Probe:	Msx1 cDNA2
Probe preparation:	Antisense labelled with S35 RNA
Visualized with:	Autoradiography
Assay notes:	Samples were fixed in 10% paraformaldehyde and embedded in Fibrowax.

Structure	Level	Pattern	Image	Note
TS13: neural crest	Strong	Regionally restricted		Intensive labelling was present in the neural folds and in the neural crest cells adjacent to the neural folds.
TS13: neural fold	Strong	Regionally restricted		Intensive labelling was present in the neural folds and in the neural crest cells adjacent to the neural folds.
TS13: heart	Present

Structure	Level	Pattern	Image	Note
TS14: future spinal cord neural crest	Strong	Regionally restricted		Intensive labelling was present in the neural folds and in the neural crest cells adjacent to the neural folds.
TS14: future spinal cord neural fold	Strong	Regionally restricted		Intensive labelling was present in the neural folds and in the neural crest cells adjacent to the neural folds.
TS14: heart	Present

Structure	Level	Pattern	Image	Note
TS18: brain	Present		2A
TS18: heart	Present		2A
TS18: pericardium	Present		2A
TS18: 1st branchial arch maxillary component mesenchyme	Strong		2C , 2A
TS18: latero-nasal process mesenchyme	Strong		2A , 2D
TS18: medial-nasal process mesenchyme	Strong		2A , 2D
TS18: 1st branchial arch mandibular component mesenchyme	Strong	Regionally restricted	2B , 2A	Intense labeling anteriorly throughout the mesenchyme that leveled off in the middle third and the posterior third was barely above background. More intense labeling in the top (oral) half.
TS18: branchial arch	Present	Regionally restricted	2B , 2A	The anterior component of the tongue anlage was heavily labelled whereas the posterior component was unlabelled.

Structure	Level	Pattern	Image	Note
TS18: limb	Present	Regionally restricted		Expression is present in the progress zone of the limb buds.
TS18: neural tube	Present

Structure	Level	Pattern	Image	Note
TS18: brain	Present		3A
TS18: latero-nasal process mesenchyme	Strong	Regionally restricted	3A	Expression in the caudal tips.
TS18: medial-nasal process mesenchyme	Strong	Regionally restricted	3A	Expression in the caudal tips.
TS18: head mesenchyme	Present	Regionally restricted	3A	Expression in the mesenchyme surrounding the top and sides of the brain (future skull bones) and in the developing brain meninges.
TS18: nasal pit epithelium	Absent		3A

Structure	Level	Pattern	Image	Note
TS18: pericardium	Present		3B
TS18: 1st branchial arch maxillary component mesenchyme	Strong	Regionally restricted	3B	Expression in the caudal tips.
TS18: 1st branchial arch mandibular component mesenchyme	Strong	Regionally restricted	3B	Intense labeling anteriorly throughout the mesenchyme that leveled off in the middle third and the posterior third was barely above background. More intense labeling in the top (oral) half.
TS18: head mesenchyme	Present	Regionally restricted	3B	Expression in the mesenchyme surrounding the top and sides of the brain (future skull bones).

Structure	Level	Pattern	Image	Note
TS19: brain	Present		5A
TS19: future adenohypophysis	Present	Regionally restricted	5A	Expression in the anterior pituitary.
TS19: latero-nasal process mesenchyme	Strong		5A
TS19: medial-nasal process mesenchyme	Strong		5A
TS19: head mesenchyme	Present	Regionally restricted	5A	Expression in the mesenchyme surrounding the top and sides of the brain (future skull bones) and in meninges.

Structure	Level	Pattern	Image	Note
TS19: nasal pit epithelium	Present	Regionally restricted	5B	IThe epithelium of the primary nares labels at the oral base of its Y shape in the region of fusion of the medial and lateral nasal processes.
TS19: latero-nasal process mesenchyme	Present		5B
TS19: medial-nasal process mesenchyme	Present		5B

Structure	Level	Pattern	Image	Note
TS19: maxillary process mesenchyme	Strong	Regionally restricted	5C	Expression was detected in an anteroposterior gradient in the mesenchyme surrounding the thickened epithelium at the site of future tooth germs.
TS19: mandibular process mesenchyme	Strong	Regionally restricted	5C	Labeling in the mesenchyme at the tip of the mandibular arch.
TS19: oral epithelium	Absent		5C	No expression in the mandibular epithelium.

