Identification and characterization of a missense mutation in theO-linked β-N-acetylglucosamine (O-GlcNAc) transferase gene that segregates with X-linked intellectual disability

Vaidyanathan, Krithika; Niranjan, Tejasvi; Selvan, Nithya; Teo, Chin Fen; May, Melanie; Patel, Sneha; Weatherly, Brent; Skinner, Cindy; Opitz, John; Carey, John; Viskochil, David; Gecz, Jozef; Shaw, Marie; Peng, Yunhui; Alexov, Emil; Wang, Tao; Schwartz, Charles; Wells, Lance

doi:10.1074/JBC.M116.771030

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

Author

Vaidyanathan, Krithika

Niranjan, Tejasvi

Selvan, Nithya

Teo, Chin Fen

May, Melanie

Patel, Sneha

Weatherly, Brent

Skinner, Cindy

Opitz, John

Carey, John

Viskochil, David

Gecz, Jozef

Shaw, Marie

Peng, Yunhui

Alexov, Emil

Wang, Tao

Schwartz, Charles

Wells, Lance

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, in OGT (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 global O-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 of OGA and correspondingly decreased OGA promoter 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 in OGT that uncovered a compensation mechanism, albeit imperfect, given the phenotype of affected individuals, to maintain steady-state O-GlcNAc levels. Thus, a single amino acid substitution in the regulatory domain (the tetratricopeptide repeat domain) of OGT, which catalyzes the O-GlcNAc post-translational modification of nuclear and cytosolic proteins, appears causal for XLID.

Language

English

Source (journal)

Journal of biological chemistry. - Baltimore, Md

Publication

Baltimore, Md : 2017

ISSN

0021-9258 [print]

1083-351X [online]

DOI

10.1074/JBC.M116.771030

Volume/pages