Probe:	Hex cDNA
Probe preparation:	Antisense labelled with digoxigenin RNA

Structure	Level	Pattern	Image	Note
TS6: primitive endoderm	Present	Regionally restricted	1B	Expression was restricted to the primitive endoderm cells at the interface between the epiblast and the blastocoel cavity.
TS6: epiblast	Absent		1B
TS6: parietal endoderm	Absent		1B
TS6: trophectoderm	Absent		1B

Structure	Level	Pattern	Image	Note
TS6: primitive endoderm	Present	Regionally restricted	1C	Expression was restricted to the primitive endoderm cells at the interface between the epiblast and the blastocoel cavity.
TS6: epiblast	Absent		1C
TS6: parietal endoderm	Absent		1C
TS6: trophectoderm	Absent		1C

Structure	Level	Pattern	Image	Note
TS7: extraembryonic visceral endoderm	Present	Regionally restricted	1D	Expression remained restricted to the visceral endoderm and was detected in a small group of cells at the distal tip of the egg cylinder.

Structure	Level	Pattern	Image	Note
TS7: extraembryonic visceral endoderm	Present	Regionally restricted	1E	Expression remained restricted to the visceral endoderm and was detected in a unilateral patch of visceral endoderm immediately proximal to the distal tip.

Structure	Level	Pattern	Image	Note
TS8: extraembryonic visceral endoderm	Present	Regionally restricted	1F	Expression was asymmetrical. Expression was clearly restricted to visceral endoderm on one side of the egg cylinder and extended from the distal tip to about half way up the embryonic region.

Structure	Level	Pattern	Image	Note
TS9: extraembryonic visceral endoderm	Present	Regionally restricted	1G	Expression remained localised to the visceral endoderm diametrically opposite the streak, which therefore corresponds to the anterior aspect of the embryo.
TS9: embryo	Present	Regionally restricted	1G	The expression domain extended from the embryonic-extraembryonic junction to within about 30um of the distal tip of the cylinder.

Structure	Level	Pattern	Image	Note
TS10: primitive streak	Present	Regionally restricted	2A	Expression was detected at the anterior end of the primitive streak.

Structure	Level	Pattern	Image	Note
TS10: extraembryonic visceral endoderm	Present	Regionally restricted	2B	At the anterior aspect of the embryo, expression was restricted to a strip of medial visceral endoderm approximately 10 cells wide.
TS10: definitive endoderm	Present	Regionally restricted	2B	During extension of the streak towards the distal tip of the egg cylinder, immunopositive definitive endoderm cells extended rostrally from the node to merge with the immunopositive cells in the anterior visceral endoderm.
TS10: anterior visceral endoderm	Present		2B

Structure	Level	Pattern	Image	Note
TS10: yolk sac mesoderm	Present	Regionally restricted	2C	Expression was first detected at midstreak stages in a narrow band of cells within the nascent blood islands of the visceral yolk sac.
TS10: extraembryonic visceral endoderm	Present	Regionally restricted	2C	At the anterior aspect of the embryo, expression was restricted to a strip of medial visceral endoderm approximately 10 cells wide.
TS10: definitive endoderm	Present	Regionally restricted	2C	During extension of the streak towards the distal tip of the egg cylinder, immunopositive definitive endoderm cells extended rostrally from the node to merge with the immunopositive cells in the anterior visceral endoderm.
TS10: anterior visceral endoderm	Present		2C

Structure	Level	Pattern	Image	Note
TS10: extraembryonic visceral endoderm	Present	Regionally restricted	2D	Expression in the anterior endoderm extended from just rostral to the node (at the distal tip) to the embryonic/extraembryonic junction.
TS10: yolk sac	Present	Regionally restricted	2D	By the late streak stage, expression was detected in an increased number of cells in the expanding blood islands and these cells formed a discrete band around the circumference of the visceral yolk sac.
TS10: embryo mesoderm	Present	Single cells	2D	Expression was detected in isolated cells in the proximolateral mesoderm immediately distal to the embryonic/extraembryonic junction.

Structure	Level	Pattern	Image	Note
TS11: definitive endoderm	Present	Regionally restricted	2E	Expression was restricted to a group of anteromedial endoderm cells immediately distal to the embryonic/extraembryonic junction. These probably correspond to the most anterior definitive endoderm.
TS11: embryo endoderm	Present	Regionally restricted	2E	Expression was restricted to a group of anteromedial endoderm cells immediately distal to the embryonic/extraembryonic junction. These probably correspond to the most anterior definitive endoderm.
TS11: blood island	Strong		2E
TS11: allantois	Present	Regionally restricted	2E	Expression was detected only in the tip of the allantoic bud.
TS11: embryo mesoderm	Present	Single cells	2E	Expression was detected in isolated cells in the proximolateral mesoderm immediately distal to the embryonic/extraembryonic junction.

Structure	Level	Pattern	Image	Note
TS11: embryo endoderm	Present	Regionally restricted	2F	The domain of anterior endoderm expression had spread laterally to generate a crescent that extended to the lateral edges of the involuting foregut endoderm.
TS11: blood island	Strong		2F

Structure	Level	Pattern	Image	Note
TS11: embryo endoderm	Present	Regionally restricted	2G	The anterior endoderm expression domain had expanded to encompass the entire ventral foregut endoderm.
TS11: blood island	Weak	Single cells	2G	Expression was detected in relatively few, isolated cells and the level of transcripts per cell appeared to be reduced.
TS11: allantois	Strong	Uniform	2G
TS11: embryo mesoderm	Present	Regionally restricted	2G	During headfold formation, expression was detected in cells in the anterior mesoderm in a horseshoe-shaped domain corresponding to the developing paired endocardial tubes.

