%0 Journal Article
%T GGCX variants leading to biallelic deficiency to γ-carboxylate GRP cause skin laxity in VKCFD1 patients.
%A Ghosh S
%A Kraus K
%A Biswas A
%A Müller J
%A Forin F
%A Singer H
%A Höning K
%A Hornung V
%A Watzka M
%A Oldenburg J
%A Czogalla-Nitsche KJ
%J Hum Mutat
%V 0
%N 0
%D Nov 2021 24
%M 34816548
%F 4.7
%R 10.1002/humu.24300
%X γ-Glutamyl carboxylase (GGCX) catalyzes the 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-hemorrhagic phenotypes remain elusive. Therefore, we have analyzed 20 pathogenic GGCX variants on their ability to γ-carboxylate six non-hemostatic VKD proteins in an in vitro assay, where GGCX variants were expressed in GGCX-/- cells and levels of γ-carboxylated co-expressed VKD proteins were detected by a functional ELISA. We observed that GGCX variants causing markedly reduced γ-carboxylation of Gla rich protein (GRP) in vitro were reported in patients with skin laxity. Reduced levels of γ-carboxylated Matrix gla protein (MGP) are not exclusive for causing skeletal dysmorphologies in VKCFD1 patients. In silico docking of vitamin K hydroquinone on a GGCX model revealed a binding site, which was validated by in vitro assays. GGCX variants affecting this site result in disability to γ-carboxylate VKD proteins and hence are involved in the most severe phenotypes. This genotype-phenotype analysis will help to understand the development of non-hemorrhagic phenotypes and hence improve treatment in VKCFD1 patients.