Human and Mouse Orthologs of a New ATP-binding Cassette Gene, ABCG4

We characterized a new ATP-binding cassette (ABC) transporter gene from human and mouse that is highly expressed in the brain. The gene, ABCG4, produces several transcripts that differ at the 5' end and encode proteins of various lengths. The ABCG4 protein is closely related to the Drosophila white and human ABCG1 genes, and belongs to the ABCG subfamily several members of which are involved in cholesterol transport. All representatives of this "reverse transporter" subfamily, including ABCG4, have a single ATP-binding domain at the N-terminus and a single C-terminal set of transmembrane segments. ABCG4 maps to human chromosome 11q23, between the markers D11S939 and D11S924, and Abcg4 to a conserved syntenic region on mouse chromosome 9. The abundant expression of this gene in the brain and close evolutionary relationship to the other members of the subfamily suggests a potential role for ABCG4 in cholesterol transport processes in this tissue.