Structure	Level	Pattern	Image	Note
TS15: extraembryonic component	Strong	Regionally restricted		The allantois remained a site of intense expression at least up to 9.5 dpc.
TS15: heart	Present	Regionally restricted		Expression in the endocardium persisted until at least E9.5.

Structure	Level	Pattern	Image	Note
TS10: definitive endoderm	Present	Regionally restricted	2H	Expression was detected in the ectoderm and endoderm layers immediately adjacent to the prospective node region, indicating expression by the presumptive definitive endoderm cells.
TS10: embryo ectoderm	Present	Regionally restricted	2H	Expression was detected in the ectoderm and endoderm layers immediately adjacent to the prospective node region, indicating expression by the presumptive definitive endoderm cells.
TS10: embryo endoderm	Present	Regionally restricted	2H	Expression was detected in the ectoderm and endoderm layers immediately adjacent to the prospective node region, indicating expression by the presumptive definitive endoderm cells.

Structure	Level	Pattern	Image	Note
TS12: gut	Present	Regionally restricted	3B , 3A	Expression continued within the ventral gut endoderm.
TS12: embryo endoderm	Present	Regionally restricted	3B , 3A	Expression in the ventral gut endoderm extended anterolaterally to include endoderm adjacent to the forming heart tube.
TS12: foregut diverticulum endoderm	Absent		3B , 3A	The blind ending 'anterior' extremity of the foregut pocket was devoid of transcripts.
TS12: lateral plate mesoderm	Present	Single cells	3B	Expression was detected in isolated or small groups of cells in the posterior lateral mesoderm.
TS12: trunk mesenchyme	Present	Regionally restricted	3A , 3B	Expression was detected in small groups of cells in the mesoderm lateral to the neural tube in the region where the dorsal aortae will form.
TS12: allantois	Present		3A

Structure	Level	Pattern	Image	Note
TS13: foregut diverticulum	Present	Regionally restricted	3C	Expression in the ventral foregut had resolved into two discrete domains, which at later stages were identified as the thyroid primordium and the hepatic diverticulum (see 18-somite stage embryo, Fig. 3D).
TS13: head mesenchyme	Present	Regionally restricted	3C	Expression was detected in the cephalic mesenchyme and in the posterior lateral mesoderm. Expression was detected in angioblasts.
TS13: lateral plate mesoderm	Present	Regionally restricted	3C	Expression was detected in the cephalic mesenchyme and in the posterior lateral mesoderm. Expression was detected in angioblasts.

Structure	Level	Pattern	Image	Note
TS14: hepatic primordium	Present		3D
TS14: thyroid primordium	Present		3D
TS14: cardiovascular system	Present	Regionally restricted	3D	Expression was detected in the intersomitic vessels.
TS14: dorsal aorta	Present	Regionally restricted	3D	Expression was detected in the roof of the dorsal aorta.
TS14: head mesenchyme	Present		3D	Expression in the head mesenchyme appeared more organized, presumably reflecting the formation of the cranial vessels and associated capillary plexi.
TS14: embryo	Present	Single cells	3D	Expression was detected between the somites where the intersomitic arteries form.

Structure	Level	Pattern	Image	Note
TS12: foregut diverticulum	Absent		3E	The blind ending 'anterior' extremity of the foregut pocket was devoid of transcripts.
TS12: gut	Present	Regionally restricted	3E	Expression continued within the ventral gut endoderm.
TS12: embryo endoderm	Present	Regionally restricted	3E	Expression in the ventral gut endoderm extended anterolaterally to include endoderm adjacent to the forming heart tube.
TS12: head mesenchyme	Present	Single cells	3E	Isolated positive cells (angioblasts) are evident in the cranial mesenchyme.
TS12: heart	Strong	Regionally restricted	3E	Strong expression was detected within the endocardial cells but not in the myocardial cell layer.

Structure	Level	Pattern	Image	Note
TS13: heart	Present	Regionally restricted	3F	Expression was detected in the endocardium.
TS13: dorsal aorta	Absent		3F	Expression was absent in the endothelial cells lining the dorsal aorta.
TS13: thyroid primordium	Present		3F

Structure	Level	Pattern	Image	Note
TS13: umbilical vein	Present	Regionally restricted	3H	Expression was detected in the lining.
TS13: vitelline artery	Present	Regionally restricted	3H	Expression was detected in the lining.
TS13: vitelline vein	Present	Regionally restricted	3H	Expression was detected in the lining.
TS13: somatopleure	Present	Single cells	3H	Expression was detected in isolated cells or groups of cells in the posterior splanchnopleure and somatopleure.
TS13: splanchnopleure	Present	Single cells	3H	Expression was detected in isolated cells or groups of cells in the posterior splanchnopleure and somatopleure.
TS13: gut endoderm	Present	Regionally restricted	3H	Expression was detected in the caudal ventral gut endoderm.

Structure	Level	Pattern	Image	Note
TS13: dorsal aorta	Absent		3I	Expression was absent in the endothelial cells lining the dorsal aorta.
TS13: blood vessel	Present	Single cells	3I	Expression was detected in small groups of angioblasts that were anastomosing to form the cranial vasculature.

Structure	Level	Pattern	Image	Note
TS13: yolk sac	Weak		3J	Expression was low in the visceral yolk sac.
TS13: dorsal aorta	Absent		3J	Expression was detected in fewer endothelial cells lining the dorsal aorta compared with flk-1 (Kdr, see Assay MGI:1306926).
TS13: extraembryonic vascular system	Trace		3J	Expression was detected in fewer cells in the visceral yolk sac vascular plexus compared with flk-1 (Kdr, see Assay MGI:1306926).