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 7

Postnatal abrogation of O-glycan formation results in impaired expression of podoplanin and lymphatic abnormalities that phenocopy EHC T-syn–/– mice.

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Postnatal abrogation of O-glycan formation results in impaired expressio...
(A) Scheme for the generation of inducible T-syn–/– mice. Inducible T-syn–/– mice were generated by crossbreeding C1galt1f/f mice with Mx1Cre Tg mice in which the Cre recombinase was controlled by the Mx1 promoter, which is responsive to interferon or synthetic double-strand RNA (poly-I:C). Postnatal deletion of the C1galt1 gene was achieved by injections of poly-I:C when mice were 2 weeks old. (B) Immunohistochemical staining of sections of small intestine from 7-month-old T-syn+/+ and inducible T-syn–/– mice using antibodies against Tn or Lyve-1. Arrows indicate blood cells. (C) Intravital microscopic imaging of intestinal vascular networks after an arterial injection of India ink (8-month-old mice). (D) Confocal imaging of cryosections of small intestine from 8-month-old T-syn+/+ and inducible T-syn–/– mice. Arrowheads mark the lymphatic endothelial podoplanin. The arrow in the merged image indicates a dilated hybrid vessel. The additional image in the inducible T-syn–/– panel is a cryosection of intestine labeled with anti-CD31, Prox1, and Lyve-1. Arrowheads in this image indicate Prox1 staining. Data are representative of at least 3 experiments. Scale bars: 50 μm (B and D); 0.5 mm (C).