NeuroD factors discriminate mineralocorticoid from glucocorticoid receptor DNA binding in the male rat brain


In the limbic brain,mineralocorticoid receptors (MRs) and glucocorticoid receptors (GRs) both function as receptors for the naturally occurring glucocorticoids (corticosterone/cortisol) butmediate distinct effects on cellular physiology via transcriptionalmechanisms. The transcriptional basis for specificity of these MRvs GR-mediated effects is unknown. To address this conundrum, we have identified the extent ofMR/GR DNA-binding selectivity in the rat hippocampus using chromatin immunoprecipitation followed by sequencing. We found 918 and 1450 nonoverlapping binding sites for MR and GR, respectively. Furthermore, 475 loci were co-occupied byMR and GR. De novo motif analysis resulted in a similar binding motif for both receptors at 100% of the target loci, which matched the known glucocorticoid response element (GRE). In addition, the Atoh/NeuroD consensus sequence was found in co-occurrence with all MR-specific binding sites butwas absent forGR-specific orMR-GR overlapping sites. Basic helix-loop-helix family members Neurod1, Neurod2, and Neurod6 showed hippocampal expression and were hypothesized to bind the Atohmotif.Neurod2was detected at rat hippocampalMRbinding sites but not at GR-exclusive sites. All three NeuroD transcription factors acted as DNA-binding-dependent coactivators for bothMR and GR in reporter assays in heterologous HEK293 cells, likely via indirect interactions with the receptors. In conclusion, a NeuroD familymemberbinding to an additionalmotif near theGRE seems to drive specificity forMRoverGRbindingat hippocampalbindingsites.