Mice lacking N-acetylglucosaminyltransferase I activity die at mid-gestation, revealing an essential role for complex or hybrid N-linked carbohydrates.
Eukaryotic cells require N-linked carbohydrates for survival. However, the biosynthetic intermediate Man5GlcNAc2Asn, in place of mature N-linked structures, allows glycoprotein synthesis and somatic cell growth to proceed normally. To determine whether the same would be true in a complex biological situation, the gene Mgat-1 was disrupted by homologous recombination in embryonic stem cells and transmitted to the germ line. The Mgat-1 gene encodes N-acetylglucosaminyltransferase I [GlcNAc-TI; alpha-1,3-mannosyl-glycoprotein beta-1,2-N-acetylglucosaminyltransferase; UDP-N-acetyl-D-glucosamine:glycoprotein (N-acetyl-D-glucosamine to alpha-D-mannosyl-1,3-(R1)-beta-D-mannosyl-R2) beta-1,2-N-acetyl-D-glucosaminyltransferase, EC 2.4.1.101], the transferase that initiates synthesis of hybrid and complex N-linked carbohydrates from Man5GlcNAc2Asn. Mice lacking GlcNAc-TI activity did not survive to term. Biochemical and morphological analyses of embryos from 8.5 to 13.5 days of gestation showed that Mgat-1-/-embryos are developmentally retarded, most noticeably in neural tissue, and die between 9.5 and 10.5 days of development.
Ioffe
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Department of Cell Biology, Albert Einstein College of Medicine, New York, NY 10461.
Stanley
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D000818:Animals; D001483:Base Sequence; D002241:Carbohydrates / Q000737:chemistry / Q000502:physiology*; D018076:DNA, Complementary / Q000235:genetics; D005314:Embryonic and Fetal Development / Q000235:genetics / Q000502:physiology; D005260:Female; D005313:Fetal Death / Q000201:enzymology / Q000209:etiology* / Q000503:physiopathology; D005865:Gestational Age; D008297:Male; D051379:Mice; D008817:Mice, Mutant Strains; D008855:Microscopy, Electron, Scanning; D008969:Molecular Sequence Data; D017351:N-Acetylglucosaminyltransferases / Q000172:deficiency* / Q000235:genetics / Q000502:physiology; D010835:Phytohemagglutinins / Q000378:metabolism; D011247:Pregnancy
D002241:Carbohydrates; D018076:DNA, Complementary; D010835:Phytohemagglutinins; C100156:leukoagglutinins, plants; D017351:N-Acetylglucosaminyltransferases; C024850:alpha-1,3-mannosyl-glycoprotein beta-1,2-N-acetylglucosaminyltransferase I