We postulate that DUSP3 promotes the dephosphorylation and consequent deactivation of the MAP kinase JNK1, which causes the nuclear translocation of the transcription factor KLF4, which promotes the phenotypic switch from contractile to synthetic VSMCs, leading to vascular wall thinning and aneurysm formation in the abdominal but not thoracic aorta. Here, KLF4 is linked to aneurysm.