Role of the transcription factor EGR1 in neuronal differentiation

Background: immediate early genes encode transcription factors which combine early signaling events with long-term changes in gene expression. They are involved in many cellular processes, including differentiation and proliferation. The transcription factor EGR1 has been hypothesized to have a role in many biological processes such as cell growth, differentiation and apoptosis during neuronal differentiation. Genes regulated by EGR1 are also involved in neuronal plasticity and in the development of learning and memory. The expression of EGR1 is often altered in neurodegenerative diseases and psychiatric disorders. However, its mechanism of action is not fully understood. Method: We used SH-SY5Y cell line as a neuronal cell model, since SH-SY5Y cells can be differentiated to a more mature neuron-like phenotype using retinoic acid (RA). We analyzed the expression levels of EGR1 after RA treatment using qPCR and Western Blot analysis. Then, in order to characterize the role of EGR1 in neuronal differentiation we used CRISPR-Cas9 technology to generate a knockout cell (KO) line for EGR1 gene. Results: EGR1 mRNA and protein levels increase significantly during the first two days of RA treatment, leading to the idea of an early involvement of EGR1 in RA-induced neuronal differentiation. Interestingly, EGR1 KO cells undergo to cell death after RA treatment. Molecular analysis of the EGR1 KO model showed a dysregulation of many differentiation markers, including those related to synaptogenesis. Conclusions: Our findings suggest a key role of EGR1 in the proper development and differentiation of neurons, in particular, in the relationship between neuronal differentiation and survival.