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Mol Genet Metab. 2015 Nov;116(3):178-86. doi: 10.1016/j.ymgme.2015.08.007. Epub 2015 Aug 14.

Asparagine Synthetase Deficiency causes reduced proliferation of cells under conditions of limited asparagine.

Author information

1
Sydney Children's Hospital, High Street Randwick NSW 2031, Australia; University of New South Wales, High Street, Sydney, NSW 2052, Australia; Genetics of Learning Disability (GOLD) service, Corner of Turton and Tinonee Roads, Waratah NSW 2298.
2
Department of Biochemistry & Molecular Biology, University of Florida College of Medicine, 1200 Newell Drive, Florida, USA, 32608.
3
Sydney Children's Hospital, High Street Randwick NSW 2031, Australia; University of New South Wales, High Street, Sydney, NSW 2052, Australia.
4
Kinghorn Centre for Clinical Genomics, Garvan Institute of Medical Research, 384 Victoria Street, Darlinghurst, Sydney, NSW 2010, Australia.
5
Genetics of Learning Disability (GOLD) service, Corner of Turton and Tinonee Roads, Waratah NSW 2298.
6
Sydney Children's Hospital, High Street Randwick NSW 2031, Australia.
7
Kinghorn Centre for Clinical Genomics, Garvan Institute of Medical Research, 384 Victoria Street, Darlinghurst, Sydney, NSW 2010, Australia; St Vincent's Clinical School, University of New South Wales, 390 Victoria Street, Darlinghurst, Sydney, NSW 2010, Australia.
8
University of New South Wales, High Street, Sydney, NSW 2052, Australia; Seals Molecular Genetics, POW Hospital Campus, Barker Street, Randwick, Sydney, NSW 2031, Australia.
9
Sydney Children's Hospital, High Street Randwick NSW 2031, Australia; University of New South Wales, High Street, Sydney, NSW 2052, Australia; Seals Molecular Genetics, POW Hospital Campus, Barker Street, Randwick, Sydney, NSW 2031, Australia.
10
Sydney Children's Hospital, High Street Randwick NSW 2031, Australia; University of New South Wales, High Street, Sydney, NSW 2052, Australia; Seals Molecular Genetics, POW Hospital Campus, Barker Street, Randwick, Sydney, NSW 2031, Australia. Electronic address: e.kirk@unsw.edu.au.

Abstract

Asparagine Synthetase Deficiency is a recently described cause of profound intellectual disability, marked progressive cerebral atrophy and variable seizure disorder. To date there has been limited functional data explaining the underlying pathophysiology. We report a new case with compound heterozygous mutations in the ASNS gene (NM_183356.3:c. [866G>C]; [1010C>T]). Both variants alter evolutionarily conserved amino acids and were predicted to be pathogenic based on in silico protein modelling that suggests disruption of the critical ATP binding site of the ASNS enzyme. In patient fibroblasts, ASNS expression as well as protein and mRNA stability are not affected by these variants. However, there is markedly reduced proliferation of patient fibroblasts when cultured in asparagine-limited growth medium, compared to parental and wild type fibroblasts. Restricting asparagine replicates the physiology within the blood-brain-barrier, with limited transfer of dietary derived asparagine, resulting in reliance of neuronal cells on intracellular asparagine synthesis by the ASNS enzyme. These functional studies offer insight into the underlying pathophysiology of the dramatic progressive cerebral atrophy associated with Asparagine Synthetase Deficiency.

KEYWORDS:

ATP binding; Asparagine; Epileptic encephalopathy; Exome sequencing; Intellectual disability

PMID:
26318253
DOI:
10.1016/j.ymgme.2015.08.007
[Indexed for MEDLINE]

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