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Non-coding sequence variants define a novel regulatory element in the first intron of the N-acetylglutamate synthase gene.
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  • Johannes Häberle,
  • Barry Moore,
  • Nantaporn Haskins,
  • Véronique Rüfenacht,
  • Dariusz Rokicki,
  • M. Estela Rubio Gozalbo,
  • Mendel Tuchman,
  • Nicola Longo,
  • Mark Yandell,
  • Ashley Andrews,
  • Nicholas AhMew,
  • Ljubica Caldovic
Johannes Häberle
University Children's Hospital, Zurich
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Barry Moore
The University of Utah School of Medicine
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Nantaporn Haskins
Children's National Medical Center
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Véronique Rüfenacht
University Children's Hospital, Zurich
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Dariusz Rokicki
The Children's Memorial Health Institute,
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M. Estela Rubio Gozalbo
Maastricht University Medical Center
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Mendel Tuchman
Children's National Medical Center
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Nicola Longo
University of Utah
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Mark Yandell
Univ of Utah
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Ashley Andrews
University of Utah
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Nicholas AhMew
Children's National Medical Center
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Ljubica Caldovic
Children's National Medical Center
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Abstract

N-acetylglutamate synthase deficiency (NAGSD, MIM #237310) is an autosomal recessive urea cycle disorder caused either by decreased expression of the NAGS gene or defective NAGS enzyme resulting in decreased production of N-acetylglutamate (NAG), an allosteric activator of carbamylphosphate synthetase 1 (CPS1). NAGSD is the only urea cycle disorder that can be effectively treated with a single drug, N-carbamylglutamate (NCG), a stable NAG analog, which activates CPS1 to restore ureagenesis. We describe three patients with NAGSD due to four novel sequence variants in the NAGS regulatory regions. All three patients had hyperammonemia that resolved upon treatment with NCG. Sequence variants NM_153006.2:c.-3065A>C and NM_153006.2:c-3098C>T reside in the NAGS enhancer, within known HNF1 and predicted glucocorticoid receptor binding sites, respectively. Sequence variants NM_153006.2:c.426+326G>A and NM_153006.2:c.427-218A>C reside in the first intron of NAGS and define a novel NAGS regulatory element that binds retinoic X receptor α. Reporter gene assays in HepG2 and HuH-7 cells demonstrated that all four substitutions could result in reduced expression of NAGS. These findings show that analyzing non-coding regions of NAGS and other urea cycle genes can reveal molecular causes of disease and identify novel regulators of ureagenesis.

Peer review status:IN REVISION

19 Apr 2021Submitted to Human Mutation
21 Apr 2021Assigned to Editor
21 Apr 2021Submission Checks Completed
02 May 2021Reviewer(s) Assigned
20 May 2021Review(s) Completed, Editorial Evaluation Pending
25 May 2021Editorial Decision: Revise Minor