May play a role in actin filament polymerization in cardiomyocytes (By similarity). Actin-organizing protein that may cause stress fiber formation together with cell elongation. Interacts with nestin/NES-based interfilament (IF). Interacts with SQSTM1. Main part of the protein localizes to actin fibers and the remaining part displays filamentous staining. Named isoforms=3. Expressed in the heart, including left ventricle, kidney, brain and skeletal muscle, including soleus and tibialis anterior (at protein level). The DAD domain regulates activation via by an autoinhibitory interaction with the GBD/FH3 domain. This autoinhibition is released upon competitive binding of an activated GTPase. The release of DAD allows the FH2 domain to then nucleate and elongate nonbranched actin filaments (By similarity). Major form in heart. Major form in kidney and brain. Belongs to the formin homology family.