DUSP6 and Apert syndrome: The Dusp6 expression domain thus grew disproportionately in the limbs of Fgfr2+/P253R mutant mice in the latest period of development (Figure 5E), which is consistent with reports of whole-body size reduction in Fgfr2+/P253R Apert mice and of the over-activation of Fgfr2 signaling by the Apert syndrome mutation (Yu and Ornitz, 2001; Ibrahimi et al., 2001).