The Role of Fgfr2 Isoforms and Frem1 in Craniofacial Development

OBJECTIVES: 1) To determine whether the Fgfr2 mutant results in the generation of additional isoforms and 2) to characterize the spatial and temporal expression of Frem1 in the developing mid-face of WT mice. METHODS: Polymerase chain reaction using primers specific to different parts of the Fgfr2 gene and gel electrophoresis were performed to compare observed with expected band sizes in WT and mutant tissues. In situ hybridization using Frem1 gene-specific riboprobes was performed on tissue sections of E9.5, E10.5, E11.5 and E13.5 mouse embryos. RESULTS: In the Fgfr2 study, the pattern and sizes of the amplified fragments appear to be identical in all three genotypes. Frem1 was found to be strongly expressed at the epithelial-mesenchymal interface and in the underlying mesenchyme of various structures located in the midline. CONCLUSION: RT-PCR analyses suggest the absence of mutant-specific isoforms in the Fgfr2 mutant. The distinct expression of Frem1 especially of structures at the midline suggests an important role for this gene in mediating outgrowth and filling of mesodermal cells in the midface.