PRG4 and dentin dysplasia: Some collagen genes show higher transcript levels in DD cord or nodal tissue [28], [29], [31], [32], [35] while other genes that have been implicated in DD include ADAMT (A disintergrin and metalloproteinase with thrombospondin motifs) genes [33], [34], [36], proteoglycans 4 (PRG4), A disintegrin and metalloproteinase domain 12 (ADAM12), fibulin-1 (FBLN1), and tenascin C (TNC) genes [36], [37].