title: Constitutive overexpression of the basic helix-loop-helix Nex1/MATH-2 transcription factor promotes neuronal differentiation of PC12 cells and neurite regeneration.
abstract: Elucidation of the intricate transcriptional pathways leading to neural differentiation and the establishment of neuronal identity is critical to the understanding and design of therapeutic approaches. Among the important players, the basic helix-loop-helix (bHLH) transcription factors have been found to be pivotal regulators of neurogenesis. In this study, we investigate the role of the bHLH differentiation factor Nex1/MATH-2 in conjunction with the nerve growth factor (NGF) signaling pathway using the rat phenochromocytoma PC12 cell line. We report that the expression of Nex1 protein is induced after 5 hr of NGF treatment and reaches maximal levels at 24 hr, when very few PC12 cells have begun extending neurites and ceased cell division. Furthermore, our study demonstrates that Nex1 has the ability to trigger neuronal differentiation of PC12 cells in the absence of neurotrophic factor. We show that Nex1 plays an important role in neurite outgrowth and has the capacity to regenerate neurite outgrowth in the absence of NGF. These results are corroborated by the fact that Nex1 targets a repertoire of distinct types of genes associated with neuronal differentiation, such as GAP-43, betaIII-tubulin, and NeuroD. In addition, our findings show that Nex1 up-regulates the expression of the mitotic inhibitor p21(WAF1), thus linking neuronal differentiation to cell cycle withdrawal. Finally, our studies show that overexpression of a Nex1 mutant has the ability to block the execution of NGF-induced differentiation program, suggesting that Nex1 may be an important effector of the NGF signaling pathway.
authors.affiliation: Department of Anatomy and Cell Biology, George Washington University Medical Center, Washington, DC 20037, USA.
authors.forename: Martine
authors.initials: M
authors.lastname: Uittenbogaard
authors.forename: Anne
authors.initials: A
authors.lastname: Chiaramello
mesh_terms: D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins; D002453:Cell Cycle / Q000187:drug effects / Q000235:genetics; D002454:Cell Differentiation / Q000187:drug effects / Q000235:genetics*; D002490:Central Nervous System / Q000166:cytology / Q000196:embryology* / Q000254:growth & development; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000187:drug effects / Q000378:metabolism; D019922:GAP-43 Protein / Q000187:drug effects / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology*; D018257:Helix-Loop-Helix Motifs / Q000187:drug effects / Q000235:genetics*; D009154:Mutation / Q000502:physiology; D020932:Nerve Growth Factor / Q000172:deficiency / Q000494:pharmacology; D009416:Nerve Regeneration / Q000187:drug effects / Q000235:genetics*; D009419:Nerve Tissue Proteins / Q000187:drug effects / Q000378:metabolism; D016501:Neurites / Q000378:metabolism* / Q000648:ultrastructure; D016716:PC12 Cells; D017434:Protein Structure, Tertiary / Q000235:genetics; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D014157:Transcription Factors / Q000187:drug effects / Q000235:genetics*; D014158:Transcription, Genetic / Q000502:physiology; D014404:Tubulin / Q000187:drug effects / Q000378:metabolism
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D019922:GAP-43 Protein; D020932:Nerve Growth Factor; D009419:Nerve Tissue Proteins; D014157:Transcription Factors; D014404:Tubulin; C493958:Cdkn1a protein, rat; C490554:Neurod6 protein, rat; C093564:Neurogenic differentiation factor 1