Localization of MyoD, myogenin, and snail1 transcripts in whole embryos. Wild-type embryos were hybridized with MyoD (A-F), myogenin (G-J), snail1 (K-N), or MyoD + snail1 (O-R) probes. spt (S-W) or ntl (X-B′) embryos were hybridized with MyoD probe. Vertical panel rows show embryos at a particular embryonic age: 7-7.5 hours (A), 8-8.5 hours (B,K,O,S,X), 10-10.5 hours (C,G,L,P,T,Y), 12-12.5 hours (D,H,M,Q,U,Z), 14-14.5 hours (E,I,N,R,V,A′), and 24 hours (F,J,W,B′). All embryos are viewed dorsally (either directly or obliquely) with their anterior end to the top except for the 24 hour embryos (F,J,W,B′) which are viewed laterally, anterior to the left. In C-E, open arrows indicate portions of the expression pattern which are absent at the position of corresponding open arrows in Y, Z and A′. In C, the arrowhead indicates cells in the tailbud that express MyoD. In K-N, arrowheads indicate regions of paraxial mesoderm and tailbud that express snail1 but not MyoD. In W, arrows indicate myotome-like bodies expressing MyoD and the arrowhead shows the position of the spade tail in which expression is absent. Scale bar in A indicates 200 µm; all panels at same magnification.
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