Table 1.

Induction of oral epithelial structures in chick mandibles

	Bud stage	Advanced stage	Shh positive	AP positive
Induction by soluble factors in organ culture
Control	0/14	0/14	0/12	nd
BMP4 (100 ng/ml)	8/18	0/18	nd	nd
RCAS-Bmp4 (in ovo)	2/10*	0/10	nd	nd
FGF4 (100 ng/ml)	2/12	0/12	nd	nd
BMP4 + FGF4 (100 ng/ml each)	13/20	5/20	3/5†	nd
Induction by skin mesenchyme in organ culture
Mandibular epithelium (distal, oral) + skin mesenchyme	3/9	6/9	15/18†	nd
Mandibular epithelium (oral non-Fgf8 exp.) + skin mesenchyme	10/14	0/14	1/6 (weak)	nd
Skin epithelium + mandibular mesenchyme	0/8	0/8	nd	nd
Induction by skin mesenchyme in organ culture + CAM
Mandibular epithelium (distal, oral) + skin mesenchyme (exp. I)	23/42	12/42	nd	nd
Mandibular epithelium (distal, oral) + skin mesenchyme (exp. II)	4/11	3/11	nd	6/7
Skin epithelium + skin mesenchyme	0/24‡	0/24‡	nd	5/20 (weak)

Bud stage is defined by invagination of the oral epithelium only (e.g. Fig. 3b). Advanced stage is defined by the presence of epithelial invagination and convolution (e.g. Figs. 3d and 4c and e). nd, not determined. See Materials and Methods for details. 

^*RCAS-Bmp4: retroviral virus expressing BMP4; these experiments were performed in vivo. Buds were observed only on the infected side. 

^† Independent experiments from those in which morphology was scored. 

^‡ In many of these experiments feather germs formed; these were not assigned a developmental stage.