Review of colton blood group: Aquaporin-1 based blood group with diverse functions

The Colton blood group is a 15^th group consisting of about 3 antigens that are present on the aquaporin1 (AQP1), present abundantly on RBCs and proximal renal tubules. Since it forms water channels and has a molecular weight of 28 kDa. It is also called a channel-forming integral protein 28 (CHIP28). The gene for AQP1 is present on chromosome 7 at 7p14. AQP1 is a homotetramer; each monomer being hexahelical with both N- and C-terminal domains in the cytoplasm and physiologically important NPA motif. AQP1 has diverse functions such as water influx, pain sensation, absorption of chylomicrons, extrusion of fluid from the cornea, etc. Though severe consequences are absent in AQP1 null or mutated phenotypes, there is a reduction in the life span of RBCs, decreased urine concentrating ability, and defective absorption of dietary fats.