Muscle assembly regulating factor. Mediates the antiparallel assembly of titin (TTN) molecules at the sarcomeric Z-disk (By similarity). 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 (By similarity).