Figure 6.

Schematic diagram on how different FLNB mutants lead to opposite phenotypes of BD and LS. Supernumerary ossification centers in LS and absence of ossification centers in BD may be resulted from counterbalance in mesenchymal cell apoptosis, mesenchymal cell migration and Runx2 expression. In LS, increased expression of Runx2 may promote the condensation of mesenchymal stem cells, while the decreased cellular migration, together with the promoted condensation, could lead to supernumerary ossification. In BD, though the expression of Runx2 was also increased, the much more increased cellular apoptosis rate might suppress Runx2’s promotion in cellular condensation, and thus lead to decrease or absence of ossification centers. ↑, increase; ↓, decrease; ↑↑, increase with more extent; -, not changed; BD, boomerang dysplasia; LS, Larsen syndrome.