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Fig. S2
Initial formation of somite borders appears normal in MZtmem2 mutants. (A-F) Immunofluorescence indicates localization of fibronectin (red) relative to β-catenin (green) at 12 so (A-B) and 15 so (C-F). (A-B) Dorsal views, anterior to the left, of the right myotome show fibronectin localization at somite boundaries. In MZtmem2 mutants (B′), fibronectin is deposited at each somite boundary, in a pattern comparable to that seen in Mtmem2 siblings (A′). Additionally, muscle precursor cells at the borders of MZtmem2 somites exhibit characteristic elongation indicative of the formation of epithelial somite boundaries (Henry et al., 2005) (B′′, arrow), just as in Mtmem2 siblings (A′′, arrow). These results suggest that the initial formation of somite boundaries proceeds normally in MZtmem2 mutants. (C-D) Lateral views, dorsal up, display fibronectin localization at somite boundaries at 15 so, when the earliest aberrations in fibronectin organization appear in MZtmem2 mutants. In MZtmem2 mutants (D′), fibronectin is present at somite boundaries, but seems disorganized, in contrast to the sharply defined fibronectin deposition present in Mtmem2 siblings (C′). (E-F) Dorsal views, anterior to the left, indicate that fibronectin is present at somite boundaries at 15 so in MZtmem2 mutants (F), as it is in Mtmem2 siblings (E). E′ and F′ show closer views of regions outlined by white rectangles in E and F.