A mutation in human CMP-sialic acid hydroxylase occurred after the Homo-Pan divergence

A mutation in human CMP-sialic acid hydroxylase occurred after the Homo-Pan divergence

^*Glycobiology Program, Divisions of Hematology-Oncology and Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA 92093; ^§San Diego Veterans Administration Medical Center, San Diego, CA 92161; ^¶The Living Links Center of the Yerkes Primate Center, ^†Howard Hughes Medical Institute and Departments of Biochemistry, Pediatrics, and Genetics, Emory University School of Medicine, Atlanta, GA 30322; and ^‡Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030

Communicated by Ernest Beutler, The Scripps Research Institute, La Jolla, CA (received for review July 6, 1998)

Abstract

Sialic acids are important cell-surface molecules of animals in the deuterostome lineage. Although humans do not express easily detectable amounts of N-glycolylneuraminic acid (Neu5Gc, a hydroxylated form of the common sialic acid N-acetylneuraminic acid, Neu5Ac), it is a major component in great ape tissues, except in the brain. This difference correlates with lack of the hydroxylase activity that converts CMP-Neu5Ac to CMP-Neu5Gc. Here we report cloning of human and chimpanzee hydroxylase cDNAs. Although this chimpanzee cDNA is similar to the murine homologue, the human cDNA contains a 92-bp deletion resulting in a frameshift mutation. The isolated human gene also shows evidence for this deletion. Genomic PCR analysis indicates that this deletion does not occur in any of the African great apes. The gene is localized to 6p22–p23 in both humans and great apes, which does not correspond to known chromosomal rearrangements that occurred during hominoid evolution. Thus, the lineage leading to modern humans suffered a mutation sometime after the common ancestor with the chimpanzee and bonobo, potentially affecting recognition by a variety of endogenous and exogenous sialic acid-binding lectins. Also, the expression of Neu5Gc previously reported in human fetuses and tumors as well as the traces detected in some normal adult humans must be mediated by an alternate pathway.

Pongidae/evolution/neuraminic acids/PCR/hominoids

Footnotes

↵ ‖ To whom reprint requests should be addressed at: UCSD Cancer Center, 0687, La Jolla, CA 92093-0687. e-mail: avarki{at}ucsd.edu.
Data deposition: The sequences reported in this paper have been deposited in the GenBank database [accession nos. AF074480 (human hydroxylase cDNA) and AF074481 (chimpanzee hydroxylase cDNA)].
ABBREVIATIONS:

Neu5Gc,

N-glycolylneuraminic acid;

Neu5Ac,

N-acetylneuraminic acid;

BAC,

bacterial artificial chromosome;

FISH,

fluorescence in situ hybridization;

EST,

expressed sequence tag;

TdT,

terminal deoxynucleotidyltransferase;

EBV,

Epstein–Barr virus;

RACE,

rapid amplification of cDNA ends;

UTR,

untranslated region