Antibody:	Anti-syndecan IgG
Detection system:	Biotinylated secondary antibody/[Strept]avidin coupled to Texas Red
Assay notes:	Embryos were fixed in Carnoy's fixative (6:3:1 of ethanol, chloroform and glacial acetic acid) and embedded in diethylene glycol distearate (DGD).

Structure	Level	Pattern	Image	Note
TS9: embryo ectoderm	Present		3	Expression was detected on the basolateral surfaces of all cells. No regional differences in staining were detected.
TS9: extraembryonic visceral endoderm	Absent		3

Structure	Level	Pattern	Image	Note
TS11: embryo ectoderm	Present		4A	Expression was detected on the basolateral surfaces of all cells. No regional differences in staining were detected.
TS11: extraembryonic visceral endoderm	Absent		4A
TS11: definitive endoderm	Present		4A	Expression was detected on the basal and lateral cell surfaces of the definitive embryonic endoderm and no regional differences in its expression were detected.
TS11: embryo mesoderm	Present	Graded	4A	Expression was detected in lateral and distal mesoderm.
TS11: primitive streak	Present		4A

Structure	Level	Pattern	Image	Note
TS11: embryo ectoderm	Present		4B	Expression was detected on the basolateral surfaces of all cells. No regional differences in staining were detected.
TS11: extraembryonic visceral endoderm	Absent		4B
TS11: definitive endoderm	Present		4B	Expression was detected on the basal and lateral cell surfaces of the definitive embryonic endoderm and no regional differences in its expression were detected.
TS11: embryo mesoderm	Present	Graded	4B	Expression was detected in lateral and distal mesoderm.
TS11: primitive streak	Present		4B

Structure	Level	Pattern	Image	Note
TS11: embryo ectoderm	Present		4C	Expression was detected on the basolateral surfaces of all cells. No regional differences in staining were detected.
TS11: extraembryonic visceral endoderm	Absent		4C
TS11: definitive endoderm	Present		4C	Expression was detected on the basal and lateral cell surfaces of the definitive embryonic endoderm and no regional differences in its expression were detected.
TS11: head mesenchyme	Weak	Regionally restricted	4C	Expression was barely detected in the anterior mesoderm of the head fold.

Structure	Level	Pattern	Image	Note
TS10: embryo mesoderm	Weak	Regionally restricted	5A/B	There was staining in the head process and its derivative, the notochordal plate.

Structure	Level	Pattern	Image	Note
TS10: primitive streak	Strong	Regionally restricted	5C/D	Cells in the anterior primitive streak stained strongly.

Structure	Level	Pattern	Image	Note
TS12: notochordal plate	Weak		5E/F

Structure	Level	Pattern	Image	Note
TS13: head somite	Strong		6A
TS13: primitive streak	Strong		6A
TS13: trunk unsegmented mesenchyme	Strong	Regionally restricted	6A	Expression was strong in the presomitic mesoderm, but was undetectable in the mesenchyme underlying the anterior neural ectoderm. The change in expression was fairly abrupt, and occurred at the level of the otic sulcus.

Structure	Level	Pattern	Image	Note
TS13: head somite	Strong		6B
TS13: primitive streak	Strong		6B
TS13: trunk unsegmented mesenchyme	Strong	Regionally restricted	6B	Expression was strong in the presomitic mesoderm, but was undetectable in the mesenchyme underlying the anterior neural ectoderm. The change in expression was fairly abrupt, and occurred at the level of the otic sulcus.

Structure	Level	Pattern	Image	Note
TS11: extraembryonic visceral endoderm	Absent		8A
TS11: extraembryonic mesoderm	Strong	Uniform	8A
TS11: primary trophoblast giant cell	Strong		8A	Both primary and secondary troblast giant cells stained intensely.
TS11: ectoplacental cone	Present	Regionally restricted	8A	Most, but not all cells in the central core showed no staining, while an annulus of cells in the zone between the central core cells and the more peripheral differentiated giant cells showed the most intense staining.
TS11: chorion ectoderm	Present		8A
TS11: chorion	Present	Regionally restricted	8A	Expression was detected at the interface of the two layers of the chorion.
TS11: extraembryonic component	Present	Regionally restricted	8A	Staining was detected at the interface of the embryonic ectoderm and overlying visceral endoderm. The syndecan present in this location is likely produced by the extraembryonic ectoderm and localized at the interface of the two cell layers.

Structure	Level	Pattern	Image	Note
TS11: extraembryonic visceral endoderm	Absent		8B
TS11: ectoplacental cone	Present	Regionally restricted	8B	Most, but not all cells in the central core showed no staining, while an annulus of cells in the zone between the central core cells and the more peripheral differentiated giant cells showed the most intense staining.
TS11: chorion ectoderm	Present		8B
TS11: chorion	Present	Regionally restricted	8B	Expression was detected at the interface of the two layers of the chorion.
TS11: extraembryonic component	Present	Regionally restricted	8B	Staining was detected at the interface of the embryonic ectoderm and overlying visceral endoderm. The syndecan present in this location is likely produced by the extraembryonic ectoderm and localized at the interface of the two cell layers.

Structure	Level	Pattern	Image	Note
TS11: extraembryonic visceral endoderm	Absent		8C
TS11: ectoplacental cone	Present	Regionally restricted	8C	Most, but not all cells in the central core showed no staining, while an annulus of cells in the zone between the central core cells and the more peripheral differentiated giant cells showed the most intense staining.
TS11: chorion ectoderm	Present		8C
TS11: chorion	Present	Regionally restricted	8C	Expression was detected at the interface of the two layers of the chorion.
TS11: extraembryonic component	Present	Regionally restricted	8C	Staining was detected at the interface of the embryonic ectoderm and overlying visceral endoderm. The syndecan present in this location is likely produced by the extraembryonic ectoderm and localized at the interface of the two cell layers.