Mechanisms of hyperactive Ras signaling in craniofacial and dental diseases

PROJECT SUMMARY/ABSTRACT The RASopathies comprise one of the largest groups of malformation syndromes known, affect >1:1000 individ- uals and cause significant morbidity and mortality. These syndromes are caused by germline mutations in ~20 key genes encoding proteins that belong to or regulate the Ras/MAPK signaling pathway. Prior work from our group and others reported a high prevalence of craniofacial and dental malformations in RASopathy patients, which we have begun to investigate through preliminary studies in mouse models, but the mechanisms by which Ras/MAPK dysregulation disrupts cranial bone and dental formation are not understood, limiting our ability to diagnose, treat and prevent these birth defects. Here, we will combine comparative morphometrics in human patients, together with transcriptomic, proteomic, and functional experiments in mouse models and human pa- tient-derived induced pluripotent stem cells to dissect the molecular and cellular mechanisms by which these Ras/MAPK deregulating mutations cause abnormal enamel formation and craniofacial development. In Aim 1, we will determine how Ras signaling dysregulation causes dental defects and enamel malformations at the cel- lular and transcriptomic levels. In Aim 2, we will test our hypothesis that variations in face shape in RASopathies are the result of developmental alterations in the cranial base through functional and transcriptomic analyses. In Aim 3, we will establish how RASopathy mutations impact signaling in the craniofacial and dental contexts and test the specific hypothesis that negative feedback regulators of the Ras/MAPK signaling pathway contribute to craniofacial and dental abnormalities in RASopathies. Together, these experiments will systematically elucidate mechanisms that underpin the craniofacial and dental birth defects in RASopathies and provide us with the foundation to move towards improving early diagnosis and therapeutic interventions.