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Toshiyuki Hayakawa,1,2*Takashi Angata,1,2*Amanda L. Lewis,1,3Tarjei S. Mikkelsen,6Nissi M. Varki,1,4Ajit Varki1,2,5
Recent studies have shown multiple differences between humansand apes in sialic acid (Sia) biology, including Siglecs (Sia-recognizing-Ig-superfamilylectins). Comparisons with the chimpanzee genome indicate thathuman SIGLEC11 emerged through human-specific gene conversionby an adjacent pseudogene. Conversion involved 5¢ untranslatedsequences and the Sia-recognition domain. This human proteinshows reduced binding relative to the ancestral form but recognizesoligosialic acids, which are enriched in the brain. SIGLEC11is expressed in human but not in chimpanzee brain microglia.Further studies will determine if this event was related tothe evolution of Homo.
1 Glycobiology Research and Training Center, University of California at San Diego, La Jolla, CA 92093, USA. 2 Department of Cellular and Molecular Medicine, University of California at San Diego, La Jolla, CA 92093, USA. 3 Department of Biological Sciences, University of California at San Diego, La Jolla, CA 92093, USA. 4 Department of Pathology, University of California at San Diego, La Jolla, CA 92093, USA. 5 Department of Medicine, University of California at San Diego, La Jolla, CA 92093, USA. 6 Broad Institute of the Massachusetts Institute of Technology and Harvard University, Cambridge, MA 02141, USA.
* These authors contributed equally to this work.
Present Address: Research Center for Glycoscience, NationalInstitute of Advanced Industrial Science and Technology, Tsukuba,Japan.
To whom correspondence should be addressed. E-mail: a1varki{at}ucsd.edu
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Present Address: Research Center for Glycoscience, National Institute of Advanced Industrial Science and Technology, Tsukuba, Japan. 
To whom correspondence should be addressed. E-mail: 
