Myomaker (Tmem8c) of 221 aas and 7 TMSs and Myomerger/Mymx/Minion of 84 aas and at least 1 N-terminal TMS, although there may be as many as 3 TMSs.  These two proteins were thought to be myoblast-specific proteins that mediate myoblast fusion, essential for the formation of multi-nucleated muscle fibers. They actively participate in the membrane fusion reaction (Schejter 2016). Fusion is dependent on the fusogenic peptide, myomixer (Bi et al. 2017).  Myomaker is also required for stem cell fusion in skeletal muscle (Goh and Millay 2017). While Myomaker initiates the fusion process by creating the hemifusion intermediate, Myomerger (Myomixer) is the fusogenic peptide that completes the fusion of the two membranes by formation of a continuous bilayer (Leikina et al. 2018). Reviewed by Hernández and Podbilewicz 2017.