Probe:	Six1 cDNA2
Probe preparation:	Antisense labelled with digoxigenin RNA
Visualized with:	Alkaline phosphatase

Structure	Level	Pattern	Image	Note
TS13: mesenchyme derived from head mesoderm	Present	Regionally restricted	3A	Authors report that expression is first detected at E8.2-8.5, restricted to the most anterior head mesoderm, extends posteriorly to include most of head mesoderm; includes most craniofacial voluntary muscles.
TS13: head mesenchyme derived from neural crest	Present		3A	Authors state that expression probably includes neural crest-derived connective tissues.
TS13: branchial arch	Present	Regionally restricted	3A	Expression in the region of pharyngeal pouches.
TS13: head paraxial mesenchyme	Present		3A	Expression in flanking axial and paraxial mesoderm (notochord and somites).
TS13: notochord	Present		3A	Expression in flanking axial and paraxial mesoderm (notochord and somites).

Structure	Level	Pattern	Image	Note
TS13: mesenchyme derived from head mesoderm	Present	Regionally restricted	4A	Authors report that expression is first detected at E8.2-8.5, restricted to the most anterior head mesoderm, extends posteriorly to include most of head mesoderm; includes most craniofacial voluntary muscles.
TS13: head mesenchyme derived from neural crest	Present		4A	Authors state that expression probably includes neural crest-derived connective tissues.
TS13: branchial arch	Present	Regionally restricted	4A	Expression in the region of pharyngeal pouches.
TS13: head paraxial mesenchyme	Present		4A	Expression in flanking axial and paraxial mesoderm (notochord and somites).
TS13: notochord	Present		4A	Expression in flanking axial and paraxial mesoderm (notochord and somites).

Structure	Level	Pattern	Image	Note
TS13: mesenchyme derived from head mesoderm	Strong	Regionally restricted	4B	Expression in anterior head mesoderm and in pharyngeal pouches.
TS13: heart	Absent		4B	No expression in neurectoderm (on dorsal side) and heart (on ventral side).
TS13: neural ectoderm	Absent		4B	No expression in neurectoderm (on dorsal side) and heart (on ventral side).

Structure	Level	Pattern	Image	Note
TS15: nephrogenic cord	Present		3B	Expression detected in otic vesicle, nephrogenic cord and presomitic mesoderm.
TS15: otocyst	Present		3B	Expression detected in otic vesicle, nephrogenic cord and presomitic mesoderm.
TS15: tail unsegmented mesenchyme	Present		3B	Expression detected in otic vesicle, nephrogenic cord and presomitic mesoderm.

Structure	Level	Pattern	Image	Note
TS14: trunk unsegmented mesenchyme	Present	Regionally restricted	4C	Expression in presomitic mesoderm, immediately posterior to the most recently formed somite.
TS14: Rathke's pouch	Present		4C
TS14: otic placode	Present		4C

Structure	Level	Pattern	Image	Note
TS14: trunk unsegmented mesenchyme	Present	Regionally restricted	4D	Expression in presomitic mesoderm, immediately posterior to the most recently formed somite.
TS14: Rathke's pouch	Present		4D
TS14: otic placode	Present		4D

Structure	Level	Pattern	Image	Note
TS14: nephrogenic cord	Present		4E
TS14: notochord	Present		4E
TS14: trunk somite	Present		4E

Structure	Level	Pattern	Image	Note
TS17: branchial arch	Present	Regionally restricted	3C	Expression in region of nasal placode, in a restricted pattern over the branchial arches.
TS17: nose	Present	Regionally restricted	3C	Expression in region of nasal placode, in a restricted pattern over the branchial arches.
TS17: 1st branchial arch mandibular component	Present	Regionally restricted	3C	Expression in the rostral compartment of the mandibular component of the 1st arch, and in the caudal compartment of the 2nd arch.
TS17: 2nd branchial arch	Present	Regionally restricted	3C	Expression in the rostral compartment of the mandibular component of the 1st arch, and in the caudal compartment of the 2nd arch.
TS17: dorsal root ganglion	Present		3C
TS17: forelimb bud	Present		3C
TS17: hindlimb bud	Present		3C

Structure	Level	Pattern	Image	Note
TS17: Rathke's pouch	Present		4F
TS17: head mesenchyme	Present		4F
TS17: trunk somite	Present	Regionally restricted	4F	Mainly restricted to dermomyotome.
TS17: dorsal root ganglion	Present		4F
TS17: notochord	Weak		4F
TS17: forelimb bud	Present	Regionally restricted	4F	Correlates with ventral and dorsal myoblast cells.

