Elevated IKKα Accelerates the Differentiation of Human Neuronal Progenitor Cells and Induces MeCP2-Dependent BDNF Expression
The IκB kinase α (IKKα) is implicated in the differentiation of epithelial and immune cells. We examined whether IKKα also plays a role in the differentiation and maturation of embryonic human neuronal progenitor cells (NPCs). We find that expression of an extra copy of IKKα (IKKα+) blocks self-renewal and accelerates the differentiation of NPCs. This coincides with reduced expression of the Repressor Element Silencing Transcription Factor/Neuron-Restrictive Silencing Factor (REST/NRSF), which is a prominent inhibitor of neurogenesis, and subsequent induction of the pro-differentiation non-coding RNA, miR-124a. However, the effects of IKKα on REST/NRSF and miR-124a expression are likely to be indirect. IKKα+ neurons display extensive neurite outgrowth and accumulate protein markers of neuronal maturation such as SCG10/stathmin-2, postsynaptic density 95 (PSD95), syntaxin, and methyl-CpG binding protein 2 (MeCP2). Interestingly, IKKα associates with MeCP2 in the nuclei of human neurons and can phosphorylate MeCP2 in vitro. Using chromatin immunoprecipitation assays, we find that IKKα is recruited to the exon-IV brain-derived neurotrophic factor (BDNF) promoter, which is a well-characterized target of MeCP2 activity. Moreover, IKKα induces the transcription of BDNF and knockdown expression of MeCP2 interferes with this event. These studies highlight a role for IKKα in accelerating the differentiation of human NPCs and identify IKKα as a potential regulator of MeCP2 function and BDNF expression.
© 2012 Khoshnan, Patterson. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Received: March 22, 2012; Accepted: June 25, 2012; Published: July 27, 2012. Funding: This work was supported by a grant (#2433) from The International Rett Syndrome Foundation. www.rettsyndrome.org. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. We thank Dr. David Anderson's laboratory for providing the REST/NRSF antibody, Dr. Mary Kennedy's laboratory for the PSD95 antibody, Dr. Michael Greenberg's laboratory for providing anti-MeCP2 phospho-Ser421 antibody, Dr. Yvonne Trottier for the REST promoter constructs, and Dr. Gail Mandel for the miR-124 promoter. We also thank Benjamin Deneen and Christian Hochstim for providing the rat embryonic cortical tissue. Author Contributions: Conceived and designed the experiments: AK PHP. Performed the experiments: AK. Analyzed the data: AK PHP. Wrote the paper: AK PHP.
Published - journal.pone.0041794.pdf
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