Vgl-2, also known as VITO-1, is a 317 amino acid protein that contains a domain through which it interacts with TEF-1, a protein that plays a role in controlling the expression of numerous genes. Specific to skeletal muscle, Vgl-2 is expressed highly in adult fast muscle and is expressed at lower levels in adult slow muscle and fetal skeletal muscle. During muscle differentiation, Vgl-2 mRNA levels increase and Vgl-2 translocates from the cytoplasm to the nucleus. Overexpression of Vgl-2 in MYOD-transfected 10T1/2 mouse embryonic fibroblasts increases expression of myosin heavy chain (MHC), which is a marker of terminal muscle differentiation. This evidence suggests that Vgl-2 is essential for muscle gene expression. There are two isoforms of Vgl-2 that are produced as a result of alternative splicing events.