N-glycolylneuraminic acid deficiency in mice: implications for human biology and evolution.
Humans and chimpanzees share >99% identity in most proteins. One rare difference is a human-specific inactivating deletion in the CMAH gene, which determines biosynthesis of the sialic acid N-glycolylneuraminic acid (Neu5Gc). Since Neu5Gc is prominent on most chimpanzee cell surfaces, this mutation could have affected multiple systems. However, Neu5Gc is found in human cancers and fetuses and in trace amounts in normal human tissues, suggesting an alternate biosynthetic pathway. We inactivated the mouse Cmah gene and studied the in vivo consequences. There was no evidence for an alternate pathway in normal, fetal, or malignant tissue. Rather, null fetuses accumulated Neu5Gc from heterozygous mothers and dietary Neu5Gc was incorporated into oncogene-induced tumors. As with humans, there were accumulation of the precursor N-acetylneuraminic acid and increases in sialic acid O acetylation. Null mice showed other abnormalities reminiscent of the human condition. Adult mice showed a diminished acoustic startle response and required higher acoustic stimuli to increase responses above the baseline level. In this regard, histological abnormalities of the inner ear occurred in older mice, which had impaired hearing. Adult animals also showed delayed skin wound healing. Loss of Neu5Gc in hominid ancestors approximately 2 to 3 million years ago likely had immediate and long-term consequences for human biology.
Hedlund
Maria
M
Glycobiology Research and Training Center, Department of Medicine, University of California San Diego, La Jolla, CA 92093-0687, USA.
Tangvoranuntakul
Pam
P
Takematsu
Hiromu
H
Long
Jeffrey M
JM
Housley
Gary D
GD
Kozutsumi
Yasunori
Y
Suzuki
Akemi
A
Wynshaw-Boris
Anthony
A
Ryan
Allen F
AF
Gallo
Richard L
RL
Varki
Nissi
N
Varki
Ajit
A
D000107:Acetylation; D000161:Acoustic Stimulation; D000818:Animals; D001695:Biology; D002851:Chromatography, High Pressure Liquid; D015331:Cohort Studies; D004247:DNA / Q000235:genetics; D007758:Ear, Inner / Q000002:abnormalities; D019143:Evolution, Molecular; D005260:Female; D017353:Gene Deletion; D006579:Heterozygote; D015186:Hominidae / Q000235:genetics; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D008822:Mice, Transgenic; D009438:Neuraminic Acids / Q000378:metabolism*; D010655:Phenylenediamines / Q000494:pharmacology; D016133:Polymerase Chain Reaction; D013216:Reflex, Startle / Q000235:genetics; D012867:Skin / Q000293:injuries; D013997:Time Factors; D014945:Wound Healing / Q000502:physiology
D009438:Neuraminic Acids; D010655:Phenylenediamines; C032592:N-glycolylneuraminic acid; C058886:1,2-diamino-4,5-methylenedioxybenzene; D004247:DNA