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RNA polymerase 1-driven transcription as a mediator of BDNF-induced neurite outgrowth.

ABSTRACT: Neurite outgrowth is essential for development of the nervous system. Neurotrophins including BDNF are among extracellular signals that regulate neurite outgrowth. The ERK1/2 pathway contributes to intracellular signaling networks transducing the pro-neuritic effects of BDNF. In the nucleolus, RNA polymerase-1 (Pol1)-mediated transcription regulates ribosomal biogenesis, enabling cellular protein synthesis and growth. Hence, we tested the possibility that Pol1 is an effector for pro-neuritic signals such as BDNF. We report that Pol1-mediated nucleolar transcription was increased by BDNF in an ERK1/2-dependent manner in rat forebrain neurons. Conversely, in cultured hippocampal neurons, knockdown of a Pol1 coactivator, transcription initiation factor 1A (TIF1A), attenuated BDNF- or ERK1/2-induced neurite outgrowth. Also, upon overexpression, a constitutively active mutant of TIF1A strongly promoted neurite outgrowth, including increases in total neurite length and branching. Finally, overexpression of wild-type TIF1A enhanced the pro-neuritic effects of ERK1/2 activation. These observations indicate that the Pol1-mediated nucleolar transcription regulates neurite outgrowth and serves as a major pro-neuritic effector of the BDNF-activated ERK1/2 pathway. Thus, development of the nervous system appears critically dependent on the nucleolus.

SUBMITTER: Gomes C

PROVIDER: S-EPMC3039349 | biostudies-literature | 2011 Feb

REPOSITORIES: biostudies-literature

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RNA polymerase 1-driven transcription as a mediator of BDNF-induced neurite outgrowth.

Gomes Cynthia C Smith Scott C SC Youssef Mark N MN Zheng Jing-Juan JJ Hagg Theo T Hetman Michal M

The Journal of biological chemistry 20101123 6

Neurite outgrowth is essential for development of the nervous system. Neurotrophins including BDNF are among extracellular signals that regulate neurite outgrowth. The ERK1/2 pathway contributes to intracellular signaling networks transducing the pro-neuritic effects of BDNF. In the nucleolus, RNA polymerase-1 (Pol1)-mediated transcription regulates ribosomal biogenesis, enabling cellular protein synthesis and growth. Hence, we tested the possibility that Pol1 is an effector for pro-neuritic sig ...[more]

PMID: 21098478

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Project description:We have undertaken a genome-wide study of transcriptional activity in embryonic superior cervical ganglia (SCG) and dorsal root ganglia (DRG) during a time course of neurite outgrowth in vitro. Gene expression observed in these models likely includes both developmental gene expression patterns and regenerative responses to axotomy, which occurs as the result of tissue dissection. Comparison across both models revealed many genes with similar gene expression patterns during neurite outgrowth. These patterns were minimally affected by exposure to the potent inhibitory cue Semaphorin3A, indicating that this extrinsic cue does not exert major effects at the level of nuclear transcription. We also compared our data to several published studies of DRG and SCG gene expression in animal models of regeneration, and found the expression of a large number of genes in common between neurite outgrowth in vitro and regeneration in vivo. Experiment Overall Design: We wished to determine the transcriptional profiles of neurons undergoing neurite outgrowth in vitro. We were particularly interested in finding genes whose expression is generally associated with the process of neurite outgrowth, rather than with cell type-specific effects. Thus, in order to avoid focusing on transcripts unique to one tissue type versus another, we used a comparative strategy to look for effects that were common to two tissue types and therefore more likely to be involved in the general process of neurite outgrowth. While these explants contain multiple cell types, we felt this was preferable to the more disruptive conditions required to dissociate neurons or obtain a pure neuron population. To this end, we monitored gene expression in cultured explants from SCG and DRG using DNA microarrays. We initiated our studies by culturing embryonic day 13 (E13) mouse SCG in vitro and harvesting tissue for RNA isolation at time points from 2 to 65 hours. Time points were selected to detect both fast, short-term responses (2, 5 and 12 hours), as well as sustained, long-term changes (24, 40, and 65 hours). Samples were hybridized to Affymetrix MG-U74v2 A and B microarrays, with RNA from acutely dissected explants serving as a baseline reference. We followed these experiments with a parallel analysis of a more heterogeneous tissue type, the DRG, which is more frequently used than SCG for in vivo studies of neurite regeneration. Cervical and upper thoracic DRG from E12 embryos were cultured with NGF (the same trophic support as in SCG cultures), harvested at time points from 2 to 40 hours, and hybridized to Affymetrix MOE 430A microarrays.

Dataset Information

RNA polymerase 1-driven transcription as a mediator of BDNF-induced neurite outgrowth.

Publications

RNA polymerase 1-driven transcription as a mediator of BDNF-induced neurite outgrowth.

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