Intracranial saccular (berry) aneurysms (IAs) are small berry or balloon-like defects in the wall of a major intracranial artery. The rate of mortaliy in affected patients is high; survivors will recover with major disability. In recent years, Genome Wide Association Studies have successfully identified novel genes associated with IAs. However, the population attributable risk of those novel genes remains quite small. To identify additional genes responsible for IA development, we collaborated with Dr. Joseph Broderick, Chief of Neurology at the University of Cincinnati to perform a Familial Intracranial Aneurysm Study utilizing advanced technology whole exome sequencing (WES) to identify single nucleotide polymorphisms associated with IA susceptibility in human patients. Among the top genes in the prioritized gene-list, our preliminary data show that knockdown of 4 independent genes (COL22A1, PKD1, HSPG2 and FASTKD3) by morpholino mediated gene knockdown each show hemorrhages in zebrafish embryos. Since the transparent embryos are advantageous for the evaluation of vascular development and stroke, we propose to use the zebrafish embryos to determine if the 4 candidate genes found in patient tissues in the WES study are associated with aneurysms. Our study also focuses on providing tangible insights into the protein function of the variants and their relevance to the IA disease pathology. We hypothesize that defects in the protein products of the 4 variants perturb vascular integrity and result in hemorrhages in zebrafish embryos. This will be accomplished by examining the impacts of the mutant variants on the characteristics of vascular development and integrity. To achieve the goals, we will generate loss of functional mutants targeting each of the variants to test for any phenotypic defects. In addition, we will create transgenic lines that overexpress human wild type and mutant variants to determine the effect of the human mutants on the protein function. These analyses will contribute to our understanding genetic causes of aneurysms that will aid screening to identify patients at risk and will enable development of new treatments.
Stroke is the fourth leading cause of death in the United States and the second leading cause of death worldwide. Subarachnoid hemorrhage due to rupture of Intracranial berry aneurysms (IAs) accounts for approximately 7% of stroke cases but they have high rates of mortality. Individuals at any age including infants and young children can get affected by IAs and die mostly due to limited treatment options and poor prognosis. Here, we propose to examine additional genes obtained from the Whole Exome Sequencing study to determine if they are causative of aneurysms in zebrafish embryos and further propose to establish zebrafish as a model to study aneurysms.
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