Structure	Level	Pattern	Image	Note
TS19: maxillary process mesenchyme	Present	Regionally restricted	5D	Expression was detected in an anteroposterior gradient in the mesenchyme surrounding the thickened epithelium at the site of future tooth germs.
TS19: mandibular process mesenchyme	Strong	Regionally restricted	5D	In the anterior and middle thirds of the mandibular arch expression decreased progressively in the caudal, aboral mesenchyme and in more posterior arch mesenchyme.
TS19: tongue	Strong	Regionally restricted	5D	Labelling was intense in the anterior two thirds of the tongue anlage.
TS19: oral epithelium	Absent		5D	No expression in the mandibular epithelium.

Structure	Level	Pattern	Image	Note
TS19: maxillary process mesenchyme	Strong	Regionally restricted	5E	Expression was detected in an anteroposterior gradient in the mesenchyme surrounding the thickened epithelium at the site of future tooth germs.
TS19: mandibular process mesenchyme	Strong	Regionally restricted	5E	In the anterior and middle thirds of the mandibular arch expression decreased progressively in the caudal, aboral mesenchyme and in more posterior arch mesenchyme.
TS19: oral epithelium	Absent		5E	No expression in the mandibular epithelium.

Structure	Level	Pattern	Image	Note
TS19: 2nd branchial arch mesenchyme	Strong		5F
TS19: mandibular process mesenchyme	Absent		5F	At the very back of the mandibular arch, where the thickened dental epithelium was absent, there was no label in the mandibular mesenchyme.
TS19: oral epithelium	Absent		5F	No expression in the mandibular epithelium.

Structure	Level	Pattern	Image	Note
TS19: brain	Present	Regionally restricted	6	Expression in the brain, including areas of the future thalamus, the third and fourth ventricles, and connective tissue supporting the choroid plexus.
TS19: Rathke's pouch	Present	Regionally restricted	6	Labelling was intense in the epithelium of the developing anterior pituitary/Rathke's pouch.
TS19: future adenohypophysis	Present	Regionally restricted	6	Labelling was intense in the epithelium of the developing anterior pituitary/Rathke's pouch.
TS19: tongue	Absent		6	Expression was absent in the posterior third of the tongue.
TS19: mandibular process mesenchyme	Present	Regionally restricted	6	Expression in the posterior third of the arch in broad areas of mesenchyme surrounding the thickened dental epithelium. Also in the base of the arch in the region of the future hyoid bone.
TS19: head mesenchyme	Present	Regionally restricted	6	Expression in the mesenchymal capsule covering the top of the brain and a layer of mesenchyme extending laterally down the sides of the head beneath the epithelium, particularly adjacent to the developing eye.
TS19: hyoid cartilage primordium	Present		6

Structure	Level	Pattern	Image	Note
TS20: mandibular process mesenchyme	Present	Regionally restricted	7A	Expression in the region of epithelial invagination for the incisor and first molar tooth germs.
TS20: maxillary process mesenchyme	Present	Regionally restricted	7A	Expression in the region of epithelial invagination for the incisor and first molar tooth germs.
TS20: oral epithelium	Absent		7A
TS20: palatal shelf	Absent		7A
TS20: tongue	Absent		7A

Structure	Level	Pattern	Image	Note
TS20: mandibular process mesenchyme	Present	Regionally restricted	7B	Labeling was more localized to the mesenchymal condensation for the dental papilla and dental follicle of the first molars and future alveolar bone.
TS20: maxillary process mesenchyme	Present	Regionally restricted	7B	Labeling was more localized to the mesenchymal condensation for the dental papilla and dental follicle of the first molars and future alveolar bone.
TS20: maxillary process epithelium	Absent		7B

