Acts as a transcriptional coactivator of serum response factor (SRF). Required for skeletal myogenic differentiation. Interacts with MRTFA and SRF. Widely expressed. High expression in heart, brain and testis. Lower expression in lung, liver and kidney. Detected throughout the embryo at 10.5 dpc. High expression in epithelial cells of the lung, kidney, bladder, colon, testis, in the smooth muscle of the colon and small intestines, and in the mesenchymal cells adjacent to the olfactory epithelium at 15.5 dpc. The N-terminal region is required for nuclear localization and the C-terminal region mediates transcriptional activity. O-glycosylated.