Complex asparagine-linked oligosaccharides in Mgat1-null embryos.
To investigate the developmental role of complex N-linked oligosaccharides, we previously inactivated the mouse Mgat1 gene which encodes UDP-N-acetylglucosamine: alpha-3-D-mannoside beta-1,2-N-acetylglucosaminyltransferase I (GlcNAc-TI). Mgat1-null embryos developed morphogenic abnormalities by embryonic day (E) 9.5 and failed to survive beyond E10.5. Prior to E8.5, mutant and wild-type embryos were phenotypically indistinguishable, raising the unexpected possibility that earlier embryonic development may not require complex N-glycans. We have now used in situ RNA hybridization to assess the temporal and spatial pattern of Mgat1 expression in normal embryos, and lectin histochemistry to determine whether Mgat1-null embryos lack complex N-glycans at pre-E9.5 developmental stages. In situ RNA analysis indicated that Mgat1 transcripts normally increase dramatically between E7.0 and E9.5, 1-2 days prior to the death of mutant embryos. However, apparently normal levels of complex N-glycans were observed in E3.5 pre-implantation Mgat1-null embryos prior to declining to undetectable levels by E7.5. Complex N-glycans were not observed in E7.5-E9.5 Mgat1-null embryos with the notable exception of vesicular structures within cells of the visceral extra-embryonic endoderm, perhaps reflecting the ability of these cells to take up and transport maternally derived glycoproteins. Mgat1-null embryos appear to complete pre-implantation development in the presence of maternally derived complex N-glycans, and may die at later stages, post E7.5, when a requirement for embryonically derived complex N-glycans arises.
Campbell
R M
RM
Howard Hughes Medical Institute, University of California San Diego, La Jolla 92093, USA.
Metzler
M
M
Granovsky
M
M
Dennis
J W
JW
Marth
J D
JD
D000818:Animals; D001216:Asparagine / Q000378:metabolism*; D001665:Binding Sites; D001755:Blastocyst / Q000378:metabolism; D003208:Concanavalin A / Q000378:metabolism; D047108:Embryonic Development / Q000235:genetics; D005260:Female; D005629:Frozen Sections; D018507:Gene Expression Regulation, Developmental / Q000235:genetics*; D017403:In Situ Hybridization; D037102:Lectins / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D017351:N-Acetylglucosaminyltransferases / Q000235:genetics* / Q000378:metabolism; D009844:Oligosaccharides / Q000378:metabolism*; D010835:Phytohemagglutinins / Q000378:metabolism; D011247:Pregnancy; D012313:RNA / Q000235:genetics / Q000378:metabolism; D013194:Staining and Labeling
D037102:Lectins; D009844:Oligosaccharides; D010835:Phytohemagglutinins; C067494:erythroagglutinating phytohemagglutinin; D003208:Concanavalin A; D012313:RNA; D001216:Asparagine; D017351:N-Acetylglucosaminyltransferases; C024850:alpha-1,3-mannosyl-glycoprotein beta-1,2-N-acetylglucosaminyltransferase I