Although aortic lesions that arise in the AngII-infused ApoE−/− mouse do not phenocopy human dissections in many regards – they occur in the abdominal, not thoracic, aorta near major branch sites, they occur at the interface between the media and adventitia rather than within the media, they do not result from a connective tissue disorder, and they do not appear to involve focal accumulations of glycosaminoglycans – they nevertheless represent an important model for study. The gene discussed is APOE; the disease is connective tissue disorder.