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Global analysis of gene expression in NGF-deprived sympathetic neurons identifies molecular pathways associated with cell death.

ABSTRACT: 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.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.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.

SUBMITTER: Kristiansen M

PROVIDER: S-EPMC3256215 | biostudies-literature | 2011 Nov

REPOSITORIES: biostudies-literature

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Global analysis of gene expression in NGF-deprived sympathetic neurons identifies molecular pathways associated with cell death.

Kristiansen Mark M Menghi Francesca F Hughes Rosie R Hubank Mike M Ham Jonathan J

BMC genomics 20111108

<h4>Background</h4>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 ti ...[more]

PMID: 22067274

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Project description:The subcellular localization of specific mRNAs is an evolutionary conserved mechanism that underlies the establishment of cellular polarity and specialized cell functions. In neurons, mRNA trafficking and local protein translation in dendrites provides an important mechanism that mediates synaptic development and plasticity. The significance of mRNA targeting and protein synthesis in axons, however, is still unclear. Only a small number of transcripts have been identified in axons to date, and their contribution to axon growth and neuronal survival remains largely unknown. Here, we report the results of a novel screen that allowed the separate identification of mRNAs localized in cell bodies and in axons of developing neurons. Using compartmentalized cultures of sympathetic neurons and Sequential Analysis of Gene Expression (SAGE), the screen identified more than 200 axonal mRNAs, including ones that encode cytoskeletal proteins and proteins that function in neural development and signal transduction. Importantly, several classes of transcripts were selectively enriched in axons, indicating that an active process drives the targeting of specific mRNAs from the cell bodies to the axons. This study is the first comprehensive and unbiased analysis of mRNA localization in subcellular domains of any neuronal cell type. We used compartmentalized chambers to culture neonatal rat sympathetic neurons (Campenot, 1977). In these cultures, the cell bodies are separated from the distal axons by a 1 mm wide Teflon divider, which maintains the cell bodies and axon terminals in separate fluid compartments. Primary rat sympathetic neurons are especially suitable for compartmentalized culture because they can be grown as a highly homogeneous population without glial cells. Neurons were seeded in the central compartment with nerve growth factor (NGF), and after a few days, the NGF was lowered in this compartment and supplied only to the peripheral compartment to stimulate axon growth. The anti-mitotic agent cytosine arabinoside C (Ara-C) was added to both compartments to remove non-neuronal cells. mRNA was then isolated after 12 days in culture (DIV) from cell body or axon compartments. As the initial mRNA content in axons was not sufficient to perform the SAGE analysis, both axon and cell body mRNAs were subjected to two rounds of linear amplification to obtain antisense RNA (aRNA). The amplified aRNA was then reverse transcribed and second strand synthesis was performed to proceed with the SAGE assay using the LongSAGE kit (Invitrogen) according to the manufacturer’s protocol.

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Global analysis of gene expression in NGF-deprived sympathetic neurons identifies molecular pathways associated with cell death.

Publications

Global analysis of gene expression in NGF-deprived sympathetic neurons identifies molecular pathways associated with cell death.

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