Endothelial cell O-glycan deficiency causes blood/lymphatic misconnections and consequent fatty liver disease in mice
Jianxin Fu, … , Florea Lupu, Lijun Xia
Jianxin Fu, … , Florea Lupu, Lijun Xia
Published October 16, 2008
Citation Information: J Clin Invest. 2008;118(11):3725-3737. https://doi.org/10.1172/JCI36077.
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Research Article Vascular biology

Endothelial cell O-glycan deficiency causes blood/lymphatic misconnections and consequent fatty liver disease in mice

Abstract

Mucin-type O-glycans (O-glycans) are highly expressed in vascular ECs. However, it is not known whether they are important for vascular development. To investigate the roles of EC O-glycans, we generated mice lacking T-synthase, a glycosyltransferase encoded by the gene C1galt1 that is critical for the biosynthesis of core 1–derived O-glycans, in ECs and hematopoietic cells (termed here EHC T-syn–/– mice). EHC T-syn–/– mice exhibited embryonic and neonatal lethality associated with disorganized and blood-filled lymphatic vessels. Bone marrow transplantation and EC C1galt1 transgene rescue demonstrated that lymphangiogenesis specifically requires EC O-glycans, and intestinal lymphatic microvessels in EHC T-syn–/– mice expressed a mosaic of blood and lymphatic EC markers. The level of O-glycoprotein podoplanin was significantly reduced in EHC T-syn–/– lymphatics, and podoplanin-deficient mice developed blood-filled lymphatics resembling EHC T-syn–/– defects. In addition, postnatal inactivation of C1galt1 caused blood/lymphatic vessel misconnections that were similar to the vascular defects in the EHC T-syn–/– mice. One consequence of eliminating T-synthase in ECs and hematopoietic cells was that the EHC T-syn–/– pups developed fatty liver disease, because of direct chylomicron deposition via misconnected portal vein and intestinal lymphatic systems. Our studies therefore demonstrate that EC O-glycans control the separation of blood and lymphatic vessels during embryonic and postnatal development, in part by regulating podoplanin expression.

Authors

Jianxin Fu, Holger Gerhardt, J. Michael McDaniel, Baoyun Xia, Xiaowei Liu, Lacramioara Ivanciu, Annelii Ny, Karlien Hermans, Robert Silasi-Mansat, Samuel McGee, Emma Nye, Tongzhong Ju, Maria I. Ramirez, Peter Carmeliet, Richard D. Cummings, Florea Lupu, Lijun Xia

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Figure 1

Generation of EHC T-syn–/– mice.

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Generation of EHC T-syn–/– mice. (A) Scheme for mucin-type O-glycan ...
(A) Scheme for mucin-type O-glycan biosynthesis. Arrowheads indicate possible further branching, elongation, fucosylation, sialylation, and sulfation. (B) Diagram of WT (T-syn+), loxP site–flanked (T-synf), and null (T-syn–) alleles of C1galt1. (C) T-synthase activity of primary endothelial cells isolated from T-syn+/+ and EHC T-syn–/– lungs. The data represent the mean ± SEM of 2 independent experiments. (D) Annotated spectra of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) analyses of 2-aminobenzamide–labeled (2-AB–labeled) O-glycans from T-syn+/+ and T-syn–/– endothelial cells. The O-glycans with mass number in green contain a sodium instead of a hydrogen. MALDI-TOF-MS did not detect Tn antigen, which is exposed in the absence of T-synthase activity, because its size is below the detection limit. (E) Immunohistochemical staining of serial intestinal sections with antibodies against Tn antigen or Lyve-1. Tn is positive in endothelial cells of EHC T-syn–/– arteriole, blood capillaries, and Lyve-1–positive lymphatic vessels. A, arteriole; L, lymphatic vessels; V, vein; E, epithelium; BC, blood capillary. Scale bar: 50 μm.