TWIST1 and Cowden syndrome 1: Osteoblasts and progenitor cells derived from both leporine and human patients with craniosynostotic diseases exhibit increased osteogenic potential in culture.[3], [4], [5] At the genetic level, mutations in at least seven genes (FGFR1, FGFR2, FGFR3, TWIST1, EFNB1, MSX2 and RAB23) result in enhanced ossification of the sutures in CS patients.[6] Most of these genes harbor gain-of-function mutations, while mutations in TWIST, an upstream repressor of FGFR (fibroblast growth factor receptor) genes, induces loss of function leading to constitutive overexpression of these genes.