Structure	Level	Pattern	Image	Note
TS17: forelimb bud	Present	Regionally restricted	6D	Correlates with ventral and dorsal myoblast cells.

Structure	Level	Pattern	Image	Note
TS17: forelimb bud	Present		6E
TS17: dorsal root ganglion	Absent		6E

Structure	Level	Pattern	Image	Note
TS17: forelimb bud	Present	Regionally restricted	6F	No expression in the ventral side of the forelimb; reduced expression in the dorsal side.

Structure	Level	Pattern	Image	Note
TS19: forelimb bud	Present	Regionally restricted	3D	Expression in forelimb restricted to narrow mesenchymal cell population at posterior limb margin, which extends distally.

Structure	Level	Pattern	Image	Note
TS19: forelimb bud	Present	Regionally restricted	7A (wm)	Expression in forelimb restricted to narrow mesenchymal cell population at posterior limb margin, which extends distally.

Structure	Level	Pattern	Image	Note
TS19: forelimb bud	Present	Regionally restricted	7A (sxn)	Expression in forelimb restricted to posterior margin, dorsally and ventrally.

Structure	Level	Pattern	Image	Note
TS20: dorsal root ganglion	Weak		3E
TS20: head mesenchyme	Weak		3E
TS20: trunk mesenchyme	Present	Regionally restricted	3E	Expression in somite-derived intercostal skeletal muscles.
TS20: oral region	Present	Regionally restricted	3E	Expression in genitalia and jaw.
TS20: reproductive system	Present	Regionally restricted	3E	Expression in genitalia and jaw.

Structure	Level	Pattern	Image	Note
TS20: mandible primordium	Present	Regionally restricted	7B (wm)	Expression progresses anteriorly.
TS20: tongue	Present	Regionally restricted	7B (wm)	Expression progresses anteriorly.

Structure	Level	Pattern	Image	Note
TS20: forelimb	Present	Regionally restricted	7B (sxn)	High expression over dorsal side.

Structure	Level	Pattern	Image	Note
TS20: hindlimb	Present		6A
TS20: trunk mesenchyme	Present	Regionally restricted	6A	Expression in future intercostal muscles.

Structure	Level	Pattern	Image	Note
TS21: head mesenchyme	Weak		5A	Weak expression in most of head and body skeletal muscle masses.
TS21: vertebral axis musculature	Weak		5A	Weak expression in most of head and body skeletal muscle masses.
TS21: arm	Present	Regionally restricted	5A	Expression in some of the arm muscle fibers.
TS21: hand	Present	Regionally restricted	5A	Expression in tendons surrounding the digits

Structure	Level	Pattern	Image	Note
TS21: hand	Present	Regionally restricted	7C (wm)	Expression in tendons surrounding the digits

Structure	Level	Pattern	Image	Note
TS21: hand	Present	Regionally restricted	7C (sxn)	Expression mostly located over dorsal side, flanking digit cartilage condensations.

Structure	Level	Pattern	Image	Note
TS22: hand	Present	Regionally restricted	7D (wm)	Expression flanking phalangeal components of digits, anteriorly and posteriorly.

Structure	Level	Pattern	Image	Note
TS22: hand	Present	Regionally restricted	7D (sxn)	Weak expression dorsally.

Structure	Level	Pattern	Image	Note
TS22: hindlimb	Present			Expression is similar to that reported for the forelimb, but delayed by a few hours.

Structure	Level	Pattern	Image	Note
TS23: axial muscle	Weak		5B	Weak expression in most of head and body skeletal muscle masses.
TS23: cranial musculature	Weak		5B	Weak expression in most of head and body skeletal muscle masses.
TS23: cranial muscle	Present		5B	Expression over most of head voluntary muscles.