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

We queried the genomes of 73 birds and 19 nonbird reptiles for CMAH homologs (table 1) . Surprisingly, we found homologs in the two lizards included in our data set, Anolis carolinensis (green anole lizard), and Gekko japonicus (Japanese gecko), but not in any snake, turtle, crocodilian, or bird. These results contradict the hypothesis that CMAH may have been lost in an ancestor of Sauropsida (Schauer et al. 2009 ). Instead, our results indicate that the gene was present in the most recent common ancestor of Sauropsida, and that it was lost at least twice during the evolution of the group: in the snake lineage, and in an ancestor of turtles, crocodilians, and birds ( fig. 3) . The A. carolinensis CMAH sequence appears to be functional. The G. japonicus sequence, however, contains a premature stop codon at the end of coding exon 4. This indicates a recent inactivation of CMAH in an ancestor of G. japonicus (table 2) .