Halleck, Margaret S., Joseph F. Lawler, Jr., Seth Blackshaw, Ling Gao, Priya Nagarajan, Coleen Hacker, Scott Pyle, Jason T. Newman, Yoshinobu Nakanishi, Hiroshi Ando, Daniel Weinstock, Patrick Williamson, and Robert A. Schlegel. Differential expression of putative transbilayer amphipath transporters. Physiol. Genomics 1: 139–150, 1999.—The aminophospholipid translocase transports phosphatidylserine and phosphatidylethanolamine from one side of a bilayer to another. Cloning of the gene encoding the enzyme identified a new subfamily of P-type ATPases, proposed to be amphipath transporters. As reported here, mammals express as many as 17 different genes from this subfamily. Phylogenetic analysis reveals the genes to be grouped into several distinct classes and subclasses. To gain information on the functions represented by these groups, Northern analysis and in situ hybridization were used to examine the pattern of expression of a panel of subfamily members in the mouse. The genes are differentially expressed in the respiratory, digestive, and urogenital systems, endocrine organs, the eye, teeth, and thymus. With one exception, all of the genes are highly expressed in the central nervous system (CNS); however, the pattern of expression within the CNS differs substantially from gene to gene. These results suggest that the genes are expressed in a tissue-specific manner, are not simply redundant, and may represent isoforms that transport a variety of different amphipaths.