The Scianna blood group system consists of 9 antigens carried on a single pass type I membrane glycoprotein (ERMAP) with 1 IgSF domain and an intracellular B30.2 domain. The 475 amino acid ERMAP protein is encoded by exons 3 to 12 from either a 3,485 bp (NM_001017922.1) or a 3,381 bp (NM_018538.3) mRNA transcript. There is a leader sequence of 29 amino acids, which is cleaved from the membrane bound protein.