FBN2 and systemic sclerosis: Fbn-1-null mice had systemic sclerosis due to abnormal activation of both TGF-β and BMP signalings.231 However, Fbn-2 deficiency in mice induced a low bone mass phenotype due to improper activation of TGF-β inhibiting osterix expression and increasing osteoblast-induced osteoclast formation.231,232 Microfibril-associated glycoprotein-1 (MAGP1) is another constitutive component in microfibril network.233,234Magp1-null mice, resembling Fbn-2-null mice, developed progressive osteopenia due to abnormal activation of TGF-β.233,234