title: Global analysis of gene expression in NGF-deprived sympathetic neurons identifies molecular pathways associated with cell death.
abstract: BACKGROUND
  Developing sympathetic neurons depend on nerve growth factor (NGF) for survival and die by apoptosis after NGF withdrawal. This process requires de novo gene expression but only a small number of genes induced by NGF deprivation have been identified so far, either by a candidate gene approach or in mRNA differential display experiments. This is partly because it is difficult to obtain large numbers of sympathetic neurons for in vitro studies. Here, we describe for the first time, how advances in gene microarray technology have allowed us to investigate the expression of all known genes in sympathetic neurons cultured in the presence and absence of NGF.
  
  
  RESULTS
  We have used Affymetrix Exon arrays to study the pattern of expression of all known genes in NGF-deprived sympathetic neurons. We identified 415 up- and 813 down-regulated genes, including most of the genes previously known to be regulated in this system. NGF withdrawal activates the mixed lineage kinase (MLK)-c-Jun N-terminal kinase (JNK)-c-Jun pathway which is required for NGF deprivation-induced death. By including a mixed lineage kinase (MLK) inhibitor, CEP-11004, in our experimental design we identified which of the genes induced after NGF withdrawal are potential targets of the MLK-JNK-c-Jun pathway. A detailed Gene Ontology and functional enrichment analysis also identified genetic pathways that are highly enriched and overrepresented amongst the genes expressed after NGF withdrawal. Five genes not previously studied in sympathetic neurons - trib3, ddit3, txnip, ndrg1 and mxi1 - were validated by real time-PCR. The proteins encoded by these genes also increased in level after NGF withdrawal and this increase was prevented by CEP-11004, suggesting that these genes are potential targets of the MLK-JNK-c-Jun pathway.
  
  
  CONCLUSIONS
  The sympathetic neuron model is one of the best studied models of neuronal apoptosis. Overall, our microarray data gives a comprehensive overview of, and provides new information about, signalling pathways and transcription factors that are regulated by NGF withdrawal.
authors: Molecular Haematology and Cancer Biology Unit, Institute of Child Health, University College London, 30 Guilford Street, London WC1N 1EH, UK.
authors: Mark
authors: M
authors: Kristiansen
authors: Francesca
authors: F
authors: Menghi
authors: Rosie
authors: R
authors: Hughes
authors: Mike
authors: M
authors: Hubank
authors: Jonathan
authors: J
authors: Ham
mesh_terms: D000818:Animals; D001665:Binding Sites; D016923:Cell Death / Q000235:genetics*; D015536:Down-Regulation; D005091:Exons; D020869:Gene Expression Profiling; D020932:Nerve Growth Factor / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism; D051381:Rats; D060888:Real-Time Polymerase Chain Reaction; D013564:Sympathetic Nervous System / Q000166:cytology / Q000378:metabolism*; D015854:Up-Regulation
chemical_list: D016755:Proto-Oncogene Proteins c-jun; D020932:Nerve Growth Factor