The MNS blood group system consists of 48 antigens carried on glycophorin A (GPA), glycophorin B (GPB) or on hybrids of these glycophorins. These proteins are single pass type I membrane glycoproteins that are heavily O-glycosylated. GPA carries an N-glycan. GPA consists of 131 amino acids, GPB of 72 amino acids and both have a leader sequence of 19 amino acids that is cleaved from the membrane bound protein. The hybrid proteins vary in length based on their composition but also have a 19 amino acid leader sequence. GPA is encoded by GYPA, GPB by GYPB. A third gene in this family, GYPE, normally does not encode detectable protein at the red cell surface but the gene has been shown to be involved in some gene rearrangements that encode cell-surface borne hybrid proteins. As described above, the proteins are encoded by GYPA or GYPB, or MNS if analysis is to predict a blood group antigen.