into the spinal cord around 6 h. Message for the chemokines MIP-1alpha and beta is expressed in a generalized way in the grey matter of the entire spinal cord around 24 h and gets again restricted to the cellular infiltrate at the lesion site at 4 days following injury. Interestingly, our data suggest that resident CNS cells, most probably microglial cells, and not peripheral inflammatory cells, are the main source for cytokine and chemokine mRNAs. The defined cytokine pattern observed indicates that the inflammatory events upon lesioning the CNS are tightly controlled. The very early expression of pro-inflammatory cytokine and chemokine messages may represent an important element of the recruitment of inflammatory cells. Additional pathophysiological consequences of the specific cytokine pattern observed remain to be determined.

ObjectiveTo identify novel epilepsy genes using a panel approach and describe the functional consequences of mutations.MethodsUsing a panel approach, we screened 357 patients comprising a vast spectrum of epileptic disorders for defects in genes known to contribute to epilepsy and/or intellectual disability (ID). After detection of mutations in a novel epilepsy gene, we investigated functional effects in Xenopus laevis oocytes and screened a follow-up cohort.ResultsWe revealed de novo mutations in GRIN2B encoding the NR2B subunit of the N-methyl-D-aspartate (NMDA) receptor in 2 individuals with West syndrome and severe developmental delay as well as 1 individual with ID and focal epilepsy. The patient with ID and focal epilepsy had a missense mutation in the extracellular glutamate-binding domain (p.Arg540His), whereas both West syndrome patients carried missense mutations within the NR2B ion channel-forming re-entrant loop (p.Asn615Ile, p.Val618Gly). Subsequent screening of 47 patients with unexplained infantile spasms did not reveal additional de novo mutations, but detected a carrier of a novel inherited GRIN2B splice site variant in close proximity (c.2011-5_2011-4delTC). Mutations p.Asn615Ile and p.Val618Gly cause a significantly reduced Mg2+ block and higher Ca2+ permeability, leading to a dramatically increased Ca2+ influx, whereas p.Arg540His caused less severe disturbance of channel function, corresponding to the milder patient phenotype.InterpretationWe identified GRIN2B gain-of-function mutations as a cause of West syndrome with severe developmental delay as well as of ID with childhood onset focal epilepsy. Severely disturbed channel function corresponded to severe clinical phenotypes, underlining the important role of facilitated NMDA receptor signaling in epileptogenesis.

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