Antibody:	anti-Isl1
Detection system:	Secondary antibody coupled to rhodamine

Structure	Level	Pattern	Image	Note
TS15: foregut	Present		1B	Expression is in the proximal foregut endoderm.
TS15: branchial arch endoderm	Present	Ubiquitous	1B
TS15: thyroid primordium	Present		1B	Expression is in thyroid progenitor cells.
TS15: outflow tract	Strong	Regionally restricted	1B	Expression is in the aortic sac endothelium.
TS15: heart	Strong	Regionally restricted	1B	Expression is in parts of the heart wall located ventrally and inferiorly of the foregut endoderm.

Structure	Level	Pattern	Image	Note
TS18: thyroid gland	Present		1D
TS18: embryo mesenchyme	Present	Regionally restricted	1D	Expression is in mesenchyme surrounding the thyroid bud.

Structure	Level	Pattern	Image	Note
TS19: thyroid gland	Strong		2A
TS19: embryo mesenchyme	Strong	Regionally restricted	2A	Expression is in mesenchyme surrounding the thyroid.

Structure	Level	Pattern	Image	Note
TS20: thyroid gland	Present	Regionally restricted	2B	Expression is in the midline thyroid primordium that extends toward the ultimobranchial bodies.
TS20: embryo mesenchyme	Strong	Regionally restricted	2B	Expression is in the mesenchyme partly encircling the trachea.
TS20: lung epithelium	Strong		2B
TS20: trachea epithelium	Strong		2B

Structure	Level	Pattern	Image	Note
TS18: 4th branchial arch endoderm	Strong		4E , 4A	Expression is in the entire endoderm at the level of the fourth pharyngeal pouches.
TS18: embryo mesenchyme	Strong	Regionally restricted	4E , 4A	Expression is in the midline mesoderm surrounding the laryngotracheal groove and extending ventrally to the cardiac outflow tract.
TS18: 4th branchial arch	Strong	Regionally restricted	4E , 4A	Expression is in the epithelium of the ultimobranchial bodies.

Structure	Level	Pattern	Image	Note
TS17: 4th branchial arch	Present		4C	Expression is in the ultimobranchial bodies.

Structure	Level	Pattern	Image	Note
TS20: thyroid gland	Present		5B	Expression is in the ultimobranchial bodies.
TS20: embryo mesenchyme	Present	Regionally restricted	5B	Expression is in the laryngotracheal groove and in a broad zone of adjacent mesenchyme. The mesoderm immediately surrounding the ultimobranchial bodies is negative for expression.

Structure	Level	Pattern	Image	Note
TS21: trachea	Present		5D
TS21: thyroid gland	Present		5D	Expression is in the ultimobranchial bodies and midline thyroid primordium.
TS21: embryo mesenchyme	Strong		5D	Expression is in the mesenchyme surrounding the trachea.
TS21: esophagus	Absent		5D

Structure	Level	Pattern	Image	Note
TS21: thyroid gland	Strong		6A , 6B	Expression is in the ultimobranchial epithelium, weak or absent in the midline anlage.
TS21: trachea	Present		6A
TS21: embryo mesenchyme	Present	Regionally restricted	6A	Expression is in the mesenchyme surrounding the trachea.

Structure	Level	Pattern	Image	Note
TS23: thyroid gland lobe	Present	Regionally restricted	7B	Expression is central.

Structure	Level	Pattern	Image	Note
TS25: thyroid gland lobe	Present	Scattered	7D	Expressing cells are scattered in the parenchyma.

Structure	Level	Pattern	Image	Note
TS25: thyroid gland lobe	Present	Scattered	7E

Structure	Level	Pattern	Image	Note
TS28: thyroid gland	Present	Regionally restricted	8B	Scattered expression around follicles, absent in epithelial cells.