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Fig. 6. Initiation of MyoD expression in vitro. (A,D) Culture of isolated
presomitic mesoderm for 3-4 hours. (A) Delta1 (n=30), (B)
Myf5 (n=55), (C) Wnt5b (n=67) and (D) Fz7
(n=8) were autonomously expressed in these conditions. (E,P). Culture
of dissociated rostral presomitic mesoderm cells. Note that the same results
were obtained in six independent experiments. In these experimental
conditions, MyoD (F), Wnt5b (G), Fz7 (H),
Paraxis (O) and Myf5 (P) are expressed. Pax1 (E)
and Shh (M) serve as negative controls. When dissociated presomitic
mesoderm cells are cultured in the presence of supernatant from
Bmp4-expressing cells, initiation of MyoD expression is not observed (N). When
Shh is added to dissociated presomitic cells, expression of MyoD (J),
Wnt5b (K) and Fz7 (L) is strongly enhanced, while
Pax1 (I) expression is activated.