title: Neuropilin-1 is a direct target of the transcription factor E2F1 during cerebral ischemia-induced neuronal death in vivo.
abstract: The nuclear transcription factor E2F1 plays an important role in modulating neuronal death in response to excitotoxicity and cerebral ischemia. Here, by comparing gene expression in brain cortices from E2F1(+/+) and E2F1(-/-) mice using a custom high-density DNA microarray, we identified a group of putative E2F1 target genes that might be responsible for ischemia-induced E2F1-dependent neuronal death. Neuropilin 1 (NRP-1), a receptor for semaphorin 3A-mediated axon growth cone collapse and retraction, was confirmed to be a direct target of E2F1 based on (i) the fact that the NRP-1 promoter sequence contains an E2F1 binding site, (ii) reactivation of NRP-1 expression in E2F1(-/-) neurons when the E2F1 gene was replaced, (iii) activation of the NRP-1 promoter by E2F1 in a luciferase reporter assay, (iv) electrophoretic mobility gel shift analysis confirmation of the presence of an E2F binding sequence in the NRP-1 promoter, and (v) the fact that a chromatin immunoprecipitation assay showed that E2F1 binds directly to the endogenous NRP-1 promoter. Interestingly, the temporal induction in cerebral ischemia-induced E2F1 binding to the NRP-1 promoter correlated with the temporal-induction profile of NRP-1 mRNA, confirming that E2F1 positively regulates NRP-1 during cerebral ischemia. Functional analysis also showed that NRP-1 receptor expression was extremely low in E2F1(-/-) neurons, which led to the diminished response to semaphorin 3A-induced axonal shortening and neuronal death. An NRP-1 selective peptide inhibitor provided neuroprotection against oxygen-glucose deprivation. Taken together, these findings support a model in which E2F1 targets NRP-1 to modulate axonal damage and neuronal death in response to cerebral ischemia.
authors.affiliation: NRC Institute for Biological Sciences, National Research Council Canada, 1200 Montreal Road, Bldg. M-54, Ottawa, ON, Canada.
authors.forename: Susan X
authors.initials: SX
authors.lastname: Jiang
authors.forename: Melissa
authors.initials: M
authors.lastname: Sheldrick
authors.forename: Angele
authors.initials: A
authors.lastname: Desbois
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Slinn
authors.forename: Sheng T
authors.initials: ST
authors.lastname: Hou
mesh_terms: D000256:Adenoviridae / Q000235:genetics; D000818:Animals; D001926:Brain Death / Q000473:pathology*; D002545:Brain Ischemia / Q000209:etiology / Q000378:metabolism* / Q000473:pathology*; D002478:Cells, Cultured; D002531:Cerebellum / Q000166:cytology; D047369:Chromatin Immunoprecipitation; D050687:E2F1 Transcription Factor / Q000235:genetics* / Q000378:metabolism; D024202:Electrophoretic Mobility Shift Assay; D017930:Genes, Reporter; D008156:Luciferases / Q000032:analysis / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008817:Mice, Mutant Strains; D008954:Models, Biological; D009457:Neuroglia / Q000166:cytology; D009474:Neurons / Q000378:metabolism* / Q000473:pathology; D039942:Neuropilin-1 / Q000378:metabolism*; D020411:Oligonucleotide Array Sequence Analysis; D011401:Promoter Regions, Genetic; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D050687:E2F1 Transcription Factor; D039942:Neuropilin-1; D008156:Luciferases