The mammalian Diaphanous‐related formin diaphanous 1 (DIAPH1) is a canonical effector for Rho small GTP‐binding proteins. When activated by GTP‐bound RhoA, DIAPH1 relies upon its formin homology‐2 domain to elongate linear actin filaments by adding actin monomers to their barbed ends. As a consequence, DIAPH1 also signals to the nucleus via the myocardin‐related transcription factor/serum response factor (MRTF/SRF) axis to effect gene expression. DIAPH1 interacts with the cytoplasmic domain of the receptor for advanced glycation end products (RAGE) through its poly‐proline‐rich formin homology‐1 domain. In response to RAGE ligand stimulation, DIAPH1 participates in signal transduction in smooth muscle cells, macrophages, immune cells, and transformed cells. While RAGE is known to be an essential component of the in vivo response to myocardial stress in diabetes, role of DIAPH1 in diabetic hearts has not been investigated. The goal of this study is to investigate the role of cardiac DIAPH1 in the physiological response to diabetes in mice. In wild type littermate (WT) mice and Diaph1 deleted mice diabetes was induced using low doses of streptozotocin and hearts harvested after 3 months of diabetes. Myocardial Diaph1 expression was significantly increased in diabetic WT mice vs non‐diabetic WT mice (p<0.05). In H9C2 cells, treatment with high glucose (20 mM) and RAGE ligands significantly increased Diaph1 expression. We observed significant increases in expression of a sub‐set of SRF target genes in response to high glucose and that these SRF target genes were attenuated in Diaph1 silenced cells. SRF target genes c‐Fos, Egr‐1, Mmp‐2, Mmp‐9 and Sm‐22, increased in response to high glucose in a DIAPH1 dependent manner, while Tgf‐β1, Tgf‐β2, Atp2a and Cofilin did not show any changes in response to high glucose treatment. We observed that high glucose and RAGE ligands induces DIAPH1 driven changes in SRF target gene expression via ERK1 and PKC αβ signaling mechanisms. We posit that DIAPH1, by its impact on SRF and SRF target genes may play an important role in mediating diabetic cardiomyopathy.Support or Funding InformationNIH HL60901This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.