Srf destabilizes cell identity (Microarray_affymetrix)

Multicellular organisms consist of multiple cell types, whose identities are maintained appropriately at locations where they are reside. The identity of each cell type is primarily maintained by cell-type-specific gene expression programs, but mechanisms that suppress these programs are poorly defined. Here we show that serum response factor (Srf), a transcription factor that is activated by various extracellular stimuli, can repress cell-type-specific genes and promote cellular reprogramming to pluripotency. Manipulations that decrease β-actin monomer resulted in nuclear accumulation of Mkl1 and the activation of Srf, which downregulated cell-type-specific genes and altered epigenetics in enhancers and chromatin organization. Mice overexpressing Srf exhibited various pathologies including an ulcerative colitis-like symptom and a metaplasia-like phenotype in the pancreas. Our results demonstrate an unexpected function of Srf via a mechanism by which extracellular stimuli actively destabilize cell identity and suggest Srf involvement in a wide range of diseases. Total RNAs of hepatoblasts expressing EGFP and overexpressing Srf were used to analyze effects of overexpressions of Srf on changes of gene expressions.