Targeted Disruption of a Murine Glucuronyl C5-epimerase Gene Results in Heparan Sulfate Lacking l-Iduronic Acid and in Neonatal Lethality

Jin-Ping Li,Feng Gong,Åsa Hagner-Mcwhirter,Erik Forsberg,Magnus Åbrink,Robert Kisilevsky,Xiao Zhang,Ulf Lindahl

doi:10.1074/jbc.c300219200

Jin-Ping Li, Feng Gong + Show 6 more

Open Access

https://doi.org/10.1074/jbc.c300219200

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Abstract

The glycosaminoglycan, heparan sulfate (HS), binds proteins to modulate signaling events in embryogenesis. All identified protein-binding HS epitopes contain l-iduronic acid (IdoA). We report that targeted disruption of the murine d-glucuronyl C5-epimerase gene results in a structurally altered HS lacking IdoA. The corresponding phenotype is lethal, with renal agenesis, lung defects, and skeletal malformations. Unexpectedly, major organ systems, including the brain, liver, gastrointestinal tract, skin, and heart, appeared normal. We find that IdoA units are essential for normal kidney, lung, and skeletal development, albeit with different requirement for 2-O-sulfation. By contrast, major early developmental events known to critically depend on heparan sulfate apparently proceed normally even in the absence of IdoA.

Highlights

From the ‡Department of Medical Biochemistry and Microbiology, University of Uppsala, The Biomedical Center, Box 582, SE-751 23 Uppsala, Sweden, the **Department of Pathology, Queen’s University, Richardson Laboratory, Kingston, Ontario K7L 3N6, Canada, and the ‡‡Division of Molecular Neuropharmacology, Neurotec Department, Karolinska Institutet, Huddinge University Hospital, Novum, 141 86 Huddinge, Sweden
We report that targeted disruption of the murine D-glucuronyl C5-epimerase gene results in a structurally altered heparan sulfate (HS) lacking iduronic acid (IdoA)
The biosynthesis of HS is initiated by polymerization of D-glucuronic acid (GlcA) and N-acetyl-D-glucosamine (GlcNAc) residues in alternating sequence and is pursued through a series of modification reactions that include N-deacetylation/N-sulfation of GlcNAc, C5epimerization of GlcA to the C5-epimer, IdoA, and, O-sulfation at various positions [4]

Summary

Accelerated Publication

Targeted Disruption of a Murine Glucuronyl C5-epimerase Gene Results in Heparan Sulfate Lacking L-Iduronic Acid and in Neonatal Lethality*. We report that targeted disruption of the murine D-glucuronyl C5-epimerase gene results in a structurally altered HS lacking IdoA. Selective protein binding is mediated by saccharide domains containing sulfate groups in specific patterns, along with Liduronic acid (IdoA) units that promote ligand apposition through their conformational flexibility [3]. The resulting phenotype is lethal, with defects that can be differentially ascribed to HS structural alterations It shows apparently normal organ development, believed to depend on selective HS-protein interactions. These findings raise intriguing questions as to the need for regulation in HS biosynthesis

EXPERIMENTAL PROCEDURES

RESULTS AND DISCUSSION

Hsepi genotype