This involves both canonical (SMAD2/3) and non-canonical downstream signaling pathways, as demonstrated by several knockout mouse models of MMVD, including the Fbn-1 (fibrillin-1; Marfan syndrome), FLN-A (filamin-A X-linked), and Fstl1 (follistatin) mouse models (23–25). The gene discussed is FBN1; the disease is Marfan syndrome.