Systematic disruption of zebrafish fibrillin genes identifies a translational zebrafish model for Marfan syndrome

BackgroundFibrillins are essential components of the extracellular matrix. Marfan syndrome (MFS), the most common fibrillinopathy, is characterized by severe cardiovascular complications, including cardiac valve abnormalities, myocardial dysfunction, arrhythmias, and, most commonly, thoracic aortic disease. Unfortunately, no definitive medical cure is available. ObjectivesTo establish a zebrafish model of MFS, to enhance understanding of the cardiovascular consequences of fibrillin impairment and identify novel therapeutic targets. MethodsCRISPR/Cas9 technology was used to systematically target all zebrafish fibrillin genes. The cardiovascular phenotype was investigated using fluorescent microscopy at embryonic stages and cardiac ultrasound, histology, and synchrotron X-ray imaging in adults. RNA sequencing and drug testing were performed during early development. ResultsFibrillin-2b mutant (fbn2b-/-) zebrafish had a reproducible phenotype, with a subset of embryos showing endocardial detachment leading to early mortality. Interestingly, the remaining fbn2b-/- zebrafish developed dilation of the bulbus arteriosus, a structure analogous to the aortic root in humans, and survived normally to adulthood. Adult fbn2b-/- zebrafish displayed cardiac valve abnormalities. Transcriptomic analysis of fbn2b-/-embryos suggested the involvement of extracellular matrix remodeling and immune-related pathways. Administration of nebivolol and losartan did not improve the phenotype of fbn2b-/- larvae. Zebrafish lacking fibrillin-1 and/or fibrillin-2a did not show any phenotype. ConclusionOur fbn2b-/- zebrafish model recapitulates key aspects of human cardiovascular manifestations of MFS and can therefore be considered a novel relevant animal model for MFS. Studying this model allows us to broaden the knowledge of the underlying mechanisms of the disease and discover much-needed disease-specific treatment options. CONDENSED ABSTRACTFibrillin defects lead to severe cardiovascular complications in Marfan syndrome (MFS), including aortic dilation, dissection, and rupture. To model MFS, we generated zebrafish mutants lacking various fibrillin genes. Among these mutant lines, only fibrillin-2b-deficient zebrafish exhibited cardiovascular phenotypes mimicking human disease. Multimodal imaging revealed early cardiac defects, bulbus arteriosus dilation, and valve abnormalities. Transcriptomic analysis identified altered regulation of pathways related to extracellular matrix homeostasis and immune system activation. Compound testing demonstrated the models potential for drug discovery. This zebrafish model, recapitulating key cardiovascular features of MFS, provides a valuable platform to investigate disease mechanisms and identify novel treatment strategies.