title: Identification and characterization of a missense mutation in theO-linked β-N-acetylglucosamine (O-GlcNAc) transferase gene that segregates with X-linked intellectual disability.
abstract: O-GlcNAc is a regulatory post-translational modification of nucleocytoplasmic proteins that has been implicated in multiple biological processes, including transcription. In humans, single genes encode enzymes for its attachment (O-GlcNAc transferase (OGT)) and removal (O-GlcNAcase (OGA)). An X-chromosome exome screen identified a missense mutation, which encodes an amino acid in the tetratricopeptide repeat, inOGT(759G>T (p.L254F)) that segregates with X-linked intellectual disability (XLID) in an affected family. A decrease in steady-state OGT protein levels was observed in isolated lymphoblastoid cell lines from affected individuals, consistent with molecular modeling experiments. Recombinant expression of L254F-OGT demonstrated that the enzyme is active as both a glycosyltransferase and an HCF-1 protease. Despite the reduction in OGT levels seen in the L254F-OGT individual cells, we observed that steady-state globalO-GlcNAc levels remained grossly unaltered. Surprisingly, lymphoblastoids from affected individuals displayed a marked decrease in steady-state OGA protein and mRNA levels. We observed an enrichment of the OGT-containing transcriptional repressor complex mSin3A-HDAC1 at the proximal promoter region ofOGAand correspondingly decreasedOGApromoter activity in affected cells. Global transcriptome analysis of L254F-OGT lymphoblastoids compared with controls revealed a small subset of genes that are differentially expressed. Thus, we have begun to unravel the molecular consequences of the 759G>T (p.L254F) mutation inOGTthat uncovered a compensation mechanism, albeit imperfect, given the phenotype of affected individuals, to maintain steady-stateO-GlcNAc levels. Thus, a single amino acid substitution in the regulatory domain (the tetratricopeptide repeat domain) of OGT, which catalyzes theO-GlcNAc post-translational modification of nuclear and cytosolic proteins, appears causal for XLID.
authors.affiliation: From the Department of Biochemistry and Molecular Biology, Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia 30602.
authors.forename: Krithika
authors.initials: K
authors.lastname: Vaidyanathan
authors.affiliation: the McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University, Baltimore, Maryland 21287.
authors.forename: Tejasvi
authors.initials: T
authors.lastname: Niranjan
authors.affiliation: From the Department of Biochemistry and Molecular Biology, Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia 30602.
authors.forename: Nithya
authors.initials: N
authors.lastname: Selvan
authors.affiliation: From the Department of Biochemistry and Molecular Biology, Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia 30602.
authors.forename: Chin Fen
authors.initials: CF
authors.lastname: Teo
authors.affiliation: the Greenwood Genetic Center, Greenwood, South Carolina 29646.
authors.forename: Melanie
authors.initials: M
authors.lastname: May
authors.affiliation: From the Department of Biochemistry and Molecular Biology, Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia 30602.
authors.forename: Sneha
authors.initials: S
authors.lastname: Patel
authors.affiliation: From the Department of Biochemistry and Molecular Biology, Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia 30602.
authors.forename: Brent
authors.initials: B
authors.lastname: Weatherly
authors.affiliation: the Greenwood Genetic Center, Greenwood, South Carolina 29646.
authors.forename: Cindy
authors.initials: C
authors.lastname: Skinner
authors.affiliation: Pediatrics (Medical Genetics), Pediatric Pathology, Human Genetics, Obstetrics, and Gynecology, University of Utah School of Medicine, Salt Lake City, Utah 84132.
authors.forename: John
authors.initials: J
authors.lastname: Opitz
authors.affiliation: Pediatrics (Medical Genetics), Pediatric Pathology, Human Genetics, Obstetrics, and Gynecology, University of Utah School of Medicine, Salt Lake City, Utah 84132.
authors.forename: John
authors.initials: J
authors.lastname: Carey
authors.affiliation: Pediatrics (Medical Genetics), Pediatric Pathology, Human Genetics, Obstetrics, and Gynecology, University of Utah School of Medicine, Salt Lake City, Utah 84132.
authors.forename: David
authors.initials: D
authors.lastname: Viskochil
authors.affiliation: the Department of Paediatrics and Robinson Research Institute, University of Adelaide, Adelaide, South Australia 5006, Australia, and.
authors.forename: Jozef
authors.initials: J
authors.lastname: Gecz
authors.affiliation: the Department of Paediatrics and Robinson Research Institute, University of Adelaide, Adelaide, South Australia 5006, Australia, and.
authors.forename: Marie
authors.initials: M
authors.lastname: Shaw
authors.affiliation: the Department of Computational Biophysics and Bioinformatics, Clemson University, Clemson, South Carolina 29634.
authors.forename: Yunhui
authors.initials: Y
authors.lastname: Peng
authors.affiliation: the Department of Computational Biophysics and Bioinformatics, Clemson University, Clemson, South Carolina 29634.
authors.forename: Emil
authors.initials: E
authors.lastname: Alexov
authors.affiliation: the McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University, Baltimore, Maryland 21287.
authors.forename: Tao
authors.initials: T
authors.lastname: Wang
authors.affiliation: the Greenwood Genetic Center, Greenwood, South Carolina 29646, ceschwartz@ggc.org.
authors.forename: Charles
authors.initials: C
authors.lastname: Schwartz
authors.affiliation: From the Department of Biochemistry and Molecular Biology, Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia 30602, lwells@ccrc.uga.edu.
authors.forename: Lance
authors.initials: L
authors.lastname: Wells
mesh_terms: D019943:Amino Acid Substitution; D002461:Cell Line, Transformed; D041321:Chromosomes, Human, X; D015971:Gene Expression Regulation, Enzymologic; D006031:Glycosylation; D006801:Humans; D008297:Male; D038901:X-Linked Intellectual Disability / Q000201:enzymology* / Q000235:genetics / Q000473:pathology; D020125:Mutation, Missense; D017351:N-Acetylglucosaminyltransferases / Q000235:genetics / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics
chemical_list: D012333:RNA, Messenger; D017351:N-Acetylglucosaminyltransferases; C449880:O-GlcNAc transferase