According to this scenario, our data suggest that PC1 has a protective role in craniosynostosis, negatively regulating ERK and RUNX2 activation and consequently cranial suture cell differentiation; by hindering this function via IgPKD1, other positive intracellular signals take over and instigate ERK signalling, RUNX2 activation and finally cranial suture cell differentiation which promotes premature suture fusion. Here, RUNX2 is linked to craniosynostosis.