Structure	Level	Pattern	Image	Note
TS20: mandibular process mesenchyme	Present	Regionally restricted	7C	In posterior regions where the epithelium had thickened to be only 2-3 layers thick, no labeling in the underlying mesenchyme. There is no labeling near the second molar primordia.
TS20: maxillary process mesenchyme	Present	Regionally restricted	7C	In posterior regions where the epithelium had thickened to be only 2-3 layers thick, no labeling in the underlying mesenchyme. There is no labeling near the second molar primordia.
TS20: maxillary process epithelium	Absent		7C

Structure	Level	Pattern	Image	Note
TS21: molar	Strong	Regionally restricted	8A , 8B	Intense labeling localized to the dental papillae, dental follicles, and future alveolar bone of the first molars. There is no expression in the enamel organ.
TS21: jaw epithelium	Absent		8A , 8B

Structure	Level	Pattern	Image	Note
TS21: incisor	Present		8C	Expression in the dental papillae and follicles of the incisor tooth germs.
TS21: jaw mesenchyme	Present	Regionally restricted	8C	Expression in the mesenchymal condensations around the invaginating epithelium for the second molars.
TS21: jaw epithelium	Absent		8C
TS21: tooth epithelium	Absent		8C

Structure	Level	Pattern	Image	Note
TS22: maxilla	Present	Regionally restricted	9A , 9E	Expression in the bony blastemata for the maxillary bones. Boxed area in A is enlarged in E.
TS22: incisor	Strong	Regionally restricted	9A	Expression in the dental follicle of the incisor tooth germ.
TS22: incisor dental papilla	Strong		9A
TS22: jaw mesenchyme	Present	Regionally restricted	9A	Labelling in the jaw mesenchyme extends the full length of the incisor tooth germ.
TS22: enamel organ	Absent		9A	All the enamel organs and jaw epithelia do not label above background.
TS22: jaw epithelium	Absent		9A	All the enamel organs and jaw epithelia do not label above background.

Structure	Level	Pattern	Image	Note
TS22: molar	Present	Regionally restricted	9B , 9C	Expression in the dental follicle of the first molar tooth germ.
TS22: molar dental papilla	Strong		9C , 9B	Expression is present in the dental papillae of the first molars.
TS22: enamel organ	Absent		9B , 9C	All the enamel organs and jaw epithelia do not label above background.
TS22: jaw epithelium	Absent		9B , 9C	All the enamel organs and jaw epithelia do not label above background.
TS22: eye skeletal muscle	Absent		9B
TS22: tongue muscle	Absent		9B

Structure	Level	Pattern	Image	Note
TS22: molar	Strong	Regionally restricted	9D	Expression in the dental papilla and follicle mesenchyme around the second molar tooth germs.
TS22: molar dental papilla	Strong	Regionally restricted	9D	Expression in the dental papilla and follicle mesenchyme around the second molar tooth germs.
TS22: cranial muscle	Present	Regionally restricted	9D	Less intense labeling in the muscle blastematae for the masseter, temporalis, and medial and lateral pterygoids.
TS22: masseter	Present	Regionally restricted	9D	Less intense labeling in the muscle blastematae for the masseter, temporalis, and medial and lateral pterygoids.
TS22: temporalis	Present	Regionally restricted	9D	Less intense labeling in the muscle blastematae for the masseter, temporalis, and medial and lateral pterygoids.
TS22: eye skeletal muscle	Absent		9D
TS22: tongue muscle	Absent		9D

Structure	Level	Pattern	Image	Note
TS23: molar	Absent		10A	There is no expression in the first molar tooth germs, in either the dental papillae or the follicles.
TS23: molar dental papilla	Absent		10A

Structure	Level	Pattern	Image	Note
TS23: molar dental papilla	Present		10C	Expression is present in the dental papilla of the second molars.
TS23: molar	Present	Regionally restricted	10C	Expression in the second molar tooth germ follicle.

Structure	Level	Pattern	Image	Note
TS23: incisor	Weak			Labeling is much less intense in the incisor tooth germs.

Structure	Level	Pattern	Image	Note
TS24: molar	Present	Regionally restricted		The second molar tooth germs resemble the first molar pattern at day 15. There is no labeling of the first molar.
TS24: incisor	Absent