The function of ARMC12 (armadillo repeat containing 12, ENSG00000157343) is as follows. Essential for male fertility and sperm mitochondrial sheath formation (By similarity). Required for proper mitochondrial elongation and coiling along the flagellum during the formation of the mitochondrial sheath (By similarity). Facilitates the growth and aggressiveness of neuroblastoma cells (PubMed:30026490). Increases the EZH2 activity and H3K27me3 levels in a RBBP4-dependent manner, and facilitates the enrichment of polycomb repressive complex 2 and H3K27me3 on gene promoters, resulting in transcriptional repression of tumor suppressors affecting the proliferation, invasion, and metastasis of tumor cells (PubMed:30026490). {ECO:0000250|UniProtKB:Q80X86, ECO:0000269|PubMed:30026490}.