Fig. 2

An illustration of COL9A3 protein structure, Pathogenic variants, Sequence alignment among multiple species and Prediction results of COL9A3 missense variant (c.1150C > T, p.Arg384Trp). A The identified COL9A3 variant (c.1150C > T, p.Arg384Trp, Red) locates within the third collagenous region, resulting in the substitution of arginine (Arg) with tryptophan (Trp) in the amino acid sequence. Previously identified variant (p.Arg103Trp) were marked in black. B Multiple species sequence alignment using MEGA11 software shows that this variant is highly conserved among common species. C Protein structure predicted by Swiss-Model reveals an altered protein structure and a charge property change by the replacement of 384th Arg residue. The 384th amino acid is mutated from a basic amino acid (Arg, Blue) to an aromatic hydrophobic amino acid (Trp, White). D The I-Mutant v2.0 software reveals that the variant can result in decreased COL9A3 protein stability at optimal pH and temperature. SP: Signal peptide; TC: Triple-helical collagenous region; NC: Non-helical collagenous region; WT: Amino acid in Wild-Type Protein; NEW: New Amino acid with the variant; RI: Reliability Index; pH: − log [H+]; T: Temperature in Celsius degrees.