Sequence and expression of the chicken membrane-associated phospholipases A1 alpha (LIPH) and beta (LIPI)

Cancer/testis antigens (CTA) are a heterogeneous group of antigens that are expressed preferentially in tumor cells and testis. Based on this definition the human membrane-associated phospholipase A1 beta (lipase family member I, LIPI) has been identified as CTA. The high homology of LIPI and the membrane-associated phospholipase A1 alpha (lipase family member H, LIPH) suggests that both genes are derived from a common ancestor by gene duplication. In contrast to human LIPI, human LIPH is expressed in several tissues. LIPI sequences have only been identified in mammals. Here, we describe the identification of LIPI in non-mammalian vertebrates. Based on the conserved genomic organization of LIPI and LIPH we identified sequences for both lipases in birds and fishes. In all vertebrates the LIPI locus is neighbored by a member of the RNA binding motif (RBM) family, RBM11. By sequencing of reverse transcriptase-polymerase chain reaction products we determined the sequences of LIPI and LIPH messenger RNA from broilers. We found that the sequence homology between LIPI and LIPH is much higher in non-mammalian species than in mammals. In addition, we found broad expression of LIPI in broilers, resembling the expression profile of LIPH. Our data suggest that LIPI is a CTA only in mammalian species and that the unique sequence features of the mammalian LIPI/RBM11 locus have evolved together with the CTA-like expression pattern of LIPI.