The Interaction of Early Growth Response Gene 1 and Myocyte Enhancer Factor 2C in the Murine Brain Cortex

Early growth response gene – 1 (Egr1) encodes a protein widely present in mammalian body, such as connective tissue, cardiac tissue, the liver, and the brain. As a transcription factor (TF), it is involved in processes that take place in the endocrine, digestive, immune, musculo-skeletal and central nervous systems, for instance, B cell maturation upon B cell receptor activation, tendon repair upon mechano-stimulation, and long-term spatial memory formation. In mammalian brains, EGR1 controls the responses to environmental stimuli such as chronic stress and physical contact. It also participates in processes such as long-term memory consolidation and synapse re-structuring. It plays a role in enacting responses and qualities of gene transcription cascades upon neuronal stimulation. Inside the epigenetic realm, EGR1 recruits Ten-eleven translocation methylcytosine dioxygenase 1 (TET1) to remove DNA methylation at target loci. Due to its critical functions during brain development and upon neuronal activation, mis-regulation of EGR1 is associated with neuropsychological disorders such as post-traumatic stress disorder (PTSD) and schizophrenia (SCZ) in humans. In this study, we performed bioinformatics analysis with brain methylomes and predicted EGR1 may interact with myocyte enhancer factor 2C (MEF2C), which is known to be involved in many similar processes as EGR1, such as synapse architecture, cell migration, and learning and memory. EGR1 and MEF2C ChIP-seq data derived from mouse frontal cortex suggest these two proteins may regulate a common set of downstream genes. To begin, co-immunoprecipitation experiments were performed with HEK293T cells co-transfected with EGR1-FLAG and MEF2C-HA tagged constructs, allowing for specific interaction identification without endogenous protein expression interference. Furthermore, co-immunoprecipitation experiments performed with brain tissues additionally indicated the two proteins interact with each other endogenously. Altogether, this study provides protein-protein interaction evidence for EGR1 and MEF2C in cultured HEK293 cells and in the cortices of adult male mice. This information provides a foundation for future examinations of how these two TFs interact to initiate cascading events following neuronal stimulation.