Muscle assembly regulating factor. Mediates the antiparallel assembly of titin (TTN) molecules at the sarcomeric Z-disk. Interacts with MYOZ1, MYOZ2 and MYOZ3. Interacts with CSRP3. Interacts directly with the N-terminal Ig-like domains of 2 titin (TTN) molecules. Interacts with ANKRD2; the interaction is direct. Heart and skeletal muscle. The disease is caused by variants affecting the gene represented in this entry. The disease is caused by variants affecting the gene represented in this entry. The C-terminal domain appears to be unstructured in solution. It may promote the assembly of higher-order TTN complexes.