Advances in molecular genetics have exacerbated the growing gap between clinical and basic genetics. A great deal of informative data is being generated through the exome and genome sequencing of patients with suspected genetic syndromes. However, without functional follow through or application in basic science labs, much of these data are wasted. Working to bridge the artificial divide between human mutations and basic developmental biology has the potential to significantly advance both disciplines. Informative patients can provide insight into new genes and variants that lead to structural birth defects, and expose novel pathways of normal and abnormal human development. Functional analysis of variants of uncertain significance generated by clinical testing can be the key to proving or disproving their pathogenicity. In this study we combine the unique training and resources of a medical geneticist with specialty training in pediatrics, clinical genetics, and molecular genetics (Bhoj), with the novel techniques and skills of a highly successful basic developmental biology researcher (Burdine). The foci of this collaboration are RASopathy spectrum syndromes, Noonan syndrome and related disorders. RASopathies are one of the leading single-gene causes of congenital cardiac and craniofacial malformations, and the genes involved have important roles in neurodevelopment, cancer predisposition, and cardiomyopathy. Despite their vital role in both the clinic and laboratory, about one third of patients with a clinical diagnosis of a RASopathy disorder have no mutations in known genes. There is a wealth of knowledge in gene discovery in these patients, functional analysis of new variants in known genes, and application of that knowledge to developmental biology. Our hypothesis is that sequencing of a highly informative patient cohort will lead to the discovery of novel RASopathy genes, and variants in these genes can be rapidly interrogated through a zebrafish system, which will lead to insights into basic developmental biology and the significance of clinical gene variants. We will utilize the infrastructure in place at the Children's Hospital of Philadelphia (CHOP) to perform exome sequencing on selected cohort of patients that have both craniofacial and heart defects, hallmarks of RASopathies. Indeed, two causative RASopathy genes, PPP1CB and RRAS2, have been identified with this approach by Dr. Bhoj and colleagues. Dr. Burdine's group at Princeton University have experience modeling RASoapthies in the zebrafish, and will use this expertise to evaluate any variants in known and new RASoapthy genes identified by Dr. Bhoj's group. By utilizing the recent advances in homologous recombination in zebrafish, new models will be generated to further explore the underlying biology of craniofacial and heart defects cause by identified genes. The researchers will meet frequently, and have developed a collaborative plan to enhance each other's knowledge base and develop additional collaborations between CHOP and Princeton University. At the end of the project period, we anticipate having generated sufficient preliminary data to support a joint R01 application to further these studies.
RASopathy mutations are one of the leading single-gene causes of congenital cardiac and craniofacial malformations, and have important roles in neurodevelopment, cancer predisposition, and cardiomyopathy. This collaborative project will identify mutations causative of RASopathy syndromes in previously undiagnosed patients, and will utilize the zebrafish to determine the significance of identified variants and develop models for further investigation of the biology underlying associated structural birth defects.
