Mice Deficient in Nervous System-specific Carbohydrate Epitope HNK-1 Exhibit Impaired Synaptic Plasticity and Spatial Learning

Abstract

The HNK-1 carbohydrate epitope, a sulfated glucuronic acid at the non-reducing terminus of glycans, is expressed characteristically on a series of cell adhesion molecules and is synthesized through a key enzyme, glucuronyltransferase (GlcAT-P). We generated mice with a targeted deletion of the GlcAT-P gene. The GlcAT-P ؊/؊ mice exhibited normal development of gross anatomical features, but the adult mutant mice exhibited reduced long term potentiation at the Schaffer collateral-CA1 synapses and a defect in spatial memory formation. This is the first evidence that the loss of a single non-reducing terminal carbohydrate residue attenuates brain higher functions.Glycosylation is a major post-translational protein modification, especially for cell surface proteins, which play important roles in a variety of cellular functions including recognition and adhesion. In the last decade, a number of glycosyltransferase genes and related genes have been cloned. Targeted deletion of these genes revealed the roles of cell surface glycans in the modulation of cellular interactions, particularly in the immune system (1, 2). We have been interested in the roles of a neuralspecific carbohydrate, the HNK-1 carbohydrate, which is expressed on glycoproteins as well as on glycolipids and is postulated to be associated with cell adhesion, migration, and neurite outgrowth (3-5). The epitope is a sulfated trisaccharide, HSO 3 -3GlcA␤1-3Gal␤1-4GlcNAc (6, 7), and the inner structure, Gal␤1-4GlcNAc, is commonly found on various glycoproteins and glycolipids. To elucidate the roles of the HNK-1 carbohydrate more clearly, we cloned two different glucuronyltransferases (GlcAT-P and GlcAT-S) 1 (8 -11), which are key enzymes in the biosynthesis of the HNK-1 carbohydrate epitope (12,13). In this study, we generated mice with a targeted deletion of the GlcAT-P gene and demonstrated clearly that the HNK-1 carbohydrate is in fact required for higher functions of the brain. EXPERIMENTAL PROCEDURESTargeted Disruption of the GlcAT-P Gene-Cloning of the genomic clones of the 129/Sv mouse GlcAT-P gene was described previously (10). Construction of the targeting vector is schematically represented in Fig. 1A. The neomycin resistance gene cassette in vector pPGKneobpA (14) and diphtheria toxin A (DT-A) gene cassette in vector pMC1DT-A (15) were used as positive and a negative selection markers, respectively. The targeting vector was transfected into E14-1 embryonic stem (ES) cells (16) by electroporation. Two ES clones among 525 tested revealed the desired homologous recombination (13C-2 and 22D-5). To generate chimeric mice, both clones were aggregated with C57BL/6 ϫ BDF1 8-cell-stage embryos, and the embryos were transferred into the uteri of pseudopregnant mice. Both clones gave rise to germline chimeras. Mice heterozygous for the mutation were obtained by cross-breeding of the chimeras with C57BL/6 mice. The heterozygotes were further backcrossed with C57BL/6 mice for more than eight generations, and the resulting heterozygous mutants were interbred ...

Diagnosis and fine mapping of a deletion in distal 11q in two Chinese patients with developmental delay

“…The smallest critical region (6.8 Mb) that they found extended from D11S1351 (127.5 Mb) to the telomere, and this region was associated with MR. 3 B3GAT1 is expressed in the brain, and this gene is located in the 11q25 at 133.77 Mb. Yamamoto et al 17 reported that when this gene was knocked out, the mice showed impaired synaptic plasticity and learning disorders. Coldren et al have reported two critical regions containing candidate genes for global and selective deficits in neurocognitive function 'BSX for global cognitive function and Neurogranin, a gene essential for synapse plasticity and long-term potentiation, for auditory attention' .…”

A novel β1,3‐N‐acetylglucosaminyltransferase (β3Gn‐T8), which synthesizes poly‐N‐acetyllactosamine, is dramatically upregulated in colon cancer

“…Polylactosamine is often modified to carry important carbohydrate structures such as Lewis-related antigens [12][13][14][15], HNK-1 antigen [16], etc., and has many major roles in physiological functions.…”

Specific Enzyme Complex of β-1,4-Galactosyltransferase-II and Glucuronyltransferase-P Facilitates Biosynthesis of N-linked Human Natural Killer-1 (HNK-1) Carbohydrate

“…HNK-1 carbohydrate has an important role in synaptic plasticity and spine morphogenesis in the nervous system (14,15). These functions are based on its specific expression on certain carriers such as NCAM and GluR2, which is a subunit of the ␣-amino-3-hydroxy-5-methylisoxazole propionate-type glutamate receptor.…”

“…HNK-1 carbohydrate has a unique structure, including a sulfated trisaccharide (HSO 3 -3GlcA␤1-3Gal␤1-4GlcNAc-) (9,10), and is biosynthesized by the successive actions of ␤-1,4-galactosyltransferase (␤4GalT), a glucuronyltransferase (GlcAT-P or GlcAT-S), and a sulfotransferase (HNK-1ST) (11)(12)(13). We previously generated mice lacking the gene for GlcAT-P, a major glucuronyltransferase in the nervous system (14). The GlcAT-P-deficient mice showed an almost complete loss of HNK-1 expression in the brain and exhibited reduced long term potentiation at hippocampal CA1 synapses along with impaired maturation of dendritic spines, indicating an important role for this glycan in synaptic plasticity (14,15).…”

“…We previously generated mice lacking the gene for GlcAT-P, a major glucuronyltransferase in the nervous system (14). The GlcAT-P-deficient mice showed an almost complete loss of HNK-1 expression in the brain and exhibited reduced long term potentiation at hippocampal CA1 synapses along with impaired maturation of dendritic spines, indicating an important role for this glycan in synaptic plasticity (14,15). In terms of the expression, we have been uncovering well controlled mechanisms of HNK-1 biosynthesis.…”