FGFR3 and achondroplasia: It is believed that in achondroplasia, constitutive FGFR3 signaling promotes premature synchondrosis inactivation/ossification in the cranial base by accelerating the transition from cartilage to bone of the skull sutures.(24) To further investigate the mechanism initiating and underlying the premature ossification of the SOS in the Fgfr3ach/+ mice, the matrix content of the cartilaginous stuctures were evaluated by histology at PND3 and PND22 in WT and Fgfr3ach/+ mice (Fig. 3).