Essential role for complex N-glycans in forming an organized layer of bronchial epithelium.
Mice lacking the complex subset of N-glycans due to inactivation of the Mgat1 gene die at mid-gestation, making it difficult to identify specific biological functions for this class of cell surface carbohydrates. To circumvent this embryonic lethality and to uncover tissue-specific functions for complex N-glycans, WW6 embryonic stem cells with inactivated Mgat1 alleles were tracked in chimeric embryos. The Mgat1 gene encodes N-acetylglucosaminyltransferase I (Glc-NAc-TI; EC 2.4.1.101), the transferase that initiates the synthesis of complex N-glycans. WW6 cells carry an inert beta-globin transgene that allows their identification in chimeras by DNA-DNA in situ hybridization. Independent Mgat1-/- and Mgat1+/- mutant WW6 isolates contributed like parent WW6 cells to the tissues of embryonic day (E) 10.5 to E16.5 chimeras. However, a cell type-specific difference was observed in lung. Homozygous null Mgat1-/- WW6 cells did not contribute to the epithelial layer in more than 99% bronchi. This deficiency was corrected by transfection of a Mgat1 transgene. Interestingly, heterozygous Mgat1+/- WW6 cells were also deficient in populating the layer of bronchial epithelium. Furthermore, examination of lung bud in E9.5 Mgat1-/- mutant embryos showed complete absence of an organized epithelial cell layer in the bronchus. Thus, complex N-glycans are required to form a morphologically recognizable bronchial epithelium, revealing an in vivo, cell type-specific function for this class of N-glycans.
Ioffe
E
E
Department of Cell Biology, Albert Einstein College of Medicine, New York, NY 10461, USA.
Liu
Y
Y
Stanley
P
P
D000818:Animals; D001980:Bronchi / Q000166:cytology*; D002678:Chimera; D004847:Epithelial Cells; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D017351:N-Acetylglucosaminyltransferases / Q000502:physiology*; D011134:Polysaccharides / Q000502:physiology*
D011134:Polysaccharides; D017351:N-Acetylglucosaminyltransferases; C024850:alpha-1,3-mannosyl-glycoprotein beta-1,2-N-acetylglucosaminyltransferase I