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GGCX variants leading to biallelic deficiency to γ-carboxylate GRP cause skin laxity in VKCFD1 patients
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  • Suvoshree Ghosh,
  • Katrin Kraus,
  • Arijit Biswas,
  • Jens Müller,
  • Francesco Forin,
  • Heike Singer,
  • Klara Höning,
  • Veit Hornung,
  • Matthias Watzka,
  • Johannes Oldenburg,
  • Katrin Czogalla-Nitsche
Suvoshree Ghosh
University Clinic Bonn

Corresponding Author:suvoshree.ghosh@ukbonn.de

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Katrin Kraus
University Clinic Bonn
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Arijit Biswas
Universitatsklinikum Bonn
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Jens Müller
University Clinic Bonn
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Francesco Forin
University Clinic Bonn
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Heike Singer
University Clinic Bonn
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Klara Höning
University Hospital Bonn
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Veit Hornung
Ludwig Maximilians University Munich
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Matthias Watzka
University Clinic Bonn
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Johannes Oldenburg
University Hospital Bonn Institute for Experimental Hematology and Transfusion Medicine
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Katrin Czogalla-Nitsche
Institute of Experimental Haematology and Transfusionmedicine
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Abstract

γ-Glutamyl carboxylase (GGCX) catalyses γ-carboxylation of 15 different vitamin K dependent (VKD) proteins. Pathogenic variants in GGCX cause a rare hereditary bleeding disorder called Vitamin K dependent coagulation factor deficiency type 1 (VKCFD1). In addition to bleedings, some VKCFD1 patients develop skin laxity and skeletal dysmorphologies. However, the pathophysiological mechanisms underlying these non-haemorrhagic phenotypes remain elusive. Therefore, we analyzed the effect of 22 GGCX pathogenic variants on γ-carboxylation of six non-haemostatic VKD proteins (UCMA/GRP, MGP, BGLAP, GAS6, PRGP1, TMG4) in a GGCX-/- HEK293T cell line by a functional ELISA. We observed that biallelic deficiency to γ-carboxylate Gla-rich protein lead to the development of skin laxity. Markedly reduced level of γ-carboxylated MGP is crucial but not exclusive for causing facial dysmorphologies. Moreover, we identified the vitamin K hydroquinone binding site in GGCX in an in silico model by docking studies, which was further validated by functional assays. Variants affecting this site result into loss-of-function or severely diminished ability to γ-carboxylate VKD proteins and hence are involved in the most severe phenotypes. This genotype-phenotype analysis will help to develop new treatment options for VKCFD1 patients, where individualized therapy with γ-carboxylated VKD proteins may represent a promising strategy.
08 Apr 2021Submitted to Human Mutation
10 Apr 2021Submission Checks Completed
10 Apr 2021Assigned to Editor
22 Apr 2021Reviewer(s) Assigned
11 Jun 2021Review(s) Completed, Editorial Evaluation Pending
15 Jun 2021Editorial Decision: Revise Major
06 Sep 20211st Revision Received
07 Sep 2021Submission Checks Completed
07 Sep 2021Assigned to Editor
20 Sep 2021Reviewer(s) Assigned
15 Oct 2021Review(s) Completed, Editorial Evaluation Pending
20 Oct 2021Editorial Decision: Accept
Jan 2022Published in Human Mutation volume 43 issue 1 on pages 42-55. 10.1002/humu.24300