Cerebral Cavernous Malformations Develop Through Clonal Expansion of Mutant Endothelial Cells

Rationale: Vascular malformations arise in vessels throughout the entire body. Causative genetic mutations have been identified for many of these diseases; however, little is known about the mutant cell lineage within these malformations. Objective: We utilize an inducible mouse model of cerebral cavernous malformations (CCMs) coupled with a multicolor fluorescent reporter to visualize the contribution of mutant endothelial cells (ECs) to the malformation. Methods and Results: We combined a Ccm3 mouse model with the confetti fluorescent reporter to simultaneously delete Ccm3 and label the mutant EC with 1 of 4 possible colors. We acquired Z-series confocal images from serial brain sections and created 3-dimensional reconstructions of entire CCMs to visualize mutant ECs during CCM development. We observed a pronounced pattern of CCMs lined with mutant ECs labeled with a single confetti color (n=42). The close 3-dimensional distribution, as determined by the nearest neighbor analysis, of the clonally domina...