"OMICs" reveal the molecular basis of a rare blood group.

Blood groups are defined by membrane proteins that are either single-pass, multi-pass, or glycosylphosphatidylinositol-linked proteins. The antigens defining the blood groups can be either the proteins themselves or the complexes of sugars that decorate these membrane proteins. For antigens that are present at high frequency on red blood cells, transfusion incompatibility problems, due to the absence of undefined blood group antigens, may cause difficulty in finding matching blood. This transfusion complication can only be remedied when the identity of the blood group antigen is discovered. In this issue of , Azouzi et al, using a combination of complementary “omic” approaches, reveal the molecular identity of a rare blood group (PEL) that was first reported almost 40 years ago by Daniels et al, the high frequency antigen, ABCC4 (an ATP-binding cassette [ABC]-transporter).