Mosaic: post-zygotic mutations in vascular malformations

PROJECT SUMMARY Defective morphogenesis of arteries, veins, capillaries, and lymphatic vessels results in vascular malformations, a relatively common congenital malformation. Current therapies are primarily invasive and can produce significant morbidity. Most vascular malformations are due to post-zygotic (mosaic) activating mutations in a few oncogenes (PIK3CA, KRAS, MAP2K1, others) in the PI3K-AKT and RAS-MAPK pathways. These mutations are never present in DNA derived from white blood cells, the most common sample for genetic testing, making molecular diagnosis challenging. Long-term, our goal is to improve treatment of individuals with vascular malformations. The proposed experiments advance that goal by expanding diagnostic options for VM patients and dissecting cellular and spatial heterogeneity in vascular malformations, using novel, cutting edge technologies. Our first aim is to determine if non-invasive “liquid biopsies” of plasma derived cell-free DNA can detect mosaic mutations in individuals with vascular malformations. Since mutations driving vascular malformations are typically present only in the malformation itself, an invasive surgery or biopsy is currently required for diagnosis. Since a molecular diagnosis is required to guide targeted drug therapies (such as PI3K or AKT inhibitors, for which clinical trials are currently open), developing non-invasive diagnostics for vascular malformations would have immediate patient impact. Next, we will study how gene expression changes in single cells in vascular malformation tissues and integrate this information with each cell's mutation status, using a novel, multi-omics method. We will also use techniques that allow us to visualize how gene expression changes in two and three dimensional space within vascular malformations. Since only a small fraction (1-10%) of cells inside vascular malformations typically possess the driving mutation, these experiments will help us understand how small cell populations can produce large, multicellular malformations. We have assembled a multidisciplinary team with non-overlapping areas of expertise to accomplish these goals. Our experiments will be performed using samples from a large, pre-existing biorepository of vascular malformation samples rich in clinical data. We expect this work to expand our understanding of vascular malformations and vascular biology specifically, and the nature of mosaicism more generally.