The pathogenic potential of the TBX5 gene variants
The analysis of results using the PolyPhen-2 software based on HumDiv and HumVar database displayed that D111Y and A210G are deleterious mutations (probably damaging) while L15Q mutation is benign (Table 3). A mutation is found to be probably damaging if the PolyPhen value exceeds 0.908, possibly damaging if between 0.446 and 0.908 and benign if less than or equal to 0.446 (Table 3 and Figure 3).

The D111Y mutation

The D111Y mutation located in exon 4 of TBX5 gene and the T-box conserved area of its protein. Here, structural stability prediction showed that D111Y mutation decreases protein stability as well as PolyPhen-2 analysis revealed its pathogenicity (Table 3 and Figure 3). This mutation in this study is found with a large defect in the heart septal (large VASD) and patent ductus arteriosus (PDA). DynaMut analysis showed this mutation can effect interatomic interactions of the D111Y mutant residue and can result in destabilization and increase protein flexibility (Table 3 and Figure 4 A). Also, Granados-Riveron et al was discovered this mutation in a patient with double outlet right ventricle, large VASD, and PDA. They by using molecular model of human TBX5 protein free from nucleic acid based on PDB file 2X6U showed that there is salt bridge between the D111 and the K126 residues. The D111Y change disrupts the this salt bridge, as the negatively charged aspartic acid (D) residue is replaced by an uncharged tyrosine residue (9).