Transcriptional activator of MEF2C involved in the regulation of adult muscle fiber type identity and skeletal muscle regeneration (By similarity). Plays an important role in spermatogenesis (By similarity). Required for the survival of spermatogonia and participates in spermatocyte meiosis (By similarity). . This is the function of Ensembl gene identifier ENSG00000198815 (FOXJ3, forkhead box J3).