 Another role is maintaining a vascular smooth muscle cells contractile under physiological or pathological stimuli.Since 2003, the European Skeletal Dysplasia Network has used an online system to diagnose cases referred to the network before mutation analysis to study the mutations causing PSACH or MED.COL9A1, COL9A2, COL9A3 are genes coding for collagen type IX, that is a component of hyaline cartilage.