Another observation that adds to the complexity of the exact role of TGF-β in aneurysm formation was described by MacFarlane et al. In their study, they found that the effect of the Tgfbr1 mutation, and subsequent disturbance in TGF-β signaling in the Tgfbr1M318R/+ LDS mouse model, varies between VSMCs that are derived from distinct lineages of origin. The gene discussed is TGFB1; the disease is aneurysm.