Fig. 4

Deletion of Tbx1 in Mesp1 lineage mesoderm results in defect in coronoid process growth. a, b Sirius red/alcian blue trichrome staining of parasagittal section through E15.5 coronoid process of wildtype mouse (a) and residual coronoid process of Tbx1 ^Mesp1Cre/− conditional mutant mouse (b). c, d Immunohistochemistry at E15.5 for muscle using muscle specific 12/101 antibody demonstrates a reduction in size of temporalis of mutant mice (d) compared to wildtype littermates (c) e Comparison of volume of temporalis muscle in µm³, estimated from histological staining (a, b), demonstrated that the temporalis muscle is significantly reduced in mesoderm specific Tbx1 mutants compared with wildtype littermates. f, g In situ hybridisation at E15.5 reveals expression of Pax9 around the coronoid process is unchanged in Tbx1 ^Mesp1Cre/− (g) when compared with wildtype littermates (f). h–k At E15.5 Sox9 is detected by immunofluorescence around the E15.5 coronoid process in wildtype mice (h), whereas in situ hybridisation for Col2a shows that this expression is not associated with cartilage at the coronoid process (j). Sox9 expression is reduced in Tbx1 ^Mesp1Cre/− mutant mouse coronoid process (i), and Col2a expression is not present (k), while expression of both is maintained in the condylar cartilage; cp coronoid process; Cdy mandibular condyle; temp temporalis muscle; Scale bar is 100 µm except c and d where bar is 1000 µm