Fig. 5. Myocyte differentiation in OFT of conditional mutants. (A-C) Immunohistochemistry with an anti--smooth muscle actin antibody on coronal sections of E12.5 control (Tbx1^flox/–) (A-C) and conditional mutant (A'-C') embryos at the level of the conus (A,A'), conal-truncal transition (B,B') and truncus (C,C'). Note the reduced immunoreactivity in conditional mutants (A'-C'), especially at the conal-truncal transition. Scale bars: 100 µm.