GNAS and craniosynostosis: Previous studies have examined the role of lineage-specific homozygous deletion of Gnas in early mesenchymal progenitors (Gnasfl/fl;Prrx1-CRE) [92] and neural crest cells (Gnasfl/fl;Wnt1-CRE) [93] and concluded that the craniofacial abnormalities associated with Gnas homozygous deletion are secondary to accelerated osteogenesis within the cranium resulting in craniosynostosis, a condition occurring occasionally in PHP1A [2, 10, 60, 93, 94].