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Type: Journal article
Title: A recurrent missense variant in SLC9A7 causes nonsyndromic X-linked intellectual disability with alteration of Golgi acidification and aberrant glycosylation
Author: Khayat, W.
Hackett, A.
Shaw, M.
Ilie, A.
Dudding-Byth, T.
Kalscheuer, V.M.
Christie, L.
Corbett, M.A.
Juusola, J.
Friend, K.L.
Kirmse, B.M.
Gecz, J.
Field, M.
Orlowski, J.
Citation: Human Molecular Genetics, 2019; 28(4):598-614
Publisher: Oxford Academic Press
Issue Date: 2019
ISSN: 0964-6906
Statement of
Wujood Khayat, Anna Hackett, Marie Shaw, Alina Ilie, Tracy Dudding-Byth ... Mark A Corbett ... at al.
Abstract: We report two unrelated families with multigenerational nonsyndromic intellectual disability segregating with a recurrent de novo missense variant (c.1543C>T:p.Leu515Phe) in the alkali cation/proton exchanger gene SLC9A7 (also commonly referred to as NHE7). SLC9A7 is located on human X chromosome at Xp11.3 and has not yet been associated with a human phenotype. The gene is widely transcribed, but especially abundant in brain, skeletal muscle and various secretory tissues. Within cells, SLC9A7 resides in the Golgi apparatus, with prominent enrichment in the trans-Golgi network (TGN) and post-Golgi vesicles. In transfected Chinese hamster ovary AP-1 cells, the Leu515Phe mutant protein was correctly targeted to the TGN/post-Golgi vesicles, but its N-linked oligosaccharide maturation as well as that of a co-transfected secretory membrane glycoprotein, vesicular stomatitis virus G (VSVG) glycoprotein, was reduced compared to cells co-expressing SLC9A7 wild-type and VSVG. This correlated with alkalinization of the TGN/post-Golgi compartments, suggestive of a gain-of-function. Membrane trafficking of glycosylation-deficient Leu515Phe and co-transfected VSVG to the cell surface, however, was relatively unaffected. Mass spectrometry analysis of patient sera also revealed an abnormal N-glycosylation profile for transferrin, a clinical diagnostic marker for congenital disorders of glycosylation. These data implicate a crucial role for SLC9A7 in the regulation of TGN/post-Golgi pH homeostasis and glycosylation of exported cargo which may underlie the cellular pathophysiology and neurodevelopmental deficits associated with this particular nonsyndromic form of X-linked intellectual disability.
Keywords: CHO Cells
Cell Membrane
Golgi Apparatus
trans-Golgi Network
Genetic Diseases, X-Linked
Membrane Glycoproteins
Viral Envelope Proteins
Gene Expression Regulation
Protein Transport
Mutation, Missense
Intellectual Disability
Sodium-Hydrogen Exchangers
Rights: © The Author(s) 2018. Published by Oxford University Press. All rights reserved.
DOI: 10.1093/hmg/ddy371
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