(1) Background: Whole Exome Sequencing of patients with thoracic aortic aneurysm often identifies “Variants of Uncertain Significance” (VUS), leading to uncertainty in clinical management. We assess a novel mechanism for potential routine assessment of these genes in TAA patients. Zebrafish are increasingly used as experimental models of disease. Advantages include low cost, rapid maturation, and physical transparency, permitting direct microscopic assessment. (2) Methods: Zebrafish loss of function mutations were generated using a CRISPRC/CAS9 approach for EMILIN1 and MIB1 genes similar to VUSs identified in clinical testing. Additionally, “positive control” mutants were constructed for known deleterious variants in FBN1 (Marfan’s) and COL1A2, COL5A1, COL5A2 (Ehlers-Danlos). Zebrafish embryos were followed to six days post-fertilization. Embryos were studied by brightfield and confocal microscopy to ascertain any vascular, cardiac, and skeletal abnormalities. (3) Results: A dramatic pattern of cardiac, cerebral, aortic, and skeletal abnormalities was identified for the known pathogenic FBN1 and COL1A2, COL5A1, and COL5A2 mutants, as well as for the EMILIN1 and MIB1 mutants of prior unknown significance. Visualized abnormalities included hemorrhage (peri-aortic and cranial), cardiomegaly, reduced diameter of the aorta and intersegmental vessels, lower aortic cell counts, and scoliosis (often extremely severe). (4) Conclusion: This pilot study suggests that candidate genes arising in clinical practice may be rapidly assessed via zebrafish mutants—thus permitting evidence-based decisions about pathogenicity. Thus, years-long delays to clinically demonstrate pathogenicity may be obviated. Zebrafish data would represent only one segment of analysis, which would also include frequency of the variant in the general population, in silico genetic analysis, and degree of preservation in phylogeny.

Marfan syndrome (MFS) is a hereditary disorder with numerous pathophysiological effects, some specifically creating elastic dysfunction in cardiovascular organs. Aortic dilatation, dissection and rupture are major concerns in the management of MFS patients. Predilection to form aneurysms is an indication for prophylactic medical management of thoracic aortic aneurysm disease in these patients. The current guidelines describe β-blockers as the standard of care with angiotensin receptor blockers (ARBs) emerging as an equal, if not better alternative. We elaborate current evidence for and against different medical regimens used for the medical management of MFS patients.

Since 1994, when a small 70-patient study seemed to demonstrate that β-blocker treatment could help prevent aortic aneurysms in patients with Marfan syndrome, β-adrenergic-blocking drugs have been increasingly believed to reduce the progression of aortic aneurysms in the general population with aortic disease. This literature review examines the scientific evidence of this treatment and questions whether β-blocker treatment for aortic aneurysms should continue to be uniformly recommended. Five separate clinical trials studying the effects of β-blockade therapy in patients with Marfan syndrome are analyzed, in addition to four other clinical trials studying the effects of β-blockade therapy in patients without Marfan syndrome. The analysis suggests that the scientific evidence for β-blocker treatment is unconvincing, because β-blockade therapy fails to consistently reduce aortic aneurysm growth in patients with or without Marfan syndrome. It is alarmingly clear that prospective, multicenter clinical trials are greatly needed to test the efficacy of this now conventional therapy in a more robust scientific fashion.

Background: ACTA2 encodes smooth muscle alpha-actin and is one of the most common genetic causes of inherited non-syndromic thoracic aortic aneurysm and dissection. Although murine models have provided important mechanistic insight, complementary vertebrate systems may enable more rapid in vivo phenotyping and future therapeutic screening. Methods: Utilizing a CRISPR/Cas9-based approach, we developed zebrafish acta2 mutant models and assessed phenotypes at larval and adult stages. At 3 days post-fertilization, larvae were screened by brightfield microscopy for edema, axis defects, hemorrhage, and a composite endpoint (any phenotype) under basal conditions and after exposure to 0.2 mM epinephrine. Phenotype occurrence was summarized as group-specific proportions across a 2 × 2 design defined by genotype (wild-type vs. acta2-deficient mutant) and treatment (DMSO control vs. epinephrine), with prespecified pairwise comparisons using Pearson’s chi-squared tests. Pooled fish-level logistic regression models were also fit for each endpoint. Adult follow-up was performed by genotyping all available acta2 fish at the facility and tracking staggered tank-level cohorts longitudinally. Results: Initial gross morphologic assessment did not reveal overt external phenotypic differences between heterozygous or homozygous acta2 mutant larvae and wild-type controls. In larval analyses, the mutant genotype was associated with a greater burden of adverse phenotypes than treatment exposure. For the composite endpoint, mutant larvae demonstrated higher proportions than normal larvae under both control (28.3% vs. 17.4%, p = 0.007) and epinephrine conditions (26.9% vs. 17.4%, p = 0.023), whereas epinephrine did not significantly alter composite phenotype frequency within either genotype. Similar genotype-associated trends were observed for axis defects and hemorrhage. In pooled logistic regression, acta2 deficiency was associated with increased odds of axis defects (OR 2.64, 95% CI 1.48–4.89, p = 0.001), hemorrhage (OR 2.40, 95% CI 1.09–5.68, p = 0.036), and the composite endpoint (OR 1.88, 95% CI 1.19–3.00, p = 0.008), whereas epinephrine exposure did not demonstrate a consistent independent effect across endpoints. Adult staggered follow-up showed greater attrition in homozygous mutant cohorts than in wild-type or heterozygous cohorts, with aggregated losses of 24%, 12%, and 3%, respectively. Conclusions: This preliminary zebrafish acta2 model demonstrated that acta2 deficiency is associated with increased adverse larval phenotype burden and suggested reduced long-term persistence of homozygous mutant fish in adulthood. The strongest signal in the current study was genotype-associated phenotype burden rather than a robust epinephrine-dependent effect. These findings support the feasibility of zebrafish-based ACTA2 phenotyping while highlighting the need for more specific vascular endpoints, refined longitudinal follow-up, and future variant-specific modeling.