Transcriptional Repression of the α7 Nicotinic Acetylcholine Receptor Subunit Gene (CHRNA7) by Activating Protein-2α (AP-2α)

The CHRNA7 gene, which encodes the alpha 7 nicotinic acetylcholine receptor (alpha 7*nAChR), has been implicated as a candidate gene in schizophrenia. Expression of the alpha 7*nAChR mRNA and protein are reduced in multiple regions of post-mortem brain from patients diagnosed with schizophrenia. Transcriptional regulation may therefore be an important mechanism for the regulation of this gene. A 230-bp proximal promoter fragment, necessary for transcription in cultured neuroblastoma cells, was used to study a putative AP-2 alpha binding site. Mutation of the site indicates that AP-2 alpha plays a negative role in regulating CHRNA7 transcription. This was confirmed through knockdown and overexpression of AP-2 alpha. Electrophoretic mobility shift assays (EMSAs) identified positive DNA-protein interaction at this same site, and supershift assays indicate that the complex includes AP-2 alpha. The interaction was confirmed in cells using chromatin immunoprecipitation (ChIP). DNA methylation was discovered as an anomalous mechanism for CHRNA7 regulation in one cell line. These studies suggest a role for AP-2 alpha regulation of CHRNA7 mRNA expression in multiple tissues during development.