he ATP binding cassette (ABC) superfamily of membrane transporters is one of the largest protein classes known, and counts for numerous proteins involved in trafficking of biological molecules across membranes. ABCG4 protein is highly expressed in both human and mouse brain, it is a 646aa molecule in human (chr 11q23) and mouse. It is an integral membrane protein may be involved in macrophage lipid homeostasis. The ABCG4 protein’s abundant expression in brain and close evolutionary relationship to the other members of the subfamily suggests a potential role in cholesterol transport.