Atypical type III intermediate filament (IF) protein that may play a supportive role in the efficient coupling of mechanical stress between the myofibril and fiber exterior. May facilitate lateral force transmission during skeletal muscle contraction. Does not form homofilaments nor heterofilaments with other IF proteins. . This is the function of Ensembl gene identifier ENSG00000162520 (SYNC, syncoilin, intermediate filament protein).