ClinVar

Description

The p.G420S pathogenic mutation (also known as c.1258G>A), located in coding exon 18 of the COL3A1 gene, results from a G to A substitution at nucleotide position 1258. The glycine at codon 420 is replaced by serine, an amino acid with similar properties. The majority (approximately two-thirds) of COL3A1 mutations identified to date have involved the substitution of another amino acid for glycine within the triple-helical domain (Pepin MG et al. Genet Med. 2014;16(12):881-8; Frank M et al. Eur J Hum Genet. 2015;23(12):1657-64). This particular glycine substitution has been detected in multiple individuals with features consistent with COL3A1-related Ehlers-Danlos syndrome (vascular EDS) (Pickup MJ et al. Forensic Sci Med Pathol, 2011 Jun;7:192-7; Wang K et al. J Hum Genet, 2018 Nov;63:1119-1128; Bowen JM et al. Eur J Hum Genet, 2023 Jul;31:749-760; Buso G et al. Vasc Med, 2023 Dec; 1358863X231215330; external communication; Ambry internal data). Internal structural analysis has demonstrated that this alteration disrupts the characteristic G-X-Y motif in the COL3A1 protein and inserts a bulky side chain into a sterically-constrained region (Bella J et al. Science. 1994;266:75-81; Hohenester E et al. Proc. Natl. Acad. Sci. U.S.A. 2008;105:18273-7; Ambry internal data). This amino acid position is highly conserved in available vertebrate species. In addition, this alteration is predicted to be deleterious by in silico analysis. This variant is considered to be rare based on population cohorts in the Genome Aggregation Database (gnomAD). Based on the supporting evidence, this variant is interpreted as a disease-causing mutation.