Transcriptional Interaction of an Estrogen Receptor Splice Variant and ErbB4 Suggests Convergence in Gene Susceptibility Pathways in Schizophrenia

Mounting evidence from clinical and basic research suggests that estrogen signaling may be altered in the brains of people with schizophrenia. Previously, we found that DNA sequence variation in the estrogen receptor (ER) alpha gene, lower ER alpha mRNA levels, and/or blunted ER alpha signaling is associated with schizophrenia. In this study, we asked whether the naturally occurring truncated ER alpha isoform, Delta 7, which acts as a dominant negative, can attenuate gene expression induced by the wildtype (WT) receptor in an estrogen-dependent manner in neuronal (SHSY5Y) and non-neuronal (CHOK1 and HeLa) cells. In addition, we determined the extent to which ER alpha interacts with NRG1-ErbB4, a leading schizophrenia susceptibility pathway. Reductions in the transcriptionally active form of ErbB4 comprising the intracytoplasmic domain (ErbB4-ICD) have been found in schizophrenia, and we hypothesized that ER alpha and ErbB4 may converge to control gene expression. In the present study, we show that truncated Delta 7-ER alpha attenuates WT-ER alpha-driven gene expression across a wide range of estrogen concentrations in cells that express functional ER alpha at base line or upon co-transfection of full-length ER alpha. Furthermore, we find that ErbB4-ICD can potentiate the transcriptional activity of WT-ER alpha at EREs in two cell lines and that this potentiation effect is abolished by the presence of Delta 7-ER alpha. Immunofluorescence microscopy revealed nuclear co-localization of WT-ER alpha, Delta 7-ER alpha, and ErbB4-ICD, whereas immunoprecipitation assays showed direct interaction. Our findings demonstrate convergence between ER alpha and ErbB4-ICD in the transcriptional control of ER alpha-target gene expression and suggest that this may represent a convergent pathway that may be disrupted in schizophrenia.