Phylogenetic Distribution of CMP-Neu5Ac Hydroxylase (CMAH), the Enzyme Synthetizing the Proinflammatory Human Xenoantigen Neu5Gc

Peri, Sateesh; Kulkarni, Asmita; Feyertag, Felix; Berninsone, Patricia M; Alvarez-Ponce, David

Neu5Gc is known to be present in most placental mammals studied so far (Davies et al. 2012 ) and has been reported in kangaroo (Schauer et al. 2009 ). In contrast, among monotremes Neu5Gc could not be detected in liver and muscle tissues of the platypus (Ornithorhynchus anatinus) (Schauer et al. 2009 ), nor in the milk of the spiny anteater echidna (Tachyglossus aculeatus) (Kamerling et al. 1982) . Schauer et al. (2009) , did not find any CMAH homolog in the genome of platypus using BLAST searches. However, our analyses revealed a CMAH pseudogene in the platypus genome. Using TBLASTN searches we could retrieve eight of the protein-coding exons (the chimpanzee CMAH has 15 protein-coding exons). Exon 5 harbors a premature stop codon, which may explain the lack of Neu5Gc in this species (table 2) . Schauer et al. (2009) identified a CMAH homolog in the genome of the marsupial Monodelphis domestica (gray shorttailed opossum). Consistent with this observation, we found CMAH homologous sequences in the genomes of gray shorttailed opossum, tammar wallaby, and Tasmanian devil.