Pbx is required for the proper initiation of fast-muscle differentiation. (A-D) Antibody staining of slow muscle with F59 antibody (green; A,B), or fast muscle with F310 antibody (green; C,D), in (A,C) wild-type control or (B,D) pbx2-MO; pbx4-MO embryos. Antibody staining of muscle with MF20 antibody (red; A-D) is included to control for somite staging. Embryos are shown in left-side view, anterior towards the left. (E,F) Quantification of (E) F59/slow- and (F) F310/fast-muscle marker expression. MF20 expression is included to control for somite (s) staging. Graphs show number of somites expressing a muscle marker at different developmental stages. Similar phenotypes were observed for both myod splice-blocking MOs (myod-splMOs). Error bars represent standard deviation. P values (Mann-Whitney test; normalized to somite number): *P<0.0001 compared to same-stage control; except for pbx2-MO; pbx4-MO F310 compared to control at 24 hpf, P<0.03.
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