ROLE OF DNA METHYLATION IN GASTROINTESTINAL SMOOTH MUSCLE CELL DEVELOPMENT & PLASTICITY

Smooth muscle cells (SMC) possess a remarkable ability known as plasticity that is defined by SMC reversibly altering their phenotype from a contractile, mature state into a non-contractile, stem cell-like state. The phenotype of SMC can be altered due to the presence of various growth factors (THBS4, PDGF-BB) and injury but the mechanisms underlying the intracellular changes are not well characterized. Previous research on vascular SMC (vSMC) has shown that inhibiting DNA methylation causes marked changes in necessary SMC-specific mRNA and miRNA transcription but similar work on gastrointestinal SMC (GI-SMC) has not been carried out. By utilizing a SMC-restricted knockout model, we have been able to successfully eliminate, from the murine genome, various enzymes involved in the regulation of DNA methylation including Dnmt1, Dnmt3a and Tet2 in both congenital and inducible models. Congenital knockout of Dnmt1 produces a phenotype characterized by a drastically remodeled transcriptome, ~20% reduction of methylation across the genome, loss of the GI smooth muscle layer, severe intestinal dilation, and death by P21 due to sepsis while the inducible knockout of Dnmt1 produces no phenotype. Furthermore, neither congenital or inducible knockout of either Dnmt3a or Tet2 shows any change in GI-SMC functioning. These results suggest that