Probe:	Frg1 probe
Probe preparation:	Antisense labelled with digoxigenin RNA
Visualized with:	Alkaline phosphatase

Structure	Level	Pattern	Image	Note
TS17: oral region	Present	Regionally restricted	1A	Diffuse expression in epithelial layers and mesenchymal cells at predicted first molar region.

Structure	Level	Pattern	Image	Note
TS20: dental placode	Present	Regionally restricted	1E	Diffuse expression in epithelial layers and mesenchymal cells at predicted first molar region.
TS20: jaw primordium mesenchyme	Present	Regionally restricted	1E	Diffuse expression in epithelial layers and mesenchymal cells at predicted first molar region.

Structure	Level	Pattern	Image	Note
TS22: tooth bud	Present		1I
TS22: tooth epithelium	Present		1I
TS22: tooth mesenchyme	Present		1I

Structure	Level	Pattern	Image	Note
TS23: cap stage tooth	Strong		1M
TS23: cervical loop	Strong		1M
TS23: inner enamel epithelium	Strong		1M
TS23: outer enamel epithelium	Strong		1M
TS23: primary enamel knot	Strong		1M
TS23: dental papilla	Weak		1M
TS23: dental sac	Weak		1M

Structure	Level	Pattern	Image	Note
TS24: cervical loop	Strong		1Q	Expression pattern similar to that on E15.
TS24: enamel knot	Strong		1Q	Expression pattern similar to that on E15.
TS24: inner enamel epithelium	Strong		1Q	Expression pattern similar to that on E15.
TS24: outer enamel epithelium	Strong		1Q	Expression pattern similar to that on E15.

Structure	Level	Pattern	Image	Note
TS26: cervical loop	Strong		1U
TS26: inner enamel epithelium	Strong		1U
TS26: stratum intermedium	Strong		1U
TS26: outer enamel epithelium	Present		1U	Expression in outer enamel epithelium weaker than in inner enamel epithelium.
TS26: dental papilla	Weak	Regionally restricted	1U	Weak expression in dental papilla. Stronger expression in cells facing inner enamel epithelium than in other cells in dental papilla.
TS26: tongue muscle	Present		1U

Structure	Cell Type	Level	Pattern	Image	Note
TS27: inner enamel epithelium		Strong	Regionally restricted	2A	Strong expression in inner enamel epithelium at central groove region.
TS27: tooth	preameloblast	Strong	Regionally restricted	2A	Strong expression in preameloblasts and preodontoblasts at lingual cusp site.
TS27: tooth	preodontoblast	Strong	Regionally restricted	2A	Strong expression in preameloblasts and preodontoblasts at lingual cusp site.
TS27: dental papilla		Absent		2A	No expression in cells of dental papilla facing inner enamel epithelium at central groove region where matrix formation was not observed.

Structure	Cell Type	Level	Pattern	Image	Note
TS27: tooth	preameloblast	Strong	Regionally restricted	2C	Strong expression in preameloblasts and preodontoblasts at central groove region.
TS27: tooth	preodontoblast	Strong	Regionally restricted	2C	Strong expression in preameloblasts and preodontoblasts at central groove region.
TS27: tooth	ameloblast	Strong	Regionally restricted	2C	Strong expression in ameloblasts and odontoblasts at lingual cusp site.
TS27: tooth	odontoblast	Strong	Regionally restricted	2C	Strong expression in ameloblasts and odontoblasts at lingual cusp site.
TS27: stratum intermedium		Present		2C

Structure	Cell Type	Level	Pattern	Image	Note
TS27: inner enamel epithelium		Strong	Regionally restricted	2E	Strong expression in inner enamel epithelium at central groove region.
TS27: tooth	preameloblast	Strong	Regionally restricted	2E	strong / RR Strong expression in preameloblasts and preodontoblasts at lingual cusp site.
TS27: tooth	preodontoblast	Strong	Regionally restricted	2E	strong / RR Strong expression in preameloblasts and preodontoblasts at lingual cusp site.

Structure	Cell Type	Level	Pattern	Image	Note
TS27: tooth	ameloblast	Strong	Regionally restricted	2H	Strong expression in ameloblasts and odontoblasts at lingual cusp site.
TS27: tooth	odontoblast	Strong	Regionally restricted	2H	Strong expression in ameloblasts and odontoblasts at lingual cusp site.

Structure	Level	Pattern	Image	Note
TS27: dental papilla	Absent		2K	No expression in cells of dental papilla facing inner enamel epithelium at central groove region where matrix formation was not observed.

Structure	Cell Type	Level	Pattern	Image	Note
TS27: tooth	preameloblast	Strong	Regionally restricted	2N	Strong expression in preameloblasts and preodontoblasts at central groove region.
TS27: tooth	preodontoblast	Strong	Regionally restricted	2N	Strong expression in preameloblasts and preodontoblasts at central groove region.

Structure	Cell Type	Level	Pattern	Image	Note
TS27: tooth	odontoblast	Strong	Regionally restricted	3A	Strong expression in preodontoblasts on lateral sides of tooth germ and odontoblasts.
TS27: tooth	preodontoblast	Strong	Regionally restricted	3A	Strong expression in preodontoblasts on lateral sides of tooth germ and odontoblasts.
TS27: tooth	ameloblast	Present		3A
TS27: tooth	preameloblast	Present		3A

Structure	Cell Type	Level	Pattern	Image	Note
TS27: tooth	odontoblast	Strong	Regionally restricted	3B	Strong expression in preodontoblasts on lateral sides of tooth germ and odontoblasts.
TS27: tooth	preodontoblast	Strong	Regionally restricted	3B	Strong expression in preodontoblasts on lateral sides of tooth germ and odontoblasts.
TS27: tooth	ameloblast	Present		3B
TS27: tooth	preameloblast	Present		3B
TS27: stratum intermedium		Present		3B

Structure	Cell Type	Level	Pattern	Image	Note
TS28: tooth	ameloblast	Strong	Regionally restricted	4A	Strong expression in ameloblasts secreting enamel matrix on latteral sides of tooth crown and at presumptive buccal cusp site.
TS28: tooth	odontoblast	Strong	Regionally restricted	4A	Strong expression in odontoblasts in presumptive cusp site.
TS28: tooth	preodontoblast	Strong	Regionally restricted	4A	Strong expression in preodontoblasts on lateral sides of tooth.
TS28: Hertwig's epithelial root sheath		Weak		4A

Structure	Cell Type	Level	Pattern	Image	Note
TS28: tooth	odontoblast	Strong	Regionally restricted	4B	Strong expression in odontoblasts in presumptive cusp site.
TS28: tooth	preodontoblast	Strong	Regionally restricted	4B	Strong expression in preodontoblasts on lateral sides of tooth.
TS28: Hertwig's epithelial root sheath		Weak	Regionally restricted	4B
TS28: stratum intermedium		Present		4B

Structure	Cell Type	Level	Pattern	Image	Note
TS28: tooth	odontoblast	Strong		4I

Structure	Cell Type	Level	Pattern	Image	Note
TS28: tooth	odontoblast	Strong		4J