GSE121780
Mandibular dysmorphogenesis due to abnormal osteogenic activity in FGFR2-related craniosynostosis mouse models
Mutations within FGFR2 are causative for various craniosynostosis syndromes. The mandibular dysmorphogenesis in these syndromes has rarely been quantitatively characterized prenatally and the cellular and molecular mechanism involved is unclear. To investigate the effects of FGFR2 mutations on development of the mandible, micro-computed tomography (µCT) images were acquired using newborn mice of three Fgfr2-mutant lines associated with Apert and Crouzon craniosynostosis syndromes. Euclidean Distance Matrix Analysis and analysis of relative bone mineral density (BMD) of 3D µCT images revealed differences in mandible morphology and BMD between the mice carrying the Fgfr2 mutations and their unaffected littermates. We further investigated the mechanism for mandibular dysgenesis in the Fgfr2+/S252W (Fgfr2S252W) mouse model that showed the most severe phenotypes. At E16.5, Fgfr2S252W embryos showed an increase in the size of the osteogenic anlagen and Meckel's cartilage (MC) and altered microarchitecture and mineralization in the mandible relative to unaffected littermates. Laser capture microdissection and RNA-Seq analysis revealed transcriptomic changes in the mandibular bone, highlighting increased expression of genes undergoing osteoclast differentiation and dysregulated genes active in bone mineralization. Increased osteoclastic activity in the mandible of Fgfr2S252W embryos was confirmed and elevated inorganic pyrophosphate concentration was identified due to upregulated expression of Enpp1 and Ank. In contrast, increased proliferation in MC was observed at E12.5. These findings provide evidence that gain-of-function mutations in FGFRs differentially affect intramembranous ossification of dermal bone and cartilage formation contributing to mandibular dysmorphogenesis in craniosynostosis syndromes. Overall design: Quantitative high-resolution micro-computed tomography (µCT) images of the mandible were acquired for 182 newborn (P0) mice to investigate the effects of three FGFR2 mutations associated with Apert and Crouzon syndromes. Samples for histological and transcriptome analysis consisted of 66 embryos of Fgfr2+/S252W model. Laser Capture Microdissection was used on embryos at E16.5 (3 Fgfr2S252W embryos and 3 unaffected littermates, all were female) to isolate tissues in Meckels cartilage, mandibular bone and mandibular condylar cartilage, respectively. Libraries were prepared with NuGEN Ovation RNA-Seq System v2 (amplification) and Illumina Nextera XT Library Prep kit. Fragments were sequenced using paired end reads (2×100 bp) on the Illumina HiSeq platform.